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flap brace cs or dimple?

tyvaf01

Member
does the flap brace receive dimpled or cs holes where it matches the hinge?
I think it is not allowed cs or dimple the hinge as I have recently seen
at one builders log blog!the instructions not really mention it.
 
One of each

I found the same on my -7 when I built the first wing I dimpled so just counter sunk the hinge to allow. On the second wing I changed and counter sunk the brace. Really it makes no difference. I wouldn't however flatten and then countersink.
Countersinking the hinge is just a little more tricky.

Cheers

Peter
 
The skin gets dimpled, the brace gets c-sunk and the hinge half gets neither.


Think about it, why would you want to have to make the .040 brace dimples fit in a c-sunk hinge when if you c-sink the brace all it has to fit is the thinner skin dimples. Plus the c-sunk part gets sandwiched between two non-cs'd parts.
 
Old thread, but some more info:

Vans recommends that after this not uncommon slip up (dimpling the flap brace), you can flatten the dimples (once), then countersink them. This is what I did. It was a hassle to do this, but I wanted it to be right. My wife had to help pry the brace away from the skin to give me access for countersinking since the brace was already riveted to the wing spar.

Another option Vans says is acceptable is to countersink the hinge and back it up with a strip of .025 sheet.
 
I followed the plans be apparently still did it wrong

Reviving this old thread yet again.

I'm at the point where I'm ready to attach the flaps to the wing, but I can't find any instructions on how to accomplish this (other than the choice of hinge pin methods). As I started digging around here on VAF for info, I discovered many builders countersunk their Flap Brace rather than dimpled it. I dimpled mine per this statement on p 7-9 of the plans:

Drill, deburr, dimple where required, and rivet the W-721 flap brace (DWG 14A) to the rear spar.

The forward side is riveted to the rear spar with standard rivets, and the only other holes in the brace are the aft ones that attach to the bottom skin, sandwiched between it and the hinge for the flap. If these holes aren't the ones that should be "dimpled where required," then what holes is this instruction discussing?

Did I miss a secret message somewhere to disregard the plans for this step and countersink instead, or did I misread the instruction?

Also, I can't find any instructions on how to mount the flaps as far as alignment. DWG 9A shows a 1/4" gap between the aileron and flap, but that's all I can find. I presume they should be even with the trailing edge of the aileron, but I can't find that written anywhere. The section titled "Attaching Flaps to the Wing" only discuss two options of securing the hinge pin. I've spent all evening scouring the plans and drawings for clues, but I can't find anything else. Can someone point me in the right direction?

Thanks!
 
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Flap brace

If the flap brace hasn't been riveted to the spar, do as mentioned earlier in the thread. Dimple the skin, countersink the cooresponding holes in the flap brace.
At this point, the hinge has not been drilled so here's a trick I learned on VAF.
Install the aileron aligned properly with the tooling holes on the outboard rib and install the aileron bell crank alignment jig. Lock it all down so it can't move.
Install the wing side of the flap hinge to the flap.
Grab a bunch of long #3 rivets. Twice the length called for. One at a time, gently squeeze them enough to fit snug in the row of holes in the skin/flap brace. They need to fit snug but not so tight they can't be pulled out with a pair of pliers. Each should be flush to the bottom side of the flap brace so the hinge can lay flat against the brace. Every other hole should be enough to keep the skin/flap brace together and aligned.
Now gentlt clamp the flap with hinge where it belongs. Move it till it's perfectly in line lengthwise with the aileron and 1/4" gap between aileron and flap. Lock it down. Take your time.
Now get a helper and a backing stick. Helper holds a stick against the flap hinge while the hole is match drilled from the skin side. Drill the open holes #41. Insert clekos as you go. Go back removing the fat rivets, drilling #41, inserting clekos till all the holes are drilled. Go back and ream #40. Keep 100% clekos in place so it can't move.
Easy peasy.
 
Unfortunately, my flap brace and bottom skin are already riveted in place. I followed the plans which lead me to dimple and then rivet them both in sequence. However, now I'm realizing the challenge with locating the hinge using this method. I'm not sure I could remove the flap brace without damaging the rear spar at this point because I don't have good access to the inside of the rear spar to back the shop heads.

Thanks for the tips on locating the flap.
 
Unfortunately, my flap brace and bottom skin are already riveted in place. I followed the plans which lead me to dimple and then rivet them both in sequence. However, now I'm realizing the challenge with locating the hinge using this method. I'm not sure I could remove the flap brace without damaging the rear spar at this point because I don't have good access to the inside of the rear spar to back the shop heads.

Thanks for the tips on locating the flap.

So if I understand correctly, you dimpled the bottom skin AND the flap brace - is this correct?

If so, DO NOT countersink the flap hinge as the fix. The hinge material is too soft to take the countersink and you risk the shop heads pulling through the knife edge - and loosing the flap.

As you have the bottom skins on, removing them to fix the flap brace would be a pain. Here is one approach - but I recommend you check with Van?s to make sure:
- Drill out the bottom skin to flap brace rivets that you installed.
- Cut a two pieces of .032? aluminum 1/2? wide that is the same length as teh flap hinge.
- Use clamps to hold this piece of aluminum to the bottom skin so you can use the bottom skin as a template. Drill the holes.
- After drilling, take the piece of aluminum and machine countersink the holes to accept the flap brace dimple. The flap hinge will then go on top of this piece of aluminum.
- Drill out the hinge rivets on the flap. You need to add the second piece of .032? aluminum between the flap spar and the hinge. You need to do this so the flap height is the same with the wing.
- As the flap spar is already countersunk, do not countersink this piece of aluminum that goes between the flap spar and the hinge.
- Hang the flap as discussed above.

I hung the flaps on my RV-8 project a few days ago. While I agree the instructions can be better, I recall somewhere they tell you to couintersink the flap brace.

Carl
 
Thanks Carl. Yes, the flap brace and bottom skins are both dimpled. My bottom skins are riveted to the wing ribs and both spars, but they aren't riveted to the Flap Brace yet.

There's a note on DWG 14B to "Dimple FL-802PP [Flap Skin] and machine countersink FL-803PP [Flap Spar]" but if there's a similar note about the Flap Brace, I missed it. The instruction to "Drill, deburr, dimple where required, and rivet the W-721 flap brace (DWG 14A) to the rear spar" were pretty clear, so I did exactly that when I got to that step.

Any idea how Van's expects builders to mount the flap when they follow the plans for this step? Your solution is a good idea that I hadn't thought of. I was considering just dimpling the hinge and riveting it together.

You're really making progress on your build! I'll have to stop in and see it next time I'm on the field.

Rob
 
Dimpling the hinge is not an option. Still recommend a call to Van?s before proceeding.

Come by the Dogwood Aircraft production site whenever you want.

Carl
 
Another option that might be easier and does not require taking the hinge off the flap:
- Mount the flap to the wing as discussed above.
- Use the now drilled hinge as a template to drill the holes in the 1/2? wide .032? aluminum strip.
- Machine countersink the holes in the hinge to accept the dimples in the flap brace.
- Use the non-dimpled and non-countersunk aluminum strip as a backing to the hinge rivets.

Here even though you countersink the hinge, you are adding a backing strip to the hinge to hold the rivet. So the hinge ends up sandwiched between the flap brace and your added aluminum strip. As you did not change the height of the hinge relative to the wing, you need not change the hinge attachment on the flap.

Carl
 
My recommendation is similar to Carl's but less steps.

Fit the flaps and match drill the holes in the hinge.

Remove the fwd hinge half from the flaps.
Cut some .032 thick strips (preferable on a metal shear so that they are straight and flat) the same length and width as the flange on the hinge.
Match drill the doubler strip using the hinge.
Machine countersink the hinge
Rivet together with the hinge sandwiched between flap brace and the doubler strip.
 
Did I miss a secret message somewhere to disregard the plans for this step and countersink instead, or did I misread the instruction?

You didn't miss anything, but this is a first indication of how sparse and even miss-leading the instructions can be from now on!

In your position with the bottom skin riveted on I would go ahead and just plan on countersinking the hinge and using a backing strip as suggested earlier in this thread. You don't really need the partially set rivet trick, if the lower flange of the brace was correctly adjusted then the skin dimples should nest into the brace dimples and will be held sufficiently in alignment. I have just today updated the photo links in my build thread on this, see here:http://www.vansairforce.com/community/showthread.php?t=109734&page=7

Having your brace dimpled will make it slightly more difficult to clamp the hinge but it should still be doable.
 
Thanks for all the advice and input. I ended up countersinking the flap hinge and adding a backing strip. I'm happy with the results.

Rob
 
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