Sonex Canopy

[mike.smith]

I guess I will be the first to agree with the original post. I think the canopy frame is one of the weaker parts of the sonex airframe design. Yes, it does what it has to but in my opinion it is very flimsy, can't be opened up in a brisk wind without risking breaking the canopy, and is not in the least bit waterproof. I would love to see someone come out with a better design.

Keith
#554

As someone who is about to build their second canopy (broke coming back from OSH), I have to agree. The Sonex canopy is what it is, and it does work just fine when it's closed and locked. But although I would not call it feeble, it is far from robust. I added two extra diagonal braces to the rear canopy frame, and that stiffened it up quite a bit. If anyone were to ask, I would recommend adding bracing to reduce the severe flexing that can happen with the rear of the canopy.

One thing you never do with a Sonex canopy: leave it open! All it takes is a gust of wind or the prop wash from a passing plane, and you'll probably be building another one. I never leave mine open, even on a no-wind day.

Just my opinion.

[ihab]

These canopy designs have the canopy supported in a carbon fiber frame around the complete profile and this canopy and frame sets into a frame attached to the aircraft.

Basically, if you create a composite insert that rivets and/or glues to the entire boundary of the existing metal airframe, from the firewall in the front all the way to the start of the turtledeck, you can build whatever sort of doors, hinges, and whatever else you want into it. This would essentially be just like the RV-10 composite cabin. It would be an interesting project to try -- get a Sonex airframe, develop your idea, and see where it fits in terms of cost, complexity and weight. Then if things look good, get some tooling together, then start selling it as an aftermarket mod!

Ihab

[Bryan Cotton]

There has been an interesting variety of responses, both pro and con for the stock canopy. Good discussion.

I have a funny story on the ASK21 canopy. One of my buddies back in NY was the chief pilot for our facility. He was my age, but all his time prior to Sikorsky he had been a Navy pilot. Flew and instructed in both fixed and rotary wing. At the Naval Test Pilot's School in Pax River they even start cadets out in gliders. The first time I chucked him in the front of the ASK21 he slammed that canopy down like it was an F18. Well, probably more like a T34C but F18 sounds better. I nearly jumped out of my skin. Had to brief him on how to close the canopy. He thought our civvie stuff was flimsy.

[Rynoth]

After installing the ASA swingback canopy I will give it a +1 for adding some rigidity and ease of opening, along with being safe to leave open. Although it lacks the cross bar across the aft arc of the canopy, the 3 swing arms add their own bit of rigidity to the shape, and the canopy is never subjected to forces that would tend to squeeze it inwards like the stock design does when opened.

[marsolgp]

I'll second that about the swing back canopy mod..... I even taxi with mine full open. Only down side is I now have bugs to clean off the inside of the canopy. So if some one was looking for a more 'rigid' Sonex canopy, this ones already been engineered (mostly).

[phenry]

I have to agree with original poster.
The design whilst light is also very flimsy and only encourages cracking.
I loved building my Waiex however I struggled with two components of the build, the cowl which apparently now comes ready to bolt straight on and the canopy.
Because of cracking I am currently working on a redesign of canopy which I hope will make it stronger, less flexible and eliminate the screws and rivets.
I would respectfully suggest considering the number of complaints (posted here) about cracking canopy's are directly proportional the design rather than the materials.

Flame Away!

[rizzz]

I wonder if you were to just rivet small triangular aluminium plates (maybe 0.060" thick) in the 4 corners to the aluminium tubing, whether it would stiffen things up a bit.
Wouldn't look very good though...

[rfidler]

Now I feel like I was not the only one who has reservations about the current design. I have a close soaring friend of mine who works on composite gliders and has been trained in Germany on sailplane repair. He can basically repair a glider that has been flown into trees and is in pieces and put it back together. There are numerous repaired gliders flying today that pilots have no reservations about his ability. He is totally capable of building a set of molds to layup a carbon fiber canopy frame, that would be one piece canopy assembly and hinged on the side very similar to numerous European composite gliders. I will have a discussion with him to get his input. I believe this improvement could really enhance the current Sonex design.

Keep tuned and thanks for all the great responses.

[DCASonex]

Agree that a stiffer frame would be welcome, but a large part of the reason for the cracking is the manner in which the standard Sonex canopy if formed with curved lower sides that are then held to the flat frame. I have seen those crack both riveted per plans and bonded without rivets. Pressing the curved surfaces flat places the inside surface under tension. On all that I have seen cracked, the canopy tries to revert to its curved shape and slightly humped shape can be seen and felt between cracks with the cracks felt as valleys from the outside. Todd's canopies are flat on the sides. This may very slightly reduce space inside, but I do not notice it, and my bonded Todd's canopy is completing its 4th flying season with no cracks. Some have said the Todd's canopies where heavier, but mine is same thickness as the original Sonex one. Looked at the swing-back design before building mine, but since I was building mine to carry two people in relative comfort, was concerned that the side arms eliminated the chance to provide side pockets, and slightly reduced width which might be a consideration for others as well.

David A. Sonex TD #1327, CAMit 3300

[rfidler]

You refer to Todd's Canopies. Could you define Todd's Canopies because sorry, I have no clue.
Thanks