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Boom Design

PostPosted: Mon Jun 03, 2019 11:20 pm
by chaertl
Hi Everyone,

It's been awhile. I pulled the Chucky B. out of winter storage today thanks to a long wet spring and discovered it didn't fare to well. After nine years of use the spars are in pretty bad shape. The mast and gaff need to be completely stripped and refinished but the boom has a bad case of rot on the end an isn't going to be reusable. This wasn't completely unexpected since I spliced a piece in last year to get another year out of it. Since it needs replacing has anyone made a lighter version? In my opinion it's probably the most over built of the spars. I'm thinking of making a hollow version.

Chris

Re: Boom Design

PostPosted: Sun Jun 09, 2019 10:32 am
by Arjen
Hi Chris,

I consider to build the spars from red cedar. I used this wood for Greenland style padles for kayaking.
Both treatment with epoxy and Tung oil hold very well. Only concern is wether it is strong enough.

From a physics point of view hollow spars can even be stronger then massive spars.Bit difficult to explain but you can imagine that a stiff core can act as a lever stressing the outside. Of course a hollow spar can’t take much perpendicular forces as it is not supported by lack of a core. So it depends on the usage.

Even around-the-world-sailors use hollow spars. And when they need more strength a solid spar is never an option

Re: Boom Design

PostPosted: Thu Jun 13, 2019 11:01 pm
by sean
Hey Chris,
Sorry to hear of the loss of your spars. For a slightly lightly boom I suppose you could rip the middle board into 3 pieces lengthwise and then leave out most of the middle one (except at the ends). Strength shouldn't suffer much at all, but you'd only save 1/9th the weight at best. Not sure if its worth the extra effort.

I'm doing a bit of the same pondering. In my first time out this season I got a bit ahead of myself and broke my yard. (Definitely user error, and not the yard strength - had the end at the mast locked down for storage when I let it out on a windy day). Other than rebuilding it the same way, I'm thinking about trying for a lighter version as a couple folks have mentioned in the forum using a carbon fiber shaft and/or leaving out the stainless steel track and use rope lashings instead.

Re: Boom Design

PostPosted: Fri Jun 14, 2019 9:21 am
by chaertl
Hi Sean,

Ouch!, Sorry about your yard. The Chucky B. is back to seaworthy since the boom is useable until the new one gets built. I still have some minor bright work to do but if you want to do some sailing while fixing yours let me know. Thanks for the advice too Arjen!

Chris