Control Your Mainsail Shape Better With a Boom Vang

The mainsail on Summer Dance is showing and acting its age. I don’t know how old it is, but it’s getting on in years and is getting a little baggy. We had a few unexpected roundups last summer, so I planned to add a boom vang while I was refitting her this winter.

Rather than buy a pre-assembled kit, I purchased the parts a la carte consisting of:

  • Two used fiddle blocks, one with a becket and cam cleat
  • Jaw snap shackles to attach to the ends of both fiddle blocks to make the rig quick to attach and detach
  • Garhauer BT-2 boom tang screwed to the boom
  • Garhauer BB-2 boom bail held by the mast step bolt
  • 30′ x 5/16″ New England Ropes Sta Set, eye spliced to the becket and whiplocked on both ends. This line is solid blue in keeping with the rigging color scheme that I will describe in a future post.
Upper fiddle block attached to the boom tang
Upper fiddle block attached to the boom tang

The vang should be mounted at a 45 degree angle between the mast and boom. The C-22 boom rests about 39″ up the mast with the main sail at full hoist, so attach the boom tang 39″ from the mast. The Garhauer boom tang comes with straight legs. You’ll need to bend them carefully to fit the combination of the boom curvature and the tang angle. When the fit is right, drill 5/32″ pilot holes and use #10 x 3/4″ pan head stainless steel machine screws.

In its simplest form, the fiddle block with the cam cleat and the standing end of the line hangs over the companionway hatch and doesn’t need to be led farther aft. You can just reach up and trim it when close hauled. But I purchased the line 16′ longer than necessary on purpose, which makes it long enough to lead aft by running the standing end from the boom back 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 work with on a reach when the boom has swung forward, especially if the bimini frame is in the way of easily reaching the line.

Lower fiddle block attached to the mast bail
Lower fiddle block attached to the mast bail

The vang works great in combination with the mainsail outhaul and the boom downhaul to flatten the sail in medium to heavy winds.

The Bottom Line

Suggested price: $173.70
$tingy Sailor cost: $106.07
Savings: $67.63

What do you like most about your boom vang rigging?

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7 Comments Add yours

  1. Orion says:

    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.

    1. kbilling says:

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

  2. John says:

    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.

    1. 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.

      1. John says:

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

  3. Garhauer says:

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

    1. 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.

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