I don't think you want to try to paint anything over Butyrate Dope. I do not know of any type or brand of paint that will go over Butyrate and stay there. Usually, once Butyrate is used the only thing you can paint over it is more Bytyrate.
Originally Posted by
CurtD
Haven't tried to use Minwax water-based polycrylic directly on fabric covering over open structure but here is something you may want to consider... Koverall shrinks with heat but only so far. Normally, I start with a base of 3 brushed coats of thinned nitrate dope to both seal and further tauten the covering over open structure, giving the structure more stiffness and strength. The polycrylic won't do that. It will not cause the covering to shrink further but will allow the covering to remain more flexible, not stiff and taut as a doped covering would be. I think you would be fine using the polycrylic over a suitably cured dope base (either nitrate or butyrate) of at least three coats. I'd let it cure a week or so after the last coat then you should be able to switch to the polycrylic.
BTW, the water-based polys like Min-wax are not hot glow fuel proof but can be made so by using Nelson's Hobby crosslinker. I suspect you're probably using a gas engine on the T-craft so that's not an issue. Built a 1/4-scale T-craft years ago with a 25cc gas engine (can't remember the brand) but sold it before first flight!
Hope this helps...
Curt