Stitch and Glue?

[stonedpirate]

Hello,

I have heard some designers speak of hull skins made with multiple layers of ply.

My question is, how do you do a multi layered ply with stitch and glue?

Is each layer epoxied onto the one beneath it?

Or do you not need epoxy between each layer, just on the edges?

THanks

[hoytedow]

Any place two pieces of wood contact, they should be glued and sealed. Pages in a book do well glued down the edge, but layers on a boat, not so well.

[alan white]

The purpose of stitch and glue is to build a hard-chined boat from plywood.
The shape of the boat is therefore made up from conical (flat panel) sections.
In a sense, what you call multi-layered is shop-made plywood, but the reason it's done is to make a hull with rounded sections.
This method is generally called cold molded. Since the whole hull is of one piece, no stitching is required.
The exception that comes to mind, where many-layered panels are stitched together, is called Constant Camber, where all hull sections are made from a simple convex panel that's built on a form.
The simple convexity is built into the panel, and the design cleverly uses that single panel shape for all of its parts. The panels look a lot like the skin of an orange slice.
The advantage is a comprimise, working best with a design specifically drawn for use with the method, but useless for building any non-constant camber design..

[boat fan]

My question is, how do you do a multi layered ply with stitch and glue?

Stitch and glue the panels .
Fillet.
Laminate one ( or ) more layers on top as desired / required.
You can use vac. , staples , screws , etc.
These can be removed after glue is set.

Is each layer epoxied onto the one beneath it?

Yes.

Other glues can be used.

Or do you not need epoxy between each layer, just on the edges?

No ! No voids. ! If you glue edges only , you will have one great big void....
See the problems of voids in plywood....

[stonedpirate]

Great, thanks a lot guys

[boat fan]

Be aware that if you add hull skin thickness , the boat gets heavier.

If you add extra layers to your hull , beyond the original design specs ,
you will lose that extra weight in payload capacity.

If you add to the hull weight , and load the "designed for" max. payload
your boat will float deeper than designed.

Generally bad........

[LP]

Multiple layers could be called for in areas of high curvature where a single thicker layer could not be bent to the desired camber. Also some builders will laminate additional layers to get the total hull thickness.


Hey, Alan. How's it going? Still not in Maine, but we are sure trying!

[alan white]

Hey! Glad you're still working towards moving. I've got a couple more boats to go through, lots of work when I can find time. Stop by when you're in town again.

[PAR]

You can also use multiple layers of plywood to conform to compound curves, much like cold molding veneers. Another option is to slit the plywood so it'll "lay down" on a compound curve, covering the slit areas with the next layer. This is common on "Carolina flare" bows.