Cypress for a laminated keel?

[outofthenorm]

I've read here and elsewhere that Cypress is rot resistant due to natural oils. Does that mean it's hard to glue in a laminate?

- Norm

[Frank Wentzel]

Norm
I doubt you will find any old-growth cypress that might give a glueing problem. I have glued lots of cypress, even the red or heart cypress and never had a glueing failure. The only area I would expect a problem is if you glued fairly thick stock (3/4" & up) cross-grain. Then, with wet & dry cycles, the joint could fail. No adhesive can stop the moisture related wood movement. For a laminated keel the glueing will be parrallel with the grain and you will have no problems.

/// Frank ///

[outofthenorm]

Searover, I'm toying with the idea of a little skipjack, maybe 20 ft or so. Just working out a materials list to figure a rough cost. The boat would be unballasted, so cypress, with its tendancy to absorb water and become heavier, seemed like a good choice for the keel. I can get it reasonably priced in 4/4, so laminating would be required.

[outofthenorm]

I saw this one last year in the yard at Mystic. Grebe was built to plans revised from Chappelle. If I go ahead with it, I'd do the same and built it traditionally - cross planked, carved forefoot -just for the fun of it.

[outofthenorm]

According to the plans dept at Mystic, Grebe was developed from the drawing on page 325 of American Small Sailing Craft. Unfortunately they don't have their plans available, so I'd be starting from scratch. Not a huge problem though. As you say, she'd be relatively easy to do.

[chuckm]

I too am using Cypress--The Keelson, some of the frames, and the outer ribbards-ribs. # lamination of 3/5 inch Cypress, glues great, machine great , and smellls good.

[pipefitter]

Searover, I'm toying with the idea of a little skipjack, maybe 20 ft or so. Just working out a materials list to figure a rough cost. The boat would be unballasted, so cypress, with its tendancy to absorb water and become heavier, seemed like a good choice for the keel. I can get it reasonably priced in 4/4, so laminating would be required.

I may be wrong but any timber that is going to absorb enough water to effect ballast, sure doesn't seem like a good candidate for a glue lam no matter which way the grain is running or what glue is used.By adding glue to the cypress,it negates the reason for why it is such a good wood and this will be it's weakness. I would spend the bucks and buy a piece of solid old growth heart cypress of the right dimension from wood reclaiming specialist such as Goodwin heart pine. www.heartpine.com or at least check into it. You'll probably have close to the cost in the labor and glue of laminating one of correct size?

[seedtick]

Avoid "new growth' cypress, it doesn't have much of the rot resistant oil that the old growth stuff has. Also if it has been kiln dried then you've lost what little oil you had to start with.

Unless you're planning on leaving the boat in the water all the time, I'd avoid letting any cypress get fully soaked. Cypress will absorb more water than its dry weight. Dry cypress has a specific gravity of something like .45 and fully saturated with water will sink (> 1.0). All that water will swell the wood significantly. An old boat builder told me that a 12" wide board will gain and lose 1/4" going from wet to dry. That much dimensional change moves a lot of wood around and leaves gaps when it dries out.

[outofthenorm]

Thanks everyone. I appreciate the input.

Pipefitter; Good thoughts. The thought wasn't to use cypress for the keel because it absorbed water and took on weight, just that if it did, it wasn't necessarily a bad thing. But from what you and Seedtick say, maybe that's wrong-headed.

Ironmule/ Searover: I have Boatbuilding and I agree. The stuff in there is invaluable with this kind of build. I've been watching for a deal on Sucher's books. My edition of Small Craft is 348 pages plus an appendix of offsets for many of the designs. 1951 edition, reprinted recently (no date listed)


Seedtick: The wood available from my usual source is air-dried, but I don't know if it's old or new growth. I'll find out. The boat would live in the water half the year and dry out in the winter. Sounds like the extreme expansion factor would be a killer on a hefty laminated structure.

Around here, cypress is an import, of course, but there are other good choices to make including good green or air-dried white oak. This is purely exploratory right now, no decisions made. Price isn't the first consideration, just one of many.

- Norm