Laminated yoke

[Fredzen]

Hello,

Reading the builder's forum, I came to the conclusion that there is no problem to laminate hardwood to make a yoke ... but is it possible to laminate hardwood and softwood to minimise weight ?

I understand though that it should be hard enough ultimatly to support the whole canoe :frightened !!!

Thank you !

[Tim Eastman]

I think technically it's doable. Sometimes it's done in paddles. I would have to consider the different coefficients of expansion in the woods though. Differing woods will sometimes have a greatly differing rate of expansion due to temps and moisture and it has been known to cause the glue joints to fail.

Other than that,.. have the hardwood laminates on the outside for both strength and protection.

[Fredzen]

Thank you Tim.

I had in mind cherry (or ash) laminated with white cedar.

[AlanWS]

You should be fine. Cherry and ash will expand and contract with moisture content a little more than will white cedar. You can look up the amount in the Forest Products Lab. Wood Handbook chapter 3
http://www.fpl.fs.fed.us/products/publi ... eader_id=p
but the difference is a lot less than you would have gluing together quartersawn and flatsawn boards of the same species. A yoke is not so wide that a little cup would be that much problem anyway.

If there are problems, all you need to do to eliminate them is to seal with epoxy. Note that your hull has a softwood core, surrounded by glass that does not expand and contract with moisture at all. Sealing off the wood keeps it stable.

[Rick]

...is it possible to laminate hardwood and softwood to minimise weight ?

This isn't about laminating woods, may be useful if light weight is your main goal... a yoke that is both lightweight and strong can be made out of any softwood. The strength comes from a sheathing of fiberglass on the underside so that tension forces will not break the wood. The wood should be able to take compression on the topside and glassing shouldn't necessary there.

A curved underside to the yoke will also help since the curve will match the concave dish on the topside while adding rigidity. Carving softwood into the most comfortable shape with cut and try is also much easier.

The greatest stress on a yoke might happen when somebody that doesn't know any better decides to sit on it. The glass reinforcement might make all the difference then.

[Richard]

Interesting article Rick, do you have a design for carving a yolk?

Thanks,

Richard

[Rick]

Hi Richard,

There is a design for a yoke at this website...

http://www.aracnet.com/~ncglad/canoe/yokedetail.htm

He used ash which will be heavy, a lighter wood will probably be OK with fiberglass reinforcement on the underside... the main thing with carving a comfortable yoke is to make sure that it fits your size properly (like collar size on a shirt) so some modification might be necessary along with carving and trying for fit along the way... good luck!

[Richard]

Hi Rick,
Simply superb,just what I wanted. Your contribution on this thread interested me as weight is a major consideration on my Hiawatha. My first build was a Peterborough using the belt and bracers philosophy, and it ended up far too heavy for lifting on and off roof racks, even though I was very pleased with the end product.So a few ounces shaved of here and there will soon add up to less pounds and less effort on my ageing frame. I ripped and machined my own strips this time and used lightweight cloth. Five layers of epoxy have gone on three on the outer and two on the inner using only one gallon of resin. The in and out whales are ash but I have kept the dimensions to the minimum with plenty of scuppers.Seats will probably have to be ash for the strength but the decks and yolk will be soft wood or a light weight hard wood derivative .
Thank you very much for you help, I could not have hoped for a better result.
Happy new year or (a blwyddyn Newydd dda) in Welsh. Try and get your tongue around that.

Richard

[Patricks Dad]

I carved a yoke based on the design in the link Rick sent out. I did add about 10 degrees of tilt to it to raise the bow a bit while portaging and made it a bit deeper to better cup my shoulders. Overall, I think it's a very nice design and it was very helpful to get me going. BTW, I "carved" it with a sanding pad on an angle grinder. It made quick work of it. If you use hard and soft woods, be careful to observe the rate at which the differnt woods are removed when you sand...

best of luck and enjoyment as you progress with your project.

[Richard]

Hi Randy,
Thank you very much. All tips much appreciated.

Richard