Mylar/tissue for sheet structures

[Jmk89]

The Mystery rubber-powered model is approaching the covering stage. I will use Mylar/tissue for the flying surfaces, which are open framework structures.

However, the fuselage is fully sheeted and I'm not sure whether to Mylar cover it first or just apply tissue.

My thoughts are that the sheet structure provides as much, if not more, strength to the tissue than Mylar so the question comes down to weight. In other words, will the weight of the Mylar and very little dope be more or less than the weight of the dope used on the sheeted structure. I suspect more dope will be used without the Mylar barrier, since it will not only soak into the tissue but also will be absorbed by the balsa.

I know that this is a clear case of over-thinking an issue, but does anyone have a view?

[OZPAF]

I think the fly in the ointment may be covering a sheeted surface with mylar. I can't speak from experience but covering sheeted surfaces with any plastic film requires careful temperature control and technique - perhaps the thin mylar may be easier to keep tight.

Perhaps a small test would be the way to go - good luck.

John

[Prosper]

I know that this is a clear case of over-thinking an issue, but does anyone have a view?

Yes, my view is that you're clearly over-thinking the issue.

Soh-reeee - couldn't resist . Actually, I'm interested to see what befalls, being completely ignorant about Mylar and Mylar/tissue. Good luck with your covering.

Stephen.

[Mike Thomas]

I've used tissue over Mylar or Doculam a fair bit. Excellent over open structures, but I don't think there's any merit over fully sheeted areas. Mike.

[Jmk89]

I've used tissue over Mylar or Doculam a fair bit. Excellent over open structures, but I don't think there's any merit over fully sheeted areas. Mike.

That's the conclusion I was coming to.  Sometime I might do an experiment. but not now!  I'll wait until I have nothing better to do....

[Jmk89]

BTW the laminating film I got through Temu is about 17g/m2, which I think is about 1/2 of the weight of the film that Mark Robinson uses and is therefore more appropriate to our kind of models.

[lincoln]

I think I would just use sanding sealer, dope, or nitrate lacquer, unless I was worried about splitting. For instance, on a Gentle Lady RC glider fuselage. I've heard of using very sparing coats of water based urethane wiped on with barely dampened paper towel. That way, maybe any dope applied later wouldn't soften it. About the same weight as Sig Sanding Sealer, but far more annoying. I wonder if anyone has experimented with gel varnish or gel stain for models. The idea was from djaerotech.com in the "ask j&d" section. No longer on the web, but might be at archive.org . They seem to be bogged down right now, though.

[Jmk89]

I am covering the Mystery model now using ordinary dope (nitrate I think) to seal the sheeted fuselage and then tissue over that.  The fuselage is only 0.8mm (1/32") balsa and is 900mm (36") long, so I feel that a layer of jap tissue doped on will help.

The flying surfaces are all open structures, so I prefer film underlay with a tissue surface for toughness and lightness.

Pictures in a few days - I am going on a trip to the Australian War Museum to look at the new aviation exhibits for a few days so I doubt I will get the covering done by the tie I lease, but we will see.