smokeyser

I was thinking about covering the PT-40 that I'm putting together as a winter toy with koverall and dope to practice with cloth before attempting it on a scale project. But when I checked out the dope at the lhs, it was pretty old and the pigment had all settled to the bottom. When I tried shaking up the jars, the pigment didn't move at all. Would that stuff be ok if I stirred it up and gave it a good shake, or should I just order some new stuff from sig?

And while we're on the subject, about how many oz of dope is required for a .40 size trainer? I was thinking about getting 2 8oz jars of color, a pint of nitrate, and a quart of thinner. Would this be enough to paint more than 1 plane?

w8ye

My Feedback: (16)

That sounds about right but if you are using a glow engine, the Nitrate will not hold up where it is exposed

smokeyser

Thanks w8ye. So that amount of paint is what's required for a single plane? That's going to take a lot of sanding to keep the weight down. The colored paint that I intend to buy is butyrate dope, so fuel proofing shouldn't be an issue. I've also got a quart of minnwax clear poly left over from another project so I should be covered if additional protection of the paint job is needed.

What about the dope at the lhs? I prefer to buy from them whenever I can, but I'd hate to go buy a bunch of paint only to find out that it'll never be the same again. How many years of settling can the stuff handle before it should just be thrown out? Or can it always be mixed back up and made good-as-new again?

chashint

I have used Sig dope and Randolph dope, including the Sig and Randolph branded thinners and retarders
The dope was applied per the directions and it looks real nice.
However all is not perfect, the dope is not fuel proof to raw fuel.
I have not had any issues from exhaust residue but if raw fuel or raw alcohol gets on the finish it will melt it.
I am heavily invested in the Rabdolph products right now so economically I will need to use it before moving on to something else.
That something else is going to be the Stits Poly-Coat products.
Here is a link to the website http://www.stits.com/store/index.html#36
I may be the only one here that has had this issue with the dope, but it has been with two different brands. If I had found the Stits products before i spent so much money on the dope that is what I would be stocked up on right now.

Rodney

Yes, butyrate is the fuel proof one. You can apply butyrate over nitrate but not nitrate over butyrate. Very often, the old timers always did the original coats with clear nitrate (it always takes 3 to 7 coats or more of dope for a good finish) then use colored butyrate for the final coats. The nitrate dope does a better job of shrinking the covering as it cures than butyrate does. Yes, the pigment settles over time but it will be fine, just use something to stir it well before using it (lots and lots of stirring).

w8ye

My Feedback: (16)

An old bottle that's been setting around for 5 years? You will never be able to get all the pigment off the side of the jar. But if the liguids are still liquid, the paint should be fine. You need something electric to mix it back up though?

Jim Thomerson

I made a dope stiring thing out of a piece of coathanger wire for use in 4 oz bottles. I found a commercial paint stirrer which works OK in pints and quarts so long as the can is not too full. If the can is too full, you will get dope on your clothes and shop.[]

smokeyser

Thanks for all the tips guys! A wire stirring tool will be easy enough to make. And maybe a drill to make the job easier. I'm just glad the supplies right down the street can probably be used. It's always nice to be able to hop in the car and head to the lhs rather than waiting on shipping from an online store.

Hossfly

That is all OK if that is what you like. However if you want to do dope finishes, first, Hooray for YOU, Way to go, as real modelers are becoming fewer and fewer.

Now if you wish to do a really good dope job with the ninimum amount of "unhappy", please let me suggest the best dope ever as far as aeromodelig goes. That is Brodak Dope. http://www.brodak.com/

Brodak is the saver of CL modeling and also active in RC. He worked with Randolph and came up with a better dope for the modeler's application that basic Randolph and IMO, SIG, which is basic Randolph repackaged.
You can have your local H-S stock Brodak if that makes you feel better. OTOH if the LHS doesn't wish to do so, then you have to make that choice.
Once you use Brodak, I think you will be well pleased.

You will need adequate Clear and filler to get some 8-12 coats put together then some 4-8 coats of color, depending on the quality of cover and color you desire. It takes a lot of filler and sanding to make cloth such as coverall look like a metal finish for a scale model. (P-40)
I suggest some retarder along with the thinner, especially for the final coats. You can use acetone (much cheaper) or lacquer thinner for clean-up and that will save a couple bucks if you wish to save.

I found that after a few early coats of clear and talac powder, using some color in the filler helps get the white powder hidden with less actual color. A good dope finish takes a long time. If you clear coat the color with several thinnn coats of clear sprayed on, and let the finish cure for several weeks, a good butyrate finish will handle glow fuel very well for years. Fly it after just a week, and, well, it may not be so pretty. []

BTW, forget that old myth about nitrate. Use butyrate all the way. Nitrate is very good for what nitrate does, and I have played every choice. However I have finally come to realize that there is no need to use nitrate to get a good finish outside FF and OHLG.

Best of luck to you.

smokeyser

So just going straight butyrate won't warp the wings due to excessive shrinkage? The plane I'm working on right now doesn't have fully sheeted wings, so they can twist a little. Also, if I understand this correctly, dope will soften the layer below it when applied. I was thinking about using white to fill the weave rather than clear (trying to save a few bucks by skipping the clear and primer), and then painting over it in some areas with red. Is that just going to smear the white and make a mess?

Oh, and I had a look at brodak's web site. They've got an amazing selection of colors and I'll definitely be going with their products. If the Miss Ashley red looks half as good on the plane as it does in the pictures, this is going to be one pretty little trainer (provided I don't make a mess of the paint job of course).

By the way, you guys should really be careful. All this support is likely to lead me to a serious building addiction coupled with a nasty case of empty wallet. I'm still in the sanding phase of my current project with another plane that I've only flown a few times and there's already another kit calling my name...

w8ye

My Feedback: (16)

White weighs more than clear when it dries.

I used Aerogloss butyrate for years and it didn't seem to cause any warping

But real Randolph butyrate clear from Randolph themselves or from the airport will literally crunch a lite framed plane. You have to put three or four drops of castor oil into 4 oz of dope to keep the shrinkage down.

The Sig and Brodak never seemed to cause any trouble

chashint

There is also non-tauntening dope (Randolph brand). But as I said earlier I have had some raw fuel and alcohol issues with it. The dope still had issues at the one year old mark so it is not because it is not fully cured.