Although I have not yet made the first flight, I believe that having the canopy open inflight might mess up my hair.... and my underwear. I therefore set about scheming on how I could tether the canopy so that it either could not move at all or at least not lift very far if it unlatched. Noise I can handle, but turning the cabin into a wind tunnel test is not my idea of a good time.

I wanted the following features:

(1) Easy to find parts.
(2) Cheap as possible.
(3) Simple to design and install.
(4) Very strong to resist canopy lift.
(5) Provide a handhold to assist in latching the canopy.
(6) Minimum interferrence with my hands, arms and shoulders inflight.

What I settled on was a pair of plain, 2" wide seatbelts (available from a host of online sources). I cut the metal anchor parts off of the female ends to allow me to make my own brackets for them.

I fabricated the brackets from 1/8" aluminum angle, drilled them to rivet to the inside of the canopy frame where they could be grasped while I sat inside.

Once the brackets were deburred, primed and painted, I got my lovely and talented wife (racking up those brownie points fellas) to sew the female ends to the brackets. I then rivetted them in place with six A5 rivets each.

It is important to sew the female ends onto the brackets as short as possible. That prevents them from dangling any farther down into your way than they have to. It also makes it as easy as possible to draw the male ends tight once you have buckled them to the female end. The male end with its factory sewn-on bracket attaches where the outboard end of the lap harness bolts to the main gear upright.

I had intended to cut the extra length from the male end of the seatbelt to minimize the amount of extra web strap dangling inside the cabin. I realized after installation however, that they can be left buckled and extended to their full length to limit the canopy opening. Unrestrained, my canopy opens so far that the front weatherstrip gets mashed against the cowling. With the tether left buckled and fully extended, it holds the canopy just short of doing that. The tether is somewhat obstructive in this mode but even my 81 year old dad can manage to work around it. For those who can't maneuver around the tether, one side can hold the canopy while the first person enters from the opposite side. That person then buckles the tether on his side and releases the other one so the second person can enter. It's very easy to do.

The finished tethers satisfy all of my design criteria without busting my brain or my budget. While I sincerely hope that they never have to actually hold my unlatched canopy inflight, I am confident that they have more than enough strength to do so.

If any of you have questions or comments feel free to contact me for discussion, additional info or fabrication techniques.


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Comment by Bob McDonald on May 2, 2009 at 5:11pm

Great idea I love it. As long as there is no patent infringement issues I think I will copy your work for my CH601HD with forward opening CH601XL canopy. A "seatbelt cutter" in the side map pocket should solve any egress problems. I love the concept of maybe leaving the passenger side long... a few times I have opened the canopy only to have the wing try to rip it off the aircraft! I am pretty sure only 1 canopy (seat) belt would be needed to prevent an opening in flight. I was thinking of doing a similar seat belt thing, but with only a single centre belt attached to the canopy frame in the centre and attached to the airframe behind the seats. I have a gap between my canopy and the round tube frame so attaching the belt should not be a problem. The CH601HD with Rotax 912 80hp has a cruise of 105mph and it pretty much "hits the wall" with an airspeed of 115mph... slower speed = less lift on the canopy.

Comment by Donnie Moore on May 1, 2009 at 7:21pm
Don't get me wrong. I'm not criticizing. Just was wondering if you had thought of that aspect.
As a tinkerer there have been many times that I've come up solutions to problems that I thought were ingenious until someone pointed out an aspect I hadn't thought of. Sometimes I've had to rethink the problem from a new perspective. Sometimes I'm fine with it the way it is.
I just wanted to offer that perspective in case, like I do at times, while focusing on the one problem you hadn't thought of the other.
Comment by Dr. Edward M. Moody II on May 1, 2009 at 6:43pm
If they need to, they will probably have a broken plexi bubble to reach through and press the cute little red buttons. If the bubble didn't break, option #1: I can push the little red button myself, or option #2: if I am unconscious, they can kick it in themselves.

Remember, my decision was to deal with the most likely problem; not to achieve a risk free world. Everything has balance... the lighter the plane, the less strength it can have, the more poweful the engine, the shorter the range, etc. It's probably not the best solution but it satisfied my design criteria.

Comment by Donnie Moore on May 1, 2009 at 5:00pm
Heaven forbid they should need to, but could an emergency crew open that if they need to?

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