chepburn

chepburn

Well Known Member
Hi,
I have just finished drilling the flap side of my hinge. Which, according to the plans, should have the hinge pin centerline set 1/8" off the edge of the flap skin. When I removed the hinge, and measured the rivet edge distance, I see it is close to 6/32"....not ~7/32 as is the minimum according to standards. I can't believe that Van's spec'd this edge distance on the hinge to be such a close tolerance to minimums... Was I supposed to ignore the 1/8 spec' on the drawing? I seem to remember a discussion along these lines in another thread a while back, but a search hasn't turned up the answers. Any comments anyone?

(However, there are *LOTS* of rivets in this hinge line... )


Chris Hepburn
RV-8 Wings
 
Chris,

There's some earlier discussion about the flap hinge issue here.

I had insufficient edge distance on the "wing" side of the hinge, and I ended up ordering wider, P4 hinge material. It is 1/4" wider, as I recall. I actually had to trim it slightly narrower by about 1/8" so it wouldn't hang on the 45-degree bend in the flap brace.

For many people, this seems to be the only way to get the trailing edge of the flap and aileron to line up, and still maintain good edge distance for the hinge rivets. Sounds like you've discovered the same issue exists for the "flap" side of the hinge. Strange that Van's hasn't addressed this and made a change in the kits, because almost every RV-8 builder I've ever talked to has commented on the flap hinges and their minimal edge distance.

My flaps line up perfectly with the ailerons now. Pictures here, here and here.

Best of luck!
 
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Do not ignore minimum edge distances on the flaps!
The flaps, by far, carry more load then any other control surface. They are the only control surface that get pushed into the air stream and stay there.
 
How are you measuring? You want to use...2D from the CENTER of the hole to the edge of the skin.
 
chepburn said:
Hi,
I have just finished drilling the flap side of my hinge. Which, according to the plans, should have the hinge pin centerline set 1/8" off the edge of the flap skin. When I removed the hinge, and measured the rivet edge distance, I see it is close to 6/32"....not ~7/32 as is the minimum according to standards. I can't believe that Van's spec'd this edge distance on the hinge to be such a close tolerance to minimums... Was I supposed to ignore the 1/8 spec' on the drawing? I seem to remember a discussion along these lines in another thread a while back, but a search hasn't turned up the answers. Any comments anyone?
Click to expand...

You need a P4 hinge. Here's what I did: http://www.rv8alog.com/wings/structural/s5.htm
 
I had the same issue on my -7, and I decided not to mess around with it even though it was only slightly over the limit. I ordered the P4 from ACS for something like $11... the problem was the $25 shipping! :eek:
 
That was the last time I ever called van's tech line was over that flap hinge. They denied ever hearing of a problem and said I had made a mistake. Oh well...
 
jeffro said:
That was the last time I ever called van's tech line was over that flap hinge. They denied ever hearing of a problem and said I had made a mistake. Oh well...
Click to expand...

That's odd. They are the ones that told me to order a p4 hinge. They even gave me a part number. Like you said: oh well ...
 
A couple of options?

dan said:
How are you measuring? You want to use...2D from the CENTER of the hole to the edge of the skin.
Click to expand...

Hi,
I am measuring from center to edge. Im adding .030" as per the 'suggested' practice from my Standard Aircraft Handbook.
Without the 030, I am OK, but right on the line, and as Mel says, the flap is the highest loaded control surface, (including an easy one to overload by not watching your AI)

I am tempted to either :
A: Cut the hinge, and shift each half inboard and outboard at the center to allow for the center hinge pin installation. Then redrill with a slightly larger edge distance.
B: Order a new hinge and start again. However, I dont think a P4 will fit the flap side.

C: Remeasure the Left flap (already riveted) and drill it out if unhappy with it too. Although I followed the 'same' procedure.....(lol) when I assembled and measured it. ( I suppose 030 error is due to my reading glasses? parallax?)


Chris Hepburn
RV8 Wings
 
chepburn said:
B: Order a new hinge and start again. However, I dont think a P4 will fit the flap side.
Click to expand...

Hi Chris - simples solution - you buy one chunk of P4 hinge, the length of the flap. Pull the pin, and use one half on one flap, and the other half on the other. You don't change the hinge already riveted to the flap - the hinge "loop" size and spacing are identical to what is there - you simple have a longer "flange" on the wing side.

The flap hinge is the only replacement part I had to order in my entire build - for the same reason you ran into!

Paul
 
Ironflight said:
Hi Chris - simples solution - you buy one chunk of P4 hinge, the length of the flap. Pull the pin, and use one half on one flap, and the other half on the other. You don't change the hinge already riveted to the flap - the hinge "loop" size and spacing are identical to what is there - you simple have a longer "flange" on the wing side.

The flap hinge is the only replacement part I had to order in my entire build - for the same reason you ran into!

Paul
Click to expand...

Thanks Paul,

I expect I will do that as well. However, my problems are on the 'flap' side....I haven't even got to the wing side yet.

Chris Hepburn
RV8 Wings
 
Oops - sorry Chris - I guess I was getting lazy in my reading....and I didn't have to deal with the flap side because I had QB flaps. You'll know a lot more about the process than I do by the time you're finished!

Paul
 
If you use a P4 hinge on the flap side, you will surely end up with the flap sticking aft of the aileron TE. Something dosen't sound right. I hate to say it but you might have done something wrong. If its good with the 6/32 edge distance I would go with it.

If it makes you feel better fay seal the whole thing with tank sealant. This should help reduce vibration and reduce the likelyhood of cracking. In theory at least.
 
briand said:
If you use a P4 hinge on the flap side, you will surely end up with the flap sticking aft of the aileron TE. Something dosen't sound right. I hate to say it but you might have done something wrong. If its good with the 6/32 edge distance I would go with it.

If it makes you feel better fay seal the whole thing with tank sealant. This should help reduce vibration and reduce the likelyhood of cracking. In theory at least.
Click to expand...

Hi,
I agree, that will probably put the Flap too far aft. I wasnt plannig on using the P4 for the flap side... only the wing side if required.
If I have to order another hinge, I will order another standard width for the flap side AND a P4 for the wing side.

I guess the main reason for my posting is that the plans seem to force a -very- close tolerance on the flap side hinge. There is 'room' to push the flap side hinge further into the flap before drilling/riveting it in place to increase the edge distance , but that would not be per drawings....and I expect that may be one of the contributing factors to having insufficient clearances on the wing side when I get to that part.

Chris Hepburn
RV8 Wings
 
IMHO there are probably many RVs flying that have mounted their flaps at the edge distances called for in the plans without adding .030". Heck, I don't think I could be that accurate when measuring, marking and drilling the holes. :)

I mounted my flap side hinge at the 1/4" mark and ran into trouble with the wing side and had to order the P4. I suspect this is what happens to lots of people. If I had to do it again, I would mount it closer to 3/16" (on the flap), eliminating the wing side problem, but still conforming to the 2D rule and within the dimensions called for on the plans.
 
Well, this is what I'm gonna do....

Hi,
After looking at that hinge line, and re-measuring...again...

I'm going to order another P3 hinge and a P4 hinge.
I'm going to draw a center line on the P3 and drill it onto the flap using the centerline instead of measuring from the edge.
I'm going to use a P4 on the wing side, because the P3 will be further into the flap now.

Looking at the flap I've already completed... since I drilled it according to 'plans'...that hinge is going to be drilled out and replaced. Its almost impossible to confirm the edge distance on the rivets now that it is in place.

I certainly dont want to be surprised by an asymmetic flap somewhere down the road going low and slow......

Thanks everyone for all the suggestions

Chris
RV8 wings
 
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