varnishing Options, 1 part varnish ok ????

[rogerh12]

Howdy;

I see everyone is using a two part epoxy varnish on the ribs. If I intend to use the poly-fiber covering process on my model 4, is there any varnish option that is sutable, maybe something I could buy at home depot? Maybe a 1 part? The plane will be hangered, and I live in Kansas, so do I really need expensive varnish?

Let me know what you think

Roger

[HighWing]

Roger,

In short no. But your question brought to mind the real old days before Epoxy and Polyfiber - the days of sewn fabric envelopes and ribstitching. With our new modern techniques, especially Polyfiber, the fabric is held on by an adhesive that would attack any single stage varnish or paint - this is why the fuselage tubing is powder coated or coated by a two part finish. The thought did occur to me that if you really want to go local, you might find an automobile paint supplier nearby that carries a two part Epoxy or Urethane coating. Except for showing the grain of the wood, I can't see the advantage of varnish over a two part top coating. I would think that both would protect the wood from moisture.

Lowell

[MotReklaw]

I'm using the Stewart's System too Roger. I agree that the two-part epoxy varnish is better. I'm putting two-part paint on the aluminum and other steel parts that will be covered with fabric. I have some of Stewart's one part primer that I will use on the painted aluminum parts and probably the cowl.
I just thought that the two-part would be more durable under the fabric.

It's fun though, isn't it?

[Dave S]

Roger,

The main issue here is compatibility. Remember that the solvents used in the covering process going over the ribs can interact with the varnish on the ribs if they are not compatible - cured Epoxy varnish can be washed with MEK - Try that with one part varnish and the MEK will work real well as a paint stripper. If the solvents in the covering chemicals are not compatible with the varnish it would be a real mess.

Sincerely,

Dave S

[akflyer]

When I did mine I used a spar varnish from the local hardware store. I was just careful to not get any on the top and bottom of the cap strip that I would be gluing the fabric to. The glue will work as a sealer for those area. I also rib stitched the wings on mine.

[rogerh12]

Howdy all;

Thanks so much for all the good advice. I finally broke down and ordered the poly-fiber 2-part varnish system. But that raised one other question. My old can of varnish said to cut the first coat with 25% reducer. When I ordered the new can, I saw a note saying to cut it 50%.

What ratio of cutting fluid should I use on the first coat? How can I tell if it's cut too much, or not enough?

Thanks again
Roger

[cap01]

the poly fiber website in their product section has all the info about each of their products . like mixing , thinning , drying times and the like . if there is ever a question about rib stiching , go ahead and do it . mine arent and i would rather they were . just a piece of mind thing .