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-   -   Bending The Longerons (https://vansairforce.net/community/showthread.php?t=182454)

RudysRV7 05-14-2020 02:04 PM

Bending The Longerons
 
The fuselage kit will be order in a few months. I am dreading, bending the longerons. Sine I have the AA6-125 longeron angles, is there any reason that I could not work on that now?
I would have to print the PDF template out, since I don't have the physical plans yet. But other than that....

Thoughts? PS. I may call Vans, but like to jump on this forum as well.

Cheers

Robin8er 05-14-2020 02:22 PM

You can do it now. Its intimidating, but once you start you'll see that it's really not that hard.

Just clamp in a vice, apply downward pressure and hit it with a rubber mallet, then measure. If it twists use a wrench to straighten it out. You'll go through the process a few times, but eventually it will be bent correctly.

RudysRV7 05-14-2020 02:25 PM

Thanks Robin8er.

PilotjohnS 05-14-2020 02:29 PM

Dies
 
I borrowed some dies and it was really easy to get a precise bend. Now after the fuse has been assembled, I realized how important it is to get this right; I would recommend you borrow a set of the dies.

But i too stressed about this, but it was straight forward and not worth the grief.

terrye 05-14-2020 02:33 PM

Bending The Longerons
 
Bending the longerons is not something to dread. My solution was to take a hydraulic bottle jack (10-20 tons would do) and build a poor man's press using angle iron at the bottom and top connected with readi-rod and nuts. I clamped both longerons back to back, and made a hardwood "bending shoe" (with a slot in the middle for a close fit around the longeron flanges) to fit over the jack ram. At the upper end, the two cross bolts of the angle irons had pipe around them as spacers to these served as the other two contact points of the longerons. I used the full size drawing of the longeron curve to make an aluminum checking template. Using the hydraulic jack made it very easy to "creep up" on the amount of curvature without kinking or overbending. Yes you can print the PDF drawing out by taking it to a blueprint place, just be careful to check that the final scale is right.

Of more importance, and a PITA is the "sharp downward bend" that you have to put in the longerons to match the side skins on assembly to the front fuselage. This was where I reverted to the dead blow hammer suggested in Vans instructions. Each longeron was clamped individually to the bench, the initial bend/twist was put in by hand, but the final "sharp" part of the bend was with the dead blow hammer. It really took some hammering to get this profile right. Again, the top profile of the side skins is the guide here. If you don't get a sharp bend in the longeron, you may find the rivet pattern has insufficient edge clearance in the longeron flange, so it pays to keep checking this before calling it "good".

PhatRV 05-14-2020 02:57 PM

The bending of the longeron was one of the the easiest task in my RV8 built. They came out perfect from the bench vise. I think the all the noise about this operation was caused by people making the mistakes when they bend in the wrong direction and ruined their longerons.

What I did was to buy a couple of short length aluminum angles from Home Depot, about 12" long. Mark these LEFT template and RIGHT template.

From the drawings, transfer the directional arrows from the plan to the LEFT and RIGHT template and mark with "ARROWS" with left/right/up/fwd depending if the template is on the LEFT or RIGHT.

Transfer this directional template to your longerons so you will not bend the real longerons the incorrect direction. The process of bending the longerons is a simple whack of a hammer. You will arrive at the correct angle mostly with one strong blow or a couple of softer blows of the hammer.

rapid_ascent 05-14-2020 03:10 PM

I used the dies and it really isn't that hard. I actually did them twice as a few other folks have done. A big Cresent wrench helps with the twisting too.

Draker 05-14-2020 03:58 PM

Make sure you measure right and do the bends at the right spots or you will end up like me: http://www.vansairforce.com/communit...d.php?t=167360

wirejock 05-14-2020 07:07 PM

Longerons
 
Lots of ways to skin that cat as others mentioned but make sure the bend is in the right place and matches the part like the canopy deck and tthe down slope of the forward skin. The paper is handy but you won't be riveting the paper.:D

RudysRV7 05-17-2020 11:50 AM

What is meant by "set of dies"? Interested.


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