glue up

[scottsabiker]

I've just finished an article that advises one to add stain to plywood panals prior to installing them in frames. And to put the final top coat of shellac or poly on after the unit is built. The use of glue on plywood is OK because it will not move. And the stain will look better in the corners & edges next to the stiles or rails. I have always thought that glue will not hold well on stained wood of any kind, including plywood. Your advise on this matter is needed. I'm thinking of using the plywood method for a blanket chest that will be constructed in a high hunidity state, & shipped to a very low humidity state. By using the plywood, & gluing decorations on the ply panels I will not have to worry about wood movement.

[Nick2cd]

i wouldn't say that plywood is completely impervious to movement.....just much less prone than naturally occurring, nature grown wood. anyways, it's my understanding that you don't glue a panel in place (assuming we are talking about raised panel type doors). you just let the panel float in the rails/stiles. this allows for wood movement. you don't have to add much space tolerance across the long grain of the panel, but you want to give the panel some room to expand and contract across its width. this is where you will see the most movement.

[bywc]

scotty are talking about making them out of a solid piece of ply not a rail and stile design then glue the "molding" to the edges to give the appearance of rail and stile?

Reason im thinking this is the last line in your post

By using the plywood, & gluing decorations on the ply panels I will not have to worry about wood movement.

if so scotty yeah I would be worried about the glue bond holding the decorative "edges" to the plywood without some form of brads or some mechanical fastening device as the stain/finish will seal the wood and not give the glue something to bond to.

[Pete Bennett]

It depends on how deep your grooves are to accept the ply. If you are using something like 10mm or 3/8" maybe 1/2" then I would mask the outer edge of the panel down to say 3/4 of which ever depth you're using, Stain as the advice is and once everything is ready for glue up, remove the tape and glue up in the normal way. This way you will get plenty of raw surfaces to achieve a good bond, plus you will disguise any movement. If you are sending this from a very dry state to a very damp state I would however, be very careful about gluing the panel in.

What Nic states is basically true but he's actually a little off the mark concerning direction of movement. In a solid wood panel the movement is indeed across the grain with almost none in the long grain. However, with plywood which is not immune from at least swelling and buckling, the movement is likely to be almost exactly equal in both directions as the plys are at right angles to each other. That said all plywoods have an unequal number of plys so there will always be one direction where you have more pieces of cross grain than the other. In some three plys this is compensated by the central ply being twice as thick as the two outer plys running in the opposite direction, but, this is not always the case, so check what you have.

On balance I'd go for a good solid frame with strong joints and leave the panel to float in plenty of space to expand without either buckling or bursting the frames apart.

Hope this is of some help.

Pete