RV8Squaz

RV8Squaz

Well Known Member
Hey Guys,
Have any of you ever experienced interference with the curved leading edge part of the flap hitting the raised inboard portion of the flap brace? If so, what did you do about it?
On my right flap, the curved leading edge of the flap hits the flap brace during the last 1/2" of travel. This is causing the motor to strain a little bit and I can see the curved leading edge flex in that area. Bending it down or curving it more doesn't do much to help because of the angle of the flap brace. The lip on the leading edge hits the flap brace pretty square. The only thing I can think of doing is to trim off the lip of the flap in that area. It seems as if the flap is mounted to far forward, but it is lined up with aileron perfectly. The left flap leading edge just touches the flap brace in the fully retracted position.

Anyone have any ideas on how to fix this?

Thank you,
Jerry
 
Jerry, I spent all afternoon today working on the same problem. It seems that if we have our piano hinges too far forward, it'd be too major a fix to re-drill and re-position. I too found that bending or over curving the leading edge didn't help, so I think that leaves us with trimming it. I'll tinker with it again tomarrow afternoon (friday) and let you know unless someone else has a better idea.
 
Sorry that I don't have the drawing number handy, but on my 4 the flap drawing calls for several inches of the inboard-most section of upper flap skin to be cut and rebent. I always figured this was to address the problem you speak of.
 
Flap Interference

Jerry...

I had that problem with my RV6...manual flaps though. If I recall, I bent the extreme inboard end of the flaps with my seamers so the leading edge assumed a "cone shaped" bend on the leading edge until the flap did not hit the brace. I am having a tough time remembering all this but I think I bent from a point about 6" to 8" out from the fuselage inboard to the fuselage. The taper bend is somewhat acute. The flap has a 90 degree flange on the end of the curved leading edge which I just rolled the inboard end in a tighter radius forming the "cone". This cannot be seen with the flaps extended as the exposed portion of the leading edge radius was not disturbed. I don't know if this portion acts as a stop for the flap but the manual lever has a notched stop in a detent which holds the flap position "in Trail" when retracted. This "stop" may work differently with the motorized flap but my flap also has the lower flap skin which retracts against the bottom of the fuselage which also functions as a stop and also closes the openings that the flap actuator rods pass through. I thought the portion striking the flap brace was interference rather than an actual stop. Hope this helps!

Dick DeCramer
N500DD 165 hrs.
0-320 Hartzell
Northfield, MN
 
Mine did this on both flaps. Just increase the radius of the leading edge bend at that point with your hands. Palm it and use your finger tips to pull in on the most forward part of the leading edge. Trial and error until you get it right. Try to only bend the most forward part, since you want a nice match against the trailing edge of the wing skin when the flap is down. It took me several tries but they work fine now and you can not tell that anything was even done.
 
Squaz!!

Squaz,
Good to hear from you. Had the same problem on my flaps. Bent the LE by hand until things moved nicely. BTW, instead of running them in and out, I put the motor to the full down position, and took the lower bolt off the actuator. Then, the flaps were free to swing all the way out of the rear spar, allowing me to bend and fuss with them without removing the flaps.

Call me if you get stuck.

Art in Asheville
 
Hey Guys,
Thanks for your help! I got rid of most of the interference with some more bending and tweaking. I think part of the problem is the position of the flap brace itself. It looks like I could have tweaked that a bit better when I built the wings long ago.

Jerry
 
Are flaps in the neutral position?

When your flaps are retracted and aligned with the ailerons, are they in the neutral position?

On my -7 wings, which I understand to be essentially the same as the -8 wings, the curved leading edge of the flap is 1/4" away from the flap brace (at the wing root end) when the flap is aligned with the aileron in the neutral position. I don't see any way that fabrication errors with pre-punched parts could result in interference.

However, interference could occur if the flaps are retracted past the control surface neutral position. The neutral position is defined by alignment of the aileron trailing edge with the tooling holes in the tip rib. If you have used some other alignment criteria, then your flaps may be retracted too far, which could cause the inferference you are seeing.

Another effect of retracting the flaps too far is that the "negative" flap position will reduce the camber of the wing, which will reduce its cooeficient of lift.
 
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It's there!

I just finished installing my left flap and the inboard leading edge contacts the spar doubler in the neutral position, almost as if it were a designed stop. All the parts are, obviously, pre-punched and the flap hinge position is as specified on the plans. The flap lines up perfectly with the neutral aileron (using the tooling holes). I haven't got my fuse kit yet, so I'm not doing anything about it until I mate the wings and hook the flaps up.
Cheers,
 
Mine is doing a similar thing plus the leading edges of both flaps rub pretty good on the wing skins. I've corrected for the flap leading edge by bending the interference slightly with seamers and by hand. Not sure what to do about the trailing wing skin rubbing the flaps skin as the flap travels. It's leaving a pretty good mark. ouch. Chris -(RV-7 QB)
 
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