A small dab of epoxy/microballoons mixture (above left) is added to the front edge of the canopy flange to provide material for the retention bolt at the front of the canopy. An 8–32 nylon bolt with flush mount head (at right) secures the front of the canopy from lateral and vertical movement.
reinforce the canopy flange. Once the epoxy/microballoons have dried in the canopy, the flange is drilled and tapped to
receive an 8–32 flush-head nylon bolt. The 1⁄8-inch ply is slotted to accommodate the body width of the 8–32 bolt.
The canopy is positioned on the fuselage, slightly aft of its proper location, and as the canopy is slid forward, the bolt head slides underneath the 1⁄8-inch ply. The height of the bolt is adjusted to provide a snug fit. The 8–32 bolt is installed with a small dab of white glue (any aliphatic will work) on the threads. The white glue is sufficient to pre- vent the bolt from loosening, but can still be broken loose should the need arise. Moving aft to the quick release latch, it is worth noting that latches come in a variety of
sizes and of quality. Several are available at F3A Unlimited, and I generally use the FH5003. The latch can be installed in the fuselage by “potting” it in a mixture of epoxy and microballoons, but this can be rather messy to maintain alignment and runs a sub- stantial risk of fouling the latch with epoxy. Instead, I glue a small birch plywood base into the fuselage, and then the latch can eas- ily be glued to the plywood base with CA. Prior to gluing in the latch, the top of the fuselage and the plywood base need to be slotted for clearance/access to the actuator pin. I estimate the center of the throw, and drill a hole just large enough for the actua- tor pin, and then slowly shape the location hole into a slot to accommodate the full throw of the latch. When the latch is fully re-
tracted, the retention pin should protrude just slightly from the fuselage flange. Before gluing the latch in place, I lightly grease the sliding retention pin for smoother operation and protection against stray glue. The aft flange of the canopy is reinforced
with a small piece of 1⁄8-inch birch ply. The tricky part of the installation of spring latch- es is accurately drilling the hole in the canopy flange to accept the retention pin. The “trick” that I use is to put a small dot of paint on the end of the retention pin. Then, with the latch fully retracted, place the canopy on the plane, and then release the latch. The paint on the end of the retention pin will transfer to the canopy flange, re- vealing the precise location needed for the hole in the flange.
A shaped piece of 1⁄8-inch lite ply (above left) is used to reinforce the fuselage flange (above center) where the canopy retention bolt will engage the fuselage (above right). A quick release spring latch (below left) holds the rear of the canopy in place and only needs to be slid aft to release the canopy. Critical to
effective retention of the canopy is that the retention pin (below right) of the spring latch fully engages the canopy to allow a margin of security for any flexing of the canopy and fuselage during aerobatic flight. The retention pin should retract just far enough to allow the canopy to be removed.
FLYING MODELS
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