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Subject:?Re: KR> wing tank building material - vinyl ester If you get nothing else out of this thread, it should be that you shouldn't build fuel tanks out of epoxy, now that we have vinyl ester. Yes, you can slosh the tank and probably get good results, but it's another step, and you have to do it right. But if you use vinyl ester resin (Aircraft Spruce sells it) you're not likely to ever have a problem with it. Mark Langford, Harvest, AL ML "at" N56ML.com www.N56ML.com[http://www.N56ML.com] to KRnet-leave at list.krnet.org ---------------------------- Absolutely true. #1) If you are building and plan to build glass tanks, build your tanks with vinylester resin. Polyester and Epoxy are both subject to degradation from alcohol and other chemicals that may be added to Mogas. #2) Always know your fuel source and test your fuel. Unless your system is designed for alcohol, and you fly your plane regularly, avoid alcohol contaminated fuels. But there are other things that get mixed into gas. Auto fuel gets pumped down a pipe line that has lots of other stuff also pumped down the line ahead and behind it. The stuff used to buffer between loads in the pipeline is often sold to cut rate stations and sold as cheap gas. It can cause damage to your fuel system as Mark showed in a couple of photos, or may cause detonation damage to your engine. We all want to fly for less, and I am a real advocate for burning Mogas as the lead in Avgas causes a lot of unnecessary engine top end wear, but know your fuel source. If you have the a set of tanks that are built from something other than Vinylester, know what you have and treat it accordingly. A set of epoxy tanks is not a problem as long as you are careful about what goes into the tank. I built the fuel tanks for my KR 21 years ago. At that time, alcohol boosted fuels were new and we were still trying to figure out what worked and what didn't. I was working with both vinylester and epoxy resins at the time and chose the epoxy resin as the most stable known resin at the time. Turns out Vinylester would have been a better choice. I had a couple of pinhole leaks in one tank, so I chose to slosh all 3 tanks with an alcohol resistant slosh compound (still available from Aircraft Spruce). Those tanks got to cure for several months before they ever saw any fuel, which has likely contributed to the longevity of the slosh compound. FWIW, Polyester is every bit as susceptible to alcohol/chemical damage as epoxy. I rebuilt a set of Polyester tip tanks off a Cherokee 235 a few years ago after the owner got a tank or two of Alcohol fuel. Those tanks were so soft they were deforming from the air pressures in flight. Aluminum tanks are also a good solution. -Jeff Scott Los Alamos, NM
