SonexBuilders.net

I put a space heater under the plane. Kept the cockpit area toasty warm for the days/weeks I worked on the canopy/windscreen. I'd leave them in place overnight and let the heat soak in. Works best if the forward fuselage floor isn't installed yet, but would also work if only the aft fuselage floor isn't installed. Heat fills the high spots (i.e. the canopy/windscreen.)

In my yet to fly Sonex, the cockpit canopy (perspex) has developed a crack, in one fixing hole, close to the point where the "stay" connect to the rear frame/hoop.

Initially I thought this was due to the canopy curve & the frame not being perfectly symmetrical, resulting in stress on the perspex when the fixings are tightened down - so I "spaced", using nylon washers of different thickness, the gap between frame & perspex.

I have come to the conclusion that the very slight asymmetry is, at best, a minor contributor.

Careful observation suggests the rear frame/hoop is flexing on each opening. Despite every care being taken, the crack has appeared. This does not bode well for the future, particularly when wind gusts might impact on the open canopy.

What mitigating strategies have other builders employed???

I posted some info on a very simple and light weight brace for my canopy, that really stiffens the structure. if you cannot find that, PM me your direct email and i will send some photos.

David A.

DCASonex wrote:I posted some info on a very simple and light weight brace for my canopy, that really stiffens the structure. if you cannot find that, PM me your direct email and i will send some photos.

David A.

Thanks David - found your old post & some very informative photos. Would seem we are on the same track - I have measured & planed for a similar "stay" on my canopy rear hoop.

For the original Sonex-type canopy (prior to the B-model changes), I followed a couple of other people’s suggestion and built additional bracing into the rear canopy bow. I found that it made a *massive* difference in the canopy stiffness. Here are a couple of photos of how I built it:

https://1drv.ms/f/s!ApMKXiyfUEPRhskCdhJeRQvrZ8j5-Q

—Noel
Sonex #1339

NWade wrote:For the original Sonex-type canopy (prior to the B-model changes), I followed a couple of other people’s suggestion and built additional bracing into the rear canopy bow. I found that it made a *massive* difference in the canopy stiffness. Here are a couple of photos of how I built it:

https://1drv.ms/f/s!ApMKXiyfUEPRhskCdhJeRQvrZ8j5-Q

—Noel
Sonex #1339

Very nice Noel - if I was starting from scratch I would go with your concept but as I am retrofitting, I will stick with Davids single stay for the moment.

I think you will find that extending the one diagonal brace up to top center of the canopy will make it even stiffer while allowing a slight bit of movement on the edge with the latch to make engagement easier.

David A.