Fuel Tank Fabrication Questions

[Brian Jackson]

Greetings All.

I am in the beginning stages of fleshing out the design for a pair of fuel tanks of my gyro and was hoping those in the know might point me in the right direction regarding ports, venting, material, etc. I don't recall building them being discussed here in great detail, and I don't want to assume they're simple.

I would like to make them from aluminum sheet of a generous but reasonable thickness, formed and welded. There is an early rendering in post #1 of the Crescendo Build thread that shows them. Fabricating the exact shape is not a problem, but things like internal lining (if any is needed), and other practical considerations would be very welcome. Thanks in advance for any feedback.

Regards,
Brian

[JPAnderson]

I built the integrated fuel tanks on my VariEze. The internal baffles are to keep the fuel form gaining too much inertia when it sloshes around. Vents and line are pretty simple but improper routing does causes a lot of engine outs on homebuilt aircraft. Either all uphill for vents and all downhill for fuel lines. No low and high points/bends in the routing to avoid a vapor lock.

The Tony Bingeles books from EAA cover building basic fuel tanks. If your a member the magazine archives should have some very good articles. The Brits make really cool motorcycle gas tanks out of welded aluminum and videos showing that are on youtube. The capacity and shape will dictate design considerations.

Welded tanks probably have a better chance of developing stress cracks versus riveted. Vans Aircraft like the RV-6 uses some nasty stuff to work with called Proseal to seal riveted seams.

I'm not real turned on about sitting on a plastic tank of 5-8 gallons of fuel in a gyro crash. A friend died in Gyro crash, probably at impact, but there was a nasty post crash fire that assured no open casket. Any thoughts on the issue appreciated. I had a hard landing with my kasperwing that broke off the nosewheel resulting a real short stop. The Kasperwing fuel tank was in it's rack behind my head and held down with two bungees and it kept going and landed 20' away intact. I liked that.

More later, lunch time.

John

[JPAnderson]

Brian,

I found the post on Crescendo build and saw what you proposed for tanks. Nice looking design. I'd try and weld them and keep a close eye on leaks. Rubber mounted for vibration isolation? What would you use for fuel cap(s)? They use a mild weldable aluminum for tanks, maybe the 3030H-14 at aircraft Spruce? I don't have a good reference in front of me but I'll do some digging.

The Brits use Oxy/Acetylene mostly. No fancy tig or anything. Maico and CZ race bikes didn't even dress the welds out with a file and the tanks had flat bends, no compound curves and a coffin shape.. The Brits dress out the welds and polish the compound curved tanks.

John

[scottessex]

Just search the web for weld in aluminum fuel tank necks, you should be able to find something, Find a good welder that knows how to TIG aluminum.
Plus there are plenty of places that make custom fuel tanks.

[scottessex]

https://www.google.com/search?client...30.TnfBbMu-qQw

[klyde]

Brian: I had TIG welded my Safari tanks and checked with 14' of water head for pin holes. I was surprised to find no holes. I recently decided to weld up an oil tank out of 0.050 5,000 series aluminum. To practice a bit before attacking the tank, I found I used up a large tank of Argon before my "Skill?" level returned. I watched you tube videos and read articles but it wasn't until my eye, hand coordination "Dropped" into the groove was I able to get a good weld. I tested the oil tank to 4psi and found and got rid of several pin holes. In my experience, welding aluminum is like hovering a helicopter. You can't until you can. Practice, Practice, Practice was my key.

[twistair]

I recently had a luck to tinker with an R44 Robinson helping guys to remove and reinstall main drive train and then to make a dynamic balancing for the bird. R44 has riveted aluminium fuel tanks which are a piece of art and very lightweight. I recall that Tony Bingelis article on riveted tanks should be somewhere in my old PC but cannot find it right now. Anyway it looks to be this article.
Riveted aluminium tank should be lighter than welded (since thinner Alu sheet can be used for safe riveting) and also I'd second JPAnderson that welded tanks has better chance to crack compared to riveted one.

[fara]

I don't know if this will help or not but wouldn't hurt. Its how our fuel system is setup in AR-1

https://www.facebook.com/media/set/?...1&l=fd2f5d8c31

[gyroplanes]

I'm not real turned on about sitting on a plastic tank of 5-8 gallons of fuel in a gyro crash. A friend died in Gyro crash, probably at impact, but there was a nasty post crash fire that assured no open casket. Any thoughts on the issue appreciated. John

Hello John,
As a former manufacturer of "plastic" seat tanks, I feel I can comment more believably, as I no longer sell them. This is what I gleaned from my research over the years.

Fuel tanks should be built to contain the fuel, before, during and after an impact. You need a strong, but relatively "soft" material. (Ideally, a combination of both) for fuel containment, ALSO, and VERY important is how the fuel exits the tank. I found that if the tank was not compromised, the usual cause of fuel loss was by lines (in, out or vent) ripped from the cell and released fuel, providing the second point of the fire triangle.

The military and the auto racing community appear to lead the field in fuel tank research, and they have produced some spectacular results. The military is primarily concerned with a fuel tank surviving taking hits from bullets (or fragments), or survivable crash landings. SCCA & NASCAR auto racing organizations are more interested in post crash fires.

The ideal fuel tank should be made from a strong, yet semi-flexible material. The best way, as proven by auto racing fuel cells, is a container of steel, aluminum or cross-linked polyethylene.

A compromised tank structure can result in an atomized spray of fuel.... not at all what we want. A hard, yet yielding to the blow enclosure, is the most desirable. Most fuel cells are steel, or aluminum, or PEX "plastic" and, especially in the case of the first two, contain a very flexible "bladder". A third component is often found in fuel cells is a foam that absorbs the fuel (like a sponge) the fire foam must be left out in the area of the fuel level sender, displaces some fuel reducing the quantity and often disintegrating, which leads to filter clogging.

Racing fuel cells are widely available in many sizes and capacities, they are often heavy, expensive and not appealing appearance wise.

Chances are that your farm tanks, pipelines, airport fuel farms and your vehicle fuel tanks are made from PEX.

Most gyroplane fuel tanks are, today, made from PEX. The earliest seat tanks were made of fiberglass, as are current molded in tanks or stand alone tanks. My opinion is that if fiberglass tanks receive a hard blow, they will rupture. I believe it is imperative that any fiberglass fuel tanks need an internal bladder installed. I wrecked my first gyro and the fiberglass seat tank split open at the seams and doused me with gasoline. I did not like being part of the fire triangle and I was awfully lucky the third part wasn't around. A properly roto-molded PEX seat tank, under your butt, is in one of the safest fuel tanks in one of the safest places it can be mounted.

Wikipedia:
Cross-linked polyethylene, commonly abbreviated PEX, XPE or XLPE, is a form of polyethylene with cross-links. It is used predominantly in building services pipework systems, hydronic radiant heating and cooling systems, domestic water piping, and insulation for high tension (high voltage) electrical cables. It is also used for natural gas and offshore oil applications, chemical transportation, and transportation of sewage and slurries. PEX is an alternative to polyvinyl chloride (PVC), chlorinated polyvinyl chloride (CPVC) or copper tubing for use as residential water pipes.
.

[gyroplanes]

I recently had a luck to tinker with an R44 Robinson helping guys to remove and reinstall main drive train and then to make a dynamic balancing for the bird. R44 has riveted aluminium fuel tanks which are a piece of art and very lightweight. I recall that Tony Bingelis article on riveted tanks should be somewhere in my old PC but cannot find it right now. Anyway it looks to be this article.
Riveted aluminium tank should be lighter than welded (since thinner Alu sheet can be used for safe riveting) and also I'd second JPAnderson that welded tanks has better chance to crack compared to riveted one.

Ironically, Robinson recently had an expensive lawsuit regarding their R44 fuel tanks and fire. IIRC

[Brian Jackson]

Thank you gentlemen very much for the info. Certainly much more to consider than volume. John and Tom, reading about your hair-razing experiences was unnerving even as a reader. I'm glad the outcomes were fortunate for you both. I will do much more studying before moving forward with any fabrication.

It's tempting to lean toward a composite tank for ease of fabricating the shape shown. But as was mentioned earlier, there are safer, more malleable materials. I'd love to discover a method of creating an internal bladder by simply pouring in an inert liquid rubberized compound and rotating the tank in all directions until it solidifies and bonds to the interior. I'm sure this has been tried by someone but am unaware.

[twistair]

Ironically, Robinson recently had an expensive lawsuit regarding their R44 fuel tanks and fire.

Oops, just read something about this problem. An R44 I've tinkered with is an ancient Astro with pure aluminium tanks.

Sure, we need to care about crash-proof but on the other hand we also need to care about weight and reliability of each part of the bird. From this point of view R44 has a lot of elegant things which are so weight-saving that I felt small looking at many parts of modern gyros.