My team this year has made the move over to E85 fuel, and from what we understand E85 reacts negatively with aluminium.
With this in mind we have fabricated a tank from stainless steel, but as the tank has grown by about 40% due to the stoichiometric fuel ratio, the weigh of the tank has increased significantly. The weight has increased from 1.5kg from last years aluminium tank for the petrol to well over 6kg for this years stainless steel tank. The stainless tank is made from 18SWG so I wouldn’t feel comfortable going any thiner.

Im just wondering what solutions other teams have arived at when trying to desing at tank to run on this fuel, or is it simply a case of having to run a safe and accepting the additional weight increase.

The only other solutions that I can think of is to run a bladder tank but this is out of the question as its far to expencive, or to somehow seal the aluminium with some sort of epoxy to prevent the aluminium coming into contact with the E85.

All thoughts would be appriciated.

James Morris
Swansea Metropolitan University

I'm not positive but maybe a hard anodize aluminum tank would work. In 2003 we ran a titanium tank, i'm not sure what the team is doing now.

Have you looked into fuel tank coatings?

We've run a coated aluminum tank the past few years without any problems so far.

We have used an uncoated aluminum tank now for two years and have not seen any problems.

AJS, have you looked in your fuel filter? e85 does errode aluminum. Not to say you can't run them, the limited run time of an fSAE car limits the damage, but we've noticed on cars that sit with fuel in them over the summer, and our dyno tank.

We actually did have to clean the filter a couple of weeks ago after the engine started stuttering and spiking lean. We weren't sure if we had just gotten some slightly dirty fuel or if it was just from being run on the car and the dyno for a year and half or so. I guess it could be from erosion in the fuel tank but we aren't too worried about it at the moment.

With just about any system running that much alcohol/ethanol in the mix you need to completely drain the fuel system after every event. Bladder systems can be designed for alcohol but even they need to be pumped out and dry after running.

Fuel cell manufacturers have issued warnings about running that kind of fuel in bladders designed for gasoline.

Brian

does anyone know how the big manufacturers are dealing with it in their flex fuel vehicles?

Polymer tanks and fuel rails and/or steel. Thats what i see at work (delphi)much of the time.

Hi,

I would say with just a month to go to the competition: stay with the heavy tank, it's just not worth it to change the tank this close to the comp. For next year I would advise a composite tank.

What type of resin would you recommend for a composite fuel tank? We've used Hysol 9430 but have not tested it for gas applications.

Hysol 9430 is an adhesive - for bonding things together.
You want a resin for laminating.
They're not quite the same.

We've run an uncoated aluminum tank for 2 years, no problems. We do drain it after running. Our dyno tank is stainless steel.

quote:

Originally posted by James Waltman:
Hysol 9430 is an adhesive - for bonding things together.
You want a resin for laminating.
They're not quite the same.

The loctite folks recommended this us. We also get it through one of our sponsors. What resin would you recommend?

Sure, 9430 is a decent adhesive. Loctite didn’t recommend it for wetting out fibers did they?
There must be thousands of different kinds of epoxy resin.
I haven’t built a fuel tank with epoxy before but I’ve done my share of work with epoxy.

I’d start with whatever kind of cheap epoxy you can get your hands on that is designed to work with dry fibers. You might be able to buy something like that at a good hardware store. The requirements for the resin aren’t very critical. It needs to hold up to prolonged exposure and that’s something you’ll have to test on your own.

You can look for a distributor that caters to home builders of boats or airplanes.

I like System Three products and they have a really helpful website with lots of good product data and generally helpful info. (They target boat builders)
http://systemthree.com/members/m_index.asp

You might try Aircraft Spruce. (Kit plane builders)
http://www.aircraftspruce.com/menus/cm/epoxy.html
Most of the things on the top half of the page should be fine.

thanks james. does anyone have any feedback on the west systems resins?

as far as the hardware store fiberglass resin, i hate that stuff. it smells god awful, and its work time is too short. the upside is you can go buy it in a pinch, and its not terribly expensive. the 9430 has very low odor, and it has about a 40 minute work time at room temp. we find it superior to the bondo styrene based resin, but we only use it for seat, body and intake.

apparently we didn't bother with coatings or anodising.

Last years car didn't bother with any coating and this years hasn't either. I believe we used 6061 - had no problems so far doing this. I won't recommend it though especially as i haven't had alook inside the fuel tank to see if it has had any effect.

I was looking to choose a composite material for the fuel tank, and im looking at kevlar, carbon fiber, and fiber glass.

Does anyone have any experience with these materials and have any advise as to which is the best path to take?