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Thanks Tracy. I'm not trying to cause a panic or anything. I believe that volatility has to be high on any list of potential problems and is aggravated by the fact that it varies a lot and we don't have the information at our fingertips. If we're using Mogas, we need to be aware of the Reid Vapor Pressure of what's being sold where we live and have some notion of seasonal changes.
I never thought alcohol could hurt metal airplanes, but I'm firmly committed to the composite community and it can be devastating to the Cozy / Velocity population. There are viable coatings available, but they don't lend themselves to retrofitting. Again, we have to be aware of the issue so as to avail ourselves of the workarounds that do exist.
Trying to get my system configured (with uncoated tanks) ... Jim S.
Tracy Crook wrote:
I agree with everything Jim is saying about alcohol, auto fuel & vapor pressure. But I want to stress that there is absolutely no reason you should have to worry about these things if your fuel system follows a few simple guidelines. The first of which is KEEP IT SIMPLE! A car's fuel system is pretty simple and there are millions of them operating with no vapor lock problems, including people who drive at high altitudes. None of the people driving cars ever even thinks about whether there is alcohol in the fuel or not. I don't either, even in my airplane.
The issue of composite compatibility with alcohol is a separate question. After experiencing problems with a couple of aircraft fuel tank sloshing compounds, I distrust all of them. The only fuel sealing agent I trust are the polysulfide compounds. ProSeal is one brand of polysulfide sealant but there are others. It is impervious to anything you might find in any fuel, including the stuff formed when alcohol is mixed with water.
Tracy
----- Original Message -----
*From:* Jim Sower <mailto:canarder@frontiernet.net>
*To:* Rotary motors in aircraft <mailto:flyrotary@lancaironline.net>
*Sent:* Wednesday, February 16, 2005 1:33 AM
*Subject:* [FlyRotary] Re: Bad day at the airport
Paul wrote:
Hi, Jim....yes, I use the same gasoline as I use in my car.
(Regular unleaded). I think Tracy and Ed Anderson also use it,
as they mentioned that their spark plug life is greatly
deteriorated when they are forced to use 100LL. Guys, please
step in here and correct me if I am wrong.
Right so far. Unleaded is MUCH better for your engine than Avgas.
Regarding alcohol, I am not overly concerned with it. I
coated my fuel tanks with 3 coats of the fuel tank sealant that
comes with the kit. (Smells like dead fish). It is supposed to be
imperviant to auto fuel and alcohol.
Alcohol is not bad for composites. Water is not bad for
composites. Alcohol and water mixed is VERY corrosive to
composites. If you have alcohol, you WILL end up with some
alcohol / water mixed. The stuff you used on your tanks might be
OK if it doesn't leak AT ALL, but how do you find that out? Your
"bad day" keeps sounding like vapor lock, and some Autogas is much
more volatile (read prone to vapor lock) than Avgas. You need to
check a bunch of suppliers around and determine the vapor pressure
of the gas they're delivering to their clients. You want the
lowest number you can get. Avgas has a VP of 6.0 or so. Some
unleaded is down around 7. Some more could be over 10. That's
where you get into cavitation / vapor lock / etc. problems. Alcohol might very well not be a factor where you live, but in any
event it's very easy to detect.
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