dreadnaut

My Feedback: (5)

A friend had talked me into using dope and silkspan on my next project. I found an article at http://winshiprc.tripod.com/covering...y_jim_ryan.htm that says to use nitrate dope for attaching the silkspan to the wood, but that since it is not fuel proof, it has to be finished with butyrate dope.

Can anyone tell me why i should not just use butyrate dope for the whole thing?

LesUyeda

Nitrate will stick to almost everything, and you can paint almost anything over it, but like the man said, it is not fuel proof. With butyrate, it is not adviseable to paint anything over it, except butyrate. It continues to shrink forever, and almost everything else will crack and peel.

Les

CurtD

My Feedback: (1)

I've used butyrate to attach silkspan many times back in my old control line days and never had a problem. I think nitrate is a little easier to work with and for some covering mat'l (like polyesters) it's a must but for silkspan butyrate will work fine. Just be sure to put several coats of butyrate thinned well for brushing on the bare structure. After it dries well you can attach the silkspan with a 50/50 mix of dope and thinner, or use an even higher percentage of thinner if the dope is fairly thick. You want it pretty thin so it will penetrate the silkspan and soften the dope underneath for good adhesion.

Incidentally, I stopped using silkspan over open structures because of its fragility and ease of puncture. It also seems to deteriorate pretty fast from what I remember.

dreadnaut

My Feedback: (5)

Thanks for both of your responses. I have also spoken to my *dope fiend* buddy, and decided to go the 100% butyrate route. The project is a modern 2m pattern plane, so there is no open structure. He is also a fan of the Brodak stuff, and they do not even make a nitrate.

F106A

My Feedback: (2)

Hi,
Butyrate doesn't adhere well to the surface and it is very difficult to mask and paint trim without lifting some of the base paint off when you pull the masking tape off. A trick I learned a long time ago is to put the tape on your forearm first before putting it on the model. You use the forearm because there's no hair. It takes some of the "sticky" away from the tape and the "sticky" is further reduced because of the oils in your skin. We also used drafting tape, but I'm not sure if it's still available. Make sure you seal the edges of the tape with clear and let dry to prevent the paint from bleeding under the masking tape. You could also try some of the vinyl automotive trim tapes, they may work better than masking tape, but try a sample first. Of course, we didn't have anything like that way back when.
BRG,
Jon

dreadnaut

My Feedback: (5)

First, drafting tape is still availabe, but you have to look harder for it. I used to use the Levis I was wearing to *de-sticky* masking tape when I ran out of the drafting stuff. I works by picking lint from the fabric. For masking, the good quality automotive stuff is all I use.

CurtD

My Feedback: (1)

Check out Home Depot or Lowe's (or a paint store) and look for "low tack" masking tape. The finish on my Pitts M12 is butyrate and I used the low-tack masking tape from Lowes with no problems. I used Certified and Randolph colors with Randolph thinner. I was spraying in hot weather so I added quite a bit of retarder to slow the drying process. Using the retarder is VERY important for proper flow and adhesion with butyrate. I've had no problems with adhesion or lifting when pulling the tape up.

jessiej

I prefer to use nitrate clear for initial coats as it has more solids and fills faster than butyrate. Just be sure not to put nitrate over butyrate.

jess

kdheath

FWIW, Brodak lists clear nitrate on their web site, and I have used it in the recent past. Also have a couple quarts of SIG nitrate. Both are fine.

The wood should have a light sheen before you apply the tissue. Sand very lightly between coats and stick the tissue down with a mix of 90% thinner/10% dope. If you want to, wet silkspan in a pan of water and spread it out on a towel to dry just a little. Apply it damp, dope it down around the edges and trim. After it is dry and shrunk tight, apply the coats of dope.

A couple of alternatives include Esaki Japanese tissue from the free flight suppliers and 0.2 oz carbon fiber veil from CST or other suppliers. I really like the Japanese tissue over solid surfaces-it fills to a shine very quickly and sands easily. The CF yields a very hard surface, but is a little harder to work with.

If you want the very best info on dope finishes from a real master, see the videos at
www.windyurtnowski.com Windy is probably better at this than anyone, living or dead! He says that he spends about 100 hours sanding the finish on just a wing. He helped Brodak develop their line of dope and colors. Brodak sells a great product.

You'll love how much better a good dope finish looks than iron-ons. Best of luck!