poster frame suggestions...

I've just gotten another contract to make some poster frames. I had quite a few problems with the last batch, and I thought I'd see what kind of Wreck wisdom I can scratch up before I embark on another disaster.
As background, these are Lord of the Rings movie posters, all about 27" x 38". They're mounted to a piece of cardboard that's just slightly smaller than the poster itself, and wrapped in some kind of super clear shrink wrap. The customer isn't willing to pay for glass or such, so they want a plain wooden frame to go around these things, using the stock shrink wrap to protect them.
The last round of frames were about 1" wide, made from KD walnut. I discovered the term "case hardening" on that project. Some of them literally bent into a bow shape as soon as they came out the tail end of the saw.
I'll try to avoid case hardened wood next time, but I'm also thinking that increasing the width to 2" (or more?) would mitigate those effects somewhat.
Getting the posters into the frames was a real mess. I cut some corner triangles out of scrap and brad nailed them on the backs. It was difficult to get the posters into the frames without screwing them up, but it was just as difficult to try to get the slightly warped cardboard to behave while nailing the triangles on after the fact.
To fix that last problem, I'm thinking about keeping the outside dimension of the frames about the same as the first batch, and putting the extra width toward the inside. That would cover the small margin of exposed cardboard better, and it would keep things simpler because all parts could swap around randomly. I'm thinking about cutting/routing/whatever a slit in the top to admit the poster, and routing a groove around the inside of the other three sides. Assemble the frame, drop the poster in through the top, and presto.
The problem with this last idea is that every one of these posters is a different size. They don't vary by much, but they vary by plenty enough to cause me problems. I'd have to make individual frame sets with different depths of grooves, or else go for the largest size and shim the smaller posters out somehow.
Finally, rigidity. The posters hanging on the wall right now are looking pretty dismal to me because the warped cardboard has actually shoved the wood out of line. The frames are bowing away from the wall. I'm thinking about the only way I might hope to fix that is to nail a piece of plywood across the entire back. Problem is, I don't want to use 3/4" ply, but everything smaller is usually slightly bowed in the store. I'm afraid if I use 1/4" or whatever, the bow of the plywood will just add to my frustration, since there's nothing to pull *it* into line. (Not unless I nail the whole effing thing to the wall anyway.)
Any thoughts?
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Michael McIntyre ---- Silvan < snipped-for-privacy@users.sourceforge.net>
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One Suggestion for proceeding. Takes a little more material and time.
Make a torsion box with 1/8" skins on both sides and some lightweight pine for the ribs. Total depth of 1/4". Could make this slimmer by using 1/2" material, for the ribs, that was not prone to changing shape once cut to size (maybe a plastic of some kind).
Build up the depth (front to back) of the walnut frame. Make the rabbet for the combined thickness of the torsion box plus the poster. Screw torsion box to the frame from the rear, three screws along larger dimension, two on the shorter. Use shims between torsion box and frame where the screws go (think along the lines of putting in a door jamb in a rough frame where you put wedges where the jamb is nailed).
Also bring the wood into final dimension slowly if the project allows for it. Ie take a couple of months.
When using s4s (s2ss2e for the exact phrase), you might have better luck in obtaining narrower stock by cutting the plank in half first. Ie, take a 1x8 and make it a 1x4 before taking it to a 1x2.
As mentioned in your OP, the customer does not want glass. If glass was used, this would allow for a slimmer profile as the glass could be the "leveler" in this pickle.
Give the customer the choice....do you want a thick frame or thin, and depending on the decision, that will determine which contruction method is used.
Good luck on however you proceed.
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Make that ==> Total depth of 1-1/4" ==<
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