Planning for Alternative Fuels

[Jalanci]

I've read bits and pieces about the placement of fuel pumps, tank fittings, hoses and a host of other issues regarding current and future fuels. This thread is intended to document the things we can do to accommodate alternative fuels in the future. The discussion isn't about will it happen, or not, but what do we need to consider in the building stages to give us options. After seeing a lot of the input on this site, I'm confident that there are some real things we can do as we are building to provide flexibility.

Fuel tanks, fuel pumps, weight and balance, engines, additives, sump drains are some of the issues I can think of that will need some sort of modification. Fortunately, experimentals have the flexibility to make these changes.

[Brantel]

I think the one thing I would do for sure if I had it to do over when building my tanks is to add some sort of provisions for a return line in each tank even though at this time I do not need one.

[David-aviator]

Originally Posted by Brantel

I think the one thing I would do for sure if I had it to do over when building my tanks is to add some sort of provisions for a return line in each tank even though at this time I do not need one.

Brian,

That's not difficult. Go with the six port Andair valve and run the return lines back to each tank forward of the pick up lines. We extended the return line through the center rib in the tank so fuel goes to the outboard bay providing for max cooling. There is a very good drawing by Gary Newsted on how to do this on the EGG factory web site under installation.

It is my feeling the RV system is pretty good as is for mogas. I've flown with it mostly for about 320 hours. The fuel pumps are on the cabin floor just forward of the valve so all fuel going through the fire wall is under pressure (30 psi) which alleviates much vapor lock concern. If you really want to cure vapor lock figure out a way to put the pumps in the tanks, that's how the auto industry has fixed that problem. This assumes you are going with some sort of FI system running at 15-30 psi. It won't help much with a carb install at 4 psi.

The down side is high pressure fuel lines in the cabin. Originally we had the fuel pumps on the forward side of the firewall because of this concern. But after a great deal of thinking on the subject it was decided the risk of vapor lock where the gravity fuel supply came through the fire wall exceeded the risk of a broken fuel line in the cabin. For plumbing we use high pressure FI hose from the auto world connected with OETiker clamps. This product is not STC'd for aviation use but has proven to be very reliable in the auto world in systems running at 40+ psi.

It is also very important to know the vapor pressure of the fuel being used. I test every time I add fuel.

I also feel there is some power loss over 100LL. Like all things in life, nothing is totally perfect. We make do the best we can with what we have. The key element here is flying....it beats anything going on on the water or at a golf course.

[Rivethead]

I think I heard this on Science Friday (radio) last week if not there it was just on a regular broadcast. A scientist at Purdue has bio engineered either a bacteria or a yeast that will directly convert sugar into a molecule very close to if not the same as diesel. One of the upside benefits of the process is that unlike the production of methanol there is far less distillation required since oil and water don't mix. Kind of reminds of a joke about Martians that used to go around.

[frankh]

The FI'd RV system is pretty good but for bullet proof against VL, my pumps are in the wingroots.

Still don't have a return except for the purge valve return to the right tank to avoid hot starts works great but a return has never proved necessary on this set up.

Frank