I have a Unionville Beaver with an 8' wingspan. I needed to do some repairs to this plane as a result of pilot error. I purchased the plane a few years ago and the original builder covered it with dope and fabric. I love the finish and bought the plane because of it. I have completed the structural repairs and done the final sanding. I started doping with the exact same can the original builder used as he gave them to me. The dope was thinned and applied with a brush. In places it went on very well and others not so good. I am doing these repairs in my airconditioned basement with a dehumidifier running constantly. It is not humid down here at all. The red stripe in the photo is where I have had most of the trouble. I hope the photo shows it clearly but the red went "chaulky", almost like ash. I don't know what I have done wrong, obviously something. I need help bad as this plane is the pride of my fleet and I really want a decent finish back on her.

It looks like blush. It happens when the dope dries too fast and traps mositure in the paint. Paint again and it will disappear. But first purchase some retarder it helps. Mix it into the dope.

[link]http://www.brodak.com[/link]

look under parts in the online shopping for retarder.

I've had similar problems with blushing dope in the past. Often it is the result of applying the dope too heavily or applying a second coat too soon. One of my mentors in modelling who built beautifully finished birds told me that if you can still smell the dope it isn't dry yet. I've found it takes several more thin coats of dope than is necessary with other finishes.
Walt

Thanks guys. I have some retarder, just never used/needed it before. The dope was thinned about 50/50 so I don't think it was too thick. Maybe it is drying too fast. This blushing happened after the first coat so I also don't think I applied the coats to quickly. I will try the retarder and hope that works.

BTW, I am using Randolf's Aircraft Finishes products.

Brodak gets their supply from Randolph. Add retarder to the red pigment dope. It will not absorb moisture as fast. Unless it is raining then there ain't enough retarder in the world to stop the blushing.

Thank you, that made me laugh and I needed that as I was fit to be tied after this experience.

Hey,

I don't think what you see is blush--it really looks as if there was a very slight amount of fuel residue present when the dope was applied. Blush does not usually show up as white as you have here.

The area to be painted MUST be VERY free of fuel residue or it will turn white just as you have seen here.

You may have to sand the bad dope off, clean with 90% or higher alcohol and try again.

A clue is that the problem seems to exist near the fuel fittings---.

Thats is exactly what I did in the end. I sanded almost down to the wood and I am masking off the lines now for repainting. I am not going to repaint/dope the entire line all the way to the tail, so am I going to be able to see where I stopped doping?

It has been too many years since I doped a model, never used Randolph, but as I remember it---the repair should be hardly visable.

If you put a final coat of clear over the whole fuse, it will help to hide the repair.

Ok so the results are, I masked off the red stripe and applied dope with retarder added. I still had the ash effect come through. So I then took a clean paper towel and used that to apply thinners to the surface effectively stripping the dope completely off the surface. Then I applied another coat of red and I still have the same effect but now I also have spider cracks showing up after the first coat. I need help bad.

Sounds like you may have some wood which has absorbed some fuel. There is a product (garment spot remover) called K2R which will probably pull most/enough of the fuel residue out of the wood to allow a decent repair.

Gunsmiths use a more effective product (It is called "whiting" ) to remove oil from gunstocks, available from Brownells;
www.brownells.com, item # 083-032-100, phone 800-741-0015.

In extreme cases, I have had to remove oil soaked wood and replace with new wood.

With any finish, all cut-outs for switches, fuel fittings, pushrods, access holes or whatever, should be done before the finish is applied to avoid allowing fuel any access to unfinished, unprotected wood.

Hope this helps.

I went to my local supplier of Randolfs and they asked me a question I was not aware was an issue and that is "How old is the dope your using?". It is 10-15 years old, I was under theimpression that dope didn't age poorly. Apperently this is not the case and Randolfs recommended shelf life is one year after opening. I bought a new quart of the same colour and tested a patch, so far so good. Only problem now is the new quart is not an exact match to the old colour, so now I have to paint all the surfaces that had that colour with the new colour.

A side note, this all started when I had to make a repair to the landing gear. I made the repair and then was using white dope thinned down to seal the new repair and I had a small run down the side of the fuse. It got to the thin black stripe and the bigger red one before I could stop it. I wiped up the dope before it dried but it left a smear of colour. So all I had to do was touch up the red and black stripes. Did the red first, just a small area as the run mark was very small. Thats when this turned into a bigger job than the original repair was. The small red touch up area turned white, so I applied another coat big enough to cover the white from the first and so on and so on. Now I am down to bare wood starting from scratch, all for a friggin run of white dope. Isn't this fun?...lol

Don't know about Randolph's shelf life--I have used Pactra, Sig and Testors that were 6-8 years old with no problems.

I just want to pass along a trick I learned from a full size aircraft mechanic about patching dope. He was showing me a repaired spot on a Bellanca Viking, and said that he would tell the customer to bring the AC back in 6 months for a final sanding and rub out. Since dope continues to dry and shrink for quite some time, if he sanded it out too soon, the patch would reappear as the dope shrank. Let your patch dry for several weeks befor you try to blend in in again.