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Bending F-1046 Longerons, Page 29-2

B

Bushwhacker

Active Member
Working on fuselage page 29-2, step 3, bending the F-1046 R & L longerons.
Following step 3 instructions, I have no problem matching the horizontal bend with the F-1046B longeron bending template. My problem is I am introducing an "out of plane" vertical bend during the horizontal bending process.
I followed the instructions about turning the longeron 90 degrees to straighten, but when I do that, the horizontal bend is reduced, requiring me to repeat the horizontal bending steps again.
I carefully check the longeron in the vise to be sure it is "square" but the vertical bending keeps occurring. After several attempts, decided I need help.
I checked the forum, but was not able to find any info. Am I the only one having this issue?
What am I doing wrong, and how do I correct it?
Thanks in advance for your help.
 
Sounds normal to me. Back and forth, back and forth until it's right. Each iteration gets a little better.

It took me 4 hours to bend those longerons. Then I managed to mess something up while match drilling a gusset to them (you drill from underneath) and I had to do them both again. And yep, it took another 4 hours.

When you get to the point of match drilling the gussets, I recommend clamping them good and tight and remove the skins enough to get access with a long drill bit. The other option will be to match drill with the skins in place. You'll need a 90 degree drill and a mirror.
 
Pretty much what Joe said

Yep, similar story here, at least a couple of hours of banging them back and forth until I got the curve right and flat with no twist. The folks at Van's told me that bending the longerons is easy, so I guess I'm just not very good with a mallet, but it took me a lot of work to get them right.
 
Thanks guys,

Guess I've become spoiled. Got used to CNC machined parts and predrilled holes. This is a far cry from that technology. Back to the hammer and vise.
 
If you know someone who has a stretcher/shrinker, it can ease the process, though you have to spend a little time cleaning up the tooling marks afterward.
 
The L/R longerons are different lengths on the RV-10 (that pesky baggage door), but if you take care to make sure you have the front ends of the longerons matched then bending them together should work. On the other hand, a mistake would be costly. I bent my RV-6A longerons together. I felt more comfortable following directions and bending the RV-10 longerons separately.
 
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