Dope for dummies

Paint the body with 50/50 Brodak & Thinner.
Sand it smooth after dry.
Using light wt silkspan...(switch to medium or heavy for the turtle deck) cut the silkspan close to the shape of each panel with a little extra around the edges.
Dip the silkspan in a cookie sheet of water.
Carefully lay the silkspan onto a waiting paper towel and squeeze the excess water out by pressing another from the top.
Lay the damp silkspan on the frame, and "paint" it on with 50/50 again.
Once dry, gently sand the corners with extra fine sandpaper to 'Trim' the edges off.
Follow with the rest of the frame, making sure you dope either side of the sheet balsa parts (rudder and elevators) as equally and close together in time as possible.
Follow up with more clear, gradully taking each coat closer to full strength, with gentle sanding between each coat.
Also, if there is a bulkhead supporting the stringers, 'scallop" it's edge between each stringer to keep the silkspan from adhering to it.

Then go with your color, remembering to use a fine brush with 50/50 clear to seal your masking tape edges before hand.

For what it's worth....

Ron,

Have a look at the video's of Kirt Blattenberger of Airplanes and Rockets on Youtube. He explains covering very well.

https://www.youtube.com/watch?v=3nC-LEeBE-w

Lieven

Kim, "scalloping" bulkheads supporting stringers is interesting. Would this have to do with physical stresses on the paper... or does it help when adhering the paper?

Can I use regular rustoleum type paint or do I have to use color dope?

roddie wrote:Kim, "scalloping" bulkheads supporting stringers is interesting. Would this have to do with physical stresses on the paper... or does it help when adhering the paper?  

It's pretty much just a "looks" thing, making the stringers form the length of their run with no "bumps".  It's also done on full-scale aircraft, again mostly for looks, but it WILL help keep the fabric from being fatigued over hundreds of wax jobs and their buffing over the life of the fabric.

I often get caught up in the excitement of finishing, and forget to do it...and just live with it afterward...

Just a couple of addendum's to Kim's excellent instructions.  When doping the silkspan or tissue down for the first time, it's OK to use your fingers to smooth out wrinkles and to help force the dope thru the silkspan to the underlying wood.  The composition of dope is such that it will revert back to a liquid state in the presence of thinner.  So doping the silkspan involves getting the underlying dope to soften and bind with the dope in the silkspan.

When you first stick the damp silkspan to the wood, after drying, it will appear whiter than the other silkspan --- we call this blushing  --- it's due to the moisture being trapped within the dope since the dope "drys" faster than the water can evaporate.  Not to worry, it will disappear when the next coat is applied.  Painting with thinner alone will also help remove blushed areas.

If you dope sheeted surfaces, as Kim said, it is absolutely imperative that you dope both sides as quickly as possible, otherwise, the shrinkage of the dope will curl the wood.  Do not use tautening dope on fuselage sides or other flat wood surfaces where you cannot apply a coat on the opposite side or your beautiful fuselage will look like a pretzel (don't ask )  .  You can get non-tautening dope in both nitrate and butyrate --- use this where you are painting sheeted areas on one side.

Where two surfaces come together at a 90 degree angle, you can get "bridging".  This is caused when the dope begins to dry and shrink, it will pull away from the joint leaving what appear to be a fillet.  This will need to be broken away ( a toothpick or fingernail will work) and flattened using thinner.  You will need to paint one surface up to the joint, allow to dry, then paint the other surface.  If you leave the bridge, it will eventually crack and allow oil to seep in under the paint coat and soak the wood.

Lot's to chew on guys. Thanks to everyone who has posted. Some really good info!

Still no answer concerning the standard paint over doped finishes.

Ron

Ron, typically you can place enamels over lacquers and not the other way around. If you chose to paint Rustoleum over dope, this can be done, but it's much more stable with nitrate dope as a base coat. My other post discussed how nitrate is a universal base for almost all paints. You do need however to let the nitrate or butyrate gas off for a few days almost to the point where you can't smell it prior to spraying enamel over it. The problems you run into is the incompatibility of the two when you need to make a repair. You won't be able to dope back over top of the enamel because it will alligator and wrinkle. I've done it with spraying dope over the enamel and used a very fine dry mist for a few coats because if you hammer on the clear it will just melt the Rustoleum finish.

Most users don't like to use nitrate dope, I do. Reasons I like it is , it dries quicker, sands without as much clogging the paper and I can recoat it faster. Sig uses the same thinner for their nitrate and butyrate while Brodak requires 2 different thinners. Butyrate dope doesn't work well with   synthetics like polyspan or Sig Koverall. The coats can shed off. Nitrate gives a better bite into the synthetic. Seeing that your quite fond of the Rustoleum finishes, have you tried Minwax Polycrilic as a base coat. I've seen some beautiful painted planes done with that method. Ken

Man, this IS good stuff ! I've got some raw-wood chuck gliders I may have to experiment on! Thanks to Ken and you guys for the info, and to Ron for starting this thread !

In the "old timey Aero-gloss days we brewed our own sanding sealer consisting of one part Aero-gloss clear, one part Aero-gloss thinner and one part talcum powder. (Parts by volume)

It worked quite well to provide nice smooth butyrate finishes.

SD of the Ancient Age.    

SuperDave wrote:In the "old timey Aero-gloss days we brewed our own sanding sealer consisting of one part Aero-gloss clear, one part Aero-gloss thinner and one part talcum powder. (Parts by volume)

It worked quite well to provide nice smooth butyrate finishes.

SD of the Ancient Age.    

I experimented a little with this on my last build.  Modern talcum powder is corn starch, so just use corn starch.  It is cheaper and does not have fragrance to mess up the chemistry.

Add the starch to the thinner, then add the dope.  Mix only what you are going to use.

The allowable proportions of starch, thinner, and dope are pretty loose.  1:1:1 is a safe starting point and sands nicely.  More starch and less dope sands easier.  More dope and less starch makes a harder surface.

Can talk about sandpaper too. Since everything is so soft using low grit paper is not going to help since the lines from one grit need removed by the next. I start and finish with the same relatively high grit paper. 400 on a "trainer" or "sport" plane.

Phil

I have a Baby Streak that was given to me a year or so ago, and it's fuse and stab/elev. are only bare wood obviously painted with some sort of clear. The plain wood grain look is really nice. When I got it, I gave the fuse forward of the wing and the roots a thin epoxy paint job just to be safe, since I use the plane rather than just look at it. Any idea what the clear he painted it with could be? It's apparently fuel proof. I'd like to build one with this bare wood look. Or use whatever he used as a base coat for my color. Maybe it was Minwax polyurethane or something???
Just wondering,

Rusty

Certain polyurethanes are fuel proof, but not all of them. I know the "water clean up" variates of min-wax are dissolved by fuel and denatured alcohol.

Phil

Some of them are alcohol resistant according to the labels. I guess one of those would be the obvious choice.

RknRusty wrote:Some of them are alcohol resistant according to the labels. I guess one of those would be the obvious choice.

You would think, but they mean "ethanol" in percentages commonly consumed as a beverage, so up to 100 proof, or 50% and not very near pure like we tend to use.

Verify and be safe. A sample to test is quite easy and prevents lots of problems down the line.

Phil

pkrankow wrote:Certain polyurethanes are fuel proof, but not all of them.  I know the "water clean up" variates of min-wax are dissolved by fuel and denatured alcohol.

Phil

I found that out when I had added a clear coat to a rebuilt fuselage and it turned into a gumball.  I was pi$$ed to say the least.

Cribbs74 wrote:Can I use regular rustoleum type paint or do I have to use color dope?

I've been having great success using rustoleum over this:
https://i.imgur.com/iGMmd8X.jpg
So far I've used black, orange, and red with fantastic results.

Jim

Cool Jim,

Thanks, that is what I have available locally.

I'm going to the HS today. Maybe they have some of that. Have you ever used it by itself with no color?

My "home brew" sanding sealer actually used baby power rather than talcum powder which is coarser and probably not as suitable to achieve a super smooth finish.

SD