[bugerdup]

I picked up this aluminum cowl online and I would like to add a radius to the front inner lip. What could I do, I have allot of idea's in mind but I could use some more. thanks.

[roscoe]

For what it's worth, a lot of radial engine cowls used aluminum tubing riveted onto the cowl as a lip. TRhe DC-3, and Beaver spring to mind, as well as lots of others.

[bugerdup]

That was at the top of the list. I was thinking of taking it to a metal fab shop and have them tig weld a tube to it. I think that might be the way to go to get the best result. thanks.

[kwm]

I remember my father years ago made a cowl from an aluminum pot an after he cut out the bottom he used a large diameter wood dowl and some elbow grease and work a curl into the pot by just rubbing on the edge till he got the look he wanted.

[Mike Emilio]

Originally Posted by bugerdup

That was at the top of the list. I was thinking of taking it to a metal fab shop and have them tig weld a tube to it. I think that might be the way to go to get the best result. thanks.

If you put any heat to it, there's a 90% risk that you will regret it.

It looks like one of mine. I made about 50 of them, different lengths.

If it is:
The material is a T-0 temper, and does not take kindly to heat.
The process to make them is called Metal Spinning.
During the spinning process, it work hardens to maybe a T1.

The lip is formed on the "spinning" mould/model.
The front is made oversize as shown in this picture, , , then it's rolled into the lip recess of the mould.

[Mike Emilio]

The one you want to replicate looks like it's a bit smaller on the diamenter. If so, that's a good thing, because it can be easilly re-shaped for the lip as well as the larger outside radius.

[bugerdup]

It is a hand spun piece, you can still see some tool marks. The opening is only 1/8" larger then the ABS one. I also thought of making a ring from Bass wood and epoxy it to the inside and then shape the radius into the wood. Then finish it off with filler and paint. As mentioned above, adding heat (Welding/Brazing) might warp it. What to do, what to do.

[Mike Emilio]

Originally Posted by bugerdup

It is a hand spun piece, you can still see some tool marks. The opening is only 1/8" larger then the ABS one. I also thought of making a ring from Bass wood and epoxy it to the inside and then shape the radius into the wood. Then finish it off with filler and paint. As mentioned above, adding heat (Welding/Brazing) might warp it. What to do, what to do.

All 50 of mine were hand spun. One-at-a-time. Tooling marks were burnished out on most, but on some I simply didn't bother.

Forget the front opening, that's not an issue because if you re-spin it the front opening hole size will change automatically, , , , smaller, , , , and that's good!

It's the body diamenter I was refering to. If it's larger on the inside than your white one, then it's a piece of cake to redo it to match your original.

Epoxy might not stick too well to a smooth aluminum surface.
It might be a QQA/250 alclad grade aluminum.

The best thing to do is simply re-spin it.

Do you have access to a wood lathe?

[bugerdup]

I am not quite sure of the type of aluminum but it is a good 1/16" thick at the opening and thinned out down the body. I don't have a lathe or a buck for the shape. It would make sense to have it re spun. As for the diameter, they are very close. It fits very well at the fuse/fire wall with about 1/8" gap all around, which will aid in the cooling flow. I also thought about adding a 1" flare to the back end to simulate cowl vents.

[Mike Emilio]

Hmmm, , , no wood turning lathe, , , that would have done it.

Not sure what other options might be available.

You got to spin it, to roll the lip inward, and push the outside radius in a bit more.

If you try bucking it in, it might start to crack.

Is it possible to get something round that fits the inside, like maybe a piece of ABS or PVC pipe and use it as a sort of a forming mandrel to push the lip in?

Something round on the inside to support it and hold it up just under the lip area, and use a drill press to push the mandrel down the center.