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Flaps on a Super Cub - Why a gap strip?

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Zoomzoooie

Well-Known Member
Joined
Feb 14, 2011
Messages
170
Location
BC Canada
I have been trying to figure out the best configuration for flaps on my 85% Super Cub project. I would like to keep them as close to the full size Super Cub as possible.

On the Super Cub, the retracted and extended flap position is fairly close to the wing and in addition they have a gap strip added on top.
I believe they are slotted flaps, however isn't there supposed to be a gap for air to flow through to keep air flowing over the top of the flap to be most efficient?

Why do Super Cubs have a gap strip on top then? I know they would help in normal flight.
What is the benefit of the gap strip on a Super Cub with extended flaps?
What would you recommend for flap configuration on my Cub? At this point I have drawn it with a 1/4" gap to the wing through the travel of the flap, but I'm trying different hinge locations to see the differences in flap position.

In addition the linkage on mine is a bit of problem to figure out. There is no space for linkage behind the rear spar. The aileron bell crank is in front of the rear spar with a push rod over top the spar which extends out of the wing.
A flap bell crank and/or pulleys would have to go there as well and the cables run in front of the rear spar as well. I could set up the flap linkage just like the aileron push rod but it extends above the wing.
The problem is clearing the rear spar and keeping the push rod from protruding out the top of the wing. I don't want long hinges or control horns hanging below either where you have to be careful not to bump into them or add drag.

However,would you advise for or against a hole through the 3/4" x 3.5" solid spruce rear spar for a 3/8" or 1/2" push rod and what size maximum hole for the spar size?
The push rod would most likely need an oblong hole since it would change angle through it's travel. The spar would have 1/16" ply sandwich there for brackets and hinges or 1/8" depending on the hole size.

I know the strength of any spar is along is top and bottom portion, but how much on a solid wood spar?
Are there guidelines for holes in solid wood spars?
 
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