Boomvang in Wood Boom and Weather Helm - SailNet Community
 
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post #1 of 10 Old 02-12-2009 Thread Starter
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Boomvang in Wood Boom and Weather Helm

Hello,

I have been reading sailnet for a good year or two but have yet to post. Hello everyone.

I have a couple questions, mostly relating to weather helm.

I currently own (fully now) and live on a 1971 Cheoy Lee Offshore 27. I spent the whole summer tearing off the teak decks, replacing the wood core on the foredeck, refibeglassing the gaping hole, filling in screw holes with epoxy, sanding and repainting the decks. The infamous Cheoy Lee deck problem has been somewhat fixed if you ignore the other soft spots. Shhh. Here are some general interest pictures:



After installing new marine plywood:


Final product with primer:


Picture of the boat today:


Out of the water:


Moving on. The boat suffers from a relatively annoying and potentially serious case of weather helm and I'm trying to address the problem in steps. My first step was going to be installing a boomvang however I am concerned about the structural integrity of my boom in withstanding the pressures of a strong wind while beating. The boom is made of Sitka Spruce. I was planning on installing a D-ring to the boom with a 4:1 purchase block to the mast. Feelings? Worth the effort, risk? Right now I just hitched some webbing on the boom and tried to bring it down that way but I can't get enough friction. Worth a try I guess.



My sails are pretty old and the main has three large burn holes that have been hand patched from an embarrassing accident that would require another post. I have heard (accurately?) that an investment in new sails would reduce weather helm. That is an investment I currently can't make right now but feedback on the issue would be appreciated.

I think part of the reason for the extra weather helm is also due to the general design of the boat. She is really narrow with low freeboard so I generally have to reef at a relatively low wind strength, generally around 12-15 knots. I am not totally used to this yet so perhaps I should expect to reef earlier and stop reefing when the rail is in the water.

Any suggestions/comments? I've read the posts about weather helm and figured there might be advice relevant specifically to the Cheoy Lee.

Thanks and Hello,

Ben Hackett
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post #2 of 10 Old 02-12-2009
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4:1 is a pretty minimal purchase and of limited effectiveness for a vang. You could easily cascade it into an 8:1 that would be better.

That said, you have a bit of a disadvantage in that the boom is rather low and the angle of the vang is a bit flat as well, again reducing its effectiveness.

You needn't worry about the load on the vang so much when beating, most of the load will be on the sheet when close hauled, but when running in a breeze the load on a vang fittings is going to be considerable and the fittings do need to be strong enough for those conditions. A strap such as you've tried might work if the sail is loose footed and you can manage to stop the strap from sliding.

Reefing early is definitely a good plan, but the weather helm you're experiencing is unlikely to be cured by the vang. Most likely the rig is raked too far aft, or the design is originally flawed. Often you'll see such boats modified with a short bowsprit (which would look OK, btw, on your boat) to move the headstay forward and relocate the center of effort more forward. This will help to alleviate extreme weather helm. If you choose this course you should consult some professionals for more precise advice.

As you already pointed out, new sails will help too.

Nice job on the restoration, the hull looks great!

Ron

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post #3 of 10 Old 02-12-2009
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Installing a vang will be less effective than adjusting mast rake, outhaul tension or even halyard tension,

Technically by installing a vang you will controll sail twist further higher in the mast, which may or may not be good...in an old lady like yours, a little spillage up top may be benefecial, so forget the boom vang.

You must concentrate all your efforts in having more sail in the front and less in the back, maybe your genoa is not working right...

Power the head sail first, (the head sail is the power driver of the boat), the main sail is the steer sail....

I made a few videos, if you can't find them let me know..have a look around...or search for Giulietta's videos...

With a tight budget like yours, leave the vang for when you are more..let's say...pocket rich..
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post #4 of 10 Old 02-12-2009
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Found them

somehow someone moved them

CLICK HERE
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post #5 of 10 Old 02-17-2009
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Just curious as to why you replaced the foredeck with marine plywood. Marine plywood is pretty much the worst of all core materials to use. It rots like balsa, wicks water and delaminates over much larger areas like foam—and it is very heavy.

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post #6 of 10 Old 02-17-2009
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SD, maybe that's all he could afford...read his first post...

In my land we say.."if you don't have a dog...hunt with the cat...but still go hunting:....or something like that.
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post #7 of 10 Old 03-13-2009
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I would not recommend a vang for your boat. Wood spars are notorious for failing when a vang is installed; and in your situation with such a shallow angle, the longitudinal load will be very high (the reason failures tend to occur).

A vang won't control upwind weather helm; for that you would need a more balanced sailplan, possibly new sails and a good mainsail traveler control (to more finely trim the main and balance out the sails). That's in addition to adjusting the rig as Giu has previously suggested.
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post #8 of 10 Old 03-13-2009
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I also wouldn't recommend a vang, because the angles aren't right. You might supplement your existing traveller, however, with some sort of preventer set-up, which would take some of the load down to the rail when going downwind. With a wooden boom, however, you need some sort of bronze band to which to affix any bail. Anything that puts a hole in that boom (aside from small stuff like cheek blocks and small self-tapping cleats) would, I think, weaken it, and I wouldn't want to be around when a loaded-up boom splinters.

A boat like this, you need to find an older rigging book to find out how people solved stuff 50 years or more ago. Either that or get on a specifically wooden or restored boat forum that will supply better ideas.

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post #9 of 10 Old 03-13-2009
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Quote:
Originally Posted by Valiente View Post
with some sort of preventer set-up, which would take some of the load down to the rail when going downwind.
OY! In consideration of a wooden boom failure I also would not want to get backwinded or dip the boom in on a round-up with a preventer!

You might check with the people over at the SF Bay Folkboat association; they have lots of background with wood spars. But IMHO if it has sailed for 50 years without a vang; it certainly should not need one now.
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post #10 of 10 Old 03-13-2009
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I also think that a vang is not the solution. My elderly Allied Mistress needs a first reef (when going to windward) when wind speed gets to 15, so reef early. In boats of this vintage a lot of the weather helm comes from heeling. Keep her on her feet and you will get to windward faster.
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