Frame and panel movement

[andreas]

Last spring I built this oak toy box for my nephew. Now that its summer, and very humid, the top rails on my frame & panel have expanded leaving a 3/32" gap between the stiles and the lid. Its not a big deal, and nobody has noticed except me, but I'm wondering if there's anything I could have done to avoid this.

I'm thinking that it might have something to do with the way I applied glue to the rail & stile. If I had put glue only on the upper half of the rail, maybe it would have encouraged the wood to expand downward toward the panel instead of upward toward the lid. Of course that also means less glue area and less strength.

Any thoughts?

[andreas]

Thinking about this some more.... I think my problem is with the vertical member in the middle of the panel (the one with the monogram inlay). That piece is preventing the rail from deflecting down and is forcing it to expand upward into the lid. If I had carried that piece all the way up, then I might have avoided this problem.

[Beechwood Chip]

How wide are the rails and stiles? Making them thinner will reduce wood movement, I'm thinking.

[TimV]

I'm not sure what the answer is, but I would have assembled the way you originally did. I don't like the asthetics of your "should have done" drawing. One way to avoid that would have been to take the top and bottom rails all the way to the edge and the stiles to the rail....kinda invert your rail/stile connection. That way when the top rail expands, it expands along the full length of the chest.

[andreas]

Yeah, that's a good point Chip. I think I used 3" rails. I probably could have gone with 2 or 2 1/4"

[Beechwood Chip]

you can check on the shrinkulator to see if that would have made a difference.

[ThomasFilpus]

After checking the shrinkulator, I have another explanations for the top rail bowing upward-- one of the floating panels is not floating enough. Assuming northern red oak, changing the relative humidity from 20% to 80%, the 3" rails would move less than 1/8" but a 12" panel would move 0.46" -- so the groove in the rails needs to be deep enough to let the panel float -- about 1/4", with a corresponding tongue on the panel.

If the groove in either rail is either too tight or too shallow, the panel below can't move vertically and forces the rail upward. Since you mentioned gluing the center stile in place, glue squeeze-out may have found it way into the groove on the inside of the rail.

Also, the finish may be keeping the panel in place, if the panel was finished after assembly, or the tongues on the panel got finish of them.

I bought a rosewood sea chest about 25-years ago, made with 3" stiles and 2 1/4" rails. It's about the same size as your chest and I've been halfway round the world with it and it's still square. The end panels have handles mounted in the middle. If you pick up the chest when it's loaded, the panels float enough to expose the raw wood where the panels meet the grooves on the top of the lower rails. BTW, the center stile on my chest is full height to allow for a hasp to latch the top down, like in your second drawing. I prefer the design of full height stiles, since the end grain on rails is hidden by the stiles, while the end grain on the stiles gets covered up by the lid.

Just my $0.02....