I've got 178 trouble-free hours on my Europa tri-gear motorglider. I
constructed a unique "egg" solution to the bowing of the canopies. No
extra latch or moving parts are needed.
Europa "egg" door latch.
I've installed a wooden egg to prevent the cabin doors from bulging in
flight. A wooden egg is trimmed and afixed to each door so that as the
door closes the pointy end of the egg inserts into a circular hole in
the fuselage. The shape of the egg draws the door to an exact fit with
the fuselage and holds it there securely.
Here's how.
Buy a wooden egg at your wife's favorite craft store and while you're
there get some modeling clay too if you don't have some alread. It
takes a chunk about the size of your fingers tightly squeezed. A glue
gun might be the third purchase. They're inexpensive and really helpful
in all kinds of tasks around the shop. Hot glue sets much faster than
5-minute epoxy so it's really great for holding things in place.
Drill a hole into the fuselage at the center, half way between the shoot
bolts that hold the door closed and centered on the fuselage lip. The
width of the hole is determined by how far you want the egg to drop into
the hole. I used ~ 1"circumnference so the hole squeezes the egg about
a third of the way up it.
To determine what to cut away from the egg to shape it into a plunger
put the egg pointy side down into the hole you've cut. Warm up some
modeling clay and squeeze it around the implanted egg. Pull, twist and
cajole the egg out of the clay. Close the door tightly on the eggless
clay. This presses the clay and defines the space you have between the
fuselage and the door. When you open the door the egg's hole has been
squished back into where the egg used to be, partially filling the hole.
Being an artist, razor out the hole in the clay so you can place the
egg's pointy end back into the clay. Push the egg back into the clay.
With a marking pen draw a line around the outer half to three quarters
of the egg where the clay contacts it. Take the egg out again and close
the door. Look down through the window and note on the clay where the
egg should not be trimmed so that it will be flush with the inside of
the door for added adhesion contact. Open the door, push an indent into
the clay where the egg should not be trimmed. Put the egg into the
clay, mark the egg's forward and rear side where you made the
indentation into the clay. Take the egg out and freehand a verticle
arch on the egg giving you a cut line.
I used a belt sander to trim the egg to gross fit. Just hold it against
the front of the belt sander as the sander is held upside down in a
vise. The cylindrical front of a belt sander grinds away most of the
wooden egg you don't want. To fine-trim the egg hot glue it into the
hole in the fuselage. Use a dremel a wood file and some disclosing
paper to shape the egg exactly to the contour of the door. Close the
door gently on the egg while you hold the disclosing paper in the gap
between the egg and the door. Pull the disclosing paper slowly out
thereby leaving a mark on the gg where you need to grind it back. Grind
away where the disclosing paper shows the egg contour is high. When you
have the egg contoured enough to completely close the door feel the
bottom of the door to be sure it is flush with the fuselage. If it's
not, then use a couple of studs, wooden studs - not masculine buffons,
and some carpenter's wooden door wedges to squeeze the fuselage-door
planes to proper fit.
If your egg is still hotglued to the fuselage twist it out leaving the
remaining hotglue on the surface of the egg so it can be reinserted into
the fuselage correctly. When you're satisfied with how everything goes
together, mix up the smallest accurate batch of Epibond 420 to afix the
eggs to the doors. It doesn't take much at all. Add a little cotton
fiber to make some stiff flox. Paint some Epibond onto the carved out
egg and onto the area on the door where the egg will be afixed. Smear
some vasolene wherever the Epibond could foul up this whole project!
Put the egg into the fuselage hole, smear on some flox and close the
door. Leave it to dry completely.
Open the door. Use some more Epibond and Bid to secure the egg onto the
door. I didn't glass up the fuselage hole to make an egg-holding cup.
I don't think it's necessary and besides it'd add weight.
The egg solution weighs ounces, has no moving parts and works like a
charm. Who could ask for anything more?
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