---Original Message-----
For anyone using a belly board on their KR's
+++++++++++++++++++++++++++++++++++++++++++++++++++++++
I sent Joe a bunch of info directly. I recalled seeing an electrical
drawing of board up / down circuit I used. Hand drawn and primitive.
This one a very basic drawing.
https://www.dropbox.com/s/6xz9puozepqk1d8/speed%20brake%20switch%20002.jpg?dl=0
This is my circuit with all terminal boards, breaker, etc..
https://www.dropbox.com/s/x4e5wt0qaukev5y/speed%20brake%20switch%20001.jpg?dl=0
Left half is electrical path with motor running up, right half is
circuit with motor running down. Looks complicated but it's just
cluttered with all the info. I used a "double pole / double throw" flap
switch out of a Cessna. If you start from + (battery) and follow the
line through the circuit you should end up at - (ground) and the motor
will run that direction until the limit switch is tripped. Then go to
the down side and do the same.
Here is the info I sent to Joe.
Joe,
Mine is 9 inches by the width of the fuselage with holes and lowers to
nearly 90 degrees
http://myplace.frontier.com/~flesner/19.jpg
It may be a bit of an overkill but not much. I use it full down on
every landing. Full down I have to carry a bit of power to keep the
sink rate from getting too high but that really stabilizes the approach
at about 500 fpm. Idle power and I'd get 1500 fpm sink rate. Holes or
no holes? Who knows. That's what the Navy used in WWII so I went with
holes. I do get a bit of "rumble" with it full down but no control
problems.
Things to consider. What is the length of your gear? Ground clearance
when down. Is yours a nose dragger? If so clearance is probably not a
problem. I use the jack screw portion of a Cessna flap motor on mine.
Heavy but it was free and had limit switches I could adjust.
http://myplace.frontier.com/~flesner/02092593.jpg
Mine is mounted to the floor immediately behind the rear spar. I got a
piece of 1/4" pine from the lumber yard , 1 1/2" X 1/4" X width of
fuselage to beef up the floor. Piano hinge bolted to the bottom and
floxed to the board with many 1/8" holes drilled in that hinge half and
a layer of glass over that. A piece of foam on the front half of the
hinge for an air ramp to streamline. My board is just a piece of 1/4"
foam with a layer of glass on both sides and a wood block laid in where
the jack screw attaches. I'd hate to think of flying without it. Big
difference on landings. I can climb with it down but slow. I normally
lower the board at 100 / 110 mph on base to kill some speed and then
bring in a bit of power at 90 mph to keep the decent at 500 fpm or so,
hold that on final till close in and slow to 80 mph over the numbers and
flare. Works for me but I'm heavy and short wings.
Check out my video and go to the end where the board comes down. Just
after the 1:40 minute mark.
https://www.youtube.com/watch?v=cgdgxVgPNAk&t=6s
Is you project rounded on the bottom? If so that could be a mounting
problem.
Larry
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