Ch 18.4 Lift and Locking Canopy (Version 1)
Implementing the Canopy Lift:
I've finished the strakes (i.e. this is about a year after finishing the work shown in Ch18 Parts I-III pages), and I'm preparing to do electrical work and finish out the interior (see Ch 22 and 25). As a part of this preparation, I'm returning to sort out how I'm going to actually do the canopy lift and and lock it when I leave the Cozy outside a hangar. I looked at lots of options for this but settled on using a locking gas strut method pioneered by Andrew Anunson in his project. Andrew was very generous with description of his installation and had documented his "Hold Fast" approach as an EAA Innovation Award application. The approach is based on the locking gas strut manufactured by Bansbach.com and I followed Andrew's approach with a couple of modifications to also enable me to secure the canopy closed from outside the Cozy. If you are interested in this system, contact Andrew, he helped me significantly in specifying the strut and button system for the order from Bansbach. NOTE: This approach was fully implemented as noted below, but ultimately didn't work out. The flexible hydraulic system used to actuate the release valve in the strut and allow the strut to extend allowed air to enter and prevented the ability to actuate the strut from either button. I sent the system back to Bansbach once and had them completely assemble the system again and test it over about 6 months (no problems) then they shipped it back to me, and I never dissassembled it but continued testing it on the bench over another 6+ months and slowly it lost the ability to retain button actuation. Andrew had similar experience, but less support from Bansbach and we both decided to shift to electric actuators, before completing our builds. I'll publish more on the electric actuator selection and install when completed in Lift Version 2 page. To open the canopy from the inside, press the hydraulic release button between the front seats. To open the canopy from outside, I positioned a 2nd release button facing into the baggage compartment just behind the pilot's seat back. I then flush mounted a locking motorcycle gas cap in the strake lower skin such that I can unlock, open, and press the open button from the outside. Pictures below on the flush mount locking access. |
Here's a picture of the locking gas strut in place and the canopy partially opened. The lower hard point is wood floxed to the seat back with an AN bolt buried in it and a nut to release the lower strut pivot. The upper hard point is firewall wood sandwiching the canopy bulkhead with a steel tube imbedded and the release pin running in the steel tube.
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A key to setting up the HoldFast system is contingent planning for failure in either release button. If you are in the aircraft, pull the release pin in the upper hard point to disconnect the strut. If you are outside the cockpit and it's closed, Andrew designed his lower hard point to allow him to drill through the belly of the fuselage and release a bolt to disconnect the lower strut attachment. I am taking a little more risk for the external access to failed release buttons, and will have to cut the TB to pull the upper release pin and then repair the TB. I may think of something better in the future, but that's my baseline.
Another note: with this system, you can't get the canopy latched down tight from the outside. It closes sufficient to prevent access (hence the previous paragraph) but to prevent rain getting in I'll use a fuselage/canopy cover when parked outside.
Another note: with this system, you can't get the canopy latched down tight from the outside. It closes sufficient to prevent access (hence the previous paragraph) but to prevent rain getting in I'll use a fuselage/canopy cover when parked outside.
To see what I did with electrical canopy lift, after the above didn't prove reliable for actuating the lift from the hydraulic buttons, see Version 2.