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Forming the longerons

A

Allan Stern

Well Known Member
Friend
I am at the stage of forming the longerons for fuselage. Is ther an easier way to form them than putting them in a vise and hitting them with a rubber mallet? Are there any forms, jigs or patterns one can use? Any companies that sell them already formed or will form them for you? How was your experiences in bending them?

Thanks

2016 paid
RV 6A sold
RV 8A flying
 
Buller dies

Allan Stern said:
I am at the stage of forming the longerons for fuselage. Is ther an easier way to form them than putting them in a vise and hitting them with a rubber mallet? Are there any forms, jigs or patterns one can use? Any companies that sell them already formed or will form them for you? How was your experiences in bending them?

Thanks

2016 paid
RV 6A sold
RV 8A flying
Click to expand...

Ask around for a set of Buller Longeron dies. Easy Peasy.
http://www.bullerent.com/longerondies.htm
 
Like most builders, I approached the longerons with a sense of dread. My advice is to follow the instructions exactly, and you will be pleasantly surprised. I spent quite some time "creatively visualising" what had to be done before starting. A small workshop press was ideal for opening up the end angle. The 'preload and bend method is really quite simple and effective. Take your time and work in small increments, your technique will improve rapidly.
You are not bashing them into shape, you are easing them. A two pound dead blow hammer works a treat.
Many words have been written on the longeron subject, and after completing them, I really don't know what the fuss is all about. It is actually one of the more satisfying tasks you will tackle up to that point in the project.
Again, follow the instructions. There are some clever people at Vans.
Cheers, and have fun.
DaveH
120485
 
Longerons

The Buller dies in a vise worked for me. I was able to bend a little at a time until everything was right on.
 
Don't do it with out Buller dies.

These dies take a[look the work out of the project. Under squeeze the vice at first. You will happy you bought them
 
I've tried both the dies and the method shown in the Orndorf videos.
I found the Orndorf worked best for me.
 
Followed the Van's instructions as closely as I could (first time builder) parts came out exactly as expected. I've heard that the dies would have made it easier but they are not essential.
 
Dies

Here's another consideration.
Totally my fault but when the fuse was going together, the longeron bend didn't perfectly match the canopy rails and aft deck. Bend was a tad too shallow.
I removed the side skins and tweaked the longerons in place with the Buller Dies using a vice clamped to a jack. Only took a few minutes to get the bends perfect.
Just another point. Nothing wrong with hammer and vice.
 
Everyone has had a different experience and therefore a different perspective on this task. There are several posts here from folks who found this job not too hard with the brute force method. However my experience was different. Six years ago when I did the lomgerons there were no dies available (at least that I knew of), and as a first time builder I struggled mightily for a couple of VERY frustrating days to get them somewhere near correct. I am pretty mechanically inclined but at the time did not have any experience with forming metal components. And, just the idea of beating the **** out of a piece of my future airplane was intimidating to me.

My advice to you is to get the dies, and if at all possible engage the help of someone who has bent longerons before. Previous experience with the task is invaluable.
 
I don't get the 'brute force' description. At best I had to use what I would call a heavy but confident tap. I've heard people describing the actual destruction of bench vices. Wow. Mechanical empathy is all it takes. Obviously a cat can be skinned many ways. I almost laid down the money for a set of dies that would be used once.
Glad I didn't. Enabled me to spend that cash on fuel line tools I'd only use once:D anyway, it's only my opinion. Do what you feel comfortable with.
Cheers,
DaveH;)
 
I used the dies, it took me about 15 minutes to make them perfect! I thought I could see problems doing it by beating them into submission so never even tried to do it that way;
 
People mentioning having to beat the *&#@~ out of them, or beat them in to submission never fully understood the desired process (not necessarily their fault.... not everyone will get the same understanding after reading text instructions).

As already mentioned, the hammering part of this process does not entail the use of brute force. It is just a firm wrap to induce the bend to take a set after a bending force has been applied by hand.

Most people that give it a try find that it was a lot simpler than it seemed....
 
DaveH and Scott,

I admire the skill and fortitude of those of you who found this task possible with a "heavy but confident tap" or a "firm wrap". I am guessing you both probably had some previous experience with metal work. When I did this task back in the day I did not have that background, and it proved very difficult. That is why I can empathsize with novice builders who are inexperienced in shop techniques who come up againsnt this job for the first time.

I think it important to remember that the RV-12 kit was designed for the novice ot first-time builder. Pre-drilled perfectly fitting parts and pop rivets etc. IMHO the longeron bending is a significant challenge to that first time builder. Sometimes what seems simple and easy to someone experienced can be very hard for the inexperienced. If there is a way to ease the frustration and end up with a better fitting part by using some kind of tool, jig, die or whatever you want to call it then I think that should be encouraged.

Scott, you are correct about some people not being able to get a full understanding of the process by reading the text. Certainly that was true in my case back in 2009 or 10. If I had someone to show me the ropes, or at least a video it might have been a whole lot easier. That is why I often suggest that for a task such as this the builder try to find a mentor.

Everyone that decides to attempt to build (some would say "assemble" in the case of an RV-12) an airplane comes to the project with a unique set of background skills and experience. For those on the lower end of that scale I would recommend using whatever tools make the job easier.
 
There's another option, a good quality shrinker, like the Erco with the proper shrinking dies
erco_kick-shrinker.htm


[Couldn't link from my computer (I'm a rookie) so I linked to Fay Butler's website]
 
First time builder here with no metal work background. I'm a quick hands on learner though. Bent my -10 logerons on the vise. The longerons did need some convincing though. I started with soft hits with a rubber mallot and progressed harder until I saw a change. Then repeated the same "firm" hit till it followed the contour of the side skins. I think the key was the preload. Took about one hour to do both which included frequent checks with the skins.
 
Every time I hear someone describe building the -12 as a simple assembly process I think back to the longeron.

BigJohn said:
DaveH and Scott,

snip

Everyone that decides to attempt to build (some would say "assemble" in the case of an RV-12) an airplane comes to the project with a unique set of background skills and experience. For those on the lower end of that scale I would recommend using whatever tools make the job easier.
Click to expand...
 
Vans must have taken heed of the on going feedback from builders with the -14 longerons being pre- bent.
The only requirement is for a slight twist to be made which was simple.
I don't feel like a builder with the -14 more like an assembler. I've only had to reorder one small part so far.
I'm glad I didn't waste money on the fast build option.

Great kit!
 
Van's directions...a good heavy duty vice..some 3/4" pipe for spreading angles. Proved to be really simple.

But I have to admit, I spent much time concerned over them before getting started...hey, if you goof...new angle is cheap!!!

Go for it...you really don't need the fancy stuff😎
 
used the dies

I used a fairly large mechanical press to open up the angle, then I used the Buller longeron dies and ended up in two nicely bent longerons at the same day.
I am glad to have gone that route.
 
rvbuilder2002 said:
People mentioning having to beat the *&#@~ out of them, or beat them in to submission never fully understood the desired process (not necessarily their fault.... not everyone will get the same understanding after reading text instructions).

As already mentioned, the hammering part of this process does not entail the use of brute force. It is just a firm wrap to induce the bend to take a set after a bending force has been applied by hand.

Most people that give it a try find that it was a lot simpler than it seemed....
Click to expand...

So the "pre loading" is a bend by hand then a set with the hammer? Is that what I am not understanding? Thanks.
 
Longerons bending

Thanks to everyone who has offered help. I am not a novice at this as the 12 is my third RV, however my first two were quick build kits. Any time saving method I can find I try to utilize. I am getting the dies and if I only use them once then I have another tool. I have got a formed left longeron that still needs a little twist that the die will make better.
 
Take a look at this page
Step: 02, 03 and 04

This was easy and worked out fine.
about 1.5 hours.

http://joesrv12.com/Builder Log/bl_23_02.htm


Allan Stern said:
Thanks to everyone who has offered help. I am not a novice at this as the 12 is my third RV, however my first two were quick build kits. Any time saving method I can find I try to utilize. I am getting the dies and if I only use them once then I have another tool. I have got a formed left longeron that still needs a little twist that the die will make better.
Click to expand...
 
Allan Stern said:
So the "pre loading" is a bend by hand then a set with the hammer? Is that what I am not understanding? Thanks.
Click to expand...

The pre-load force will not produce any permanent bend, but it will be bending the longeron.
If you remove the pre-load, the angle will go back to the position it previously was.

The pre-load can be applied 24 " from the point the actual bend is desired. The wrap with the dead blow hammer close to the vise is what converts the pre-load into a concentrated bend at the end of the vice jaws.

It has been a while since I bent any longerons but my guess would be that at 24" the desired pre-load deflection would be on the order of 1".

For the sharp bend at the aft end of the longerons (which the bending dies wont do), you can just keep repeating the same bend process as used to make the curve.... keep making small bend increments in the same spot without re-positioning, until you have the desired angle.
 
That is what I did.

Allan Stern said:
So the "pre loading" is a bend by hand then a set with the hammer? Is that what I am not understanding? Thanks.
Click to expand...

Many people acted like this was a big deal, made me procrastinate on bending the rail. I just applied a slight bend by hand and then set it with a rubber mallet. I spent more time marking the location of where to start and end the bending than I did to bend the rail (along the line of "measure twice -cut once" ;-). I place blue painters tape on the the angle to keep from marring up the aluminum, that worked well. I was worried about the non symmetrical aluminum angle not bending uniformly, but that was total folklore, no issue at all. The is a very gentle bend, noting drastic. Remember that you do not have to bend it all in one pass. Bend it some on the first pass, compare to the interface template and then bend more as needed.
Good luck!
 
Bending

joedallas said:
Take a look at this page
Step: 02, 03 and 04

This was easy and worked out fine.
about 1.5 hours.

http://joesrv12.com/Builder Log/bl_23_02.htm
Click to expand...

Thanks for the web site. It helps. So you used an arbor press to open up the 5.4 degree longeron before you twist it back to level. I see you used a scrape piece of angle on top and a "pipe" inside the channel during the pressure of press. What size pipe did you use? Thanks.
 
My experience was that it helped to have a friend apply the pre-load and then I applied the dead blow hammer. Recommend that the pre-load helper wrap the longeron in heavy gloves or towels. Otherwise that first heavy hit is a real zinger on the hands!
 
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