> Particle board is glue and sawdust. It is not strong at all, tending to
> sag. Just look at what happens to cheap kitchen cabinets and bookshelves.
> If it you build a four sided box wall tube out of it, it will still sag
> between the supports it rests on. Especially with the weight of a boat
> upon it.

What I have in mind would be much like Nick has in his book. The difference is that I am not ripping it from plywood or fiberboard. Instead I have store bought fiber board strips of roughly the same dimensions as his proposed box beam. Sounds like you are not thrilled with Nick's method in general.

> While it's easier to set up the forms on a perfectly straight strong back,
> it isn't essential. Using lines and other measuring techniques, you can
> set the forms onto a squigly strongback in a nearly perfect manner. The
> key is that the strongback must (must, must, must) hold its shape. If it
> doesn't, you're wasting your time.

I understand. Will a fiber board beam reach a point where it stops sagging or will it continue to sag?

chris