PARIS threatened by the bends
Careful with that dope
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El Reg's Paper Aircraft Released Into Space (PARIS) team continues to work on the Vulture 1-X aircraft structure, while attempting to refine the skinning process.
It's all been a bit of a palaver, as followers of our audacious space programme know. We've tried various lines of attack, and recently thought we'd cracked the covering problem with tissue paper and a couple of coats of shrinking dope.
However, the model aircraft experts among you noted that the traditional method is to fix the tissue paper to the structure with PVA after giving it a light spray of water. Once the paper's nice and dry - and tight - you slap on the dope.
Well, we thought we'd put this to the test, to probe the effect on the paper straw structure of what is effectively two bouts of shrinkage. Here's a piece of test structure with the pre-moistened tissue paper glued to the straws, then given a coat of 50/50 shrinking dope and acetone:
A nice finish, but most of you will already have worked out what's coming next. Here's what happened to the structure as the dope dried:
We're aware that this is a common problem with balsa and tissue aircraft wings, if you don't keep a tight grip on them. Balsa's stronger than paper straws, though, and while our robust Vulture 1-X fuselage...
...would probably withstand the shrinking forces, the wings are a serious concern if we continue down this road.
While we mull the problem, your comments and/or suggestions are warmly welcomed. Further skinning will, however, have to wait, because we're back off to QinetiQ's hypobaric chamber next week to try out the Mk 2 release mechanism, on which the whole project currently hangs. More soon... ®
Additional PARIS resources
- Our dedicated PARIS section, with all previous updates, is right here.
- New to PARIS? We have a basic mission summary here (pdf).
- Our Flickr page, with all previous photos.
- Check out our YouTube channel - currently featuring a few kit tests.
COMMENTS
Re: Solarfilm for model aircraft
Is that what you call a Banner advert?
Skin up...
...with some primo dope, lie back and don't give a shit man!
My stash is in a hidden pocket.
Wet after glued to both sides.
I've made plenty of balsa/tissue planes. And once even made the mistake of covering a single side before shrinking the tissue; now you know the results too. But I agree with other posters here. You glue (with dope - on the balsa and then through the tissue ) the tissue dry to one side of the wing, and only glue the leading edge, trailing edge, and outermost ribs. You trim that paper with fine sand paper. Fix paper to the other side the same way, and trim. Now you have the wing fully covered but only fixed with dope around the circumference of the wing. Now, you steal your mom's best perfume sprayer empty and fill with water. Very lightly spray the tissue uniformly so that it shrinks uniformly and does not warp your structure. You may need to do this three to six times being patient to let it dry between spraying. Hang dry using a thread. The tissue will now be taught uniformly and the structure should be fine. At that point further dope through the tissue at the ribs to fix the tissue to the ribs. After that you can choose a 50/50 dope/thinner spray - again in mom's perfume bottle - to coat the whole wing. But I never did as it will add too much weight. Good luck.
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