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RV-12 longeron help.

S

scberry

Member
I am in Wichita, KS. I am at the point in the construction of the fuselage where I need to form the longerons. I have had NO luck doing this so far with the equipment that I have. Can someone in the area who has already passed this hurdle give me a call with some help/advice?

Steve Berry
120154
316-641-9434
 
See my build log. It details what I considered and tried. Ended up bending them by hand in a 8" bench vise. Just take it very slow!
 
Steve,
I'm not close enough to help you but here is a pointer to my build log, where for this day and the next few I battled the dreaded longerons: http://www.mykitlog.com/users/displ...hn&project=639&category=4746&log=88883&row=44

If you can find someone local to help you that will be of tremendous value. It's all about experience, and when you have to struggle through by trial and error it is tough. My advice is to assemble all the side structural members and the skins with clecos before you rivet anything. You will end up taking the longerons on and off multiple times, each time getting them closer to the ideal shape.

Good luck. This is the hardest task in the kit, and once you get past it, it is all downhill!

Best, John
 
And more logs;
Longeron page1

Longeron page 2

I found the idea with the vise and fitting on Marty's site and it works much more controlled than the hammer method. Marty was unlucky with this method but with my vise it worked great.
I used a steel vise (not a cast iron one) and a 3/4' fitting to open the angle. I had a cast iron one but that broke.
For the bend I used the vise, my hands and a rubber hammer.
Took me about 5 hours to complete.

Good luck!
 
Last edited:
RV-12 Longeron Help

There are three challanging tasks during hull construction of the RV-12. They are in my opinion the longerons, the fuel tank and canopy. I have found the canopy most difficult and the longerons the easiest of the three. They all require reading more than once and understanding the instructions before starting.

You will need a minimum of a 6" vice with padded jaws and a small sledge hammer ~3lb. After you trim the longeron to length you should have two pieces of scrap angle. Use one of these, shortened to a convenient length, as a sacrificial piece to hammer on when opening the angle of the longeron.
Make the bends in the longeron by pulling it by hand in one inch increments. You may not think you are making any progress, but you'll be surprised. You may even over do it. Just bend it back. It will distort 90 degrees to the bend. Just correct the bend by turning the angle in the vice and correcting the bend.

The longerons are critical to the future assembly of the fuselage, so accuracy is important. They provide strength to the fuselage and many additional part are attached to them. They will be on and off the fuselage several times before you get a satisfactory fit, so be patient.

Happy building,

Art Pennanen
 
I USED A BEARING PRESS TO OPEN THE ANGLE. IT WAS EASY AND VERY PRECISE. THEN A VISE AND RUBBER HAMMER FOR THE BEND. JUST TAKE YOUR TIME!!
 
Longeron help

Thanks to everybody for the help with the longerons. I contacted four or five local shops for help but none were interested in trying to form the longerons. I finally contacted a friend who refurbs airplanes an he and I finally got the job done in his shop. We used his 2 ton mechanical press to open the angle at the front end, and used the "armstrong method" for the curve and the 4 degree bend at the aft end. They fit in the fuselage about as good as one could expect. The ends curled up a bit when formed and required a bit of tweeking but all-in-all pretty good I think. To any new builders: I would not use the blacksmith (hammer) method described in the plans, not enough control.

Thanks again to all for the help and pictures.
 
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