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Old 02-07-2018, 12:08 PM
bkervaski's Avatar
bkervaski bkervaski is offline
Join Date: Mar 2017
Location: Birmingham, Alabama
Posts: 894
Default Canopy Final Fitting before Fiberglass

Just a heads up to others headed towards getting their fiberglass canopy fairing laid up ... Check at least 3 times and make sure you don't have to trim material from the bottom sides of the canopy ... use weights per the manual and make sure those weights are adequately pushing your canopy down.

Mine fit perfect in every test fit phase and on the final assembly apparently the riveting of the side skins pushed my canopy up about 1/16th (a guess, no way to tell) which caused a compounding gap in the front of about 3/16th on both sides. I don't think clecos apply enough pressure to the side skins to expose this issue. It appears I should have removed a bit of material from the bottom of the canopy or possibly an inner bevel so it matches up with the curve of the frame.

I cut a relief slot and drilled out at the top (like you treat a canopy crack) to take the additional stress of pushing the two sides down a bit. There is still a gap, going to handle the remainder with filler.

While nobody will likely notice after the fairing is laid up I just wanted to put this out there for others so they don't have to deal with the frustration.

This has happened to at least 2 other people that I collaborate with off the forum so it may be a common thing to look out for.

Hope it helps somebody!
#140376 RV-14A QB IO-390 Thunderbolt
Registered: N196
Progress: Flying!

Last edited by bkervaski : 02-07-2018 at 12:23 PM.
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Old 02-07-2018, 06:09 PM
Bavafa Bavafa is offline
Join Date: Oct 2007
Location: Sacramento, CA
Posts: 2,549

Good tip, thanks for the heads up.

I agree clecos do not apply enough force to some of the parts in the final position. Two experiences in my 7A was the rudder stop which I worked hard to get it to the proper angle/shape only to be off when it was riveted, the other was the canopy with the front deck skin again in the 7A.

I will be watching for this. Just finished the canopy frame and working hard to keep myself from moving to the canopy till the weather warms up.
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Old 02-08-2018, 08:21 AM
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Bootscooter Bootscooter is offline
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Location: Sydney, Australia
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Default Relief Slot

Thanks for the post I came across this as well, and I did many more than 3 fits.

Was just wondering if I could get a pic of the relief spot, to show where it is and how it looks.

Rgs Chad
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Old 02-08-2018, 08:32 AM
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bkervaski bkervaski is offline
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I don't have a pic of the relief slot, it's filled now.

Basically, with a cutting disc, make a 3/4 x 3/32'ish slot and then drill the end of it out with a radius greater then the width of the slot to prevent cracking/spreading.

Make sure the slot fits comfortably within the parameters of the top of your fairing on the plexiglass, mine went over a bit so my fairing is a probably a 16th or so higher than the instructions.

The location is going to have to be where you need the relief, mine was dead center.

This just allows more torsional (twisting?) movement on both sides of the slot so there isn't a bunch of stress built-up in one area that leads to a crack later.

Edit: If you haven't riveted the side skins on yet it's going to be better to shave some material off the bottom of the canopy and continue working towards a better fit, I didn't really have this luxury. In my judgement, trying to pull the canopy out of the dimpled side skins and get it back in a few times to get it right would have caused more cosmetic damage that it was worth, assuming it would even be possible.

Hope this helps!
#140376 RV-14A QB IO-390 Thunderbolt
Registered: N196
Progress: Flying!

Last edited by bkervaski : 02-08-2018 at 08:39 AM.
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Old 02-10-2018, 11:05 AM
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czechsix czechsix is offline
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Location: Spring Hill, KS
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I'm having a hard time visualizing exactly where the interference was, or how to prevent the same issue when I get to the canopy phase, but the idea of cutting a slot to relieve stress makes me nervous. Seems you are just transferring the stress riser from the edge of the canopy up to the end of the slot, and I have seen numerous stop-drilled canopies that continue to crack over time. Sure stop drilling helps reduce the stress concentration compared to a crack (which is why we do that to attempt stopping a crack from spreading), but the stress concentration is gonna be a lot higher in that small hole compared to what it was along the straight, smooth edge of the canopy.
Mark Navratil
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Old 02-10-2018, 02:01 PM
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bkervaski bkervaski is offline
Join Date: Mar 2017
Location: Birmingham, Alabama
Posts: 894

@czechsix Thus the reasoning behind my post .. to help you guys avoid a similar situation a few of us have already had to deal with. Other options included buying another canopy which would be almost impossible to get drilled properly so that would probably end up starting the whole canopy frame over.

Not interference. When you cleco the side skins on to get everything lined up they don't apply enough force to push the canopy up, rivets do. The inner frame is curved so when the side skin is riveted it shifts the inside of the canopy completely into that curve which pushes it up a bit. A chamfer or removing material fixes it.
#140376 RV-14A QB IO-390 Thunderbolt
Registered: N196
Progress: Flying!
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Old 02-10-2018, 02:55 PM
Pixair Pixair is offline
Join Date: Jul 2017
Location: Napa Valley
Posts: 12
Default Cleco clamping force

If cleco clamping force is the issue I would suggest a few of the "screw" style clecos as they can provide greater clamping force than the normal spring version.

Haven't used them in this exact situation, but in others where more clamping was needed to bring layers together. They worked well.

May the force be with you......
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