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  #1  
Old 11-20-2012, 02:47 PM
tyvaf01 tyvaf01 is offline
 
Join Date: May 2012
Location: PATSCH TIROL
Posts: 19
Question flap brace cs or dimple?

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.
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  #2  
Old 11-20-2012, 05:46 PM
smiller smiller is offline
 
Join Date: Feb 2008
Location: Hillsboro, Oregon
Posts: 102
Default Countersunk

It would appear that it should be countersunk, which I discovered after dimpling. :-( I'm building a -7A and the manual is definitely lacking in this area! But see for example http://www.vansairforce.com/communit...ad.php?t=63964. I will probably do as written there and flatten out my dimples and countersink.
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  #3  
Old 11-21-2012, 02:53 AM
kiwipete kiwipete is offline
 
Join Date: Oct 2007
Location: Birmingham United Kingdom
Posts: 367
Default 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
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  #4  
Old 11-21-2012, 09:11 AM
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briand briand is offline
 
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Location: Grand Rapids MI
Posts: 741
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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.
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  #5  
Old 01-05-2013, 12:42 PM
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grayforge grayforge is offline
 
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Location: Kirkland, WA
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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.
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  #6  
Old 10-26-2017, 09:43 PM
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Nihon_Ni Nihon_Ni is offline
 
Join Date: Jun 2011
Location: Fredericksburg, VA
Posts: 213
Default 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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Tail kit completed on Feb 8, 2012 (180 hrs)
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Last edited by Nihon_Ni : 10-26-2017 at 09:53 PM.
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  #7  
Old 10-26-2017, 10:17 PM
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wirejock wirejock is offline
 
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Location: Estes Park, CO
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Default 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.
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I cannot be, nor will I be, held responsible if you try to do the same things I do and it does not work and/or causes you loss, injury, or even death in the process.
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  #8  
Old 10-26-2017, 10:23 PM
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Carl Froehlich Carl Froehlich is offline
 
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+1 on what Larry said.

Carl
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  #9  
Old 10-27-2017, 05:42 AM
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Nihon_Ni Nihon_Ni is offline
 
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Location: Fredericksburg, VA
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Default

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.
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真喜志友幸
RV-8 under construction as of Sep 30, 2012
Tail kit completed on Feb 8, 2012 (180 hrs)
Wing kit mostly completed, fuselage under construction as of March 6, 2014 (750 hrs)
Paid up for 2017
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  #10  
Old 10-27-2017, 10:53 AM
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Carl Froehlich Carl Froehlich is offline
 
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Location: Dogwood Airpark (VA42)
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Default

Quote:
Originally Posted by Nihon_Ni View Post
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
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