Advice on wood/polycarbonate project

Effects

Hey, I'm looking for some advice on a project. Hopefully it's something you guys can advise on.

I'm building something similar to the image below:


The beams at the top and bottom are made from cedar, held with steel brackets at the sides. The 'glass' louvres will be made from 10mm frosted polycarbonate.
The poly won't run past the edges as shown in diagram.
The plan was to cut a rebate channel into the wood for the poly to sit into.

The issue that I'm concerned with is thermal expansion on the poly. I can't just cut a bigger rebate and leave a gap around the poly, as this would rattle in the wind. Can anyone advise on something else I can do? Do I need to cut a 14mm wide rebate and have a 2mm gasket or something?

Any help is much appreciated.

peter bermingham

Are you doing an engineering course your over thinking it i would cut them just tight enough that they just slip in but are tight so as not to rattle, if your worried about thermal expansion of the panels do a test on them. Just done a google on polycarbonate it expands 0.79375 per 300mm at 100 deg. I understand its a project and you want to get it right you could always cut a few groves of different sizes when doing the thermal expansion test see what happens i would say your results will be around 10to20 microns of expansion. Oh and if your worried about expansion in the height cut the polycarbonate a little short

Effects

Thanks for the reply. It's a real world project and I'm not an engineer, that's probably why I'm overthinking it!

So my sheet sizes are 1314 H x 650 W. Going by your expansion figure there I'm looking at roughly 2mm on the width and 4mm on the height, is that about right? For the height I was thinking of cutting the rebate deeper to allow it to expand upwards if it needs it.

I think maybe I'll cut the rebates with a 12mm router bit, or 11mm if there is such a thing. That'll leave me with a small amount of play.
If I need any more than that, after I see how it plays out, I can always cut them bigger.

Effects

Here's part of the data sheet for the actual product that deals with thermal expansion.

peter bermingham

Yes 2mm is around right by what they are saying yes you can get 11mm cutter better to start with 11mm than cutting 12mm and finding out its to loose.

Effects

The supplier is mentioning bedding silicone for the sheets. But I think he thinks I'm mounting them on the flat, rather than sitting in to the timber rebates.

peter bermingham

Tell them what your doing with them see what they say

Effects

I'll send him the diagrams again and current stage photos.
Project is taking a while as I'm working on it in my spare time so he's probably forgotten what I'd previously sent on to him.