Plexy back plate of the panel?

[amiklic1]

I plan to use 3mm plexy (acrylic) sheet as the back plate of my panel.

The panel would be produced like this:

U-shape aluminium frame (grey). Looking from the back: 3mm acrylic sheet, 3x20 mm aluminium bar, 4mm tempered glass, everything sealed with black silicon used for car windshield sealing (UV and weather extremely resistant). At the back side I'll put two 20x20mm square aluminium tubes to improve the strength and make it easy to install.

Maybe to put some distancers between the glass and the back?

Any suggestions?

[ghurd]

The temp coefficient is different.  It'll probably warp or crack. And maybe yellow.

G-

[amiklic1]

I did not undestand. Different from what?

The plexy i'll use is widely used in marketing busines for marketing panels production, and has 10 year warranty for non-yellowing.

So, I plan to put just one silicon spot to connect each cell to that plate, and to put some spacers to support it to aviid movement to the front. At the back, It would be supported with two bars, not allowing it to go backwards.

If they often use it for marketing panels, even painted to black, why couldn't I use it? Maybe to arrange some ventilation to improve air flow and so cool it better. Let's say two or three holes near the low end and the same nar the upper end, on the plate between the cells (quasy square).

[Tom in NH]

Ghurd is right. the glass will expand at a different rate than the plexy. If you cement the edges together in the channels, the plexiglas will buckle when it gets warm. This is probably not a huge problem other than unsightliness, but eventually, the uneven expansion will most likely result in a broken seal and the ability of moisture to get inside the panel. This again is not a huge problem as long as you allow for ventilation. My panels are now entering their second year and I am a firm believer in going the ventilated route rather than trying to seal the panels against the weather.

I would be concerned about the flexibility of the plexiglas leading to distorted panels. If I understand you right, you intend to mount the cells on the plexiglas. The weight of the cells is going to cause the plexiglas to sag even without any thermal expansion effects. Do you have access to a stiffer material you could mount your cells onto?

[amiklic1]

I can find any material that's good. What do you suggest? I just don't want to use wood or some water-sucking material, because even when I seal or paint it good aginst water, I can never be totaly sure.

Again for plexy. My back plate dimensions are 350 x 840 mm. What is possible thermal deformation of such material at this dimensions? . And, what temperature I can expect in the panel, due to black cells?