Hi Glen,

The marine plywoods are made to higher standards than the luaun plywood. The main difference is that the marine plywood will not have voids in the core where luaun may.

That being said, I have been making kayaks from luaun for years with no problem. Where strength is a real concern or in high stress kayak designs the marine plywood is preferable. For my type of paddling [small rivers and lakes] luaun is an adequate material.

The companies selling kayak kits/plans promote the use of the more expensive marine plywood for two reasons. First, since they cannot control where/how their designs are going to be used or the quality of the workmanship of the construction - they [rightfully] promote the stronger marine plywood. The second reason [IMHO] is they can't make any money selling luaun which can be bought locally for less money that it would cost to ship to you.

A couple of comments about building with luaun...

- luaun comes in a wide range of qualities, don't assume that it is all the same. I buy my luaun from a place that makes wooden garage doors, the quality is excellent - very few voids, the top side is pristine and the "back side" of the sheet has few flaws.

- buy all the materials [plus an extra sheet if you can] from the same batch to get consistent grain, color and thickness.

- inspect the edges of your panels after you cut them out. Fill [inject] any voids with epoxy - or if you get a bad panel - cut a new piece from your extra sheet of material. I have yet had a piece that was bad enough to have to re-cut the panel.

- 1/8" [3mm] luaun seem to have a higher quality core than the 1/4" luaun and bends easier. I use 3mm for my boats and join the panels with butt joints in the cockpit area. I use a 3 or 4 foot "backing board" to support the butt joint which doubles the panel thickness in the cockpit area to 6mm. The backing boards [on the side panels] are feathered for about 5 inches at each end to allow the panels to bend smoothly. The bottom panels bend very little and the backing boards have not needed feathering.

- don't worry about how waterproof the glue is in the panels - epoxy coating inside and out is standard construction and will take care of that. I read a comment that said luaun was inferior and you had to "slather on $100 worth of epoxy" this is bunk - even the marine plywood has to be coated with epoxy.

- if I want to increase strength/durability there are a two of things I do. 1) I seal the wood with epoxy using a heat gun to thin the resin and get better penetration. 2) I put a layer of cloth [scraps left over from glassing the hull] on the inside of the hull. Since I use a light weight cloth and the weave need not be filled, glassing the inside does not add too much weight or use that much extra resin. The money that can be saved building with luaun buys a lot of resin and cloth.

I am just finishing up [a couple more coats of varnish/paint and a cockpit rim to be added] a Chesapeake 17 LT made from luaun using the construction as described above. Present weight [on a scale] is 35 pounds.

Hope this helps.

Hank