> Why not laminate up from plywood ripped on a table saw and laminate the
> layers with staggered joints? give you a stiffer straighter and more
> durable beam than one from Particle board. AL

I just built my box beam using the instructions in Nick Schade's book "The Strip-Built Sea Kayak". I modified it slightly though. I did use 1/2 inch plywood which was rabbited and staggered the joints. My modification was in the dimensions. I took 1/8 of an inch off the outside dimentions in order to adjust the forms a little more than the 1/16 of an inch in the book. I was worried that building it at night in my small garage without enough lighting would result in a less than straight build. It wasn't as straight as I would have liked but the size decrease worked very well and my forms were set in a straight line.