boom vang for small sailboat

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A boom vang or kicking strap on a sailboat used to exert downward force on the boom and thus control the shape of the sail. Boom vangs helps control boom height which determines twist, or the shape of the mainsail leech during different wind conditions.

Sailboat Block & Tackle sets come with both of the blocks and a cleat to create a full boom vang system in one product. Simply select the purchase that you need and the working load based on your boat size.

If you are expecting a lot of light wind sailing and want to add some extra shape to your leech, add a rigid boom vang to hold up your boom so you don't have to. Instead of having to install and remove a topping lift, just keep a Sailboat Rigid Boom Vangs on your boom to keep it up even while you are gone.

Hydraulic Boom Vangs are used on larger sailboats and controlled by manual or electric hydraulic pumps.

Find Boom Vangs at MAURIPRO Sailing. We are your go-to online store for all sailboat equipment!

MAURIPRO Sailing, your direct access to Boom Vangs and all your other sailing and boating needs.

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The $tingy Sailor

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

Control Your Mainsail Shape Better With a Boom Vang

A boom vang is a useful control for your mainsail, especially if the mainsail is older and acting its age. That is, if it’s getting baggy and is difficult to flatten, particularly when you’re pointed off the wind. For better performance and safety, you need to be able to pull excess twist out of the mainsail and flatten the leech. The best way to do that is with a boom vang. It has the added benefit of preventing the end of the boom from raising so high during gybes that it can snag the backstay, a potentially dangerous situation if the wind is strong enough.

Before I continue, a bit of legal housekeeping. This post contains affiliate links. That means I receive a small commission if you make a purchase using those links. Those commissions help to pay the costs associated with running this site so that it stays free for everyone to enjoy. 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 .

How a boom vang improves mainsail shape

A boom vang is a tackle system attached at a 45° angle between the mast and the boom. Its purpose is to pull the aft end of the boom down when the mainsail is fuller and more twisted than desired. It can be used on any point of sail but is most useful on a reach. For this reason, the lower end of the vang is typically attached near the mast tabernacle so that the vang can rotate with the boom and keep equal tension on any point of sail.

Tightening the vang flattens the mainsail and provides more balance so that the headsail can be trimmed to make more forward power. Easing the vang allows the top of the mainsail to twist and spill air to avoid overpowering the rig. This technique is called vang sheeting and is an effective way to control heeling without adjusting the main sheet.

DIY materials list

You can spend hundreds of dollars on a pre-assembled kit or you purchase standard parts à la carte and save a lot.

What you’ll need:

• Two fiddle blocks , one (upper) with a becket and cam cleat. The other (lower) can be standard.
• Jaw snap shackles to attach to the ends of both fiddle blocks. These make the vang quick to attach and detach.
• Garhauer BT-2 boom tang  or equivalent screwed to the boom
• Garhauer BB-2 boom bail  or equivalent held by the mast step bolt. If your sailboat has a mast step plate with a vang loop built in, you can use that instead.
• 16′ x 5/16″ New England Ropes Sta Set , tied or eye spliced to the fiddle block becket, 30′ if you want to lead the line through a deck organizer with other lines from the mast.

Installation instructions

To install a boom vang on a C-22 or similar sailboat:

1. The vang should be installed at a 45 degree angle between the mast and boom. Measure the height of the top of the boom above the cabin roof with the mainsail at full hoist. For a Catalina 22, it should be 39″.

2. Measure the same distance along the bottom side of the boom from the aft side of the mast and make a pencil mark. This is where you will attach the boom tang.

3. Attach the boom tang so that it is angled toward the base of the mast as shown below.  If the boom tang has straight legs, carefully bend them to fit the combination of the boom curvature and the tang angle. When the fit is good, drill 5/32″ pilot holes and use #10 x 3/4″ pan head stainless steel tapping screws. Leave enough space between the tang and the boom to connect a snap shackle as shown in the following picture.

4. If your sailboat does not have a mast step plate with a vang loop built in, remove the mast step bolt, align the boom bail holes with the mast holes, and replace the mast step bolt as shown in the following picture.

5. Attach the snap shackles to the fiddle blocks as shown in the preceding pictures.

6. Tie or splice one end of the line to the becket on the upper fiddle block.

7. Reave the line through the fiddle blocks and the cam cleat.

8. Use the snap shackles to connect the lower fiddle block to the bail and the upper fiddle block to the boom tang.

9. Test for smooth operation of the vang and that the boom rotates freely.

You can rig this boom vang in one of two ways. In its simplest form, the fiddle block with the cam cleat and the standing end of the line can hang over the companionway hatch and doesn’t need to be led farther aft. You or your crew can just reach up and trim it as needed.

You can also rig it with the line long enough to lead it aft with other running rigging. For that, lead the standing end outside of the cam cleat, down through a turning block at the mast base, over the cabin roof, through a deck organizer, then aft to a cleat over the bulkhead. The advantage of this setup is that it’s easier to trim on a reach when the boom is swung forward. It’s also easier if you have a bimini that is in the way of reaching the cam cleat.

The longer line also makes the vang more versatile as a utility tackle system. With its 4:1 mechanical advantage and quick release shackles, you can easily detach it and move it to wherever you need some heavy lifting or pulling power such as hauling up a crew member that’s fallen overboard.

To get full control of your mainsail, also see  Flatten Your Mainsail Foot with an Outhaul  and Control Mainsail Draft with a Boom Downhaul .  All three controls work great in combination with each other to flatten the mainsail in medium to heavy winds.

For the complete collection of rigging projects like this one, purchase my ebook  Do-It-Yourself Small Sailboat Rigging .

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16 thoughts on “ control your mainsail shape better with a boom vang ”.

You may find it more convienent to reverse the way you have your vang mounted in the pictures. By placing the cam at the mast base you can adjust vang tension at any boom position. Also, this would eliminate the need for a turning block if you do decide to run the line aft.

That’s a good point that I forgot about when I wrote this one. Thanks for noticing!

I’ve only read a couple of your solutions so fa, but I plan on reading them all! I’m already wondering where you find parts so inexpensive though. You reportedly completed this whole project for the price I would have to pay for a single snap shackle.

Ah, that’s what separates the ordinary sailboat owners from stingy sailors! If I had to pay normal retail prices, I couldn’t afford to own a boat. Check out The 6 best sources for sailboat parts and supplies for where I shop.

Fantastic! I will definitely be including ebay in my search from now on. Thanks so much!

Why or what advantage to using a tang on the boom instead of another bail? (Great article by the way.)

Good question!

You could theoretically use another bail but the attachment to the boom would be a challenge. The holes in the arms of the bail accept a 5/16″ fastener so that would either be oversize sheet metal screws going into the boom or if you used a through-bolt, you’d want to prevent compressing the boom cross-section. Either that or let the bail swing freely on the bolt, which is unnecessary.

The holes in the tang accept much smaller sheet metal screws that are more appropriate for the thin wall of the boom extrusion and because there are four holes, the tang can be solidly attached without allowing any movement.

The bail works ideal for the tabernacle connection since it lets the vang snap shackle slide side-to-side in an arc with the boom movement and without affecting vang tension. It fits perfectly over the tabernacle as you can se, and the mast bolt fits the bail as well. It’s also nice to be able to remove the bail for stepping the mast or to fold it out of the way.

Have you ever done a piece on how to string holiday lights? I looked on your site and couldn’t find one.

I haven’t written one yet, but I did string LED lights all over Summer Dance for the night-time boat parade this past 4th of July. Since she’s out of the water until spring, I won’t be doing it again for Christmas. I do need to raise the mast for another project coming up so maybe I’ll write this one too.

Stay tuned.

Over the years, I have participated in numerous lighted boat parades. The first one taught me not to put white “icicle” lights on the lifelines. Looking forward, I couldn’t see outside the lights. Had to position a crew member on the bowsprit for visual relays. Hang them from your tow rails along the hull.

Great article! Thanks!

GOOD STUFF STINGY! I learned something I will DEFINITELY incorporate in my sailing. I have an ’86 C22, and will be utilizing your advice for several projects!

Stingy, Thanks again for all the great articles!! What diameter mast step bolt do you have? I wanted to make sure I ordered the right Boom Bail and would like to configure like yours using the mast step bolt.

The C-22 mast and mast step accept a 5/16″ diameter bolt but I prefer a 1/4″. It’s easier to insert through the 6 holes of the bail, step, and mast while stepping the mast. It only acts as a pivot pin and isn’t subjected to much force at all so the reduced size isn’t a strength concern. But a 5/16″ bolt would work too.

Thank you and see how 1/4″ would make things easier to insert. Does the BB-2 accept a 5/16?

Yes, so you can use either size.

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What is a Sailboat Boom Vang?

Last Updated by

Daniel Wade

June 15, 2022

A boom vang is a set of blocks and lines or an adjustable pole used to pull the boom down and shape the sail.

The boom vang (or “kicking strap”) is a system used to control the shape of the sail. It counteracts the upward force of the boom jack and the mainsail by pulling the boom downward. This results in the ability to control the shape of the sail.

Table of contents

Boom Vang vs. Mainsheet 

What's the difference between the boom vang and the mainsheet? On many sailboats, the boom vang and the mainsheet look similar, as both use a set of blocks to control the motion of the boom.

The easiest way to tell the difference between the boom vang and the mainsheet is location. The boom vang typically begins close to the base of the mast and connects to the base of the boom at about a 45-degree angle.

The mainsheet is much further back and generally vertically-oriented. Sometimes, the mainsheet is located far at the end of the mast and connected to the stern of the vessel. Just remember boom vang forward, mainsheet aft.

What Does a Boom Vang Do?

A boom vang is a simple device consisting of a pole or a set of blocks and lines. The primary purpose of the boom vang is to control the vertical orientation of the boom and to exert a downward force on it.

Without the boom vang, the wind would blow the sail uncontrollably and make it difficult to maneuver efficiently. The mainsheet, which appears to exert downward pressure on the boom, wouldn't be able to adjust the sail effectively without a separate system like a boom vang.

Importance of the Boom Vang

A properly-adjusted boom vang becomes more important as you let out the mainsheet. The further from the centerline the boom travels, the less downward force the mainsheet provides.

This means that you'd lose a tremendous amount of control without a boom vang, especially as you loosen the sheet. A boom vang exerts a constant downward force on the sail regardless of what position the boom is in. This keeps the sail shape consistent in all conditions.

Boom Vang Types

There are two primary types of boom vangs used on sailboats today. The first and most common type is the standard boom vang. Standard boom vangs consist of a block and tackle arrangement that mounts to the base of the mast and bottom of the boom.

The second type is the hydraulic boom vang , which is more advanced and offers unique benefits. The hydraulic boom vang uses a hydraulic piston that looks like an oversized automobile shock or door opener.

The benefit of a hydraulic boom vang is that it holds the vertical position of the boom without assistance. It's rigid in both directions and doesn't require upward force to keep the boom in place.

Hydraulic boom vangs are costlier than traditional block-and-tackle setups. That said, they're easy to install and generally simple to operate. Hydraulic boom vangs are common on newer sailboats, especially those that exceed 30 feet in length.

What is a Boom Gnav?

A boom gnav is one of the most intuitive pieces of sailboat equipment. The word "gnav" is "vang" spelled backward, and it performs the exact same task on the opposite end of the boom.

A boom gnav exerts a downward force on the boom to counteract the upward force of the wind or rigging. A boom gnav pushes the boom down, whereas a boom vang pulls it down. Not all sailboats have a boom gnav, and those that do often use it as a substitute for a boom vang.

Boom gnav systems are most common on small sailboats , where the added lower triangle of a boom vang gets in the way. A boom gnav takes up no extra cockpit space as it mounts atop the boom and to a higher point on the mast.

In other words, the boom gnav operates within the sail area, which is a part of the boat that's already unusable due to the sail. A boom gnav is usually a pole that adjusts by sliding forward and aft on the boom, which changes the angle and downward force.

Boom Vang Maintenance 

Maintenance is essential to keep your sailboat in safe and working condition, and the boom vang is no exception. There are a few boom vang parts you should inspect and maintain regularly.

Check the Mounting Points

The mounting points of the boom vang are subjected to a considerable amount of force, and they should be inspected regularly. Look for signs of corrosion (galvanic or otherwise) and bending.

If you notice any deformation, replace the mounting points and hardware with marine-grade hardware. Make sure the aluminum mast is solid, as corrosion can weaken the areas around the mounting holes.

Inspect Blocks and Tackle 

For traditional boom vangs, regularly inspecting the blocks and lines can prevent problems down the road. Over time, nylon lines become salt and sun-damaged and begin to fray. If the lines are brittle and leave excessive dust on your hands, it may be time to replace them.

Blocks are generally reliable and don't require a significant amount of maintenance. That said, you should inspect your blocks and make sure they spin freely. If they don't (or they become too loose), they could be failing and should be replaced with high-quality marine blocks.

Hydraulic Boom Vang Maintenance

Hydraulic boom vangs are simpler than traditional block and tackle setups, but they still require regular inspection. A hydraulic boom vang uses a piston and a working fluid instead of lines and pulleys.

On hydraulic boom vangs, the primary failure points are the seals and the mounting points. If your boom vang begins to leak, you'll notice a decrease in stability, and the vang won't hold tension.

Another common failure point is the spring, which can weaken or break and make the vang almost unusable. In most cases, the best option when your hydraulic boom vang fails is to replace it entirely.

What is a Boom Jack?

A boom jack (also known as a lazy jack) is the rigging that exerts an upward force that the boom vang or boom gnav counteracts. The boom jack begins at the boom and reaches up to the top of the mast.

Boom jacks resemble any other rigging on a sailboat. They roughly form the triangular shape of the sail and usually mount to the boom at multiple points.

A typical boom jack begins as a single line at the top of the mast. About 1/4 of the way down the mast, it splits into two lines. At the halfway point, each end of the two lines splits again into four. These four lines run down to the boom and mount evenly-spaced apart.

The purpose of the boom jack is to exert even upward force on the boom. The tension of the boom jack is set as to counteract the tension of the boom vang, which holds the boom at a steady 90 degrees. The boom jack line runs down from the top of the mast to a block or cleat on the opposite end of the boom vang.

Adjusting the Vang

Generally speaking, the boom vang isn't as important when traveling upwind as it is when traveling downwind. This is especially true once you've maxed-out your mainsheet traveler.

At this point, the vang controls the twist of the mainsail. With an improperly-adjusted vang (or lack thereof), you could experience a lot of up-and-down play of the boom. This can cause you to lose control of the mainsail.

A properly-adjusted boom vang can help you keep your mainsail shaped correctly and keep your boom in the proper position. It also gives you precise control of your speed when traveling downwind.

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I've personally had thousands of questions about sailing and sailboats over the years. As I learn and experience sailing, and the community, I share the answers that work and make sense to me, here on Life of Sailing.

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