I would not put Polycrylic over dope -- I don't think you'll have any appreciable adhesion at all.  If you have buterate dope I'd switch to that, since you're over wood you can probably stick to nitrate.  In either case I'd just finish it out with dope and put Superpoxy on top of that.  If you're looking for sanding sealer and you don't have any, mix baby powder with clear dope -- it works great.

Of course, a really ratty finish on a Ringmaster is probably more period-correct than a pristine one, so maybe you should stay on course.

I've done five models that were finished with polycrylic direct onto wood.  With the exception of the center sheeting on one model getting warped, I haven't seen any problems -- and that center sheeting was slightly oversized and jammed down to fit, instead of giving it a few more strokes with the sanding block so that it eased itself into place.

I do brush the first couple of coats on very dry before I really go to town.

Ideally you probably want to give it a week to really gas off, but I think you'll be OK with 24 hours.  At least you'll know...

  Like Tim mentioned, if you are going to top coat with epoxy, why even bother with the polycrylic stuff? It has been preached and mentioned more times than I can remember in Stunthanger's existence that it is best to stick with one finishing method though out the finishing process to avoid compatibility issues, and the difficulties in making patches and repairs later on. It avoids questions like the one you are asking. A couple more coats of the nitrate (or buterate) with some sanding, then the epoxy, and you should be good to go .
  Good luck and have fun,
  Dan McEntee

thought this thread would get more traction.

Probably no one has tried that particular combination and thus doesn't know the answer.  You may be the word's foremost expert on Polycrylic over nitrate dope.

Several weeks ago, the owner of this site clearly stated that there is not a question that can't be asked.  Lets not start this again.

  No one is "starting anything again." Don't take the statement out of the context of the post. If one wasn't trying to pile on so many different materials on top of a model you wouldn't have to worry about drying times and compatibility issues. It's that simple. I just don't see why guys are trying to find the magic "quick bullet proof finish" when it doesn't exist and complicate the matter by using multiple finishing materials .Stick with the nitrate all the way through, and you can be done with build up coats in a day or so. Let gas off a day or so. The finish with the epoxy which only needs a day or so for it to be ready if applied properly. Since all he is doing is the solid balsa parts, there is no reason he shouldn't be ready to fly by this weekend if he had started last weekend.
   Hey Doc! Nitrate is not intended to go over anything. It is supposed to be a primary coating, but if fuel proofing isn't an issue, such as in stick and tissue rubber models, or hand launched gliders, it can be used through to finish. Some think that it has the best adhesion for applying tissue paper. Lots of different things work for lots of different people but if you look into it, they did a lot of trial and error to come to the system they like best. Allen Brickhaus had his favorite finishing method that he described on this forum several times and published in construction articles several more times, that some people have problems with, but Allen used to quite good effect. I finished several airplanes the way he described with very satisfying results. You just have to find what works well for you in your situation and stick with it.
  Type at you later,
   Dan McEntee

So true, that last statement. 

That he'll type at us later?  I hope so.

I like this method because polycrylic doesn't smell and cleans up with water and you don't have to thin it. It's just so easy to use. Also, you can paint anything over it and you can get it at any hardware store. Love the polycrylic.

I use the nitrate for good adhesion and protection from any water base problems. Then you have to top coat it with something fuel proof and SuperPoxy cures fast and only takes enough coats to fill in the color in this case black so probably 2 coats. Done in one week with monokote wings.

MM

 

I like this method because polycrylic doesn't smell and cleans up with water and you don't have to thin it. It's just so easy to use. Also, you can paint anything over it and you can get it at any hardware store. Love the polycrylic.

I use the nitrate for good adhesion and protection from any water base problems. Then you have to top coat it with something fuel proof and SuperPoxy cures fast and only takes enough coats to fill in the color in this case black so probably 2 coats. Done in one week with monokote wings.

MM

 

     I think you can leave either the nitrate or the poly-stuff out and save a step and a bit of weight. Since you are finishing it off with epoxy, you could eliminate one or the other. I don't know what kind of "water base problems" you might be expecting, but if it's a material made to be applied to wood, I wouldn't think there would be anything tragic. With either you are going to have to use the sanding block to knock down raised up wood grain after the initial applications. I think it's just a redundant and unnecessary step and since it was untried, made for an needless worry about compatibility issues.
    Type at you later,
    Dan McEntee

Motorman,

Just took a look at your model.

You did a nice job. 

Charles