> > > >I always thought it would be best to have a darker coloured paint > >job, although could anyone comment on if that would affect the frame > >(In relation to trapping heat, hence heating up the airframe)? >
Dark colours are an absolute no-no with the current type of resins used in gliders. They're a wet resin and at temperatures around 55ºc they start to soften and lose strength. You can see this with the wing droop on some open class gliders on a hot day. So anything which increases the temperature of the glider and the resin will adversely affect the strength of the glider. Pre-preg resins are cured at higher temperatures and carbon pre-preg products don't have such a low temperature limit. So most aircraft which use pre-preg spars including hang gliders, can get away with heat absorbing colours. Dark coloured lower surfaces and vertical surfaces are less of a problem. All this is covered in the visibility articles on the DG web site. Even down to tests on heated wing structures. I'm fairly deaf and I have some parts of the glider covered in white fur (ermine) since it increases the noise for the handicapped. Works for bees and owls, but you have to fly in their Reynolds number regime to make it work. DmcD
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