Forming The S-1-11 Fuel Tank

Every time I work with Wayne or Dave I realize how impossible this project would be without them. I never imagined how much I would be learning, about so many things, and today(1/24/08) would be no different.

A quick recap: I spent Saturday morning with Wayne. We finished up drilling and installing the left wing attach plates and angles. We also cut the plywood for the wing tips. Things are progressing along nicely.

So today I met Dave down at his shop. When I walked in, Dave was cutting out the templates we would use to draw, shrink and form the ends of the fuel tank. We traced out the form on the aluminum and added a 3/4 extension to it. We sheared the two tank ends and are ready to rough cut the outside line.

Tank Ends Drawn on Aluminum

Tank Ends on Aluminum Cut Out

One of the nice things about working with Dave and Wayne, beyond their expertise, is that they have all the tools! The right tool makes all the difference. Here’s a pic of Dave using a Beverly Shear. It makes short work out of cutting these out.

Beverly Shear

Tank Ends Cut Out

The next step is to anneal the edges so it is easier to form and shrink the normally very hard aluminum. In essence you need to heat the aluminum to a specific temperature to temporarily soften it. The trick is to get the right heat on it. One way to do this is called the Torch Soot Method. If you have ever put a flame to aluminum or the like you notice it puts a black film on the surface. If you run a torch over the sooted area, the soot will burn off. The heat needed to burn off the soot, just happens to be the right amount to anneal the aluminum. This is a great article explaining it. Here is Dave applying the soot indicator.

Tank Ends Annealing

Tank Ends Annealing carbon

Now he is burning off the soot.

Tank Ends Annealing

Tank Ends Annealing

Tank Ends Annealing

Annealing complete!

Tank Ends Annealed

Next we need to form the end of the tank. We clamped the sheet between the two wood cutouts. One is the former, that we will bend the edges around to give it the shape we need. The other holds it in place while we do this.

Sandwich End

Sandwich End Clamps

With the aluminum sheet tightly in place, we use some persuasion to shrink and form the edges of the tank end. A great analogy Dave told me, was to think of the metal as putty that you hammer into shape. And as you pound the aluminum, shrinking and forming it into the shape that is exactly what it works like. It is amazing how the metal sort of flows into shape.

Starting to Form End

Forming and Shrinking

Forming and Shrinking

With the Edge nicely beat into submission, it is time to take it out of the former.

End Formed

First End Shrunk and Formed

No to shabby! Now Dave will use a hammer and bucking bar to clean up the shape and smooth any imperfections out.

First End Clean Up

First End Shrunk and Formed

After watching Dave, it was my turn to take a whack at it. 😉 Here are the two ends pounded into shape.

Ends Formed Body Cut

Tank Ends Formed

Now we need to add strength to the pieces. This is achieved by rolling a bead into them. Once again, it’s nice to have the right tools for the job!



One Done

And finally here are the two ends and the body of the tank. The next steps are to roll the body into shape and then tack the ends on. Finally, we’ll cut and weld in the filler neck and fittings.

All Done

All Done

This is a similar tank and what ours will look like.


3 Responses to “Forming The S-1-11 Fuel Tank”

  1. perhaps you can put it all together in a doc, and let’s get it into the biplane manual ?

  2. hey rob, you getting involved with its construction. is that you working on a lathe. reminds me of college. i was pretty good on lathes and 6 axis millers, they were alot of fun. are the wings made of wood? what kind? is that strong enough for the loads placed upon it durring fight. when you fly can you hear the plane react to you? i bet you can. very cool rob. be safe ok

    love to see you fly sometime when im back there again


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