Two or three laminations for my gaff and boom?

[Art Read]

My spruce supplier ought to have in the lumber I need to finish off my spars, but before I put my order in, I'd like to confirm my thoughts on this...

I built the mast up out of three layers of full-length scarphed laminations. Mostly because that's the size of the stock that was available, but also because of the reasoning behind always using an odd number of laminations on any glue-up.

I've since read about, and seen, several small, laminated, solid spars made from just two layers. It sure would be a lot less work! Originaly, I'd planned to just get 'em out of one big timber each, (they do have big enough stock to do it) but having seen how out of "true" my mast laminations were after re-milling, and how well they "straighted up" by gluing them up with opposing grain orientations, I'm really hesitant to try getting the smaller spars from one piece now.

Any reason I'm not considering to not just use two laminations for this? Thanks!

[capt jake]

Art, FWIW All of my 'small' spars are all made from 2 laminatations. They are very straight. Just have to make sure they are clamped straight to begin with.
My 2 cents, and now I don't have any change left. :D

[Bob Cleek]

Well, the rule is always go with an odd number of laminations because, as you know, and others might not, when the wood moves, the stronger piece will dominate, but if there are three, the other two will overcome the strongest piece's tendency to take a bend. Fact is, you may well find wood that doesn't want to go haywire, but you can never tell until it's been sitting for a while and by then, if it does, it's too late. Better safe than sorry?

[Dave Fleming]

The Cleekster and I are of a like mind in this.
Unless you have had absolute control of the stock go with odd.

[Bayboat]

Art: Odd numbered laminations for spars work out best, but for small ones it is possible to laminate just two lengths, if done right. Start with well-seasoned lumber. As you say, the grains should be opposed. In dimensioning the two laminates, rip them wider than they will be when ready to glue. Very probably they will take a curve as the wood cells are eased by the cut. Then with a taut line or straight edge lay out the two laminates and re-rip them. There is a good chance that they will stay straight. Then spread your glue and clamp in two dimensions to straight boards. I've done this successfully with El Toro, Nutshell Pram, Shellback Dinghy and other dinghy masts and spars using Sitka or Doug. fir.

[ 01-24-2003, 08:09 PM: Message edited by: Bayboat ]

[capt jake]

Told ya I didn't have any sense left! :D I only made the 2 lamination due to material, and the rig I am building is small besides. smile.gif

I agree, three would be better. I would have done the same, though material was getting pretty pricey at that time. smile.gif

Happy laminating! smile.gif

[Art Read]

Thanks folks... Sounds like my "instincts" were right this time. I just hope I won't have to plane down the rough stock "too" much. Seems a crime to waste good spruce like that, but I'm not sure they offer anything under 5/4"... and the boom at it's thickest is only 2 1/2". The gaff, of course, even less. Ah, well...

[Dave Fleming]

Art, you try Flounder Bay for Spruce?

[Art Read]

First place I called, Dave. I think my "source" is probably were they get theirs. It's really more of wholesale supplier, but they don't mind helping out "locals" with interesting little projects if you don't mind waiting for them to get around to it. At any rate, it was about half the cost! $4.00 a foot for clear, straight Sitka Spruce. I'll waste a little at that price...