This has been answered before on several threads about ethanol but it bears repeating. Don't even think about doing this. What you have left after pouring water into the gasoline to separate the ethanol from the gas is ethanol with water and some gas and other stuff which you can't just pour down the drain and you have some unidentifiable fuel with some ethanol still in it. How much ethanol? You won't be able to tell accurately. But the most important thing is you will have some kind of unrecognizable fuel, called BOB.
E10 auto gasoline is
NOT made with gasoline to which ethanol has been added. It is made with BOB (Blendstock for Oxygenate Blending) which among other chemical changes to finished gasoline has about 3 AKI (AntiKnock Index) points less than the finished product. But it was probably never legal finished product to start with.
This is what the Director of the Division of Air Resources, New York State Department of Environmental Conservation said in his comments on the E15 waiver:
"E10 is not simply ethanol added to finished gasoline. Since most gasoline at retail contains ethanol, the industry factors the addition of ethanol into the formulation of the petroleum-based portion of the final blend. The chemical properties of ethanol and its dilution impact allow refiners to produce a petroleum-based blendstock which when combined with a specified amount of ethanol (or other oxygenate) results in a final blend with the desired legal and market properties. The petroleum-based blendstock, in most cases, would not qualify as gasoline or be legal to sell as gasoline. For RFG this blendstock is RBOB. For conventional gasoline it is CBOB, and for California RFG it is CaRBOB.?
What you have left after trying to remove the ethanol from E10 is not gasoline meeting ASTM D4814 specification, so unless you are willing to state that your homebuilt works just fine on BOB, it would not be a legal fuel for your aircraft.
If you want more information about this problem see
www.e0pc.com and especially the link to a fuels forum that Kent Misegades, Todd Petersen and I gave at AirVenture 09.
Regards -- Dean