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  #1  
Old 08-15-2021, 03:04 PM
Michael Burbidge Michael Burbidge is offline
 
Join Date: May 2006
Location: Sammamish, WA
Posts: 697
Default Is my table flat?

When I built my 9, I discovered during phase 1 testing that one of my flaps had a twist in it that gave me a heavy wing. I ended up buying a built one from Vans, which solved my problem.

I assume the twist was due to not building on a flat table, but not sure.

Anyway before building the ailerons and flaps for my 14, I'd like to measure the flatness of my workbench?

Do you have any good tips for doing that? Do you use a level in all dimensions?
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Sammamish, WA
RV-14A Wings
RV-9A Flying 390 hours!
Last Donation: December 2020
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  #2  
Old 08-15-2021, 03:47 PM
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bjdecker bjdecker is offline
 
Join Date: Jun 2005
Location: Georgetown, TX
Posts: 876
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Quote:
Originally Posted by Michael Burbidge View Post
When I built my 9, I discovered during phase 1 testing that one of my flaps had a twist in it that gave me a heavy wing. I ended up buying a built one from Vans, which solved my problem.

I assume the twist was due to not building on a flat table, but not sure.

Anyway before building the ailerons and flaps for my 14, I'd like to measure the flatness of my workbench?

Do you have any good tips for doing that? Do you use a level in all dimensions?
You can use a laser mounted at each end to determine the high/low spots along the length/width of the table.

For smaller critical pieces, I use a remnant from a granite counter top -- my own "micro-flat"

On the work piece, another trick is to flip clecos over in alternating holes, and if you want to go truly bonkers, change the clocking of the clecos to 45° from hole to hole...
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  #3  
Old 08-15-2021, 03:51 PM
noelf noelf is offline
 
Join Date: Nov 2007
Location: Cary, N.C.
Posts: 1,256
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I believe the easiest way is to use a length of monofilament fishing line and three NEW 1/4 inch drill bits. Drive a series of nails into the lower edges of the table and run the line across the table and secure at each end. Use the drill bits to raise the line off the table, one on each end of the table. Now use the third drill bit to "gauge" the distance between the line and the table top. By moving the line between the edges you can create a matrix of patterns and look for discrepancies in the desired flatness of the surface.

Oh, and use the solid part of the drill bit for measurements and not the spiral flutes.
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  #4  
Old 08-15-2021, 04:12 PM
woxofswa woxofswa is offline
 
Join Date: Sep 2007
Location: Mesa Arizona
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Maybe I'm up in the night, but I would believe that the factory holes in the RV14 assemblies are so precise that table flatness should be a non issue. It should perfectly align itself as you cleco together with the less external constraint the better.
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Last edited by woxofswa : 08-15-2021 at 04:16 PM.
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  #5  
Old 08-15-2021, 08:10 PM
rv9builder rv9builder is offline
 
Join Date: Jan 2005
Location: Irvine, CA
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Quote:
Originally Posted by woxofswa View Post
Maybe I'm up in the night, but I would believe that the factory holes in the RV14 assemblies are so precise that table flatness should be a non issue. It should perfectly align itself as you cleco together with the less external constraint the better.
I thought this was true, too.
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  #6  
Old 08-15-2021, 09:15 PM
Michael Burbidge Michael Burbidge is offline
 
Join Date: May 2006
Location: Sammamish, WA
Posts: 697
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Of course the 9 kit is prepunched also. I wouldn’t think there is much difference between undersized and final sized in this regard.

At some point during the assembly of the 9 flap you’re instructed to weight the flap down to the table with lead shot. Maybe it is that that actually deforms the parts rather than the match drilling offsetting the final hole position.
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RV-14A Wings
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Last edited by Michael Burbidge : 08-15-2021 at 09:20 PM.
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  #7  
Old 08-15-2021, 09:26 PM
Michael Burbidge Michael Burbidge is offline
 
Join Date: May 2006
Location: Sammamish, WA
Posts: 697
Default Mute question

I was just looking at the 14 flap instructions and it looks like you construct it in a cradle like the horizontal stabilizer. So I guess my question is not as important for the 14.
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RV-14A Wings
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  #8  
Old 08-15-2021, 09:38 PM
Mlew Mlew is offline
 
Join Date: Dec 2009
Location: Northern CA
Posts: 15
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I had the same problem on my flaps of my RV8A. I had clekos in each hole and then riveted from one end to the other. Mistake. I sent all the stackup tolerance to one side and the bend occurred. Looked just like a banana!

On the replacement flap, I removed the cleko from the center of the flap and set that rivet. Now I had two halves. Removed the cleko from the center of each half and set those rivets. Now I had four quarters. Continued to set the rivet in the center of each fraction that was left. Ended up with a straight flap. All the tolerance was left in each hole and not moved to one side to cause a bend.

I now use this method in all my building. I had to rivet up the 15 foot spar for my Fiesler Storch wings and they came out perfectly straight!
Hope this helps.
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  #9  
Old 08-15-2021, 10:40 PM
Michael Burbidge Michael Burbidge is offline
 
Join Date: May 2006
Location: Sammamish, WA
Posts: 697
Default Thanks

That’s a great tip. Thanks.
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RV-14A Wings
RV-9A Flying 390 hours!
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  #10  
Old 08-16-2021, 06:22 AM
Freemasm Freemasm is offline
 
Join Date: Nov 2017
Location: Orlando
Posts: 482
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Added to Mr. Mlew's advice:

Follow that methodology. Others do every forth rivet or so. It is also helpful/recommended to not give those rivets a "full squeeze" initially. Sorry but I can't quantify this with anything measurable. The idea is to swell the rivet shanks to establish the skins relative positions versus subject the holes to the full final strain. Repeat your methodology to give them a final squeeze to the final shop head dims. Walk them down in more than two increments if you wish.

An old A&P/IA Charles Taylor award winner showed me this when rebuilding a relatively long Mooney flap (trailing edge rivets/no wedge). Came out straight as an arrow.

Best of luck.
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