Original URL: http://www.theregister.co.uk/2010/09/07/paris_bends/

PARIS threatened by the bends

Careful with that dope

By Lester Haines

Posted in SPB, 7th September 2010 14:10 GMT

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:

Section of skinned and doped test structure

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:

Bent straws in the section of test structure

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...

The Vulture 1-X fuselage structure

...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