A little info Please!
I need to know the difference between polyurethane and a polyester finish.
Ive a feeling I can get the answer here.
Hi Charlie
Dick gave an excellent response, In addition I will add this, In Model airplanes people have been using what they call polyester finishes for on and off about 35 years, Bob Hunt used to do this, What they call a polyester finish is simply a Fiberglass resin base. To do this many used Polyester resin brushed onto the airplane and taken off as soon as possible with many differant methods, many used toilet paper or paper towels to soak and wipe the resin off, this took most of the weight back off the airframe and when dry it left a hard polyester (fiber glass resin) finish that you could sand smooth and apply dope or whatever. Most did not use any paper (silkspan) on any of the solid wood surface, this was used widely back in the late 70s early 80s on foam or fully sheeted wings.
The Poly U finish you hear about is just that polyurethane paint. either 1 or 2 parts . these finishes are like an Imron finish, and quite heavy, So most people would use dope or Lacquer, then when cured out they would top coat a final clear coat of Poly U catalysed 2 part and have a much lighter finish that was totally fuel proof, you could clean this with dope thinner and not hurt your finish, many people use this method today. Bill Werwage for one.
I will also mention that there is also a " CA finish" many people will coat the wood surface with CA just like they did with Polyester resin and sand smooth, using it as the base for there finish.
Go fly something :-)
Randy