8.11.5-10 Bending Longerons

Helpfully, Vans provide a full scale template of the curve/bend required and suggest making a cardboard template for accuracy. To be honest, I’ve never had much joy with the accuracy of cardboard templates but luckily I had a bit of 4mm plywood lying around so I decided to use that instead. I cut out the paper template and stuck it to the plywood. Then, using a stanley knife with new blade, I carefully followed the curve of the paper template. I repeated the cut numerous times until I cut through the plywood and had a nice template.

Earlier in the week a very kind RV builder offered to lend me their bending dies which involved a quick trip over to Wycombe airfield to collect them and swoon at their flying RV. With that in hand I felt quietly confident about getting these bends done.

The first problem I encountered however is that the longerons wouldn’t fit in the vise because various items on the workbench were in the way. I decided to relocate the vise to the portable workbench instead. Once there I then sat the dies in the vise but found that they would sink to the bottom of the vise and be tricky to keep in place. I popped a piece of wood below the dies and it was problem solved.

I then put the longerons in the dies in the vise and set about squeezing the vise until I could feel the dies touch the longerong and the felt it bend slightly. On first attempt it was clear I didn’t bend it enough. So on the second round I added another 1/4 turn of the vise handle. Unfortunately that was too much and I over bent the longeron. Not a problem as it is easily unbent by gripping it in the vise and unbending by hand. Eventually the bend matched the template perfectly.

Once the curve was bent it was time to do the sharp downward bend. This was a lot more draconian and involved clamping the longeron in the vise and whacking it with the mallet several times. Nothing too difficult though but it did make everything on the workbench ‘dance’! The last task was to twist the sharp bend so the end of the longeron was at 17 degrees. I used a large wrench to make the twist without any difficulty.

After lunch my wife joined me to help bend the right longeron. It is amazing how much easier (and more fun) it was with an extra pair of hands.

That’s two longerons bent! I’m not 100% confident that all the angles are perfect but it was pushing 30 degrees in the workshop and I was losing motivation fast. Time to stop for the day before I make a silly mistake. I popped them on the floor before I left to avoid any silly accidents overnight.

Not bad for a days work, but I think it does need another check.

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