Bonding Perspex to aluminium

Andrew Leak · Post by **Andrew Leak** » Tue Aug 12, 2008 5:34 pm

I can't seem to get a straight answer from many quarters as they all seem to be confused by what I am trying to do. I have a new aluminium canopy frame (pretty standard so far), what I want to do is bond the new perspex to the frame of the canopy rather than drilling holes every 3-4 inches or so and have raised screws & cups, that quite frankly, look ugly. The other issue is the canopy is in two halves and the centre rail of the frame is only 18mm dia round tube that looks almost impossible to accommodate the join with the two canopy halves and screws in between (I could have some plates welded at measured intervals but I want it to remain fairly original). I have seen a few aircraft of this vintage with a 'screw-less' canopy and it looks very neat and streamlined. I have heard it rumoured that I can use a standard auto windscreen bond - clamped in place overnight would do the trick, however, I've also been told that standard silicon 'goo' would do the job as well. As I realize that the perspex will 'grow' and shrink in the heat/cold, does anyone have an idea of the most suitable bonding agent to get over this. Or I am I going to have to start drilling and welding bits on? Aargh!

Oh, it's a SIPA 903 by the way...

Andrew

ian herdis · Post by **ian herdis** » Tue Aug 12, 2008 10:32 pm

Andrew

The Sportsman which I am building has all the windows bonded in with Silpruf a structural glazing adhesive, the method is to paint each surface with a thin coat and leave to set, then bond together with a generous bead of adhesive.

Ian

Andrew Leak · Post by **Andrew Leak** » Wed Aug 13, 2008 12:34 pm

Thanks Ian, a quick question though. Do you have to bond the Silpruf to bare metal only or does it bond to paint as well? The pdf on the website mentions cleaning paint/surfaces with an appropriate solvent but not if it sticks to it properly.

regards,

Andrew

Mark A · Post by **Mark A** » Wed Aug 13, 2008 12:59 pm

Sikaflex adhesives are commonly used for this purpose. The LAA have accepted it as an alternative to drilling and rivetting for a few of the RVs.

Steve Samson gives a good explanation on http://gikonfinsh.blogspot.com/ - scroll about halfway down.

ian herdis · Post by **ian herdis** » Wed Aug 13, 2008 11:52 pm

Not sure about bonding to paint as the weak point may be the paint bond, the Sportsman is composite and the windows are bonded in before paint, the method requires an initial sanding of the surfaces and a clean with solvent

Ian

Andrew Leak · Post by **Andrew Leak** » Fri Aug 15, 2008 11:45 pm

Thanks to everyone who replied. After much debating I've had to go with the Sikaflex 221, purely because it is more flexible as I need to sand & paint it, this made absolute sense.

Thanks again for all your input chaps.

regards,

Andrew

Pete · Post by **Pete** » Sat Aug 30, 2008 12:57 pm

I bonded a KR2 canopy using sikaflex UV and am very happy with the result - that stuff is sticky. once set it is virtually impossible to remove. It sets into very hard black rubber resembling the rubber found in car engine mounts.

The canopy has been in now for more than 2 years, no sign of separation.

The only point of caution I would add:-

That stuff is very difficult to get off anything, so mask absolutely everything and wear disposable overalls, have several pairs of disposable gloves ready