Aluminum Stringer

[Helicopter D]

Does anyone know how to duplicate this bend on the aluminum style stringers? I have tried several types of metal benders but it just seems to flatten out.

[Hank Jarrett]

Re: Aluminum Stringer

It was probably done with a set of rollers that matched the outside and inside of the profile. The three rollers have the outside ones fixed and the inside one can be tightened between them with a screw pushing he shaft. It is pretty easy to make fora factory where you will use it every day, but a lot of work to make for one plane. You might try making the rollers from wood like Maple on a laith, but they won't last for many stringers. I need to look for a picture of the kind of tool. It looks a lot like a tube rolling bender.

Hank

[Bird]

Re: Aluminum Stringer

I remember a shop teacher back in the 70's that was working on a pvt project and I will try to explain what I remember.
He used several pieces of plywood cut and screwed together in the shape of the inside radius, then he used some bags filled with small shot (I believe)- long bags not just a sandbag type of setup- these were from 1 inch to 2 inches in diameter that he placed on the outside of the piece and he pressed against them, if I remember right I thing he also said something about using a bench press at some point and also about not going fast and being able to reset the bags as needed.
I hope that this helps or maybe someone else can build up on this message.

[Robert Lees]

Re: Aluminum Stringer

For some reason this thread was locked; I've unlocked it.

Rob

[astjp2]

Re: Aluminum Stringer

Why build when you can buy them? It makes it legal...and saves so much time...Tim

[Hank Jarrett]

Re: Aluminum Stringer

I think he already has them, he just needs to put the curve in the ends. I think he implied the metal ones are shipped straight.
Hank

[Helicopter D]

Re: Aluminum Stringer

I have taken a section of stringer to a local machine shop and they are making a set of dies for my roller, should be done this week, I will update if it works or not.

[Bird]

Re: Aluminum Stringer

Yeah that will work too!

[astjp2]

Re: Aluminum Stringer

You have 2 problems, one is getting the dies made to compensate for the spring back in the material. The second is getting the correct material and getting it approved, if its being manufactured, you will not get them approved through an owner produced part if you actually notify the faa for a field approval because its still being made by an FAA PMA. Tim

I have taken a section of stringer to a local machine shop and they are making a set of dies for my roller, should be done this week, I will update if it works or not.