[Adam]

Hi All,
I'm working on the canopy and am wondering if it wouldn't be better to use flush screw instead of rivets to fasten the canopy to the frame? You would have good tension control and less chance of cracking the plastic. I would still fiber-glass over the heads and use locking compound on the threads of the screws which would be drilled and taped into the frame..
So what do you think?

Thanks for the help,
Adam Silverstein
RV-8 Finnish in 2007

 

[Rick6a]

.....wondering if it wouldn't be better to use flush screw instead of rivets to fasten the canopy to the frame? You would have good tension control and less chance of cracking the plastic....

Adam,

My immediate concern is not tension, but shear loading using non structural screws. I can envision the random screw thread potentially riding against and gouging as the Plexiglas shifts, expands and contracts, thus possibly generating slight nicks or undo stresses in the 'glass that could ...down the road...encourage cracking. I don't know if you can generate a "stress riser" in Plexiglas the way you can in aluminum but there is a reason we normally dress and bevel edges of rough cut Plexiglas. These are merely my random uninformed impressions and thus should be noted as so.

 

[Mel]

I used soft aluminum pulled rivets on my canopy 14 years ago and have no cracks. Make sure that the holes in the plexi are slightly oversized to take care of temperature expansion. Also use a hand rivet puller, not pneumatic.

 

[Andy Hill]

You would have good tension control

Fine, if, errr, you "know" the torque to use, and are disciplined enough to apply it. The "soft" rivets Van's supply remove these elements of doubt... and our (RV-8) Canopy did not crack at assembly with the rivets. Who knows down the road

As stated above, you will have to find screws that mean there is no thread against the plexi. Also NB that someone in the 21 years of RVs book used "Loctite" or similar to "hold the screws in" and the Loctite caused canopy damage...

As also stated above, hours of work with v fine "polishing" sandpaper on / around the holes will probably pay off...

Andy Hill
RV-8 QB