Hi Lars,

I build kayaks that have bulkheads and stringers covered with thin plywood. The bulkheads are the equivalent to your forms - they just stay in the kayak.

The beam that I use is made of a pair of 2x4's, on edge, spaced apart with short pieces of 2x4 (also on edge, looks like a very narrow ladder about 4 1/2" wide). This construction tends to stay straighter that a solid wood beam. These spacers are also used as a "splice" to lengthen the beam. I bolt everything together so that I can take the beam apart for storage, change the length or move the spacers if they get in the way. I use the gap inbetween the beams to mount uprights to which the bulkheads are attached. With my style of construction the kayak is built over top of the beam. The beam support legs and a tool tray also mount using the gap between the beams.

The beam does not have to be perfectly straight because you should work using a string as reference (any lines put on the beam will warp with the wood). The beam should be stable and not twist or warp during the kayak building process - make it from dry good qualilty lumber. A couple of coats of paint is a good idea if you plan to keep the beam for future use (can you make only one kayak? I can't!!) When not being used, the beam should be stored in reasonable conditions - leaning it in a corner will warp it.

If you need any more information, contact me. Enjoy your project.

Hank