BJohnson

BJohnson

Well Known Member
Why do the instructions state to drill the plexi holes to 5/32 in areas where only the AACQ-4-4 rivet is used, such as the forward and aft bow of the slider frame and the top center tube?

A 1/8" hole would provide a much better fix. Tighter fit would allow all fasteners to spread the load as the canopy warmed and cooled. Loose holes for the rivets, would cause only some of the rivets to carry the thermal expansion loads, possibly overloading any particular rivet and initiating a crack.

Or is the 5/32 only for the screws holes? I cannot find in the directions any differentiation between how to open up either for a -6 screw or a -4 pull rivet.

And yes, I have seriously considered bonding the canopy to the frame but chose not to.
 
To reduce stress on the edge of the holes...

It lets the canopy "float" and find it's own position without inducing stresses on the edge of the plexi holes. Hopefully this will reduce the chance of cracks at the holes over time.

Jim Sharkey
Rv6 - Phase 1
 
Therory vs practice

I understand the concept of floating the canopy a bit, but don't the countersunk plexi and use of the AACQ-4-4 rivets really lock things in place, putting all of the stress on the countersink and not on the shak of the rivet? The resultant bearing loads are not fully distributed across the hole.

By running a few numbers, assuming a 70 degree plexiglass installation onto a steel frame, and max temeprature swings of 80F (-10F to +150F), and E of 450 ksi, a CTE of 41e^-6, and no slop in the hole, the thermal induced stresses are 1150 psi, below the 1500 psi that some websites call for to prevent crazing from occuring.

If only the chamfer is engaged (5/32 hole for a 1/8" rivet), the stersses are higher than if the chamfer and shank are engaged into the material.

What am I missing?
 
Try it with the tighter holes.....

.....and let us know how it works. That's what EAB is all about :)

Also pulled rivets don't swell as much as solid rivets when set so perhaps it won't be a problem.

Jim Sharkey
RV6 - Phase 1
 
A different way

I didn't really like just the rivets in contact with the canopy at the front canopy bow so I just made a 1 inch wide strip of aluminum and dimpled it for the countersinks in the canopy. Then Prosealed the strip down and riveted everything down just like the centerstrip on top of the canopy. Not sure why they give you a reinforcing strip on top and not for the cross bow but it was pretty easy to make.




Filled the rivets with West Systems Epoxy and then filled and primed. I like it so far.

Bill S
7a finishing (everything to the airport for assembly)
 
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