FPL-16A, also known as "Hughes Glue", is the granddaddy of all epoxies used in aircraft applications. FPL-16A has lacquer thinner as one of its component parts. See Forest Products Laboratories report:
Olson & Blomquist; 1962; "Epoxy resin adhesives for gluing wood"; Forest Prod. J. 12(2), pages 74-80 Poly-Fiber "varnish", used on wood structure under their fabric covering, is two-part epoxy. It always has been, since Ray Stits developed his covering system way back when. The epoxy formulation is necessary to resist the MEK in the liquid components of the coatings. Poly-Fiber also sells a polyurethane "varnish". But... If you cover a certified airplane with Poly-Fiber, the STC (SA1008WE) states that the procedures in Poly-Fiber Covering Procedure Manual #1 must be followed in order to maintain certification. The manual specifically states to use Poly-Fiber EV-400 Epoxy Varnish with EV410 catalyst. The polyurethane product is not mentioned and is therefore not legal to use on a certified airplane using the Poly-Fiber covering process. The STC for Poly-Fiber covering products is good for just about all pre-war Aeroncas, Pipers and Citabrias/Decathlons with wood spars, Stearmans, Beech Staggerwings, Howards, Taylorcrafts, Monocoupe 90s, a number of Wacos, Fairchilds, Mooney Mites, and a large number of wooden gliders, along with many other types. I've used Polyfiber varnish on a number of homebuilts and restorations and it has worked great. I have also used FPL-16A thinned with lacquer thinner as a varnish and it also works great. When it is scuffed in areas where the surface will be bonded to another component, the bond is extremely strong, proven by making test coupons with every batch of epoxy that is mixed and used, including the varnish coat. That's probably because the stuff I used to bond the parts together is the same stuff as the varnish - as in Mark's suggestion about using laminating resin for "varnish". I've been involved in aviation for over 40 years and some of my work is on display in museums. Your boat may sink but "my" airplanes are still flying. It's perfectly fine if you do things your own way, but I've proven to myself what works for me, and I've seen that epoxy works for people who know a lot more about epoxies, chemistry, and airplanes than I do. Chris On 1/1/2014 9:26 AM, Timothy Witmer wrote: > Epoxy soaked glass is great !!! Glass gives it all strength it needs. But > epoxy alone is somewhat brittle &Canot be reduced other than acetone. It > looses all its properties. Maximum water resistance is not achieved with > epoxy alone. Its always mixed with another agent ( like paint ) best of > both worlds .... > On Jan 1, 2014 11:15 AM, "Mark Langford" <ml at n56ml.com> wrote: > >> Timothy Witmer wrote: >> >> Or all the boats would SINK !!! SPAR VARNISH OR POLYURETHANE GUYS !!!!! >>> SINK OR >>> SWIM ......OTHERWISE !!! >>> >> Hmmm, we've been coating KR wooden structure with epoxy-soaked glass, and >> coating the insides with epoxy for years, but I guess they were all wrong, >> and all those KRs that have been flying for 40 years are lucky to have >> survived. I suppose I'll just torch this one, and build a new one using >> spar varnish instead! I sure am glad I was enlightened before I flew this >> dangerous thing... >> >> Mark Langford >> ML at N56ML.com >> website at http://www.N56ML.com >> -------------------------------------------------------- >> >> >> _______________________________________________ >> Search the KRnet Archives at http://tugantek.com/archmailv2-kr/search. >> To UNsubscribe from KRnet, send a message to KRnet-leave at list.krnet.org >> please see other KRnet info at http://www.krnet.org/info.html >> see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change >> options >> > _______________________________________________ > Search the KRnet Archives at http://tugantek.com/archmailv2-kr/search. > To UNsubscribe from KRnet, send a message to KRnet-leave at list.krnet.org > please see other KRnet info at http://www.krnet.org/info.html > see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change > options > > >
