why are gliders white?
 

Why are gliders the same colour as the clouds they like to fly around?

At least for those build of composite its a temperature problem to use another color. It can heat up too much and endanger structural integrity. Sad but true.

Yup, same reason Cessnas and most airliners are white - stops the darn things getting too hot!

There you go. there had to be a a good reason why they make them harder to spot.

and why are white vans white???

As for the above... I DO know why;)

But as an aside... would you believe,.. that in Aberdeen/Highland,.. known as the most mean region on the planet,... the fire engines are white!!!

Perhaps 'cos red, costs a few quid more?!!!:)

I guess white shows damage and scrapes really well too, so you can easily see structural problems / missing screws etc on a preflight.

As far as I know black is the preferred colour for visibility. The RAF switched their Hawk & Tucano training aircraft from white&red to black because they found it was the most visible colour.

Not strictly true. The scheme was changed to black to improve contrast, not because it "was the most visible colour"

The UK ATC VGS gliders had orange flourecent stripes put on the wings as a result ( I believe, could be wrong on this) of a gliding accident at Sealand back in 95.

Massively increases vis, especially, as you say, of gliders habit of flying round the bases of clouds. As a former glider pilot, always scares me witless when you get radar descended through the significant cloudbase on a bubbly day; you could argue the transoport aircraft is likely to win; not an experience I would wish to experience though. (I belive all composite gliders are particularly difficult to see on Radar).

Some fire engines are pale yellow they show up better under sodium lights.
I think Coventry was the first.

Paint is weight.

"But as an aside... would you believe,.. that in Aberdeen/Highland,.. known as the most mean region on the planet,... the fire engines are white!!!"

Maybe it's just the Scottishness of the Highlands and Aberdeen? :)

evansb, you beat me to it. Many gliders were anything but white in the pre-composite days. Some aerobatic gliders still are, though that obviously has more to do with visibility issues. Quite a few natural metal-coloured ones around too, witness the Blanik, or the I.S.
Now, why do most bizjets have boring, dopey-looking stripes down the side? My personal jet will be black, with hot-rod style FLAMES down the sides! :}
(Note the 'will', ain't giving up on the dream, nuh-uh!)

A common complaint when we'd show up over a fire in a bright yellow airplane was that the air attack or leadplane couldn't see us. Eventually a national paint scheme was instituted requiring all aircraft to be white with red trim. I'd have certainly bet that a white airplane in a very smoky environment would be tough to spot, but the contrast between the colors makes it visible against nearly any backdrop. If the white disappears, the red stands out, and surprisingly,the white stands out very well, too.

As for composite airplanes, both the heat absorbed by the material, and the UV reflectivity are both issues. The structural strength and integrity of a fiberglass or epoxy surface suffers under high heat, and while you can certainly paint an airplane any color you like, white with a silver underlayer is often the best choice for protecting the structure.

It's also a very easy basic color to paint production airframes that any type of trim can be placed over...meaning paint all the airplanes white and then they can be customized any way you like.

On the ground most of the fire vehicles I've operated, or on which I've operated, have been red. Some agencies, such as the BLM, have gone to light green, which shows up very well, even against dense vegetation. I've seen some white vehicles down there, and from the air they stand out well. However, since there are so many white vehicles on the road, they don't stand out nearly so well. Especially to other drivers; a unique color that separates them from other traffic makes them more conspicuous, which enhances safety and alerts other drivers to their presence. In flight, unless I'm doing something discreet, I want to be seen. I turn on all the lights I've got, I prefer to be painted the most glaringly visible color that can be seen under most conditions, and strangely, white with some contrasting trim works about as well as anything.

Here in the desert, we have yellow school busses. Today is a relatively cool 106 degrees F, and it gets toasty inside vehicles (to say nothing of aircraft structures. Yellow school busses have white tops to reflect more heat and keep them cooler, and most aircraft are painted white for protection from heat, and for visibility. White works.

There was a composite glider, the PIK-20, made in the '70s in a range of colours. I believe it was post-cured/autoclaved so that it wouldn't lose any strength with heat build-up.

I used to have a Std. Libelle and the manual for that said that you should leave it in a matt-painted airtight trailer in full sun on a really hot day to cure some more.

Here's a PIKture:

http://www.strato.co.nz/pik20/idapik4.jpg

Fullwings
Libelle, now there's a machine for you! Our club had the 'Rennklasse' version with flaps and brake-chute. Sadly it got parked in a tree.