What size dowel for folding trailing edges?

[danielhv]

Working on folding the elevator trailing edges... I've heard some ppl using 1/8" dowels, and some using 1/4" dowels... which do I need to buy?

[RV8N]

Originally Posted by danielhv

Working on folding the elevator trailing edges... I've heard some ppl using 1/8" dowels, and some using 1/4" dowels... which do I need to buy?

I tried to use the dowel but it didn't seem to help.

My favorite way to bend the trailing edges is with a seamer made out of vise grips. I adjust the seamer fairly wide and gradually clamp it to the trailing edge, working my way down the length. Gradually adjust the seamer a little tighter and repeat until the end ribs slide in and are making contact with the skin.

Karl

Now in Sandpoint, ID.

[FredMagare]

A 1/4" dowel will give you a 1/8" radius on the traling edge. (go smaller and you may crease/crack the trailing edge.) Tape it in position so it doesn't move away and apply gentle/even pressure with something like a straight 2x4 or piece of aluminum angle. (originally learned through construction of an RV-6 emp.)

Good luck!

[Hawkeye7A]

I got a nice straight piece of 2 x 8 lumber, trimmed it to the length needed for the control surfaces (can't remember how long, been awhile) and had a friend with a good table saw rip it down the middle. I fastened the two halves together with three heavy hinges. I then drilled a few crossholes through the lower half to bolt it to the edge of my bench with the split flush with the benchtop. A couple of vertical holes partway into the top of the upper piece to allow me to stick a couple of steel rods in to give me levers to apply the breaking action. Didn't use dowels and just added a bit more bend until the ribs slipped in and just touched the skin. Took longer to write this than it did to fabricate the tool. Hope this helps.

[osxuser]

Originally Posted by Hawkeye7A

I got a nice straight piece of 2 x 8 lumber, trimmed it to the length needed for the control surfaces (can't remember how long, been awhile) and had a friend with a good table saw rip it down the middle. I fastened the two halves together with three heavy hinges. I then drilled a few crossholes through the lower half to bolt it to the edge of my bench with the split flush with the benchtop. A couple of vertical holes partway into the top of the upper piece to allow me to stick a couple of steel rods in to give me levers to apply the breaking action. Didn't use dowels and just added a bit more bend until the ribs slipped in and just touched the skin. Took longer to write this than it did to fabricate the tool. Hope this helps.

Yep, I did the same, per the plans. Pics at RVproject.com too...

[chunt0]

My 7 drawing 4PP says the elevator trailing edge radius should be 3/32, and that certainly appears to be an outside dimension. Because of metal thickness and springback, a 3/16 diameter dowel magically held in position (dowels will want to squirt out) won't let you get a radius as tight as the drawing calls for. a 1/8 (4/32) diameter dowel should allow you to get there, but over squeezing is bad news. Too tight a radius results in a weak structure, increases the risk of cracking, and makes it more likely you will end up with a crooked trailing edge.

My drawing 5PP shows a radius of 3/32 for both the elevator and rudder (early, bent trailing edge rudders).

My drawing 7PP shows a radius of 1/8 for the same early rudder--Van's can't be accused of making things restrictively consistent for us. I take this to mean they are comfortable with anything between the two numbers, but a call to them would never hurt.

My aileron instructions say to use a radius of 3/32 to 1/8. My aileron drawing seems to show a 1/8 radius.

I made a simple go-no go gauge from a flat piece of aluminum. It has two notches. One notch has a 3/32 apex radius, and the other has a 1/8 radius.

Make sure you have a very flat surface leading up to the trailing edge. Another hint is to make sure your bending brake surface is as flat as possible.