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Boat test from the Multihulls World #81 (april/may 2005)

My chief editor said "whatever happens I want some wind for this test!". So I made a date for a march day when the wind and the snow were expected...and perhaps dreaded...

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Going boomless? Magnum 21 Trimaran

Discussion in ' Multihulls ' started by nacrajon , Jan 27, 2014 .

nacrajon Junior Member

Having just got a new boat (Virus Magnum 21) the boom is a pain and right at eye level when on the tramp. How easy is it to convert the main to boomless? The mainsheet attaches about a foot forward of the clew. I'm uncertain if a good shape could be set. Ideally I would like to be able to buy a boomlet from NACRA and get a sailmaker to attach it. Is going boomless that simple? Obviously I would have to work out a reefing system, but that has been done before.  

Richard Woods Woods Designs

So instead of the boom hitting you in the face you'll now have a free flying mainsheet block that can hit you, but is probably less obvious to keep an eye on (literally). The boomless rig doesn't work well unless you are going to windward or never ease the mainsheet past the traveller There are reasons why my Strike 18 trimaran has a windscreen and a high boom. Keeps the cockpit and crew nice and dry as well as safe Richard Woods of Woods Designs www.sailingcatamarans.com  

Moggy Senior Member

A wishbone boom may be an option.  

I don't see why boomless is not an option on a family boat. I raced boom less NACRAs in the past and they were competitive against similar cats. I have an asymmetric kite with the wind so the main would be tight anyway to support the mast. So back to sail shape, is it as easy as riveting on a boomlet?  

TeddyDiver Gollywobbler

Just IMHO but comparing to big genoas there's no reason not to have similar sheet arrangement for boomless main aswell...  

The Clissold TC10 is boomless with a radial traveler. http://www.tcdesign.co.nz/TC_Design/Sailing_Designs/Pages/TC_10.html It works for him.  

warwick Senior Member

The Ian farrier F 22 is also boomless in the production version http://www.f-boat.com/pages/News4/FM-Factory2014.html  

I have sailed boomless beach cats. I've also sailed most of the newer Farrier designs, but not the F22. They are performance boats, as is the Weta, so pretty much always sail with the apparent wind forward of the beam. I've also sailed a Virus Magnum (there is one by my office). It isn't a performance boat. Furthermore, unlike a beach cat it has a very short mainsheet track Another problem with boomless rigs is that you tend to have to have the mainsheet track aft of the clew, otherwise you cannot flatten the sail. I suspect the clew on the Magnum is aft of the track (sorry I cannot remember it was a long time ago that I sailed one) Richard Woods  

teamvmg Senior Member

On a boomless mainsail, the main sheet has to angle forward so that aswell as pulling the leech down, it also pulls along the foot to flatten the sail. [It sounds like yours is angling the opposite way] They are tricky sails to get right, even when specifically designed for the boat. You would also need to upgrade your mainsheet as it will be working harder.  

upchurchmr Senior Member

Interesting to call the F-22 boomless. That is a really big bottom "batten" Perhaps there needs to be a new term - they could probably turn it into a salesmanship gimmick. I didn't read the whole thing to understand the "variable stiffeness" batten. The boat and web site is really impressive, wish I would win the lottery. It was somewhat amusing to see the wide cabin at the gunwale which did not appear usable due to the narrow settee opening. Possibly just an impression since I have never sailed any of the Farrier boats.  

ianfarrier Junior Member

The bottom batten is just that, a batten, but with more torsional stiffness so that it can roll the mainsail. http://www.f-boat.com/Media4/F-22Photos7/ReefedandFurled.jpg But it still bends enough to allow the best possible shape to the reefed sail. Still very light, and easy on one's head if you get in the way. It is also of variable stiffness so that it can be stiffened up downwind, but so far it does not look like this will be necessary. The wide cabin at the gunwale is very usable, for storage behind setbacks, or for the old style wing berths, but which I never found very practical, and have preferred to use settee berths since the F-27 in 1984. The wide cabin also avoids that claustrophobic feel of a narrow cabin. I had tried such a cabin on the original prototype, with side decks: http://www.f-boat.com/Media4/News6/TT18prototype.jpg The idea of having a flat side deck around the cabin appealed at the time, but it was a big mistake and never did it again. Ian Farrier Farrier Marine.  

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Thanks for all the replies, it seems boom less is not as easy as I was hoping it may be. A F22 was on the top of the list, however I couldn't make the stretch financially and I thought the Magnum met my needs better than a Hunter Tramp.  

A Cat on fire!(going very fast) / M2 on foils

What is going with Hydrofoiler SCAT (experimental boat) ?

Is there going a local 30 ft. trimaran circuit in sweden .

Bazooka Trimaran going back into production

Ormas going to Hobart

Seawind Catamarans going into voluntary administration

Boomless double masted catamaran....

Re-cutting beach cat sail to go boomless

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Design Reviews & Comparisons

With the amount of work required to undertake articles comparing various existing boats, it has been decided to deal with this challenging subject through a number of separate reports that will be available at the lowest possible cost. The first of these has now been on sale for several years (at just $7), and presents some personal thoughts and assessment by the writer (plus numerous photos) about the following designs:

In addition to the above, this Report#1 also includes two spreadsheets, giving a wealth of technical data for each design, as well as the results of formulae for comparisons dealing with cost, build time and performance. This data is not only given for the 12 small tris noted above, but for a total of 20 small tris that include the following:

Magnum 21; Magnum 21S; Kolibri 23; Cardiff 21, A21 and Z65; Warren 23 Mk2; Scarab 670; Scarab 22; Corsair Sprint; Discovery 20; Leneman L7; Day Tri20; Spitfire 20; KH-23; KH-24; Trinado; Tremolino Mk4; Farrier K24T and F22.

After completion, the report was sent out to five internationally-noted designers, and their appreciated comments on this work are noted at the base of the text on this page Small Trimarans Review

So if this interests you as I think it will, please go to the Sales Page to place your order. It's quick and it's safe. The report will then be delivered to you as a PDF file for printing out at home in full color. We recommend to select the 'Print Both Sides' print option that comes with most printers today and then get the 22 pages plus a cover, wire bound for future use and reference.

Footnote: As stated in the Report, the reviewing comments and comparison data are naturally only that of the writer, but they do come from 60+ years of experience with small boats, the personal ownership of 4 small trimarans over the last 30 years, as well as qualifications as a professional engineer and naval architect from one of the most reputable universities in the world in this field.

On receipt, please let us know if you've enjoyed this report and have any suggestions for another. Many have in fact written in already with most favorable comments. Thank you.

"New articles, comments and references will be added periodically as new questions are answered and other info comes in relative to this subject, so you're invited to revisit and participate." —webmaster.

Yachting Monthly

• Digital edition

Astus 20.5: Fast, fun and affordable trailable trimaran

• David Harding
• August 20, 2021

For fast yet undemanding sailing, easy trailing and simple camper-cruising, the Astus 20.5 trimaran is likely to find wide appeal says David Harding

The Astus 20.5 is taut and responsive to sail. Credit: David Harding

Product Overview

• Fast and easy to sail
• Can be trailed behind a small car
• Easy to reduce beam for marina berthing
• Less accommodation than a monohull of similar size
• Rigging process could be simplified
• Slightly stark interior finish

Manufacturer:

Price as reviewed:.

Boats that are small and light enough to keep in your driveway and trail to where you want to sail make a lot of sense.

One drawback, however, is that they tend to be slower than bigger boats – especially if they’re of a size and weight that allows them to be easily managed short-hand, both afloat and ashore.

If you want to sail from Poole to Weymouth for the weekend in a 20ft trailer-sailer, for example, it might take a while.

This is where speedy trailable trimarans like the Astus 20.5 come in.

When I sailed its predecessor, the 20.2, about 10 years ago, we regularly hit 15 knots on a reach without breaking sweat and maintained an easy 6.5 knots upwind.

This 20 footer can match 50 footers for speed. Credit: David Harding

You can cover a lot of ground at those sorts of speeds.

I first met the Astus 20.5 at the Düsseldorf Boat Show in 2019. Since it’s a newer boat and designed by no less a design team than VPLP, I had high hopes that it would offer even more than the 20.2.

Quite apart from the sailing potential, the trailing is as simple as can be with a boat like this.

If you choose the resin-infused hull, the Astus 20.5 weighs under 500kg (1,100lb), or just over 500kg with the standard solid laminate.

The lighter weight means you can use an unbraked trailer , saving money, maintenance and yet more weight, so you can trail it behind a normal hatchback vehicle.

Getting somewhere fast under sail is one thing. Having somewhere to sleep when you arrive is another.

The Astus 20.5 is simple to sail for two people. Credit: David Harding

Though its cabin is smaller than on a monohull of similar size, the Astus provides seating, stowage and space for a companionable couple to be able to stretch out.

Then of course you have the trampolines each side on which you can rig a tent for more sleeping space.

The opportunity for a sail on the Astus 20.5 finally came when Hein Kuiper of Boats On Wheels brought his first demonstrator to the UK.

In fact we went out twice – first for a photo session in Poole on a brisk winter’s day and then a few months later in Chichester Harbour.

Since the boat arrived in Poole on its trailer, I was able to see how it went together.

Pulling out the hulls is pretty straightforward: their aluminium beams slide in and out of the fixed beams on the main hull. You can do that ashore or afloat.

There’s nothing complicated about raising the rig, either, and it can all be done singlehanded .

The whole process, from arriving with the trailer to sliding the boat into the water, took Hein a couple of hours or so the first time or two (comparable with a monohull of similar size, he reckons) but would undoubtedly get quicker with practice.

Continues below…

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Dragonfly 28 Sport

Whether you choose the standard or the Sport version, the mast is the same height.

The difference is that the latter comes with a square-top mainsail to give appreciably more sail area.

If you want to save as much weight as possible and make raising and lowering the mast easier, you can have it in carbon. A wing mast is another option.

The rig and hardware don’t appear to be modified in any way as a concession to the boat’s trailer-sailer nature.

Here and there, the odd ready-made loop or strop would save fiddling around with bits of line.

It is basic down below but there’s seating and sleeping space for two people. Credit: David Harding

All that is forgotten as soon as you’re under way.

On our second outing, once the electric outboard had pushed us out of Northney Marina – where the boat proved to be surprisingly manoeuvrable with the centreplate fully down – we headed off on a beam reach at 12.5 knots in 12-15 knots of wind.

In most boats, 12.5 knots would be going some. In this 20-footer, it felt perfectly relaxed.

Over the course of the following couple of hours we covered every point of sail including, of course, reaching under spinnaker.

With the gusts rarely exceeding 16 knots in the flat water of the harbour, we didn’t quite manage to break 15 knots.

It wasn’t a bad speed-to-effort ratio nonetheless.

The boat felt rock solid the whole time, and I knew from the photo session in Poole that she could carry the kite on a beam reach in appreciably more wind than we had in Chichester.

It is easy to reduce the beam of the Astus 20.5 for marina berthing. Credit: David Harding

It’s hard to imagine that 20 knots wouldn’t be perfectly achievable.

Upwind we maintained between 7 and 8.5 knots most of the time.

As you would expect, you need to keep the bow down a little to maintain full power.

You also need the purchase of the 6:1 mainsheet to maintain sufficient tension in the upper leech. It makes a big difference.

You won’t need more than two people to go out and have fun on the Astus 20.5. Credit: David Harding

Tacking was pretty positive provided we had adequate boatspeed going into the tack, and leeway appeared minimal.

All told the Astus 20.5 was great fun to sail and easy to manage two-handed.

There was little for a third person to do except enjoy the ride or contribute to the righting moment by joining the helmsman on the windward trampoline.

If you were racing, you could use a longer tiller extension and fit toe-straps to maximise the advantage.

Beating our way back up the harbour, we demonstrated the windward ability of the Astus 20.5 by sailing straight past a 15m (49ft) monohull.

Creature comforts aboard the Astus 20.5

David Harding has been testing boats for decades and is also a sailing photographer

Above decks the Astus offers a vast amount of sitting and lounging space thanks to the trampolines.

Down below, the hull’s narrow beam makes things cosy but you still find a seat either side, space for a chemical toilet under the aft end of the berth and a fair amount of stowage beneath and to either side of the companionway.

The centreboard is offset to port to leave the middle of the boat clear.

The finish is simple and uncomplicated, largely to save weight. There would be plenty of scope to fit a slide-out galley and devise lightweight stowage solutions to make better use of the space.

Astus 20.5: the test verdict 

More than anything else, this boat is tremendous fun.

She feels taut and responsive to sail. I found that it took an hour or so to begin to find her sweet spots, but after that she just makes you want to sail her.

She inspires confidence and is easy to handle, too. In most conditions you could manage perfectly well single-handed and for cruising you won’t need more than two.

The Astus 20.5 has less accommodation than a monohull of similar size

Then there’s the speed. No matter whether or not you’re in a hurry to get anywhere, it’s easier to slow down in a fast boat than to speed up in a slow one.

Speed is fun in itself, and it’s hard not to enjoy sailing straight past a monohull more than twice your length.

Niggles are relatively few.

I thought the rudder blade could do with a touch more balance and I wasn’t sure that the fixed end of the 2:1 jib sheet was quite far enough aft on deck.

Other than that, it all works.

Hardware is mostly from Harken and the spars are by Sélden, so there’s no skimping in these departments.

Would she suit you and your crew?

The Astus 20.5 will attract attention. Several people stopped for a chat and to admire her back in Northney having seen her on the water.

If you’re a dinghy sailor moving up but not ready to slow down, this is a good choice.

Just as much interest is coming from big-boat sailors moving down or wanting a second, smaller boat that still has a good cruising range. Few boats of this size go so fast with so little effort.

The Astus 20.5 is ideal for exploring harbours, estuaries and rivers

As for the inevitable monohull-versus-multihull debate, there are trailable, family-friendly boats of this size with one hull that sail very nicely.

I have clocked over 12 knots in one or two, but only under spinnaker, with good sailors on board and not for sustained periods.

As long as you’re prepared to accept that sailing regularly at double-figure speeds means sacrificing some interior volume, the Astus could suit you perfectly. And for exploring harbours and estuaries, camper-cruising and nudging into the beach, it’s absolutely ideal.

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Discovery 20 Trimaran

See  Discovery 21 .

The Discovery 20 trimaran is a fast, fun daysailer with the potential to be a camper/cruiser for the adventurous. The D 20 design has been updated as an exciting and powerful new daysailer. It is available as a kit or a complete boat. This design is intended for enjoyable day sailing, although there is space below deck for camping gear. There is a 7' by 7' cockpit that is roomy for 4. You sit upright, with a backrest, not sprawled on a trampoline. My 75 year old mother-in-law found the boat very comfortable. The D-20 is quite fast; the all up weight of the boat is 527 pounds. She utilizes a daggerboard, a rotating aluminum mast and streamlined crossbeams. Construction is wood/epoxy/glass composite.

I really never appreciated how fast the Discovey is until about 10 years after she was designed when I raced mine in a Wednesday night yacht club series against a new Newick 24' trimaran (longer, wider, taller rig, new laminate sails). The other boat was sailed by a very experienced sailor and I was expecting to get my butt kicked. During the first upwind leg (in about 8 knots breeze) the Discovery 20 blew everything away, including a fleet of Etchells. I was so impressed I hove to at the weather mark and waited for the other tri to catch up so that I could get a better comparison on the down wind leg (he had a spinnaker I didn't). As expected, I lost some ground here but not really that much, and I was able to get it all back on the next upwind leg.

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