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REFLECTOR: Doors - Eliminate the twist
I'm sure that I'm not the only one who has noticed that on the Elite door
Velocity's, the doors always have a tendency to bump and rub on the strake
at the door cut as the door comes down. The reason is that there is enough
flexibility of the hinge tab (and fuselage top) that the weight of the door
and the force of the gas strut twists the bottom of the door back. Nate
Calvin's mod addressed the bulging of the top corner when the door is closed
by directing the strut force directly at the hinge line; but this doesn't
stop the twisting of the door as it is being closed.
There are some things you can do to alleviate this condition (if you're
concerned about this sort of thing). First thing is to stiffen the hinge
pad area of the door. I cut two plies of triax, and a ply of BID for
finish, to the shape of the tab (cut a square out to go around the hinge)
that extends about 1" wider than the hinge on each side. Extend it around
the corner and across the top side of the door frame. Yes, it crosses the
area of the door seal, so put some peel ply over it and sand it nice and
smooth in that area. I was surprised by how much it reduced the movement of
the door fore and aft at the bottom. A little flexiblility at the hinge
translates into much bigger movement at the bottom.
Stiffening the fuselage in the hinge area also helps. I wanted structure
around the door anyway so I first put a beam across the top between the tops
of the carbon beams. I used about a 4" wide piece of 1/2" blue foam, glued
it to the fuselage top with microslurry, let it cure, micro coated the foam
and laid over 2 plies of triax, and a ply of fine BID for a nice finish.
You know, round the corners; put in fillets, etc. Lap the plies an inch or
two onto the fuselage top. Extending the covering ply of fine BID 1/2" or so
more than the triax makes a nice transition. Very strong; doesn't weigh
much. Then across the top of the doors (from the cross beam forward to the
front frame, about an inch from the top of the door opening) I used 1/4"
foam and 1 ply of triax covered by 1 fine BID; again about 4" wide. This
provides good stiffness in the hinge area, covers the hinge openings, and
carries structural loads around the door. Keep the layups from being too
wet, and you've only added a couple of pounds and lots of strength. (Note:
main axis of the triax always goes in the long dimension.) This, and the
hinge tab reinforment, virtually eliminated any tendancy of the doors to
twist and rub at the back.
If you want to go further (or in lieu of something else), move the attach
point of the strut to the door about 2" forward so the force gets applied
just in front of the rear hinge. Significantly reduces the twist action,
but your rear seat passengers may be a little more likely to bump their
heads on the strut when getting in and out. And, of course, you will have
to make a new attach bracket because you want to be sure to anchor into the
pre installed hardpoint that resides inside the door frame.
Some ideas you might like to try; and use at your own risk. I may have some
picutures to post when I get the next roll of film developed.
Al Gietzen RG Elite 755V