Using Brodak Dope

After following the discussion about Brodak Dope, I decided that is what I will use on the new plane I am building. I am about ready to order, but need some clarification;

l. What is rejuvenator? Under what conditions and how would I use it?

2. What is retarder? Under what conditions and how would I use it.

After reading this forum for several months I an excited about starting this project.

Rejuvenator is used to repair old dope. If you are building a new plane, you don't need it. If you have an old plane that you wish to refinish over the old dope that is getting brittle, you may want to spary it with rejuvenator first.

Also, if you have a small crack or tear in the silkspan on an old or not so old plane, you may be able to brush rejuvenator over the crack or tear and melt the dope together over the area to "fix" it without having to put a patch over it. Even if you end up putting a patch over it, this little "trick" can help blend things together and make the patch less noticable.

Retarder, on the other hand, slows things down while drying. Now, one of the nice things about Brodak dope is the fact that it dries very quickly. Under humid conditions, however, it may dry too quickly and you will end up with "blushing" (where the rapid evaporation causes moisture condensation which then gets trapped in the finish.) Using some retarder in place of thinner helps to slow down the drying process and can prevent, or at least, reduce this problem.

Use retarder only when needed, however, for, not only will it cause the dope to take longer to dry (longer before you can sand, longer before you can rub out, longer while it continues to stink up the workshop) but it can actually lead to melt down, a condition where the top layers of dope eat down into the lower layers and bring the lower layers up where they can merge and mix with the top layers. If you use silver of Polar Gray for a blocking coat, for instance, these could bleed up through your top color coats if you slow down the drying process too much.

This is an extreme case, however, and will happen only when you use too much. This is another case of "if a little is good, stop!" A little more may be too much.

These are both specialty items that each have their special purposes which may or may not be applicable for your needs.

Leonard Neumann

On the subject of "bleed thru" of bottom coats, I can offer a warning-I recently did something that I now realize was stupid, but I am just getting back into serious building. On a completed wing panel, with clear coats already applied and sanding done, I was uncertain about the color scheme I wanted to use. Thinking I might use one of the new candy cokors by Brodak, I foolishly tried some to see what effect it would have, what the color looked like on the plane, etc. When I decided not to use it, I found that it would bleed thru anything I tried to cover it with. The plane's basic color is white, and silver, sanding sealer, clear plus more sanding, more white, etc. and it just keeps coming thru. This is one of those lessons learned the hard way.USE A TRIAL PIECE.
On the subject of re-finishing an older or existing plane, I have a large plane that I would like to refinish. The existing paint is covered with a clear coat, with the base being white, with trim in black and yellow. All needs to go. What would be the best way to remove it?

You can sand some of the top dope off if you have heavy coats, but you want to make sure you don't sand through into the wood or paper underneath. One way to remove the old dope is to use thinner soaked in a paper towel and a lot of rubbing. You can get some cheap thinner at your local auto paint supply store. You aren't concerned about compatibility here or whether it even mixes well. You just want something that will eat into the coats so you can rub them off. This takes patience, a fair amount of thinner and rubbing, but it does work. Matt refinished his '96 ship this way and even changed color schemes.

But it is a lot of work.

Did I mention that already? It is a lot of work.

I couldn't agree with you more. I had an old airplane I didn't like the old finish. I used the thinner and paper towel method to remove the old paint. About half way through I was wondering what was so bad about the old paint scheme.

Lots of work!!!

"Z"

Jim:

I think you'll like the stuff! I also think that you are better off with too much thinner than too little.

Retarder is nifty, and I have seen Windy use it at about 75% with thinner when conditions warrant! I wait a bit, as retarder is more expensive than thinner. I would strongly advise not "mixing" brands (i.e.: SIG / Aerogloss or whatever) , the closest might be to use Randolph's thinner from your local real airplane paint place.

I mixed up some "extra" stuff once as a primer for a butt ugly trainer that I had created. The mix gurgled and bubbled and swelled up all foamy. I poured it onto a tree stump to kill the termites, and it is still "rubbery" today!

Better, i guess, than having it ooze and fester on a plane?

See Ya

I appreciate the replies. Thank you all.

I have already disposed of all other brands of dope and thinner I had. I plan on only using Brodak from now on.