Wood – Making of durable plywood frame

adhesiveplywoodwood

I am making a custom camera rig for the kite aerial photography and I need a ┏┓-shaped frame like this:

frame

(depth × width × height = 40 × 200 × 100 mm, thickness ~5 mm).

I cannot use bent aluminum as it is pretty dense (2.7 g/cm³) and I do not have any bending machines.

I cannot use 3D-printing as I don't have an easy access to a 3D printer. The plastic seems to be dense too: 1 – 1.4 g/cm³.

So, my choice is old-school wood. Plywood. As a bonus, it is very lightweight: about 0.6 g/cm³!

I could probably cut tree ▌-shaped plates and glue them together at 90°. But I am afraid that the whole frame would not be rigid enough if forces applied to like this:

forces

Just get me right: I am pretty sure that it would not break, but I am just uncomfortable with that feeling.

Moreover, as the plywood is pretty thin, I would probably need extra plinths to glue the surfaces:

plinths

So, I am thinking about CNC-cutting ~ten ┏┓-shaped parts and gluing them together:

composed

It seems for me, that the resulting frame would be much stronger to forces applied in all the directions, compared to the three plates versions above.

Question is: am I right? Or should I just make the frame of three plywood plates? Any nuances in assembling together such a stack of parts?

Best Answer

I agree with fred_dot_u, and I'd add a few points:

  • The grade and type of plywood is important. CDX will have 3-4 plies, gaps, knots, etc. that could dramatically weaken the critical corner areas of your piece. Better plywood has no voids, many thin plies, and higher-quality veneer.
  • A bias might be the best approach. If you cut square with the sheet, half of the plies will be aligned in the weak direction. If you were to go with a 45 degree bias, every ply would lend strength (though none would provide full-length grain).
  • Cutting a series of fairly large circles out of the center area of the panels could dramatically lighten the structure without undue weakening.

All that said, a few pine boards with a small block inside each corner (cut from the same boards, in lieu of the plinths) and high-quality adhesive would save you a whole lot of cutting. 

____________________________________________
|  *     *                                   <-- top board
|
|___________________________________________
|     |     |
| *   |     | <-- block
|     |_____|                  * screw locations
|     |
|     | <-- side board
|     |
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