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  #1  
Old 06-29-2021, 02:04 PM
N8DAV8R N8DAV8R is offline
 
Join Date: Apr 2007
Location: Salida, Ca
Posts: 91
Default One More Longeron Thread

The topic of opening up the longeron is a recurring one and there seems to be a variety of approaches and varying success. I know that before this step I read a lot of different ways to go about it. The HF hydraulic press seems to be a popular way to go and I have that tool, but ended up doing something different. My opinion is that this approach offered more control and it ended up being really easy. I'm just posting here to add one more data point for future builders approaching this step.

We stuck with using a good strong vice. Instead of the socket in the KAI, we used a 3/4" pipe coupling per the published wisdom of other builders. Alignment of the vice jaws with the angle stock and the coupling is key to getting nice easy bends. The vice jaw pictured is available on amazon, you want the style that will hold a round part horizontally. We put the plastic jaw in place, tightened to capture the coupling, then tacked the coupling down with a silicon bronze tig braze. No flying sockets, no slipping longeron...just easy progressive squeezes down the length.

I also 3D printed a gauge to confirm the deflection but I threw that away before taking a pic. If anyone cares about this part reply or DM and I'll provide the file. Easy enough...it's just the correct angle with a round back and 1 3/4" long to slide along the longeron and get a good visual reference for the angle and taper.
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  #2  
Old 06-30-2021, 05:23 AM
MDeCraene13 MDeCraene13 is offline
 
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Location: Asheville
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Do you have a part number for the vice jaw?
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  #3  
Old 06-30-2021, 07:49 AM
N8DAV8R N8DAV8R is offline
 
Join Date: Apr 2007
Location: Salida, Ca
Posts: 91
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Quote:
Originally Posted by MDeCraene13 View Post
Do you have a part number for the vice jaw?
Here is the jaw we used...

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
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  #4  
Old 06-30-2021, 08:36 PM
rv9builder rv9builder is offline
 
Join Date: Jan 2005
Location: Irvine, CA
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Quote:
Originally Posted by N8DAV8R View Post
We stuck with using a good strong vice. Instead of the socket in the KAI, we used a 3/4" pipe coupling per the published wisdom of other builders.
What's the advantage of the pipe coupling over the socket? Was there a thread about this on VAF? I must have missed it.

Thanks
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  #5  
Old 07-01-2021, 07:24 AM
N8DAV8R N8DAV8R is offline
 
Join Date: Apr 2007
Location: Salida, Ca
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Quote:
Originally Posted by rv9builder View Post
What's the advantage of the pipe coupling over the socket? Was there a thread about this on VAF? I must have missed it.

Thanks
Good question, and not something I recall now or could answer clearly...at least with respect to the actual squeeze. I'm not sure if I saw it on VAF but it popped up on a couple of the popular blogs or build sites. Maybe it's just a case of monkey-see-monkey-do. I did find that when I used the socket recommended in the KAI it took quite a bit of force to get very little deflection. Larger sockets were a little better. I think the coupling is just a good sweet spot in terms of diameter and length and for me it did seem to flare a little easier when doing trial runs.

As far as the coupling goes, there are different styles of coupling. It seems obvious, but worth mentioning that you want the type that is just smooth around the outside. I think that these are typically stainless steel, mine was.

I do know that at least in this application, I'd rather keep sockets in the socket drawer for their intended use and 'sacrifice' a coupling. Once the job was done it took just a few seconds with a grinder to remove and it was left a little messy. I tossed it in with the misc. airplane tools so I'll have it for the next build.
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  #6  
Old 07-01-2021, 07:34 AM
Bob Y Bob Y is offline
 
Join Date: Jul 2017
Location: Piedmont, SC
Posts: 287
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Looks like a coupling for 3/4 rigid galvanized steel (RGS) electrical conduit.
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  #7  
Old 07-01-2021, 08:26 AM
N8DAV8R N8DAV8R is offline
 
Join Date: Apr 2007
Location: Salida, Ca
Posts: 91
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Quote:
Originally Posted by Bob Y View Post
Looks like a coupling for 3/4 rigid galvanized steel (RGS) electrical conduit.
Looks like it, but mine is not an RGS coupling. The coupling I used is for pressurized/vacuum plumping for fuel, water, etc. None of that matters as far as squeezing in a vice of course, so an RGS coupling may serve well for the same purpose.

As a personal choice, I'd rather not be lighting up the tig on galvanized material so I think the stainless coupling is a better choice. Amazon will deliver it for $8. That makes it a cheap airplane tool in my book.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
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  #8  
Old 07-01-2021, 02:35 PM
rv9builder rv9builder is offline
 
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Location: Irvine, CA
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Thanks for the info, Nate!
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