Hi Guys--I guess this topic is as old as the hills as I am-70. I need the difference beteen these dopes. Which one is the non shrinking and what brands make them. What rattle can paints are fuel proof?? Thanks for the help for an old 50's flyer. Ken
Hi Ken,
Both nitrate and butyrate dopes are available in tautening and non-tautening types. "Tautening" dopes shrink about 12%-15% linearly, "non-tautening" dopes shrink about 5%-6%. Nitrate shrinks slightly more than butyrate but the dried film has a lower tensile strength than does butyrate. Nitrate is not readily available in colors anymore and hasn't been since the early fifties. Nitrate dope (both the liquid form and the dried film) ignites easily and burns almost explosively; butyrate dopes were developed to provide a finish that burns much more slowly than does nitrate (an important consideration if you are flying along in your Taylorcraft at 5,000 agl and develop an in-flight fire).
Although many modelers use nitrate clear for the first coats on the airframe and to attach the covering (silkspan or silk), I see no reason to do so except for personal preference. I always use butyrate dope as it is much more fuel-resistant than nitrate and gives just as good results. I use the tautening type butyrate for the first coats on the wood, to attach the covering, and for the first three brush coats on the open bay areas to tauten the covering. After that I switch to non-tautening butyrate for the remainder of the finish.
Also, I always use the appropriate dope thinner rather than trying to substitute lacquer thinners for it. While you can get away with using lacquer thinners (as long as it is not the new VOC compliant type) in dope, you really get the best results using dope thinner. Dope thinner contains different drying agents and other solvents that contribute to the slower drying and film-forming qualities that enables you to get a good finish with dope. Butyrate thinner can be used with no problem in nitrate dopes, but nitrate thinner cannot be used in butyrate dope.
Brands available for dopes include Brodak and Sig in the purely model airplane world, and Certified and Randolph brands in the full-scale airplane world. Personally I use Randolph dopes for the basecoats of clear and most colors, and for the top coats of clear I use Sig Light-coat clear as it is more fuel-resistant than any of the other brands.
Randolph and Certified are available at many full-scale airplane supply houses such as Aircraft Spruce and Specialty. Randolph has a huge selection of colors and is a high-quality product. Certified is also good quality but has a limited range of colors. Randolph is much less expensive than the dopes provided for the model airplane industry. For example, a gallon of Randolph butyrate thinner is listed in the Aircraft Spruce catalog at $25.40, and a quart of Randolph butyrate non-tautening clear is $14.50. The Randolph dopes require quite a bit of thinning and go a long way. I have great results with Randolph products (and am not sponsored by them, just FYI), they are consistently high quality and have great coverage.
There are no truly fuel-proof rattle can paints, despite manufacturer's claims to the contrary. To have a truly fuel-proof paint you have to go to a two-part paint such as an automotive polyurethane or an epoxy such as Klass-Kote (Brett Buck is very knowledgeable about Klass-Kote) that use cross-linking of long-chain polymers to give a highly chemical resistant finish. Two-part means the polyurethane paint plus its isocyanate ester catalyst, and the mix is usually thinned with the appropriate thinner.
Topic: DIFFERENCE BETWEEN BUTYRATE AND NITRATE DOPE and also paint. (Read 10082 times)
