Tank sheet metal thickness?

[TiAvenger]

Hey all,

I'm currently working on making the buck for my custom gas tank. I keep going in between 16 gauge steel and ?? gauge aluminum.  Question is, I cant find what thickness of aluminum I should be comparing the steel too.

Anyone have any ideas?

[ducpainter]

I think you're approaching the issue from the wrong direction.

Aluminum tanks are not as strong or 'durable' as a steel tank.

They dent extremely easily and are known to crack from vibration and stress risers in the construction.

Try to decide what gauge you need by how much formability and rigidity you need and the construction methods available to you as well as your welding ability.

That's my idea.

[TiAvenger]

Im looking at weight.

Its going to be "capped" with carbon fiber.  It wont need to look pretty, just need to hold gas.

[Popeye the Sailor]

Define "capped".


I'm a bit busy at the moment but I can figure it out for you this weekend.

[TiAvenger]

Define "capped".


I'm a bit busy at the moment but I can figure it out for you this weekend.

Foam will be added to the exterior then sanded to shape and have a vacuum bagged layer of carbon fiber as the exterior of the tank.

[ducpainter]

Foam will be added to the exterior then sanded to shape and have a vacuum bagged layer of carbon fiber as the exterior of the tank.

Then make a rectangle out of 1/8" and be done with it.      

[TiAvenger]

Then make a rectangle out of 1/8" and be done with it.      

That was the original plan, but I need a minimum of 750 cubic inches (about 3.25 gallons) and to be able to get that and keep the profile I want would be near impossible

[Speeddog]

I think you're approaching the issue from the wrong direction.

Aluminum tanks are not as strong or 'durable' as a steel tank.

They dent extremely easily and are known to crack from vibration and stress risers in the construction.

Try to decide what gauge you need by how much formability and rigidity you need and the construction methods available to you as well as your welding ability.

That's my idea.

Most important sentence highlited.

Vacuum-bagging an aluminum tank may be a problem.
I would expect that it would crush it quite effectively, unless you support it internally somehow.
Even a modest vacuum of 10 psi adds up to large forces very quickly.

Then make a rectangle out of 1/8" and be done with it.      

He's got a point.

[ducpainter]

Most important sentence highlited.


He's got a point.

They were all important until he added it didn't have to look like anything.

...and it's on my head.

That was the original plan, but I need a minimum of 750 cubic inches (about 3.25 gallons) and to be able to get that and keep the profile I want would be near impossible

You can modify the shape. I'd still use 1/8" and brace it internally if you're going to try and squash it before it ever holds fuel.

[TiAvenger]

Most important sentence highlited.

Vacuum-bagging an aluminum tank may be a problem.
I would expect that it would crush it quite effectively, unless you support it internally somehow.
Even a modest vacuum of 10 psi adds up to large forces very quickly.

He's got a point.

I had planned to put vertical cross members for anti slosh/ structural integrity.

[mookieo2]

Vacuum-bagging an aluminum tank may be a problem.
I would expect that it would crush it quite effectively, unless you support it internally somehow.
Even a modest vacuum of 10 psi adds up to large forces very quickly.

He's got a point.

Fill tank with 2 part polyurethane foam and then when finished wash it out with some acetone it will dissolve the foam. That`s common practice.

[TiAvenger]

They were all important until he added it didn't have to look like anything.

...and it's on my head. ;)You can modify the shape. I'd still use 1/8" and brace it internally if you're going to try and squash it before it ever holds fuel.

You mean I shouldn't try and bag it full of gas?  

While I have your attention, I assume por 15 should be used to back up my welds internally?

[ducpainter]

You mean I shouldn't try and bag it full of gas?  

While I have your attention, I assume por 15 should be used to back up my welds internally?

It's not a bad idea.

I'd assume that all the ethanol would create some corrosion in an aluminum tank...i may be wrong.

Just follow the directions like it was a steel tank.

[TiAvenger]

It's not a bad idea.

I'd assume that all the ethanol would create some corrosion in an aluminum tank...i may be wrong.

Just follow the directions like it was a steel tank.

doing the rough math....  6061 is .0975 lbs per inch³ or .0122 per inch² (1/8th inch)

The Al would be around 9 lbs alone 

[Speeddog]

Glue together blue styrofoam blocks to rough shape.

Finish shaping to your heart's desire.

Lay carbon.
Aircraft Spruce probably has fuel-resistant epoxy.
See what they say.
Tell them about the next step:

Dissolve blue foam with acetone.

Seal tank with POR.

Check for leaks.

Paint/clearcoat or whatever.

Run it.

No FHE with this method, but it's what I'd do.

Aluminum and carbon in intimate contact will suffer galvanic corrosion if there's any water.