Aluminum fuel tanks

I'd think that would be a sufficient test, unless your application will have the tanks pressurized. But if you want to have real assurance coat the inside of the tanks with one of the products designed for restoration of old steel gas tanks. Those leave a coating on the tank that's impervious to gasoline and will plug any pinholes.

I'd think a gasket & sealer between the plate and the tank would be called for.

I have made gas tanks for boats from aluminum. You should pressurize it to 5 PSI and see if it holds pressure overnight.

SNIP

And you might try colouring strongly with some food dye, then you'll see and hopefully be able to locate any leaks. And next time make the access port as a sandwich piece, with the inner piece being thick enough so that when you drill and tap for the holes, the inner ring isn't "pierced through". You'll have to provide bolts of specific length though, but then the bolts and holes won't be in communication with the fuel. Instead, the gasket does all the work.

Reading between the lines, the filler cap will be located at the highest point when installed, and I would assume fitted to this access plate, so the only time the plate/bolts will "see" fuel is from vibration and splashing. Am I wrong?

Aircraft Spruce & Specialty Company sell two or more tank sealants, one of which is called "Pro-Seal". I can't recall specs, but be aware that ther is a difference in the products if they will be used with alchemy based or with alcohol-additive fuels. Ask if you call.

Take care.

Brian Lawson, Bothwell, Ontario.

ps.. 30 PSI is pretty high for any decent sized tank with slab sides. What shape is yours?

If you can't detect any leaks at 30 psi you're probably OK. I've built a few aluminum and steel diesel tanks and standard procedure is to pressurize to a couple psi with a gage installed and monitor for any drop in pressure over a period of a few days. Obviously the larger the tank, the longer it will take for a given leak to show on the gage. A gage with a low range (0~15 psi or less) is needed to do this reliably.

Ned Simmons

If installation is difficult, then consider very carefully how you install these tanks. Two big problems with aluminum tanks are abrasion and corrosion. Don't foam them in (trapping moisture), hold them securely in place, isolate them from abrasion and vibration.

There is considerable literature on the subject; Powerboat Reports has covered it among other publications.

-- --Pete "Peter W. Meek"

On a related note, what kind (alloy & thickness) is suitable for a fuel tank? The one I'm thinking of will be a replacement for a small car.

The existing tank a) is too small b) is old and will probably leak if not now then soon c) has no baffling so i) the low fuel light goes on when it's half full and we're in any kind of a left-hand bend that's fun. ii) fuel dribbles out the cap vent and down the side panel when the fun level gets into big grin territory

In regard to c) above, how much baffling would do?

alchemy!?! Alchemy!?!?!? my speel chucker didn't like alcool I guess. Of course, I meant "alcohol based or with alcohol-additive fuels." as a percentage. Read Ethanol. In Canada, that will be approaching 10% by volume very soon. And I live in "corn country" which is the raw product. We'll be rich!!!! Well, maybe not "We'll", but farmers around here will.

Sorry.

Brian.

That's good to hear. In the US, it's Archer-Daniels-Midland that's the primary beneficiary of gasohol.

I *liked* the idea of alchemy-based fuel, BTW. It sounded like we were in for a good story.

Ed Huntress

And do the readings at a steady state temperature. Very important. Pressurize, wait a few hours in a regulated room, note the pressure then and say again 12 to 24 hours later. Air in volumes this large is really effected by temperature. We had our first medium heavy frost last night. When I got the mail at 7:30 this morning it was still pretty cool out, and in the van I noticed that the two plastic bottles of drinking water had the sides WELL sucked in. One was full, and the other was 1/2, but both were sucked in quite a bit, even with that small amount of air cooling down. By the time I got back home, with the car warmed up, they were back to their normal "shape" again.

Take care.

Brian Lawson, Bothwell, Ontario.

Odd, I think they were also the prime beneficiary of MTBE when *it* was in use. Or something like that.

Jim

For experimental aircraft (read home-built type) fuel tanks, 5052H-32 is the recommended. Commonly available (well, not really "common") in either 0.040" or 0.050" thick.

Most fuel tanks I've seen are "formed" to fit the available area, and to provide structural strength to themselves for many reasons, not the least of which is "oil-canning" noise. Baffling will help that, but the method of placement, and the attachment points location, of the baffling requires a lot of thought.. Hard to do with a welded fabricated one-off.

If you are doing this to a car driven on street, make sure that the insurance company you deal with is happy with what you are doing.

Take care.

Brian Lawson, Bothwell, Ontario.

Yes, but what type of sealer?

Yes, the bubble soap is already colored orange.

Next time yes. The plates are already done, they are 1/8" and mount inside the tank with nutserts. The bolts go through the tank (.050") and through the cork gasket, access plate, and into the nutserts. Can you recommend a sealer for the threads?

no, you are correct

slab sides but long and narrow, about 7"x7"x60". I'm not positive on that 30 psi, I was just pressurizing for the bubble check, I'll have to put a gauge on it.

Cork gaskets seem to be the best for sealing the sender to the tank and use soft copper washers under the screws to seal them. Better yet is to build the interface for the tank with blind holes for the screws.

-- Why isn't there an Ozone Hole at the NORTH Pole?

ProSeal is what the airplane homebuilders all use:

-- Bob (Chief Pilot, White Knuckle Airways)

I d> > > >

restoration

Good point. I tend to forget that sort of thing as the temperature never deviates more than a few degrees from 75F here in Maine.

Ned Simmons

snip

Ya, right!!! So Cal you are not!! :)

Aluminum and copper do not get along well together if there is any dampness. A car that might be driven on salted roads could develop serious leaks from corrosion in short order.

Ted