fairing a sailboat keel

The $tingy Sailor

Diy trailerable sailboat restoration and improvement without throwing your budget overboard.

fairing a sailboat keel

Refinish Your Swing Keel for Best Performance – Part 3: Fairing

This post is the continuation of Refinish Your Swing Keel for Best Performance – Part 2: Cleaning . I will describe common keel defects, the fairing system I used, sealing a freshly sandblasted keel, applying body filler to build up an accurate hydrodynamic foil shape, and paying extra attention to the shape of the leading edge of the keel.

Before I get started, a bit of legal housekeeping. This post contains affiliate links. That means I receive a small commission if you make a purchase using these links. You can purchase these products anywhere you like, of course. For a complete explanation of why I’m telling you this and how you can support this blog without paying more, please read my full disclosure .

Congenital keel defects

Most older C-22 keels are misshaped from the “factory”. The urban legend is that they were cast by one guy on a beach in Mexico. A big MEXICO stamped into the starboard end and the Swing Keel Refinishing DVD confirm that they were made somewhere in Mexico, beach or no beach. The DVD also says that most keels have one flatter side and one concave or flared side, which can cause the boat to point better on one tack than the other. It also explains that most of the foil shape is only in the lower quarter to third of the keel, which increases drag.

That was all true with the keel on Summer Dance . The port side shape was pretty close to the 13% template that comes with the DVD for the bottom quarter of its length but the shape quickly tapered to almost flat at the top. The starboard side was only shaped near the bottom. Over half of that side was nearly flat. To top it off, the keel hung at a slight angle to port, presumably because the pin hole wasn’t drilled perpendicular to the keel’s center line.

Like a seven layer cake

To refinish the keel, I applied a system of coatings that: seals the raw metal and provides a base for the rest of the coatings, shapes the keel to a proper foil, provides a moisture barrier, guards the leading edge against abrasion, and tops it all off with the same bottom paint as the hull received . The complete system with all its layers is illustrated in the following picture.

Keel finish layer system

Start with a waterproof foundation

The same day that I picked up the keel from the sandblasting shop, I hung it by cables from the center beam of my shop so that I could work on the entire keel at the same time without having to flip it over.

To start, I applied  West System 105 epoxy using cheap, disposable 3″ chip brushes. For the first coat, I mixed 10 pumps each of resin and hardener per side. I scrubbed it on using a circular motion to work the epoxy into the pits to seal the bare surface.

After two coats of epoxy

Then I lowered the keel flat onto a fork lift pallet on my utility trailer to apply a second coat to one side at a time. The reason for this was the pits in the surface. With the keel flat, I was able to fill the smaller pits (up to about 1/2″ in diameter) with epoxy. With the keel hanging, the epoxy flowed out of the pits. The starboard (worse) side took 16 pumps each of resin and hardener for the second coat. The port (better) side took 13 pumps.

Close-up of the cavity after epoxy sealing

After I applied the second coat this way, I wiped it down twice with acetone and then scuffed the surface and knocked down the high points with 80 grit sandpaper. The surface was smoother and ready for fairing. Except for that big cavity, that is. That took several layers of filler to correct.

Houston, we have a problem

To fair the keel for best performance, I turned to the template that is included in the Swing Keel Refinishing DVD. To use the template, you trace the curve onto a piece of thin plywood so it is easier to handle and then cut it out with a sabre saw, jigsaw, or bandsaw. You hold the wooden template perpendicular to the keel centerline (as shown in the picture below), to check the keel shape and thickness as you add the fairing compound.

The goal of the template is to make a standard  NACA 13% foil shape for minimum drag and best pointing ability at the average hull speed of the C-22. Unfortunately, the template that is included with the DVD is the wrong shape because it is based on the wrong keel angle. It results in a keel that is 1″ too thick, creates excess drag, and stalls (stops producing enough lift to offset the excess drag) too soon compared to the 13% foil. Describing it is quite technical, so I described it in detail in The Error in a Popular DIY DVD That Will Slow Down Your C-22 . Don’t buy the DVD or, if you already have it, don’t use the template until you read that blog post. You could be wasting your time and money.

Bell bottom keels

The maximum thickness of my bare, unfaired keel near the bottom end was 3.5″ thick. That point is also nearer the midpoint of the keel than it should be when compared to the template as you can see by the gaps in the following picture.

19% curve near the bottom

Doing the math told me that the keel ends in about a 19% foil curve, almost 50% fatter than the design goal of 13%.

Since removing the extra curve by lots of grinding wouldn’t be worth the trouble, I chose to shape the keel to 13% as much as possible except where it is 19% at the bottom. The extra thickness at the bottom should not make a noticeable difference. I also rounded the leading edge, which was cast to a slight point as you can also see in the picture above.

The top end of the keel doesn’t need to be shaped to a foil where it rotates up into the keel trunk, so I drew a line below the pivot pin at 60° from the edge of the keel (parallel to the bottom of the hull). That is where I stopped the foil shape so it wouldn’t bind in the keel slot when the keel is lowered.

Fair thee well

Tools and supplies for fairing

For the first coat, I wanted to establish a flat, smooth base for the areas that didn’t need to be built up, so I just skimmed the surface to fill in any low spots and to fair the edges. After that cured, I used my template to draw an outline of the area that needed to be built up right on the keel with a Sharpie marker. Then I divided the maximum build-up thickness (about 1″) into 1/4″ layers and drew approximate outlines on the keel like a topographical map.

Lines drawn for applying 1/4" layers

With the lines for visual guides,  I was able to build up the area in multiple layers that weren’t too thick to work with and with minimal waste. Frequent checks with the foil template revealed the low areas that needed to be filled.

Remarkably, it took about one and a half gallons of filler to build up each side for a total of three gallons.

If you don’t feel confident about fairing by eye or you’re running short on time, there are some excellent techniques described in Appendix B of the Final Fairing and Finishing  guide available as a free download from West System.

fairing a sailboat keel

After the filled area was close to the template shape, I applied a thin layer of U-Pol Dolphin Glaze  to fill in the smallest imperfections and give a smooth overall surface on which to add the top epoxy layer. The DVD recommends this step but, in my opinion, it’s unnecessary. You should only apply the sanding glaze to a maximum thickness of 3mm. That’s pretty noticeable on a show car hood, not so much on a sailboat keel. You can get similar results with fairing material or epoxy.

Tools and supplies for sanding

In contrast to the filler in which a lot doesn’t go very far, a little bit of glaze goes a long way. Only two cookie-size batches covered an entire side of the keel. Plastic spreaders and rubber squeegees don’t work well with this material, which is very dense. A 4″ steel putty knife gave the best results.

Check fairing lengthwise with a long straightedge.

After fairing one entire side of the keel, I flipped the keel over and repeated the process on the other side. When I finished that side, I hoisted the keel up and set it upside down in the sled on top of the trailer so that I could fair the leading edge, which is difficult to do while the keel is laying on its side. With the keel upright, the job was much easier.

The foil template and the casting itself both come to a high-angle point at the leading edge. A true NACA foil shape is rounded at the leading edge.

I experimented with making a 1/4″ plywood template of just the leading edge and using it to screed the filler down the length of the keel but it didn’t work very well. What did worked well was to bend a plastic spreader to the desired curve and, holding it at a low angle to the keel, pull a blob of filler down the leading edge, effectively extruding the filler to the correct shape. After it cured, I only needed to sand it a little to remove the high points and to feather the edges.

This technique also worked well to put near-perfect rounded edges on the end of the keel that swings up into the trunk.

Flatten the trailing edge of the keel to 1/4″-1/2″ wide for minimum turbulence. Don’t fair it to a sharp edge.

DSCN2165

With the long process of fairing complete, I finally moved on to the top coats described in Refinish Your Swing Keel for Best Performance – Part 4: Sealing and Painting . In that post I describe: building a fiberglass reinforced guard on the leading edge, applying the last shell coats of epoxy, bonding centering shims onto the pin end of the keel, priming with a barrier coat of epoxy paint, and applying anti-fouling paint last.

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17 thoughts on “ refinish your swing keel for best performance – part 3: fairing ”.

Excellent write up! My keel doesn’t have the mexico stamp. Have you uncovered any indication that later models didn’t have the stamp? Also, I used the template from the video and made a plywood template, but it seems to not fit my keel too well. The length of the template is shorter than my actual keel. All this makes me wonder if it’s really for a C-22.

Also, I don’t understand “bend a plastic spreader to the desired curve”. How did you keep it bent to the exact curve as you used it?

Hi, Cap’n!

I have heard speculation that during the peak of the Catalina 22s popularity, their keel mfr. may not have been able to keep up with the demand and Catalina Yachts might have contracted with an additional mfr. to help them fill orders and keep the production line moving. Makes sense. So, you might have one of the rare, US made keels. That would also suggest why yours is wider than 15.75″. If you look at some of the later mfg. drawings on the web, you’ll see notes on the drawing from when they did checks against the molds and corrected the drawing. The one I’m thinking of shows 16.5″ since 1985. Other owners I’ve heard of with these US made keels stated that theirs were more symmetrical, better shaped, had few pits, and were of a higher quality than the Mexican keels. So while you have the problem of the keel pin repair to contend with, you might have an overall better quality keel that will take less to refinish!

The yellow plastic spreaders are fairly flexible. I just bent and held it by hand, then it sprang back into its original shape.

Thanks for the clarification. Since the overall measurements seem to fit, I expected it might be something like that. My keel is definitely not as pitted as yours.

Sure wish I found this a few years ago when I had to rebuild my keel. Perfect post. Looking forward to reading “Part 4: Painting”

I’m reading the West System info preparing to purchase, and sales blurb says ” #205 Fast Hardener, mixed at a 5:1 ratio with #105 resin, results in a pot life of 9-12 minutes at 72°F, with solid cure in 6-8 hours. ”

The tech sheet http://www.westsystem.com/ss/assets/Product-Data-PDFs/TDS%20105_205.pdf also only mentions 1:5 ratio.

What was your reasoning in deciding to use equal pump count of resin and hardener?

I use the West System pump dispensers that automatically meter the right amount of resin and hardener per pump for a 5:1 ratio.

Ah, thanks for the clarification. Haven’t seen the pump system yet. Ordered it today.

I’m not having much luck finding affordable 80 & 120 grit wet/dry aluminum oxide sandpaper at affordable prices. Where do you get yours?

It depends on the project and the tool (belt, disk, block) but I usually get general purpose coarse grit sheets at Harbor Freight. For fine grit sheets and important projects, I have a couple of auto paint supply stores I shop at. One is a NAPA Paint & Supply that carries good quality supplies. Maybe there’s one near you?

Guess I missed it at Harbor Freight. Will go back and check. Yup, NAPA is nearby – thanks for the info.

I assume the USC Pro-Glass filler was a polyester. I am concerned about putting a polyester over an epoxy base even with an 80 grit tooth. I know West Systems says its OK to put epoxy over poly, but most boat builders shy away from the opposite ploy over epoxy for adhesion reasons. What were your thoughts on that mix?

From the MSDS sheet, USC Pro-Glas is composed of 15-20% styrene, 40-50% non-fibrous talc, 5-15% calcium carbonate, and the rest milled fiberglass and other minerals. I chose it more for its resistance to water absorption than its compatibility with epoxy. Polyester fillers are well known for absorbing water. Considering that and how porous the keel was even after sealing in epoxy, I can’t imagine how it could come unbonded. There was a LOT of mechanical bonding. I also applied the filler soon after the epoxy had mostly cured so there could also have been some chemical bonding as well.

The manufacturer (US Chemical & Plastics) recommends it for use over steel, aluminum, fiberglass (including marine applications), wood, masonry, concrete, and sheet molded compound (SMC) automotive body panels. That’s a pretty wide range of good adhesion and I couldn’t find any warnings against use over any particular substrates.

I’m not a chemist, so if you find any information to the contrary, I’d like to hear about it. A year later and the keel still looks like I just refinished it but I’ll be sure to update this post if I notice any longer-term problems.

Thanks for your question!

Stingy, Thanks for the wonderful and very detailed descriptions. I will be refinishing my swing keel in a year or so. I get the “thing” about the 19% vs 13% foil and commend you on your attention to this detail. But, unless I’ve missed it, you suggest that the template be placed perpendicular to the vertical center line of the keel instead of parallel to the bottom of the keel i.e. racked “up” at the leading edge by 30%. Am I missing something? You’ve gone to all this effort to recalculate the foil size only to place it so that it does not orient parallel with the waterline. Help please… A long-time Stingy follower

That’s what I try to explain in The Error in a Popular DIY DVD that Will Slow Down your C-22 :

So to wind up with a 13% foil in the water, we need to start with a template that has the same length as the keel width (so we can work with it at 90°) and the template (full shape) width should be the same as the width of a 13% foil at 30° from vertical.

I compensated for the angle of the keel by shortening the foil template so that it could be held perpendicular to the keel while still producing the desired shape at the waterline angle. It’s a little counter-intuitive, I’ll admit.

Hope that helps, $tingy

Thanks for the explanation, it works for me. Keep up the wonderful job.

Hey Stingy!

I’m about to take on this behemoth project and I wanted to know if you’ve had any problems with the fairing compound delaminating after a few years. I’ve got a can of the same stuff and I’d like to get started on the process soon here, but I’m nervous about it.

Thanks, Chris

Hello, Chris

I haven’t had any delamination that I can see. Go for it. Just be sure to wash the amine blush off the whole keel thoroughly after you seal it with epoxy.

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filling and fairing cast iron keels

  • Thread starter dunkelly
  • Start date 3 Oct 2020

Anyone any thoughts on the merits or otherwise of filling and fairing badly pitted cast iron keels .  

Well-known member

Seems reasonable; I would think major pitting would create turbulent flow over the keel.  

wully1

I kind of half did mine... in the past I’ve found they just rust again so didn’t expend too much effort on that job but I’d aquired a Terco Blaster so gave it a go. Got to say how impressed I am by it - took my keel back to the metal in very short order. So then I tried applying some Fertan which was equally impressive but I’ll wait to see hoe completely impressed I am in a few months time. I filled in the worst of the pitting with some ‘marine’ epoxy filler then primed and anti fouled just before the rain came on otherwise I might have spent more time filling. I’ll make a better job of it next lift if the Fertan works..  

Active member

To get the job done if you have an SDS drill, you can get a needle gun attachment that remove the rust well. I believe it is an annual chore along with the antifowling. (Katy Louise has encapsulated lead ballast.)  

convey

Slight aside, be wary while using a heavy duty twisted wire brush cup on them. They have sufficient bite to remove chunks from the edges even with a fairly low powered angle grinder. Ask me how I know ... Worth using the search feature as this is discussed often here and on other forums. Which boat?  

wully1 said: I’d aquired a Terco Blaster so gave it a go. Got to say how impressed I am by it Click to expand...
Lucy52 said: you can get a needle gun attachment that remove the rust well Click to expand...
convey said: be wary while using a heavy duty twisted wire brush cup on them Click to expand...
Lucy52 said: I believe it is an annual chore along with the antifowling. Click to expand...
wully1 said: I’ll make a better job of it next lift if the Fertan works.. Click to expand...

rogerthebodger

Following all the chipping and blasting paint on sone brick cleaner to remove any pust left. then wash with fresh water the paint on phosphoric acid before painting and filling . If you don't remove all the microscopic rust it will just come back.  

Dankilb , the instructions say to wash off the dust before overcoating The Fertan? I wiped it off but there was still residue coming off on my fingers when I primed it which is a bit of a worry.  

fairing a sailboat keel

wully1 said: Dankilb , the instructions say to wash off the dust before overcoating The Fertan? I wiped it off but there was still residue coming off on my fingers when I primed it which is a bit of a worry. Click to expand...
dankilb said: Yes, absolutely, the dust seems pretty stubborn, even after washing. Plus the higher-tech paint systems for this sort of application are specified for bare metal, whereas with Fertan (or Vactan or Hydrate80 etc.) there is still a layer of unspecified something below the paint! Click to expand...

pvb

wully1 said: I suppose I’ll find out in a year or so... Click to expand...

I stripped my keel before going back in this year. Tercoo for first strip for old filler and loose rust, then polycarbide disks on grinder. Cleaned back with thinners then zinc based 2-pack epoxy primer, fairing filler/sanding, another zinc primer, 2 coats of epoxy primer for antifoul, 2 coats of hard antifoul. I'll let you know at the end of the month how it fared (albeit a short season).  

Zagato

RUST CURERS. The most common way to cure rust is to use an acid convertor, these are most commonly water based, epoxy (glue) based or gel based. They have an acid content roughly somewhere between 4-8%. The names of these you will recognise as Ku-Rust, Jenolite, Fertan, etc and then company named products that sell you a complete rust cure and protection system such as Dinitrol, Supertrol, Bilt Hamber, POR-15, Buzz Weld etc. ACF-50 is an entirely different product and not relevant for keels, very good stuff however! For any of these rust convertors to cure the rust, the corrosion has to be taken right back to pretty much bare metal for them to be 100% effective, this is why they have not worked for the majority of cases of DIYers! Unfortunately they do not soak into deep rusty metal or even shallow rust. You really have to get the surface rust right back to near good metal, every pit, every rust worm and of course this is not easy where welds or seams are involved. RUST PREVENTORS So with expected results to be poor, very tough, or thick or rock hard rust "preventers" are used to coat over the rust convertor as part of a rust protection package. Some of these products are misleading as they say they stop rust... they don,t they just stop rust showing through. In fact long term they can be worse in many situations as they trap in the rust and moisture when a gap is created from corrosion underneath and it actually accelerates the rust. Sometimes if the metal was just open to the elements to dry out say on a car chassis it would have been better... I.e. Just spraying with oil actually can be very effective... no good for a keel of course. Rust preventors like POR-15 chassis original, which used to be marketed with the toughness of being resistant to hitting it with a hammer do have there place. They are excellent for protecting guaranteed rust free metal that is new or has been shot blasted for instance or as part of a treatment where the metal in question will take years to rot out anyway, e.g. Thick heavy duty axles. Unfortunately these products are used to hide rust and they can mislead many customers into thinking they do actually stop corrosion. Sadly they are becoming more widespread on the market, one company actually uses a video of a bloke painting his rusty trailer in the rain claiming that it will stop his rust... sigh! This is all just happening as effective clear coat products have recently been developed such as Dinitrol 4010. Sorry this Is more vehicle based insight now. This is great as you can keep an eye on the areas you have previously treated over the years and if you request it, it will stop all the cowboys in the undersealing world just slapping on rock hard coverings or thick coverings that hides the complete lack of preparation to the metal. Easy money for them! Thankfully most do a good job.  

MikeCC said: I stripped my keel before going back in this year. Tercoo for first strip for old filler and loose rust, then polycarbide disks on grinder. Cleaned back with thinners then zinc based 2-pack epoxy primer, fairing filler/sanding, another zinc primer, 2 coats of epoxy primer for antifoul, 2 coats of hard antifoul. I'll let you know at the end of the month how it fared (albeit a short season). Click to expand...

Are there no electronic rust proof protection systems, like Finalcoat for cars?  

Birdseye

convey said: Are there no electronic rust proof protection systems, like Finalcoat for cars? Click to expand...
Birdseye said: But what do you do about the keel joint? Or the bottom of the keels where they ground? Truth is, the keels should be lead not iron. Click to expand...

BabySharkDooDooDooDooDoo

BabySharkDooDooDooDooDoo

convey said: Excuse the idiot's question, how would lead work for keels that were structural, as on typical bilge keels that support the boat on the hard? I've seen a gentleman make up kevlar shoes for his boat, a shallow draft, centre keeled clinker that is ,as per tradition, pulled up and left on gravel beaches. No idea of the likely longevity, does anyone have any idea? Joints is a problem, I'm presuming they flex a little and that blending them over and joining the matt to the hull is out of the question, or is it? (I've seen the photos of a fully encapsulated bilge keeler that lower edge had worn through and ballast dropped out). Is part of the problem that we're just getting into the end phase of this issue due to the age of the respective boats? As in it's just becoming an issue now for 60s, 70s boats? I've seen an old, very abandonned Westerly who keels where flaking apart impressively, crumbling like old slate, and I would have thought there's were of a better batch of castings. What's the sticking value of matt covering them even when allowing for the joint? As in how long will it remain sufficiently stuck to act as a rot deterent? Click to expand...

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  • Boat Maintenance

Keels: Minor Maintenance and Repair

Remedies for rusty iron keels.

fairing a sailboat keel

The best way to treat an iron keel that’s rusting is to sandblast the whole thing and apply a complete, new, epoxy-based coating system. But that’s not always feasible or desirable. Because of the mess involved, many boat yards do not allow sandblasting. Even when this is permissable, a complete recoating job also means a complete re-fairing job, and that in turn means lots and lots and lots of slow, boring, dirty work if anything approaching a proper, smooth foil is to be achieved.

Because of the problems involved in complete refinishing of an iron keel, patch painting of rusted spots is often the only practical way to go.

Begin by cleaning the rusted spots as thoroughly as possible. Take your time here as this is the most important step. Chip off any scale with a cold chisel or welder’s chipping hammer, then wire brush-use a drill-powered brush where possible – and sand with coarse paper until you’re down to clean, bright iron. Use fine sandpaper (#150) to feather in surrounding, sound paint, and you’re ready for your new coating. Get paint on the bare, prepared iron as soon as possible. Iron will begin to oxidize almost immediately, and leaving it bare overnight will make much of your preparation go for naught.

Unfortunately, the best possible anti-rust coatings – those with epoxy bases which are true vapor barriers – are not compatible with other paints. Epoxies just won’t stick to other coatings; and, thus, because patch painting must lap over onto other paint, epoxies can’t be used in this application.

Our own experience backs up the recommendations of the paint manufacturers. The best coating to use in patch painting iron is zinc chromate paint. All the major manufacturers of marine coatings make a good zinc chromate. Take your choice and follow the directions. The most important rule to follow is three coats must be used. The object is to form as nearly an impenetrable barrier to water as possible, and three coats give a far better chance than one or two.

Patch painting isn’t the ultimate answer. Actually the ultimate solution isn’t even the sandblast – epoxy route. It’s replacing the damned iron with lead. But that’s even less economically feasible than sandblasting! Careful preparation and three coats of zinc chromate paint, however, make for a good, economically and manpower effective, finite solution.

-John Pazereskis

As a rule, lead keels require far less care than iron. Nevertheless, they are not maintenance free. While you don’t normally think of your lead keel as corroding away, lead keels can develop significant problems that both degrade performance and reduce the value of your boat.

The main culprit is bottom paints with a high copper content. Copper paint on a lead keel creates a galvanic couple, just as copper paint does on an iron keel. Fortunately, the difference in potential between lead and copper is far less than the difference between iron and copper, so that corrosion problems are commensurately smaller.

However, it is common to see lead keels with crumbly, whitish surface deposits, which when scraped away reveal a porous surface where the lead has corroded. Fortunately, the surface of a lead keel does not corrode and pit in the same manner as an iron keel, and reasonable repairs can be made without expensive equipment.

A drill-powered wire brush will usually grind away surface deposits and do an adequate job of cleaning out shallow corroded areas. It is important to remove as much of the crumbly oxidized lead as possible, to create a good surface for filler bonding.

With the lead clean and bright, fill corroded areas immediately with an epoxy filler. The best epoxy fillers for this purpose are the ones you make yourself from epoxy resin, such as the Gougeon Brothers West System epoxy, and a filler such as phenolic microballoons or microspheres. Remember that lead is pretty soft, and you don’t want your filler to be significantly harder than the surrounding material.

When filling, give the area to be faired a prime coat of unfilled epoxy before applying the thickened epoxy mixture. This will allow a better bond between the filler and the surface. You can allow the clear epoxy to partially kick off before over-coating with filler, but don’t let it cure completely or you’ll get a poor bond.

When the filler has cured, sand or plane it level and smooth. A belt sander or conventional hand bench plane can be used, since lead planes almost as easily as wood.

With all corroded areas and damaged areas cleaned and filled, sand or wire brush the rest of the keel to bright metal. A belt sander or disc sander works fine here, although proper use of either tool to avoid gouging the surface takes a little practice. A lead keel is far easier to bring to bright metal than an iron keel. The fin keel of a 30-footer can be done in an hour or so.

To make sure your keel doesn’t begin to corrode again, you must completely isolate the surface of the keel from the bottom paint with an epoxy barrier.

This is a two-stage process. First, the keel must be primed with a vinyl primer, such as Regatta Vinyltex 50/51 or Interlux Viny-Lux Primewash 353. The primed keel can then be over-coated with an epoxy mastic such as Regatta Epoxydur Mastic 3630-3631. Surface preparation and the timing of application of the coats of vinylepoxy systems are critical, so the manufacturer’s instructions must be followed to the letter.

The epoxy mastic coating does not sand well, so special care must be taken in application to get a smooth keel surface. This same epoxy system can be used on iron keels that have been blasted or ground to bright metal, but is only effective on a completely clean surface free of any rust or scale.

Several coats of the epoxy mastic can be used. The thicker the coating, the more effective the barrier between the keel.

The only drawback of epoxy sealing of an external keel is that it no longer functions as a good ground plane for Loran and single sideband, or as access to ground in a lightning protection system. To compensate, you should install an external grounding plate such as the Dynaplate.

Surface corrosion is not limited to the lead keels on older boats. Poorly alloyed keels on new boats can also corrode. Fortunately, the cure is not difficult – only labor intensive – and the prognosis is for complete recovery and a long life. Yearly checkups are recommended, with local retreatment as necessary.

Beauty of Internal Ballast Really Is Skin Deep

If you’re gloating because you think your encapsulated keel frees you from any worries, forget it. Encapsulated ballast frequently requires more complicated care than an external ballast keel.

The danger is damage to the fiberglass shell surrounding the keel.

Even if you haven’t run aground this year, there’s a good chance that some where along the way you have acquired at least some superficial gouges in the lower part of the keel shell. These should be treated before they become problems. Even superficial damage to the gelcoat can allow water penetration into the laminate.

Treatment of superficial gouges in gelcoat or the first layers of the laminate is straightforward. First, wash the damaged area thoroughly with high pressure fresh water. Dry the gouged area with a handheld hair dryer. Roughen the edges of the gouge with very course sandpaper – 50 grit or 36 grit.

Wash the area again thoroughly with acetone. Use a small, stiff bristle brush to clean the gouge completely. Dry again with the hair dryer, after most of the acetone has flashed off. Don’t breathe the stuff.

With the area thoroughly clean and dry, brush on a clear coat of epoxy resin, followed by resin thickened with microspheres or micro-balloons. Stick waxed paper over the epoxy patch to keep the epoxy from sagging out.

When it’s dry, sand smooth and touch up any voids or hollows with more filled epoxy.

When everything is filled, prime the patch and the surrounding area with a two part epoxy primer, such as Woolsey MFP. This is important, because the gelcoat that you have sanded is now pretty porous, and is more likely to develop blisters than polished gelcoat.

More extensive damage to encapsulated keels, requiring structural fiberglass repair, will be dealt with in another article. How do you tell if you’ve got structural damage? As a rule, any time the shell is ground away so that any of the ballast is exposed, or any time laminate is exposed over an area’ greater than a square foot, you probably need to do more than patch with putty. 

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keel fairing

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:hothead How do you fair a keel. are there any websites showing how. my boat is 28 yrs old and has bumps on the keel.  

US27inKS

the bumps are at the botoom half of the keel where the lead is  

You have to figure out what is causing the bumps before you decide how to fix them. On an older boat, they might be caused by many layers of old antifouling paint, that are splitting and blistering. If your keel is lead, with paint over it, then all you need to do is strip the old paint off the keel with a chemical paint stripper (preferably one that is suitable for use on fiberglass). If your keel is lead encased in fiberglass, then you still need to strip the old paint off the keel, but, when you're done with that, you'll see whether the fiberglass casing is damaged, and whether it needs to be repaired. First identify the cause of the problem, and that will dictate how you fix it.  

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Fairing support

Fairing a surface removes the highs and lows so the surface is level. It can mean filling holes and low areas, reshaping voids, or grinding down bumps so they blend in with the surrounding surface, appearing level, or "fair" to the eye, to the touch, or to the fairing batten.

The material for filling or shaping is called a fairing compound or fairing putty, which contains some type of resin—either epoxy, polyester, or vinyl ester. For convenience, there are premixed fairing putties, or you can make your own.

There are a lot of reasons to fair a surface while building or repairing a boat. Examples include:

  • Making the entire hull surface fair during construction, especially for wooden boats
  • Fairing large areas of a hull surface misshapen due to, for example, bowing out at the bulkheads as a result of years of hull stresses
  • Fairing small gouges and dents on wood, fiberglass, aluminum, or steel hulls before applying primer and painting
  • Fairing gelcoat imperfections above the waterline
  • Filling in holes after grinding down gelcoat blisters below the waterline before finishing with an epoxy barrier coat and antifouling bottom paint
  • Fairing a hull surface prior to wet layup with fiberglass to ensure an even surface because fiberglass is difficult to sand
  • Fairing a small area of fiberglass cloth that didn’t quite get filled in by the epoxy overcoats after wet layup and before priming and finishing
  • Reshaping and fairing damaged underwater appendages such as the rudder and keel for added speed
  • Filling holes after removing hardware
  • Fairing an entire hull before a paint job

Choosing a Fairing Compound

  •      What’s in a Fairing Compound?
  •      Types of Resins Used in Fairing Compounds
  •      Types of Fairing Compounds: Premixed or Make Your Own

Supplies for Fairing

Steps for fairing.

  •      1. Surface Prep
  •      2. Mixing the Fairing Compound
  •      3. Applying the Fairing Compound
  •      4. Sanding and Wiping

Using TotalBoat TotalFair to Repair Crazing

Fairing is more than just fixing dings and dents for cosmetic reasons. It entails everything from filling surface scratches in gelcoat, seamlessly repairing osmosis blisters on a hull, reshaping the leading edge of a keel, making a hull repair disappear, or smoothing the hull to get the fastest underwater profile.

A fairing compound contains resin—either epoxy, polyester, or vinyl ester, and each resin is designed for different purposes. Before deciding on a fairing compound, think about whether the faired area is above or below the waterline, and how you plan to finish the faired surface. Will you be finishing with primer, barrier coat, topcoat, or gelcoat? The answers to these questions determine the type of resin required in the fairing compound.

The key to successful fairing  is to use a fairing compound that contains the appropriate resin and thickening agents to do the job properly. The fairing compound needs to bond to the substrate being faired, and the finishing material (such as primer, paint, or gelcoat) needs to bond to the faired surface.

What’s in a Fairing Compound?

Fairing compounds or putties typically contain the following:

  • A resin such as epoxy, polyester, or vinyl ester
  • A hardener (for epoxy) or catalyst (for polyester/vinyl ester) for activating the resin and ensuring that it eventually cures to a hard, plastic material. Always use the exact amounts of hardener or catalyst specified by the manufacturer, or the resin will not cure properly.
  • A low-density filler such as fumed silica (epoxy) or chopped fiber (fiberglass strands) (polyester/vinyl ester) for thickening the putty so it won’t run or sag
  • An additive (such as glass microballoons) that makes the compound easier to sand after curing, since the resin and thickening agent alone result in a cured substance which is very hard to sand smooth

Types of Resins Used in Fairing Compounds

Whether to use a fairing compound containing epoxy, polyester, or vinyl ester resin depends mainly on:

  • The material to be used to finish the faired area
  • Whether the fairing is being done for cosmetic or structural reasons
  • Whether the faired area is above or below the waterline

Use the following table to determine which type of fairing compound is best for your fairing needs.

Types of Fairing Compounds: Premixed or Make Your Own

Fairing putties either come "premixed" with the resin and thickener already mixed and you just mix in the hardener or catalyst when you get ready to use the compound. Or you can use the "recipe method" to mix your own fairing compound using separate resin, hardener/catalyst, filler, and additive. Always follow the manufacturer’s safety instructions and wear appropriate personal protection when working with all resins, fillers, and additives.

Epoxy Fairing CompoundsThe Recipe Method: With this method, you take separate ingredients and mix them together to the desired consistency (think peanut butter). Ingredients include epoxy resin , hardener, a thickener (colloidal silica) to thicken and prevent sagging, and microballoons to make the putty easier to sand after curing, which might take a day or more. It’s very important to always mix the epoxy resin and the hardener first before mixing in additives. Also, you want to work quickly as the curing reaction, and, therefore, the working time, starts once the resin and hardener are mixed.

TotalBoat TotalFair . It has a yellow resin paste (part A) that already has the fillers blended in, and a blue hardener paste (part B). Mix them 1 part resin to 1 part hardener by volume until the putty turns a solid green with no swirls, and apply. Its simple 1:1 mix ratio and obvious color change make it much easier to use than other pre-mixed epoxy fairing putties.

With epoxy fairing compounds, the recipe method is good if you’re already using a liquid epoxy resin system for other projects. It’s also good if you’re finishing wood bright and don’t want the fairing putty to show. If this is the case, you would use your liquid epoxy resin, a clear hardener, and a filler that matches the wood to thicken the mixed epoxy. An example of a filler would be to use the dust from the particular wood being used, such as mahogany. Wood flour is a thickening agent, but the color of it does not match all woods, and it is typically used for fillets.

Otherwise, the pre-mixed method has the following advantages over the recipe method:

  • Fillers are pre-mixed in the resin, saving you time and guesswork.
  • A simple mix ratio makes it easier to get the perfect consistency every time.
  • It cures much faster and is ready to sand in a couple of hours.
  • The cured color stands out on the surface, making it easy to sand.

The Recipe Method: This method involves mixing together separate polyester resin containing wax and catalyst (MEKP or methyl ethyl ketone peroxide), a thickener such as (colloidal silica) to thicken and prevent sagging, and microballoons to make the putty easier to sand after curing. The resin and catalyst are mixed thoroughly first, then the filler and microballoons are added and mixed to the desired consistency (think peanut butter).

The Pre-Mixed Method : The faster, easier, cheaper way to fill dents and small gouges is to use a pre-packaged filling/fairing compound. These products typically contain a thickened polyester or vinyl ester resin compound and separate hardener. They provide easy instructions for mixing resin and hardener in precise amounts.

Some of the supplies you’ll need depend on what type of resin you’re using and whether you’re fairing a small area or a large area, such as a hull. The list below begins with general supplies for fairing, and concludes with optional equipment depending on your particular repair.

  • Heavy, abrasive tools such as an angle grinder or a Dremel rotary tool with right angle attachment for grinding out and beveling the edges of cracks, or for grinding down gelcoat blisters
  • Clean tongue depressors or a putty knife to dispense resin and hardener
  • Plastic spreaders or a putty knife for mixing and spreading the fairing compound
  • Personal protection for grinding, sanding, mixing, and application – a NIOSH-approved respirator, with organic vapor cartridges (for grinding/sanding fiberglass or gelcoat), an N95 respirator with vent valve or without (for grinding/sanding wood), eye protection, a hooded paint suit , and gloves
  • Sandpaper – From 60 to 180 grit for surface prep; 220-320 grit for sanding fairing compound
  • A long, flexible sanding block, or fairing board makes it easier to sand large areas effectively. It bends to the shape of the surface, but is long enough and flexible enough to bridge the low areas and knock down any high spots. To make your own fairing board : For a surface that’s more curved, use ¼" plywood; less curved, ½" plywood will do. The width of the board should be 3". The length should be a multiple of 11" to make the best use of sheets of sandpaper that are 7½" x 11". To make the board easier to control, bond a hand-grip at each end.
  • Sanding blocks – For sanding smaller areas. Choose from a variety of commercially available hard and soft sanding blocks for different purposes when sanding by hand. For example, a soft sanding block aids in sanding curves and contours; a hard sanding block is best for sanding straight surfaces.
  • Masking tape – For protecting areas immediately surrounding the area to be faired, if necessary, while sanding. Use a high-quality masking tape that removes cleanly. For taping curved surfaces, use a flexible tape .
  • Clean, lint-free wiping rags and denatured alcohol or acetone for cleaning the surface to remove dust, dirt, grease, and oil after sanding
  • Optional sanding items – Random-orbit sander (dustless, if possible) to expedite sanding large areas during surface prep, large diameter sanding disks and a vacuum cleaner to remove all sanding residue
  • Optional if using a recipe method fairing compound made with epoxy resin/hardener and fillers , peel ply is a special fabric that doesn’t bond to epoxy, releases easily, and leaves a smooth-textured surface. Use peel ply to prevent amine blush, which must be removed before applying additional coats of recipe method epoxy fairing compound or a coat of primer.
  • Optional if using an epoxy resin recipe fairing compound and finishing the faired wood surface naturally (bright) : Sanding dust from the type of wood you’re using to make a fairing putty that matches the wood. As with any thickening agent, the epoxy and hardener are mixed first, then the wood dust is added and mixed thoroughly.
  • Optional if using a recipe method fairing compound made with polyester resin/MEKP catalyst and fillers : If your polyester resin is a "laminating" resin (no wax), you need to add wax
  • Optional if fairing is to repair gelcoat blisters below the waterline : Epoxy barrier coat
  • Optional if fairing a hull or large area : Plaster’s hawk or hand board to hold a large volume of fairing putty. If the hull or other surface is very unfair, a notched applicator is ideal for applying putty instead of a flat plastic spreader. Also, for leveling the fairing compound after it’s applied, you’ll need a plastic fairing batten.
  • Optional if applying fairing compound to a metal surface : Need to apply an etching primer first so the fairing compound can bond properly

1. Surface Prep

Attention to surface prep ensures the fairing compound will adhere to the surface and stay in place once it’s cured.

Clean If the surface isn’t clean, sanding will grind dirt, wax, and other contaminants deeper into the substrate, compromising the effectiveness of the fairing compound, and subsequent primers and topcoats. Clean the surface with a solvent, such as acetone or denatured alcohol, using clean rags and the two-rag wipe on/wipe off method: one rag to apply, one rag to remove. Change rags often so you aren’t smearing contaminants or residue over the surface.

(Optional) Grind Any surface cracks, crazing (micro-cracks), or gelcoat blisters need to be ground out and have their edges beveled using a right angle grinder or a rotary tool with a right angle attachment. Grinding and beveling roughs up the surface so the fairing compound can achieve a sound mechanical bond. The repair will look better and last longer.

Sand If necessary before sanding, mask any areas that you do not want to be roughed up. Roughing up the surface by sanding helps the fairing compound adhere better. Use 60-180 grit sandpaper, and sand down to solid material.

Clean Again If not using a dustless sander, remove all sanding residue with a vacuum cleaner. Clean the area again with acetone or denatured alcohol, and allow the solvent to flash.

Additional Surface Prep Considerations :

WOOD Wood is a very absorbent material, so if you’re using an epoxy fairing compound made with a liquid epoxy resin system, you need to ensure the compound achieves a sound bond on this porous surface. Before applying the compound, brush on a thin coating of properly mixed (that is, resin and hardener only) epoxy resin to first wet out the area to be faired. Then you can do one of two things:

  • Wait for the wet-out coat to cure, sand to ensure sufficient key (roughness for mechanical bond), remove sanding residue, and apply the fairing putty.
  • Or, you can apply the fairing putty to the wet-out surface once the surface is tacky to the touch.

2. Mixing the Fairing Compound

Mixing epoxy fairing compounds.

  • Combine the accurately measured resin and hardener in a clean container and mix thoroughly for approximately three minutes.
  • Working quickly, add the thickening agent and mix thoroughly. The reason you want to work quickly to mix the thickening agent (and the microballoons in Step 3) is that the mixture starts curing once the resin and hardener are combined in Step 1. Don’t be surprised if the epoxy resin absorbs a decent VOLUME of thickening agent before you achieve the desired consistency. For fairing purposes, the desired consistency is typically like peanut butter.
  • Add the glass microballoons and mix thoroughly.

For best results, measure and mix only as much putty as you can apply according to the indicated working life (pot life) and temperature specified by the resin manufacturer.

Use clean, dry tools and work as quickly as you can to mix fairing putty thoroughly when using the recipe method. The mixing of the resin and hardener creates an exothermic reaction which begins the curing process, so you’ll only have a small window of time to apply the fairing putty before it becomes unusable.

After adding and mixing in the thickening agents to the mixed epoxy resin, use the mixing stick to "wrap" the mixture evenly around the inside of the mixing cup. This action will reduce the amount of exotherm (heating process the resin goes through while curing), and increase the time you have to work with the fairing compound.

Always be sure of your measurements in order to achieve the proper cure. If improperly mixed, the unwanted results include no cure, soft cure, or shrinkage from too much heat caused by an excessive exothermic reaction.

To create larger quantities of fairing putty, you can gain greater accuracy measuring by weight. Before you begin, know the working time (pot life) of the product and mix only as much compound as you will be able to use in that time, or it’ll be wasted.

Note that even though the mix ratio by volume of a certain pre-mixed fairing compound might be 1:1, 2:1, or 3:1, the mix ratio by weight will not be equal ratios because the resin and hardener are different densities. Be sure to read the product technical data to determine the proper mix ratio by weight.

  • Measure the resin (Part A) quantity first. Place a clean, empty container on the scale and adjust the scale to zero so the weight of the container is not counted. Dispense the desired quantity of resin paste (Part A) into the bottom of the container, taking care to keep it off the sides. Take note of the weight and remove it from the scale. For this example, let’s say you have measured 12 ounces of resin.

In this case, the equation would be: 90/100 x 12 oz. = Amount of hardener needed

So, 1080/100 = 10.8 oz.

  • In this example, in Step 1 you measured 12 oz. of resin (Part A), so you would need to measure 10.8 oz. of hardener (Part B) into the second clean container (making sure the scale is set to zero again before adding hardener).
  • Place the two weighed amounts of resin and hardener on a clean surface and mix as indicated below.
  • Use a clean tongue depressor to dispense and place the correct mix ratio of Part A and Part B on a clean surface.
  • Use a plastic spreader to mix the two parts together.
  • Mix thoroughly until the putty is a uniform color, with no swirl marks.

Mixing Polyester or Vinyl Ester Fairing Compounds

  • Combine the accurately measured polyester finishing resin and MEKP catalyst in a clean container and mix thoroughly.
  • Add the thickening agent and mix thoroughly. Don’t be surprised if the polyester resin absorbs a decent VOLUME of thickening agent before you achieve the desired consistency. For fairing purposes, the desired consistency is typically like peanut butter.

3. Applying the Fairing Compound

Use a plastic spreader to apply the fairing putty. It’s not a good idea to try to fill deep holes in a single application because a layer of epoxy that’s too thick can cause excessive heat build from the exothermic curing reaction.

  • Fill the low areas proud (meaning just above the fair level) so you can sand them down to fair without having to refill.
  • To avoid extra sanding after the compound cures, use the spreader to smooth out the compound as close to the desired shape as you can. Blend it into the surrounding areas.
  • For fairing larger areas , use a spreader to apply the compound, slightly overfilling the area to be faired. If the surface is very unfair, use a notched spreader to apply the fairing compound. To level the applied compound, bend a plastic fairing batten so it matches the contour of the surrounding fair areas, and drag it slowly over the filled area.
  • Allow to cure completely before sanding.
  • You may need repeat the process of filling and sanding low spots until you are happy with the fairness of these areas. Before you know it, your hull will be fair and ready for priming.

Optional for Certain Epoxy Resins: Use of Peel Ply to Prevent Amine Blush

If applying a fairing compound made from the recipe method of epoxy resin, hardener, thickening agent, and filler, the cured surface may develop a film of amine blush, depending on the particular brand of epoxy resin. If amine blush is present, it must be removed before sanding. You can remove it using a ScotchBrite pad and water, and allow the area to dry completely. It’s not hard to do, but it does add extra time, especially if you have a number of areas to fill. Check with the resin manufacturer to determine if amine blush is an issue.

If it is, you can prevent amine blush, by placing a layer of peel ply over the applied fairing compound. Peel ply won’t react with the epoxy, and it’s easy to peel off after the epoxy cures. Be sure to remove the peel ply before sanding. Amine blush is not an issue if you’re using a pre-mixed epoxy fairing compound.

4. Sanding and Wiping

To prepare for application of a primer, barrier coat, topcoat, or gelcoat, allow the last layer of fairing compound to cure completely, then sand. Sanding makes the surface fair by smoothing down the high spots, and it roughs up the surface so the primer can adhere better. How much sanding you need to do depends on how smoothly the fairing material was applied. Sand the surface until it is fair and smooth.

Use a vacuum cleaner to remove sanding residue, then use a clean, lint-free cloth and denatured alcohol or acetone to wipe down the surface. Allow the solvent to flash.

Note that if using a high-build primer, it will only cover fine sanding marks or small pinholes in the faired surface. Refer to the primer manufacturer’s recommendation for the type of sandpaper to use for surface preparation prior to priming with a high-build epoxy primer.

Sanding generates toxic dust, so work in a well-ventilated area and wear protective clothing, and use proper dust collection methods. Be sure you also wear appropriate eye protection and a high-quality respirator at all times during this process.

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keel fairing?

Discussion in ' Boat Design ' started by kapnD , Nov 8, 2013 .

kapnD

kapnD Senior Member

I have my 50' Willard (displacement hull) hauled out, and am looking at the deadwood at the end of the keel. It is about 8" wide and is rounded, though not exactly what I would call "fair". The keel ends several feet in front of the propeller, so this is probably not as direct an issue as would be it it were right against the prop, but I want to make sure the hull is as slick as possible to squeeze the most speed out of the least rpm's. Would there be any measurable gains in adding taper at the back of the keel?  

PAR

PAR Yacht Designer/Builder

It's tough to tell without a picture or two, but generally yes, you'll have some net gain if you fair down the aft end of the deadwood. How much gain - well time will tell, once you splash her, but don't expect all that much. On your boat, you could do a nice job of "sweetening up" that skeg. I'd put a 2:1 or 3:1 parabolic on the leading edge (full length) then taped the crap out of it. If my understanding of that skeg is correct, it's not as structural as you might think, it's just a skeg for directional course keeping. This would offer a nice clean bit of flow to the prop, easing it's burden. For this boat 2:1 will be fine. If this is the 'glass version (MK-4), the laminate in this area is really, (really, really) thick, so you have a good bit of room to do some damage. If not interested in itching to death, a foam nose could be added, with a light layer of fabric to fair it in. As for the back, I'd cut a few "pie wedges" in the laminate and force it into the new, tapered shape. Or you could do it a different way if you like. Make the taper as long as practical.  

Attached Files:

Byyb-278.jpg.

FAST FRED

FAST FRED Senior Member

What price will you pay for a .0001 gain?  

Petros

Petros Senior Member

An 8" thick bluff keel trailing edge? That is a huge drag creator, and it would put a lot of very tubulent water into the prop, making it much less effective as well. Taper it down at about 6 to 1, with sharp corners on the TE, just as narrow as you can (like 1/8", the smaller the better, but keep the edges square). it will be noticeable. Anything else you can do to clean up the area around the prop and the rudders should help as well. Post some pictures so we can pick it apart and give you some ideas.  

viking north

viking north VINLAND

If as you say the keel ends several feet in front of the prop you do have room to do some fairing on that 8 in. keel end width, streamlining the flow to the prop and reducing some drag. I have included a couple of photos showing that very idea as done direct from the factory on my keel. Magnify the second photo you can see the tapering (narrowing ) as the keel end extends aft to the cutlass bearing and prop. In your case you could add tapering foam sections to form the shape and simply glass it over as it is not structural. As previously mentioned without photos it is impossible to see your set up but I caution if you have a cutlass bearing do not block the water lubrication intake feeds. I post this only as a reference that one of the designers could use as an aide to guide you along. I think there is also some rule of thumb on the spacing between prop and keel end. As shown here the cutlass end is 6 in. long plus I would allow another 3 in. to install a set of Spur rope cutters between the keel end and the prop. In my case on this conversion build this whole cutlass assembly will be eliminated for one that will be housed inside the tube. Luck would have it i still had photos of the original setup that will give you an idea of a factory layout. Hope it is of some help. A yacht is not defined by the vessel but by the care and love of her owner ---  

DSCF1507.JPG

Dscf1501.jpg.

As you can see this is a bit different then most keel/prop interfaces, with lots of room for flow to "reassemble", though some gains can be picked up with a good fairing. If it was me, I'd consider removing most of the skeg, with just enough of a well shaped appendage to offer grounding protection. Of course, this is wholesale surgery on this 'glass hull, but doable.  
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Thanks for the replies, I will snap some photos next time I'm at the boat. As you can tell from Par's attachment (thank you very much) there is plenty of room to add some fairing without having to remove anything. I think I will glue on some foam, shape it out and glass over. As for cutting the keel off, I would hesitate to do so as I operate the boat in open ocean, frequently rough and windy conditions, and appreciate the directional stability the keel imparts under way, and the rocking it damps while stopped.  

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Boat Design Net

Yachting World

  • Digital Edition

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5 tips: faster foils – make sure your keel and rudder are in tip top condition

Matthew Sheahan

  • Matthew Sheahan
  • May 5, 2016

Matthew Sheahan talks to two racing boat experts about below the waterline improvements that will cost you less than the price of one new sail

fairing a sailboat keel

If you want to go faster, which would you choose: a new headsail or a fully faired and professionally finished set of foils?

If you currently have a silky smooth keel, which is symmetrical in section and blemish free, along with a rudder that’s as smooth and as slippery as a dorsal fin, then the headsail could well be the most effective option. But a walk around a typical marina at this time of year suggests that foils are often the most neglected part of the boat.

What lies below the waterline may be out of sight and out of mind, but the keel and rudder are crucial lifting surfaces and are every bit as important as the sail plan. You wouldn’t trust an aircraft with a pristine wing on one side and a battered and abused one on the other and a boat should be no different.

Underwater neglect doesn’t stop with the foils. From rough surface finishes to yawning gaps around saildrive legs and skin fittings that sit prouder than a cluster of giant limpets, there are plenty of areas that cause underwater drag.

Tidying up below the waterline

Tidying up what lies beneath the waterline can make a big difference to a boat’s pointing ability and straight-line speed.

If you take that off-season stroll around the boatyard, you will soon see what you’re up against. Look at that hot ship with its marble smooth surfaces and as many hard angles as you’ll find on a dolphin – is it any wonder that they often have the first windward mark rounding to themselves?

If you can assemble your crew for a few working weekends to tackle the underside, all will gain in the collective effort of making the boat more competitive. In reality, this is often difficult to achieve, but getting the job done professionally may not be as expensive as you might think. There are plenty of builders who can do it for you in a fraction of the time, to a greater level of accuracy and at roughly the price of a new headsail.

I talked to two UK South Coast racing boat experts, Hamble-based Richard Faulkner and Cowes-based David Herritage. Based on their suggestions, here are five key underwater areas that could change the performance of your boat.

1. Section symmetry

P1070920

Checking that sections are perfectly symmetrical is second nature to those running grand-prix boats and high end racing one-designs such as TP52s and King 40s. But many production cruiser-racers can have asymmetrical keels and/or rudders that will produce uneven performances on each tack. Making sure the foil section is as the designer intended is a good starting point.

There are two basic options here: 1) Ask for section templates from the designer or, 2) simply test to see whether your foil is different on each side. Then pick the better section shape and re-profile the other side to match.

“It’s not that difficult a job, but it is time-consuming so people tend to employ an expert,” says Richard Faulkner. “Broadly speaking the process involves stripping all the old paint off and getting back to the original epoxy coating. From there the correct sections are built up using a micro-balloon filler, if required, and a high build epoxy paint.

“Given the potential for improvement it always amazes me that more people don’t do this, but I guess modern electronics and other go-faster gear is sexier.”

2. Perfect foil

P1070993

“On foils we would rub back initially with 120-240 grade before moving to 400 grade and then finishing with 1,000 grade. For boats that will stay in the water, we use Nautix A4 antifouling as it is a good hard coating.”

One of the tricks of the trade, especially when wet sanding a white-painted finish, is to use a guide coat which can be sprayed on before the rub down. This allows you to see any low spots.

3. Weed cutters/skin fittings

The gap between the top of the rudder and the underside of the hull is not just an obvious trap for weed, but an area that is extremely hard to get at from aboard the boat.

Keels & Appendages

A short stainless blade with a sharp leading edge is fitted just ahead of the leading edge of the rudder. Some boats fit weed cutters ahead of the saildrive leg as well.

Ideally all skin fittings should be flush with the hull. Skin fittings that stand proud should be replaced with flush fittings, but if this isn’t possible then fittings should at least be faired in with filler to reduce drag.

4. Hull finish

For drysailed boats with no antifouling, the top end racers will rub down to 800-1000 grade although there are differences in opinion as to whether this level is really necessary. For antifouled surfaces, 400 grade is generally the practical limit.

P1070927

Teflon-based antifouling tends to be favoured over the soft self-polishing types, as it is harder. In addition to Nautix A4, Tri-Lux and Interspeed, both from International, are also popular choices.

“McLube’s HullKote is a popular surface finish for underwater,” says Heritage.

5. Saildrive leg/prop blades

The popularity and simplicity of saildrive units has been driven largely by the ease with which engines can be installed. For raceboats they are also lighter than a conventional shaftdrive. But the gap between the strut and the hole in the hull through which it protrudes can create unnecessary drag.

“A simple composite fairing can be fitted to reduce the gap,” says Faulkner.

Keels & Appendages

Prop blades should be kept smooth and clean with a simple ten-minute rub down using 180 grade. Anodes can also be tidied up in the same way.

Ballpark costs

Costs will vary depending on the size of the boat and its condition, but for a typical production racer-cruiser of 38-40ft approximate prices would be:

  • Keel and rudder coated and fully faired £4,000
  • Advanced foil work – including alloy section templates and keel weight checks £7,500
  • Saildrive fairing £500
  • Weed cutter £100
  • Skin fitting fairings £350

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Fairing out the trailing edge of the keel.

  • Thread starter jpekas
  • Start date Jul 25, 2009
  • Forums for All Owners
  • Ask All Sailors

Working on a 1981 Lippincott 30, and and just completing a fairing out the hull after a restoration due to pox, many mini blisters. Anyway, my question is on the trailing edge of the keel, should it be squared off or faired smooth to an edge as I did on the lead egde of the keel. Does anybody have an input on this? Thanks, JP...  

jpekas said: Working on a 1981 Lippincott 30, and and just completing a fairing out the hull after a restoration due to pox, many mini blisters. Anyway, my question is on the trailing edge of the keel, should it be squared off or faired smooth to an edge as I did on the lead egde of the keel. Does anybody have an input on this? Thanks, JP... Click to expand

Ted

Trailing edge The trailing edge of the keel and rudder should be squared off. Depending on your foil shape, it will probably be between 1/4" and 1/8" wide. Definitely do not shape it come to a point or round it. Square end with sharp corners is what you want.  

Ted said: The trailing edge of the keel and rudder should be squared off. Depending on your foil shape, it will probably be between 1/4" and 1/8" wide. Definitely do not shape it come to a point or round it. Square end with sharp corners is what you want. Click to expand

fairing a sailboat keel

Sailing Theory & Practice - extract Herewith below an extract from page 284 of Prof C.A. Marchaj's book "Sailing Theory and Practice". Professor Marchaj was the renowned hydrodynamicist from the Wolfson Unit of Southampton University:- "The trailing edge is of relatively little importance, as it lies in the area of turbulent wake. There is no scientific foundation for the popular belief that the centerboard or fin must taper as sharply as a razor. Experiments have proved that cutting the trailing edge off blunt for up to 5 per cent of the profile length does not influence resistance, and is undoubtedly more practical."  

Donalex said: ...Professor Marchaj was the renowned hydrodynamicist from the Wolfson Unit of Southampton University:- ... Click to expand

RichH

The leading edge shape of a keel or foil is vastly more important than the exit shape. Usual is cut a square 1/8" flat at the aft edge ... less vulnerable to damage, damage that can propagate destructive 'upwash'. Marchaj is/was probably right in his analysis/advice. The sharp exit shape is subject to too much vulnerability. My scows' boards and rudder aft shaped used to be 'sharp' ... 1. class rules made them illegal. 2. didnt matter all that much. (BTW/FWIW - these were flat plate foils ... also with 'sharp' leading edge / entry angles)  

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Sailboat Keel Types: Illustrated Guide (Bilge, Fin, Full)

The keel type is one of the most important features of your boat. But the different designs can be confusing, so I've set out to create a very clear guide that will help you understand sailboat keels once and for all.

What are the most common sailboat keel types? The most common sailboat keel types are full-length keels, fin keels, bulb keels, wing keels, bilge keels, and lifting keels. Full keels are popular among cruisers, while fin keels are generally used for racing. Bilge keels and lifting keels are typically used in tidal waters, on small fishing boats for example.

In this article, we'll explore the most common keel types together. I'll use diagrams to really hit home the differences of all these keel types, and we'll discuss what keel types are best for liveaboard, ocean cruising, and lake weekend trips. After reading this article, you'll know what to choose - and why.

fairing a sailboat keel

Sailboat Keels Explained

fairing a sailboat keel

On this page:

Overview of sailboat keel types, keel types: fundamentals, modified full keel, centerboard, daggerboard keel, canting keel, how to pick the perfect keel.

If you just want a quick overview, here's a list with the most common keel types and a short description. More detail will follow below.

The most common keel types

  • Full keels run from front to aft and are the most stable keel type, making them the most popular cruising keel.
  • Fin keels offer the best performance but are less comfortable. This makes them popular for racing. Fin keels are bolted on to the hull and generally run deep and thin.
  • Bulb and wing keels are both variants on the fin keel.
  • Bulb keels carry additional ballast in the tip, making them more stable.
  • Wing keels have two tips at the end of the keel, which reduces crossflow, improving directional stability.
  • Bilge keels are double fin or double full kees, which allows the boat to be beached, making them the most popular keel for tidal waters.
  • Lifting keels are moveable keels that can be lowered and raised, allowing the boat to enter shallow waters as well.
  • Centerboard keels are a pivoting lifting keel, allowing to sail both coastal and inland waters.
  • Leeboards are fins on the sides of flat-bottomed hulls boats, making a keel unnecessary.

Properties of each keel type

fairing a sailboat keel

What does a keel do?

What does the keel do? A keel is a vertical blade running down from the hull. It is weighted and acts as a ballast, countering the boat's tendency to heel and preventing it from tipping over. The wetted surface under the waterline reduces slippage to leeward by creating a track, which counters the sideway force of the wind on the sails.

fairing a sailboat keel

The reason sailboats don't tip over is that the weight of the keel counters the buoyancy of the hull, which means it will pull the boat downward. This downward force reduces heel and prevents the boat from rolling.

A canoe doesn't have a keel. Try stepping into that: it will want to roll.

It counters the horizontal force the wind puts on the sails. Whenever the force on the sails increases, the resistance of the water on the keel increases proportionally.

The heavier the keel, the less heel you'll get.

A keel reduces slippage to leeward. Slippage is simply the amount you fall off course because of the direction of the wind and current. Leeward is the side of the boat behind the wind.

So if you don't have a keel, you will fall off course quite a lot because the wind will push you over the water surface.

You will also heel quite a lot since there is nothing beneath the water surface to counter the force of the wind high up in your sails.

A keel fixes both of these issues and makes sailboats one of the most reliable boats in heavy winds and storms.

You can read on about how keels work here.

Keels can be classified by multiple dimensions. You can look at them from the side or the front. You can also classify them based on properties.

Before I dive into each keel type in-depth and show examples, let's make sure we have the same starting point.

There are essentially two sorts of keels:

Fixed keels

Movable keels.

fairing a sailboat keel

Fixed keels are keels that are integrated into the hull or bolted on. They can't be moved or lifted.

When looking at fixed keels, you can divide them up further based on the side view. There are three main categories:

Bilge keels

Full keels are more comfortable, provide better stability and protection, but are also slower than fin keels.

Fin keels are less comfortable, provide less stability, are more vulnerable, but they're also a lot faster than full keels.

Bilge keels are double keels: one on each side of the hull. This allows them to be beached, which comes in handy in tidal waters. They are generally a lot slower and less maneuverable compared to fin keels.

Movable keels can be lifted from the water, creating a shoal (shallow) draft, allowing the boat to enter both shallow waters and coastal waters. This makes it a very versatile keel type. There are two main designs:

Lifting keels

Lifting keels can be lowered and raised through a slit in the hull. Examples of lifting keels are the daggerboard and centerboard.

Leeboards are wooden swords attached to the side of the hull and prevent slippage to leeward, but they don't stabilize the boat, nor counter heel by adding ballast.

fairing a sailboat keel

With fin keels, there are different tip designs available. The most common two tip designs are:

These are both variants of the fin keel. Generally, these keel designs are mentioned in one breath with full keels and fin keels, creating confusion on what kind of keel they are. But it's important to understand that they are a sub-category of fin keels.

fairing a sailboat keel

Rudder design

As with the tip of the fin, there are different rudder designs that may apply to both fin and full keels. The two most common rudder designs are:

Skeg rudder

Spade rudder.

A skeg is a structural part of the keel in front of the rudder that protects the rudder. The keel encompasses the rudder, preventing any rogue ropes, weeds, or rocks from damaging the rudder.

fairing a sailboat keel

A spade rudder is an unprotected rudder: it doesn't have any structural protection from the keel design. It is simply attached to the hull. This design is very common.

Alright, we understand the big picture. Let's dive into more detail for each keel type and discuss the pros and cons.

Fixed keel Good for cruising and liveaboards Comfortable

fairing a sailboat keel

What is a full keel? A full keel runs from front to aft for at least 50% of the hull and is fully integrated into the hull. It has the largest wetted surface of any keel type, and it is also the heaviest. This results in directional stability and reduced heeling, providing the most comfortable ride, but also the slowest.

The wetted surface simply means the amount of water contact area. With such a large wetted surface, it decreases slippage to leeward the most of all keel types, while it counters heeling the most as well.

The full keel is the most comfortable and stable keel type available. However, comfort comes at a price. It delivers the worst performance due to this large wetted area. It is the slowest of the keel types, and it has the worst windward performance.

This makes full keels particularly great for longtime cruisers or liveaboards who prefer comfort over speed, but less ideal for daysailers who need to navigate in and out of slips regularly.

Since it runs for at least 50% of the hull, it doesn't need to run as deep as a fin keel, resulting in a more shoal draft.

Heavier keels result in increased displacement, so a full keel boat will need a larger sail area to compensate for its weight.

For a more detailed discussion on full keel advantages, I recommend reading William's excellent article 5 Surprising Advantages of a Full Keel Sailboat here.

Example sailboats with a full keel:

  • Nicholson 22
  • Island Packet 380
  • Beneteau Oceanis 411 Clipper
  • Beneteau First 50
  • Jeanneau Sun Shine 38
  • Dufour 455 Grand Large

There are a lot of great cruising boats with full keel designs , some of them considered classics.

Full Keel with skeg rudder

Full keels with a skeg rudder design have a protected rudder, thanks to putting a structural part of the keel directly in front of the rudder. This helps with fending off any hazards to the rudder, like floating pieces of rope, rocks, or garbage, and protects it in case of running aground. The skeg design ensures the rudder is nearly impossible to break off.

Fixed keel Good for cruising and liveaboards Faster than a regular full keel

fairing a sailboat keel

What is a modified full keel? A modified full keel is a full keel with a cutout at the front, reducing the wetted surface slightly, which increases performance without sacrificing too much comfort and stability. After the full keel, it has the best directional stability and the least amount of heel.

The modified full keel is popular among (bluewater) cruisers, thanks to its increased handling and performance. Most modified full keels have a skeg rudder, ensuring it is well-protected.

The slightly reduced weight and wetted surface improve windward performance quite a lot, but it is still one of the most stable keel designs out there.

Example sailboats with a modified full keel:

  • Hallberg-Rassy HR 40
  • Dufour Arpege 30
  • Beneteau Oceanis Clipper 281
  • Jeanneau Sun Odyssey 37.2
Fixed keel Good for racing Fast

fairing a sailboat keel

What is a fin keel? A fin keel is a long, weighted blade attached to the bottom of the hull. It is lighter, faster, and more maneuverable than a full keel, but also more vulnerable. The increased distance between ballast and sails provides a lever, reducing the need for a large wetted surface or additional ballast.

Fin keels are generally bolted onto the hull and run deeper and thinner than a full keel. They are also lighter. This helps increasing performance (a lot), making fin keels a lot faster in all situations.

There are some major disadvantages to fin keels, however. Fin keels are a lot less comfortable than full keels and allow for more heel and a less solid track, so less directional stability. Fin keels are also a lot more vulnerable than full keels. They can break off when running aground, or get damaged.

They are very popular among racers and perform better when maneuvering in tight spots, like getting in and out of slips.

Example sailboats with a fin keel:

  • Catalina 30
  • Jeanneau Sun Odyssey 36.2

Fin keel with skeg rudder

Fin keels with a skeg rudder use a small structural part in front of the rudder to protect it. This design is mostly integrated into the hull, making it less vulnerable, and a great compromise between speed and safety.

Fin keel with spade rudder

Fin keels with a spade rudder have a completely exposed rudder, and typically a fin that is simply bolted on. The keel isn't integrated into the hull, making it more vulnerable and less comfortable.

fairing a sailboat keel

Fin keel variant Good for cruising Less crossflow

fairing a sailboat keel

What is a wing keel? A wing keel is a fin keel with a horizontal foil at the tip, which is wing-shaped and generally weighted. Its shape reduces crossflow, improving directional stability, and its ballast decreases heel, resulting in a more comfortable ride. The addition of a wingtip allows for a shorter fin, reducing draft.

Wing keels are good for cruising since this design improves directional stability compared to a regular fin keel or a bulb keel.

We'll discuss the wing keel's advantages and disadvantages in more detail in this article.

Fin keel variant Good for cruising Stability

fairing a sailboat keel

What is a bulb keel? A bulb keel is a high-aspect-ratio fin keel with additional ballast at the end, which generally has a bulb or teardrop shape. This ballast improves stability and utilizes the distance between force and counterforce as a lever. This design reduces the need for a deep fin, resulting in a shoal draft.

By placing the weight at the largest possible distance from the force on the sails, you need relatively little extra weight for the same reduction in heel, making bulb keels very effective for cruising.

This design reduces the wetted area while increasing the weight of the keel just slightly, which increases sailing comfort big time.

Example sailboats with a bulb keel:

  • Bavaria B/One
  • Beneteau First 24
Fixed keel Good for racing Can be beached

fairing a sailboat keel

What is a bilge keel? A bilge keel is a twin keel which uses double fins, allowing the boat to be beached and rest on its keel upright. Bilge keels have double the wetted surface, which increases comfort and directional stability while decreasing heel. Modern bilge keels often provide decent windward performance, thanks to better design.

The bilge keel does sacrifice speed compared to the fin keel but doesn't necessarily offer worse performance overall. Older designs performed considerably worse than other keels and were especially slow.

fairing a sailboat keel

Bilge keels have some major advantages over full keels and fin keels. The most important is that the boat can be beached, making it a popular design in tidal waters. Bilge keels are especially common along the British coastline, where fishermen keep their boats in tidal harbors.

Another major advantage is that the boat can be stored resting on its keels, making dry storage and maintenance a lot easier.

Of course, there are many more pros and cons to the bilge keel , which we go into here.

Example sailboats with a bilge keel:

  • Dufour Dynamique 62
  • Hunter Duette
  • Patagonia Patago 39
  • Macwester 27
Lifting keel Good for daysailers Versatile

fairing a sailboat keel

What is a centerboard? A centerboard is a type of retractable keel that rests on a hinge and can be lowered through a slot in the hull. It folds out like a pocket knife and allows you to increase or reduce the draft of the boat. Centerboards are mostly used on small fishing boats.

The centerboard is a very versatile keel type, allowing you to have both a very shoal draft for inland waters, as well as steadying the boat and reducing heel for larger bodies of water, or even oceans.

I've sailed a Cornish Crabber with a centerboard for a week, and while we stayed inland, having the option to increase the keel depth really came in handy when crossing the IJsselmeer (a former sea in The Netherlands).

There's more to the centerboard design than we can go into here. I recommend you read my article on swing keels for an in-depth explanation of the mechanics and pros and cons of the centerboard keel design .

Example sailboats with a centerboard:

  • Cornish Crabber
  • Jongert 45C

There are many more models using this design - we've discussed 13 of the most popular sailboats with centerboards here.

fairing a sailboat keel

What is a daggerboard keel? A daggerboard is a type of lifting keel, which can be lowered through a slot in the hull. It lowers straight down and allows you to increase or reduce the draft of a boat. Lowering the daggerboard will decrease heel and increase directional stability. This design is mostly used on small daysailers.

Because of its simplistic design, daggerboards are not commonly used on larger boats. You will find them mostly on small daysailers and lesson boats. Generally, the daggerboard is a wooden board that is carried in the hull - it isn't attached to the hull.

Pivoting keel Good for river sailing Shoal draft

fairing a sailboat keel

What are leeboards? Leeboards are a form of pivoting keel, mounted to the side of the hull, used to reduce slippage to leeward, hence the name. Since leeboards are unweighted and don't run below the waterline, they don't decrease heel substantially. Leeboards are primarily used for inland or tidal waters.

The advantage of having leeboards instead of a keel is the incredibly shoal draft. Boats with leeboards don't need a keel, so they can be flat-bottomed, which is a very stable hull design, as long as the water remains calm.

In troubled waters, you will notice the lack of a keel, which is why they are used on trading ships for inland waters.

Another large advantage of leeboards over a keel is the ability to beach the boat. In The Netherlands, leeboards are widely used on barges that sail the Waddenzee. The Waddenzee has very large tidal movement, and whenever the tide retreats, these boats just lie flat on their belly.

Example sailboats with leeboards:

  • Dutch barges

Moveable keel Good for racing Increased performance

What is a canting keel? A canting keel rests on a hydraulic canting hinge under the boat, which can be moved to windward, using the keel's position as a lever in countering the forces on the sails. This improves performance substantially by reducing the wetted surface and overall weight of the keel while increasing maneuverability.

Canting keels are mostly used in high-performance sailing and are not yet used on cruising sailboats, mainly because of the need for underwater hydraulics in this keel design. It is a vulnerable keel type, with additional moving parts that are difficult to repair when they break.

The canting keel is an interesting design, and the promise of increased performance and maneuverability is seductive. However, I think most cruisers will continue to prefer fixed keel designs since they are more reliable.

In sailing, safety comes over performance. The slight increase in speed is not worth the potential downside of having to fix underwater parts while cruising.

Example sailboats with a canting keel:

  • Beneteau First 211
  • Dehler Sprinta 70
  • Northshore Yachts Southerly 105
  • Laurent Giles Keyhaven Yawl

In deciding on the perfect keel for you, there are three main factors that determine which keel is best for you. These are the three I've mentioned above: speed, maneuverability, and comfort.

Each type of sailing requires different characteristics. Liveaboards will prefer stability and comfort above all. Cruisers will prioritize comfort and a bit of speed. Daysailors need a shoal draft and good maneuverability.

So what keel is best for you all comes down to what kind of sailor you want to be .

For each situation, the following keel types are generally a safe bet:

  • For cruising , you want a modified full keel or a fin keel with a skeg rudder.
  • Coastal liveaboards probably want a full keel, while inland liveaboards might prefer a flat-bottomed hull with leeboards.
  • Coastal daysailors will generally prefer a fin keel with a skeg rudder or a centerboard.
  • For racing , you want a fin keel or wing keel.

What type of keel is the best?

The most stable and reliable keel is the full keel. It is the heaviest and longest keel available, and also the least vulnerable. Full keels are fully integrated into the hull, reducing the risk of damage in case of running aground. Its weight ensures maximum heel reduction.

While it depends on how you will actually use the boat, full keels are generally considered the best keels for most people. However, they are slow. If you're going for performance, I definitely suggest looking at a fin keel.

What's the best keel for offshore sailing?

The best keel for offshore sailing will be a full keel or modified full keel. Full keels decrease heel the most and provide the best directional stability of any keel type. These two characteristics are important in sea weather conditions, where wind force and wave height can get especially alarming.

But there are many more considerations when picking a bluewater cruiser. Keel design is one of the most important factors, and we discuss it at length in our article on the best keel design for bluewater sailing .

Further reading:

If you want to read on, I recommend this outstanding article by Yachting Monthly (new tab): How keel type affects performance .

Pinterest image for Sailboat Keel Types: Illustrated Guide (Bilge, Fin, Full)

Olaf Roethele

https://www.theyachtmarket.com/en/new-boats/cornish-crabbers/adventure-17/218/

My name is Olaf and I am the owner of a Cornish Crabber 17 Adventure boat.

I would like to ask you if you can imagine to install on this boat a Torqeedo 2.0 Pod motor? Therefore i guess a modification of the keel/skeg is necessary ?!

Best regards from Uruguay,

You completely missed the hybrid planing/water-ballast keel of the Macgregor range

Thanks a lot for this explanation

Roger Bannon

Very well written article which provides an excellent guide for us small wooden boat builders. Thanks.

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IMAGES

  1. Fairing Compound and Wood Keel Fairing, S2-E28

    fairing a sailboat keel

  2. Haven Boatbuilding -Keel, Fairing Frames

    fairing a sailboat keel

  3. Fairing the Keel(s)

    fairing a sailboat keel

  4. Sail Life

    fairing a sailboat keel

  5. Fairing the HULL of our SALVAGED wooden sailboat

    fairing a sailboat keel

  6. Yacht Hull and Foil Fairing

    fairing a sailboat keel

VIDEO

  1. Picking up a SAILBOAT KEEL and DROPPING IT 🤯🤯 #sailboat #boat #salvageyard #subscribe

  2. Part 4: The Making of 90footer Fiberglass Passenger Boat and the Sea Trial

  3. #sailboat #keel

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COMMENTS

  1. Fairing the Keel(s)

    The plan to extend the keels trailing edge was simple: Make cores from half-inch, pre-laminated structural fiberglass (fiber-reinforced plastic, or FRP) and grind the trailing edges down to a quarter-inch edge to follow the gradual tapering of the existing keel. This required about 5 inches of taper.

  2. Sailboat Refit #18: fiberglassing and fairing the keel to hull joint

    - YouTube 0:00 / 14:52 Sailboat Refit #18: fiberglassing and fairing the keel to hull joint. before bottom paint. Findit Fixit Sailit 1.34K subscribers Subscribe Subscribed 892 Share 16K...

  3. Refinish Your Swing Keel for Best Performance

    I will describe common keel defects, the fairing system I used, sealing a freshly sandblasted keel, applying body filler to build up an accurate hydrodynamic foil shape, and paying extra attention to the shape of the leading edge of the keel. Before I get started, a bit of legal housekeeping. This post contains affiliate links.

  4. filling and fairing cast iron keels

    MikeCC. I stripped my keel before going back in this year. Tercoo for first strip for old filler and loose rust, then polycarbide disks on grinder. Cleaned back with thinners then zinc based 2-pack epoxy primer, fairing filler/sanding, another zinc primer, 2 coats of epoxy primer for antifoul, 2 coats of hard antifoul.

  5. Iron Keel prepping and fairing and painting

    I have an '84 Hunter 31 with an external iron keel. I cleaned the entire keel in several hours with a wire wheel in a die grinder, then primed with barrier coat, faired, three more coats of barrier coat and three coats of bottom paint. Six years later, still looks great. I don't remember what products I used, but they're sold by WM.

  6. keel fairing

    #1 Joined: Jan 2003 Posts: 1,438 Likes: 59, Points: 0, Legacy Rep: 841 Location: Southern England Tim B Senior Member I'll assume you have a single keel, not two assymetric keels. A single Assymetrical keel will cause you to go faster on one tack than the other.

  7. Keel Fairing

    1 2 sailingdog 43281 posts · Joined 2006 #2 · Mar 18, 2008 (Edited) You can use thickened epoxy. Don't use the colloidial silica or microballon filler. I'd recommend using the chopped fiberglass filler.

  8. 3 Steps to Fairing a Hull, Building a Fairing Tool, S2-E27

    0:00 / 16:40 3 Steps to Fairing a Hull, Building a Fairing Tool, S2-E27 The Art of Boat Building 68.2K subscribers Subscribe Subscribed 1.6K Share 63K views 3 years ago #theartofboatbuilding...

  9. Keels: Minor Maintenance and Repair

    288 Because of the problems involved in complete refinishing of an iron keel, patch painting of rusted spots is often the only practical way to go. Begin by cleaning the rusted spots as thoroughly as possible. Take your time here as this is the most important step.

  10. Used Boat Buying: Keel Repair and Hull Fairing

    1. Tarps Down The first step was to put down some tarps to catch the dust and debris (a boatyard rule, and a good one). 2. Chip & Grind After knocking off any loose filler, I used a 4 ½" grinder with a 50 grit disk to rough up the bare metal and feather the edges of the remaining filler. My grinder is a Milwaukee 6148.

  11. keel fairing

    If you have a bolt on lead keel, the most likely answers are: up high near the keel stub, and water intrusion into the filler that was used to fair the keel. If this is correct, I can help you out. The first step is to remove the old fairing compound. Many boat manufacturers used automotive body filler, which is why you have a problem now.

  12. Fairing

    Fairing is more than just fixing dings and dents for cosmetic reasons. It entails everything from filling surface scratches in gelcoat, seamlessly repairing osmosis blisters on a hull, reshaping the leading edge of a keel, making a hull repair disappear, or smoothing the hull to get the fastest underwater profile.

  13. Your Guide to Keel Maintenance

    As in the case of the lead keel the water will tend to loosen the fairing on the keel. The exposure to water will lead to a cycle of fairing failing, exposing more of the iron to water and more corrosion, making the problem worse. ... For safety reasons, the act of removing the keel bolts makes the boat unable to balance the keel in the ...

  14. keel fairing?

    keel fairing? Discussion in ' Boat Design ' started by kapnD, Nov 8, 2013 . Joined: Jan 2003 Posts: 1,277 Likes: 395, Points: 83, Legacy Rep: 40 Location: hawaii, usa kapnD Senior Member I have my 50' Willard (displacement hull) hauled out, and am looking at the deadwood at the end of the keel.

  15. Yacht Hull and Foil Fairing

    Yacht Hull and Foil Fairing — Specialists in yacht keel, foils and hull fairing. Get your boat and foils performing at their best with a high standard race finish.

  16. 5 tips: faster foils. Keel and rudder

    1. Section symmetry Checking that sections are perfectly symmetrical is second nature to those running grand-prix boats and high end racing one-designs such as TP52s and King 40s. But many...

  17. Fairing out the trailing edge of the keel.

    Working on a 1981 Lippincott 30, and and just completing a fairing out the hull after a restoration due to pox, many mini blisters. Anyway, my question is on the trailing edge of the keel, should it be squared off or faired smooth to an edge as I did on the lead egde of the keel. Does...

  18. Sailboat Keel Types: Illustrated Guide (Bilge, Fin, Full)

    The most common sailboat keel types are full-length keels, fin keels, bulb keels, wing keels, bilge keels, and lifting keels. Full keels are popular among cruisers, while fin keels are generally used for racing. Bilge keels and lifting keels are typically used in tidal waters, on small fishing boats for example.