Almost.

Issues to be aware of:

1, Dimensional accuracy - the stack will be thicker than 18mm because of the adhesive layer, the panel may be warped unless the clamping and work surface are very carefully arranged.

2. Strength - the homemade panel will not be as strong as a commercially-made 18mm panel because the plywood factory has better adhesives and equipment.

3. Durability - the homemade panel will not tolerate temperatures above 120° F (49° C) as well as the commercial panel because of the adhesive.

4. Labor - gluing and clamping the 2 panels to form 1 is messy, takes a fair bit of room and has to be completed before the epoxy kicks.

5. Cost - when you consider the cost of the epoxy and thickener there may not be that much of a difference between the total cost of the commercial and homemade panels, especially if you consider the cost of your time.

All that being said, depending on what use you want to make of the panel and your local situation it may be an excellent idea to go the homemade route,

Laszlo

If you do go this route, put the epoxy only on one sheet, not both, and spread it with a serrated putty knife like the kind used to lay tile. Otherwise you'll be wasting adhesive and making a huge mess.

Screws that are removed after the epoxy has cured may give you better results than weights or clamps, but then you'll have all those holes to plug.

Laszlo

   Thank you for all the advice Laszlo!

It isn't a very big section (60cm x 120 cm) and it's for the mast steps and partners and the rudder yoke.

My local lumberyard will only sell full sheets and 18mm okume is $250 a sheet. I hoped that this would be a reasonable solution.

I will use screws to clamp them together.

Another tip I saw was to use a brayer roller to spread the epoxy out over the plywood.

Should I use any thickener or just apply straight epoxy?

Ken.

The homebuilt panel would work very well for those applications and for that size and shape clamps, weights and a flat surface would be fine. You can skip the screws. Those are necessary for larger pieces of wood.

I wouldn't use a brayer roller. Those make a smooth flat layer of glue and about half of that would be squeezed out when you apply the proper clamping pressure. The serrated putty knives leave hills and valleys of glue. When the boards are pushed together, the hills are pressed into the empty valleys and waste much less glue.

Definitely thicken the epoxy, otherwise it will just run out of the joint. Also paint the 2 sides with unthickened epoxy and then apply the thickened glue to one side only with the serrated putty knife. That will help prevent a glue-starved joint and not waste the glue.

Here's how I glued 2 18mm pieces to make a 36 mm blank for a rudder. The edges were held together with spring clamps and 115 lbs (52 kg) of lead provided the rest of the pressure. The cabinetmaker's bench provided the level surface.

Laszlo

   I haven't done this with okoume but when gluing up two  pieces of fir plywood to make router table tops I made sure to put the convex sides of the plywood together. Then when the clamps are applied around the edges the natural slight warp of the plywood works to your advantage, sort of like a caul. Virtually all sheet goods have a slight warp - at least that's been my experience, might as well make use of it. The few router table tops I've made have come out very flat doing it this way.