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-   -   Rigid Boom Vang (http://www.sailnet.com/forums/gear-maintenance/83473-rigid-boom-vang.html)

weephee 02-04-2012 01:10 PM

Rigid Boom Vang
 
I have a 27 foot Columbia and I am looking to purchase a rigid boom vang. I found a used one a my local chandlery for less than half the price of a new one. The distance from bottom of boom to base of mast is 33 inches. The vang compressed is approx 45 inches so the angle is somewhat less than 45 degrees. Question is, will this work or should I pass. Thanks

Faster 02-04-2012 01:43 PM

That should be fine.... for 45 deg you'd need 1.414 x 33 = ~46.5 inches.. so your angle won't be that far off.

Make sure you mount it on the boom with enough clearance to fully sheet in/vang the sail for proper leech tension (ie so you won't bottom out the vang when you need it most)

MarkSF 02-04-2012 09:45 PM

What I did (following the Garhauer instructions) was compress the boomvang fully, then sheet the main in hard while sailing close hauled. Then I marked the mounting points with black marker. Back to the dock and drill the holes.

They tell you to mount the vang as close to the mast base as possible. What you need to check for is that the vang will lift the boom - it might not if the angle is much less than 45 degrees. If that is the case, I suggest simply making the angle 45 degrees by having the base of the vang slightly higher.

I used 1/4" s/s rivets, for which you will need one of these :

Amazon.com: Astro Pneumatic 1426 1/4-Inch Heavy-Duty Hand Riveter: Home Improvement

Some people recommend drilling and tapping, I prefer rivets especially for the boom which is thin so a tapped thread will be weak.

weephee 02-07-2012 12:17 AM

Thanks for the replies. I have just one other question. Something I don't understand is do boats with a rigid boom vang have a fiddle block with a cam at the bottom of the vang or do they make use of a cleat or spinlock aft of the mast (near the cockpit). If the latter is true then isn't there binding or restriction of some sort at the block at the bottom of the vang when the boom swings out to the port or starboard side. Thanks
Larry

MarkSF 02-07-2012 12:59 AM

Quote:

Originally Posted by weephee (Post 827596)
Thanks for the replies. I have just one other question. Something I don't understand is do boats with a rigid boom vang have a fiddle block with a cam at the bottom of the vang or do they make use of a cleat or spinlock aft of the mast (near the cockpit). If the latter is true then isn't there binding or restriction of some sort at the block at the bottom of the vang when the boom swings out to the port or starboard side. Thanks
Larry

Normally they'd bring the control line back to the cockpit as it's handier. I plan to, but haven't yet. I replaced the single block at the base of the vang with a fiddle cam cleat block, temporarily.

The block on mine is attached to a tang that swivels independently of the vang, presumably to avoid the binding you mention.

casey1999 04-25-2012 03:44 PM

Re: Rigid Boom Vang
 
I am also considering adding a rigid boom vang primarily to make reefing easier. Do the rigid vangs increase the chance of breaking your boom at the connection of the rigid boom vang, or breaking your gooseneck. The forces of the rigid vang are much different than those of a topping lift.
Regards

Faster 04-25-2012 03:51 PM

Re: Rigid Boom Vang
 
Quote:

Originally Posted by casey1999 (Post 863161)
I am also considering adding a rigid boom vang primarily to make reefing easier. Do the rigid vangs increase the chance of breaking your boom at the connection of the rigid boom vang, or breaking your gooseneck. The forces of the rigid vang are much different than those of a topping lift.
Regards

I don't think those concerns are, in fact, concerns. The support function is a 'push up' rather than a 'hold up' of a topping lift, no real difference otherwise.

Depending on what sort of rigid vang you choose, you need to be sure the support function is off (if it's selectable as some are) before tensioning the sheet.(ie make sure it's in 'VANG' mode) Most spring or gas cylinder supported styles won't have this issue.

jackdale 04-25-2012 04:17 PM

Re: Rigid Boom Vang
 
Quote:

Originally Posted by casey1999 (Post 863161)
Do the rigid vangs increase the chance of breaking your boom at the connection of the rigid boom vang, or breaking your gooseneck.
Regards

The weak point will be the vang, rather than the gooseneck or boom. I know. :o

casey1999 04-25-2012 04:19 PM

Re: Rigid Boom Vang
 
Quote:

Originally Posted by Faster (Post 863168)
I don't think those concerns are, in fact, concerns. The support function is a 'push up' rather than a 'hold up' of a topping lift, no real difference otherwise.

Depending on what sort of rigid vang you choose, you need to be sure the support function is off (if it's selectable as some are) before tensioning the sheet.(ie make sure it's in 'VANG' mode) Most spring or gas cylinder supported styles won't have this issue.

Yea but a rigid boom vang is operating differently from the topping lift. Topping lift produces a near vertical lift on the end of the boom. A rigid boom vang produces a vector force in the middle of the boom. Say you need 100 bls to lift the end of your boom (using topping lift). A rigid boom vang (at 30 degrees from horozontal) could be required to produce 200 lbs of vertical in the middle of the boom to give the same lift. At the same time the rigid vang would be pushing the boom out (force would be pulling the goose-neck) with a force of 346 lbs. The vang itself would have a spring (or gas) compression force of 400 lbs. On top of all this, the boom is being held in the middle instead of the end. Therefore from middle to the boom end it is a cantiler force- totally different than forces a topping lift would put on the boom.

Faster 04-25-2012 04:29 PM

Re: Rigid Boom Vang
 
Yes.. I see what you were getting at.. sorry.

Still, unless you have a very thin sectioned boom ultimately there should be no issue.. looking at the other side of it (the vanging side) arguably larger loads downward are generated upon the boom section when aggressively vanging in a stiff breeze.. if the boom can take that it can likely take the 'support' forces too. And those vanging forces are present whether the vang is rigid or not.


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