marksires

Since this topic comes up occasionally here, I thought I'd post these from the Cozy forum I hang out on.  The Cozy fuel tanks are built into the strakes, no way to do them but fiberglass.
Joe Person  Jan 21  Per multiple sources (and in general terms), cured epoxy resins have excellent resistance to ethanol (among other things) below 120 Deg. F.  Polyester resins (far-more likely in the boating world)?  Not recommended for many alcohols.   I have a 2-ply BID sample layed up with Saf-T-Poxy & #87 hardener (now EZ-Poxy and EZ-87 hardener), post-cured, and residing in a jar of nasty ol' 87 Octane car gas (with up to 10% ethanol).  Gas is changed a couple of times a year, and this experiment has been going for around 30 YEARS.  No discernable changes in the characteristics of the sample (stiffness, surface feel, etc.) over that time span.   Simply noting that "fiberglass tanks are damaged by alcohol" leaves out a whole bunch of other pertinent information.  Go talk to Gary Hunter, if you need a more scholarly discussion.   -Joe Person - show quoted text - Mark as complete   Phillip Johnson  Jan 21  The problem is that people are still building fuel tanks using incompatible epoxy.  It not in the plans to use Ezpoxy with slow hardener, and many builders are not on this list or join this list after they have completed the fuel tank construction. I built my tanks using Ezpoxy and I still have test coupons submerged in 94 octane fuel from back in the 1990’s.  94 octane has ethanol even in Canada.  That same fuel destroyed my automotive test fuel lines in less than a year whereas my test coupons look no different 20 years later. I use 100% Shell V-power 91 octane in the Cozy and have been doing so for close to ten years with no noticeable effects.  Phillip Johnson (From iPad)Cozy MKIV RG Powered by Subaru IO-200 (SN 0030)http://www.canardaviation.com/PhillipJohnson - show quoted text - Mark as complete   Joe Person  Jan 21  FWIW, from the ACS website:   Is E-Z Poxy 83 acceptable for use on a composite fuel tank? Is it resistant to ethanol? Yes, our E-Z Poxy line of products are the most fuel resistant epoxy systems we offer. E-Z Poxy has a long history of use in the aviation industry, being originally developed for the Long-EZ kit aircraft. Of the Hardeners, E-Z 83B, 87B and 92B are almost identical with only a slight variation in accelerator to help vary gel time. This series of hardener has undergone long term fuel resistance studies, being exposed to diesel (containing 5% bio diesel), gasoline (containing 10% ethanol) and strain solvents (50/50 isopropyl/xylene blend). The differences in fuel resistance between these 3 should be negligible. E-Z 10A/83B is a great option for integral fuel tanks.   -Joe Person - show quoted text - Mark as complete   Izzy Briggs  Jan 21  So your fuel sample, was it summer or winter blend? What other additives were included? Is it chemically identical to fuel you can buy now? The problem with Auto fuel is that it’s contents are not publicly declared. Kinda like cigarettes or natural GNC supplements or organic gummy bears...ok maybe the bears have the ingredients listed on the package. We are still dealing with MBTE pollution in our wells here in New Hampshire. No doubt your sample and your fuel is holding up. But it’s a stretch to extrapolate those results to all auto fuel blend and all epoxy types.  There’s enough people out there who had problems and had to replace strakes to warrant ongoing caution. Izzy - show quoted text - Mark as complete   Joe Person  Jan 21  My 30-ish year test of auto fuel & Saf-T-Poxy & #87 compatibility has utilized 87 octane auto fuel, sourced (intentionally) from Arco, Shell, Chevron, Exxon, 7-11, Fred Meyer, etc., over the time span noted.  Probably accounts for most of the crappies, light ends, etc. blended into auto fuel.   Yes, YMMV, but, reading the data available over the years, properly mixed, applied, and cured epoxy is quite good against the ravages of ethanol percentages in auto fuel.  As Gary Hunter noted years ago (my words) consider that a lot of chemical holding tanks are coated on the interior with epoxies.   -Joe Person - show quoted text - Mark as complete