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Q-talk 156 - Quick-Release Canopy

by Harold Dirks
Quickie 2 - N32DK

This article is a brief discussion of what we did to construct and install the quick-release canopy on our Q2. Our plane has a front-opening canopy like many other Q’s. Most of these canopies use gas struts, but ours has aluminum-tube struts that easily disconnect from the canopy. The first picture below shows the struts in place. Each strut starts out as a long tube that is cut in half to make a top and a bottom piece. The strut tube bottom halves are reinforced with a short piece of aluminum rod inserted into one end. These ends have a slot cut into them to fit over the vertical part of aluminum angles that have their horizontal part bolted to the plane’s longerons. The strut bottoms and the vertical parts of the angles are drilled for a bolt which serves as a pivot to allow the bottom half of the struts to move backward. The bottoms of the struts do not quick-release.

Canopy Struts

The next 2 pictures show the home-made hinge/lock that allows the struts to fold in the center and lock when they are vertical. The lock portion consists of a spring with a moveable collar underneath. To open the lock, you push the collar up against the spring until the extended portion of the lower tube is free of the collar, and then pull back on the lower tube and release the collar. This is easily done with one hand. Once one side is unlocked, you use your other hand to unlock the other strut while holding the canopy up with your first hand. You can then use one or both hands to lower the canopy. The folded struts then lie out of the way alongside the longerons. To open the canopy, you reverse the procedure and again push the locking collar against the spring until you can lower it over the extended portion of the lower tube to lock the strut. A close examination of the lock reveals that it is made out of 2 lengths of larger diameter aluminum tubing that are a slip fit on the strut tubes. The collars are an even larger diameter tube that slip-fits the lock tubing.

Hinge Locked
Hinge Unlocked

The hinge is made up from six small pieces of aluminum plate. 3 pieces are L-shaped and the other 3 are rectangular. The bottom portion of the hinge is made of 1 rectangular piece and 2 L-shaped pieces that are sandwiched together with the rectangular piece in the middle. The sandwich is filed round on its outside edges to fit down inside of the bottom strut tube. The bolt shown below the hinge holds the bottom hinge part and the bottom lock tube part in place. The top hinge portion is another sandwich with the L-shaped piece in the middle. It is filed to fit up into the top tube and is held in place with the bolt shown below the movable collar. This bolt also serves as the lower stop for the collar.

The canopy struts attach to the canopy sides with special ball-head bolts that we obtained from a local farm store. These special bolts are used in many applications. The ones we used are originally installed on tractor carburetors as a throttle connection and are usually available as spare parts. The top strut connection to the canopy is shown in the next two pictures. In the first picture the strut is shown attached to the side of the canopy. In the second picture, the strut is detached and the ball-head bolt is visible. The ball-head bolt has threads on its other end, which allows the use of a washer and lock nut to fasten the bolt to the vertical portion of the aluminum angle whose horizontal portion is bolted to the canopy frame. This aluminum angle is similar to the ones used to attach the bottoms of the struts to the fuselage longerons.

The top of the strut uses a piece of aluminum rod that fits into the strut tube and is held by the bolt shown. The rod accepts the ball via a hole drilled part-way through (hidden in this picture). When the ball is inserted in the hole, it is held in place by the spring-loaded steel collar. A hole is drilled in the collar to fit the neck behind the ball and the hole is cut and filed to provide a U-shaped slot that extends to the top of the collar. The spring provides upward force on the collar to keep the ball securely in place. A cotter key placed at the top of the rod stops upward movement of the collar. To release the ball, you pull the collar down below the ball and then pull the strut away from the ball. The struts can be released from the balls at any time.

Strut Attached
Strut Detached

In addition to the quick-release struts, the canopy itself can be released from its mounting hinges. This is accomplished with the mechanism shown in the next two pictures. The first picture shows the release handle next to the compass box at the front of the canopy shroud. This aluminum tube handle pulls the small cable that operates the hinge release cam shown below the big word “EXPERIMENTAL.” The handle is easily accessible when the canopy is closed.

Canopy Release 1

The second picture shows a closer view of the release cable, cam, spring, and shaft. When the cable is pulled, the left end of the cam goes up, causing the shaft to move to the right, which retracts the hinge pins out of the hinge attachments and allows the aluminum hinge bars to fall down and free the canopy. The hinge bar attachments were milled out of solid aluminum blocks and the shaft is made from steel tubes and pins.

Canopy Release 2

The cam revolves around a lobe bolt that is barely shown under the shaft. The other bolt shown at the top part of the cam lobe provides an attachment for the right end of the spring. The spring provides tension to prevent any vibration from moving the cam. This spring also provides tension on the cable to keep the release handle firmly in its place at the front of the canopy shroud. We have used this release mechanism many times to remove the canopy for maintenance, but we have never used it in an emergency.

For normal use when the canopy is closed, a lever is located on the inside rear of each canopy side as shown in the next two pictures. The head of the screw for the knob is inserted into the hole on the tab to lock the canopy closed. The lever is shown open and closed in the pictures. Each lever is attached to the canopy frame with another handy aluminum angle like the ones used at the top and bottom of the struts. The head of the screw for the knob is inserted into the hole on the tab to lock the canopy closed. The lever is shown open and closed in the pictures. Each lever is attached to the canopy frame with another handy aluminum angle like the ones used at the top and bottom of the struts. These levers are easy to operate and can be quickly opened and closed.

Canopy Lock Lever Open
Canopy Lock Lever Closed