Canopy retention

[harry curzon]

On my K-18 canopy, I have hinged it at one side, and put a couple of small magnets holding to bolt heads on the other side. Will little magnets to bolt heads be enough or does the airflow manage to pull canopies open unless they are mechanically locked? If it needs mechanically locking, is there a hidden external device that can be made to avoid the need to cut out a vent window in the canopy?

[Peter Balcombe]

Harry,
Losing a canopy is definitely to be avoided in my experience, largely due to CoG change. However, with hinged canopy, it probably takes a bit more force as the hinges should help a lot.

I’ve used magnets successfully on smaller models - using pairs of the 6mm ish diameter magnets, with one mounted each side of the join. Not sure if this is better than one magnet to a bolt head, but you try getting two magnets apart from a stack other than sliding them off each other!

I’ve also used magnets on the switch/charging compartment hatch door on a DLE powered Titan tug - no complaints about that opening in flight, even with the vibration.

My belt & braces suggestion is to use a bowden cable exiting underneath one wing root, close up under the wing near the TE. I’ve used this on 4 & 5m gliders.
Solder a small brass ball to the outboard wire end to provide something to grip & paint it the fuselage colour.
If the ball butts up against the fuselage when in the ‘closed’ position then it should be hidden from view until the model is in the air, and even then only barely noticeable - not strictly scale though.
Peter

[Chris Bowles]

Hi Harry, when I built my 18, I used a servo to lock the canopy, worked very well, also used the same system to keep my ASW15 locked
Chris

[Barry_Cole]

Hi Harry, when I built my 18, I used a servo to lock the canopy, worked very well, also used the same system to keep my ASW15 locked
Chris

Chris,
How do you turn the power on and off??

What happens if the servo, Rx, or battery fails. How do you get in???

BC

[Peter Balcombe]

Good one Chris.
Do you have a small hole or similar in the fuselage to be able to manually push the arm to the release position if the servo/power fails?
(Murphy’s law says that “if it can fail then it will”)

[Jolly Roger]

I use 5 pairs of 5mm dia neodymium magnets to hold the cowl shut on my 1/3 Cub and am really happy how it's worked out. Despite the motor vibration, powerful propwash and bumpy landings, the cowl has never opened in flight. The join line is almost invisible too.

[Chris Bowles]

Hi Barry, magnetic switch, never had a failure, how often do you have a RX, servo or switch fail, I would be more concerned with the flight controls than a servo operating a lock on a canopy
Peter, good idea, a small hole would allow you to open the canopy, if any of the above fail

[harry curzon]

Thanks everyone for the ideas. I've gone with Peter's bowden cable suggestion.