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  #1  
Old 01-20-2013, 12:54 PM
JimMac JimMac is offline
 
Join Date: Jun 2012
Location: Madison, AL
Posts: 67
Default RV-12 Longeron Forming

I'm about to start the twisting and bending required to fabricate the RV12 longerons. I've read some horror stories about how difficult this step is. Has anyone devised a slick method that reduces the time and effort while maintaining accuracy? Has anyone tried using a small hydraulic jack in some kind of jig to produce the bending pressure rather than pounding it with a small sledge hammer? Thanks for any tips on this subject.
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  #2  
Old 01-20-2013, 01:31 PM
RFSchaller RFSchaller is offline
 
Join Date: Oct 2010
Location: Phoenix, AZ
Posts: 2,820
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I used a sledge hammer on an anvil to spread the angle. Cut a paper angle template for use to check the angle as it spreads. The curve was done with a vise by hand using a template made from the canopy ledge. It's not as difficult as it originally sounds.
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  #3  
Old 01-20-2013, 01:32 PM
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joedallas joedallas is offline
 
Join Date: May 2010
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Default Longerons from AA6-125 X 3/4" X 3/4"

See
www.joesrv12.com/Builder%20Log/bl_23_02.htm

Went good for me
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  #4  
Old 01-20-2013, 01:37 PM
RFSchaller RFSchaller is offline
 
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Wow! Wish I had seen this before I did mine. I got mine done, but the use of an arbor press is certainly a more controlled approach than Thor's Hammer!
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  #5  
Old 01-20-2013, 01:46 PM
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Bill_H Bill_H is offline
 
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Location: Marshall TX (KASL)
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See here: "A longeron success story" http://www.vansairforce.com/communit...ad.php?t=69024
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  #6  
Old 01-20-2013, 01:53 PM
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Gagarin737 Gagarin737 is offline
 
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Another longeron story



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  #7  
Old 01-20-2013, 04:57 PM
DHeal DHeal is offline
 
Join Date: Sep 2006
Location: Windsor, California
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I had no success with the big hammer approach. I used a good strong polished socket and a medium-duty vice -- that worked very well. A big padded left-handed Crescent adjustable wrench also proved useful for the twisty parts. Don't trim the supplied length of aluminum angle to length until you have successfully spread open the end -- that way, if you mess up the initial spread, you can still try it again. It's kind of a Zen thing.....
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  #8  
Old 01-20-2013, 07:04 PM
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MartySantic MartySantic is offline
 
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See my builder's log. Not hard, but it takes some time.
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  #9  
Old 01-21-2013, 08:51 AM
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WingedFrog WingedFrog is offline
 
Join Date: Mar 2010
Location: Raleigh, NC
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I used Larry Buller's longeron die:
http://www.bullerent.com/experimental.htm
Quite happy with the way it worked. Still have the die in my shop if anyone is interested send me a PM.
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  #10  
Old 01-21-2013, 09:29 AM
FredC FredC is offline
 
Join Date: Nov 2010
Location: Shalimar, Florida
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Default Longeron Forming

JimMac,

You will find several posts in "Search" under Longeron Bending. The ones most helpful to me were the descriptions of the "Orndorff Method." I used it and it worked great. No hammering required to bend the Longerons. They are both bent at the same time, come out identical, and have no twist. Only takes a few minutes. Here is a summary of the Orndorff Method.

1. Mark a series of lines about every inch along the bend and label them 1, 2, 3, etc. This is so you can see where to add or subtract bend when compared against the template.

2. Put about 6 strips of duct tape, one over of the other, on the top and side of each vise jaw. Just cut a strip of tape, place on the top then bend down over the jaw face. The tape is to prevent dents to the Longeron flanges.

3. Bend both Longerons at the same time using the following method.
a. Clamp the flanges of the Longerons securely together in a "T" configuration. I used "C" clamps.
b. Place Longerons in a vise with the "T" shape down.
c. Leave vise loose enough to slide the Longerons.
d. Push down on Longeron on each side of the vise to bend some curve. Unless you are really strong, a person pushing down on each side works best
e. Slide the Longeron a few inches at a time and keep bending. Lift Longerons from vise frequently and check bend with template. If a "C" clamp gets in the way of the vise just move it.
f. If you over bend, just turn Longerons over and take out the overbend.

4. I only had a 5" vise and was afraid it might break if used with a socket to squeeze open the 90 deg. angle. I cut off about a 4" piece of Longeron, put it on top of the end to be opened, and I hammered on the cut-off piece using a small sledge hammer and anvil. That worked but did take a bit of pounding.

Cordially,
Fred Carnes
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