For the same reason jets are black? But then again white planes (passenger planes) are white because white reflects more sunlight and keeps the plane "cooler"?
I was told by a kite repairer yesterday that black kites last longer because they are black and allow heat to pass through the canopy material better. However, white canopies heat up more because they reflect sunlight more and hence make the kites more "stiff" or "brittle" over time which takes away any flex in the material allowing it to take more knocks, water crashes, etc. He said older kites which are not black (or have mostly darker coloured canopies) are more prone to shock and will rip more easily. He said the common term "still crispy" is frustrating, because it implies the canopy has no more flex and hence is like dried up paper which can easily tear.
True or bull****?
I don't know if it's true for kite canopies, but for plastics in general carbon black is often added to them to make them more UV stable - for example black cable ties are UV stable (and more expensive) than the white ones. So it could well apply to kite canopies as well.
I reckon the worst thing you can do to a kite is leave it lying on the sand with the canopy flapping - the flapping just chews up the canopy. That's why flags get so hammered so quickly as well.
I can smell it from here. Black absorbs IR to UV which is why it's... black. Absorption or reflection of UV would be a property of the material itself, not the color.
Someone trying to sell you a black kite? They sound like a used-car salesman...
The only black jets I can think of are things like SR71 or U2 which had special anti-radar reflecting coatings -- again, black absorbs.
I don't know how well this would translate to black and white, but I heard dr. Karl the other day saying that blue paint last longer on a car than red paint, because of the colour of the damaging element in sunlight, but who really cares anyway, just buy a brand new kite, you know they get better every year.
From my technical textiles days..................one of the most significant enemies of outdoor fabrics is UV....
If you have unpigmented pure polymer without delustering agents (in case of nylon it looks a bit straw coloured, through can be silvery like fishing line, polyester looks silvery, opaque) the UV rays pass through the fibre and bust apart the chains of atoms that make up the polymer. It doesn't happen overnight but it happens eventually.
We've all seen plastic bags rot in the sun, get brittle, haze up and then rupture.
Polyester is inherently more resistant to UV degradation than most of the other synthetic fibres, ....certainly heaps better than nylon and others such as the lightweight modified polyethylenes that are sometimes used for depower ropes (spectra, Dyneema).
If you prevent or inhibit (depending on the shade/dyestuff u use) the UV rays from passing through the fibre by dyeing the fibre or the finished fabric you can further improve the UV resistance and slow the degradation.
Yes, black will probably be the best colour to prevent UV entering the fibre...
BUT
It will also cause the fabric to heat up (IR absorption) and elevated temperature increases breakdown of both the dyestuff that is used to colour the fabric (it fades!) and the fibre itself. UV is heavy stuff!
So, it gets kinda complicated.
U can put fancy UV stabilisers in the yarn (even polypropylene can be stabilised sufficiently to be used for automotive carpet....and the car makers are tough on fading and degradation) but it COSTS...
Its always a trade off between quality/expected lifespan/value of the fabric.
My advice, if you want to be particular, is get 'em out of the sun if they don't need to be there
And if you can stop them flapping in the wind when on the beach I'm sure they'll last longer.
And try not to worry about it too much, go kiting!
Select to expand quotebrinm said..
And try not to worry about it too much, go kiting!
Oh not worried, just curious.
But the "flapping" comment is interesting. I was told (someone else this time), that all kites at the trailing edge flap or vibrate very frequently when the kite is in the air. So it would make sense to me, to have something in the trailing edge to reduce vibrations? Maybe another layer of ripstop tape? Or a thin wire? Or even a thin bladder?
Why does it need to be prevented? Because the material in the canopy is nylon (?? correct me here) and over time becomes brittle from UV (as you said above - thanks) and it will eventually *snap*, so at worst you could have a tear in your kite simply by using the kite as per normal, and never having it crash on the water or some other disastrous event.
Ideas, ideas, just ideas.
A friend and I both flew the same kite a few seasons: his was in black, I had the white. Didn't notice much difference in fabric degradation but never thought to check. I think flying a bigger kite OP and trimmed for depower is what causes that wear in the trailing edge area. Fly smaller kites and keep them powered, you don't see that buzzing going on. When I beach a kite I pack it away or cover it with so much sand that it stops moving, and is screened from the UVs. But for black vs. white I am going to check the 2 kites if possible. I flew the white one till it was a rag. I will also ask our busiest repair guy. It's a good question. Another factor is tar stains. There is a ton of it here and all my white kites get defiled instantly.
I have no idea what sort of change in lifespan is possible by stopping the flapping on the beach, but every little bit obviously contributes to stress and wear...so if you can avoid it, so much the better.
As for flapping in the air, its just turbulence at trailing edge isn't it? And, again, if u can reduce or eliminate it, its better. Provided you don't compromise other aspects of performance.
Canopies are generally polyester ..... polyester has (if the yarn and fabric are properly specified and manufactured), less stretch and elongation than nylon so things don't go out of shape..... and there is also the UV resistance thing. Polyester is clearly superior.
On the minus side, polyester is harder to dye than nylon; it requires pressure dyeing to be really good......so if they get the dyeing right, its usually pretty long lasting and robust...as the dyestuff is pretty well anchored on the fibre.
It might explain why some kites with screen printed logos and patterns lose them after a while; screen printed inks aren't applied under increased pressure (like the dyes that are used to dye the rolls of fabric) so may not be less durable.
All of these properties and processes are very well understood by reputable companies (like Teijin in Japan who make the Technoforce fabric, and others).
Select to expand quoteLoftywinds said..brinm said..
And try not to worry about it too much, go kiting!
Oh not worried, just curious.
. So it would make sense to me, to have something in the trailing edge to reduce vibrations? Maybe another layer of ripstop tape? .
Back line pressure does it, pull on that bar and extract every last ounce of power.
Select to expand quoteLoftywinds said..
For the same reason jets are black? But then again white planes (passenger planes) are white because white reflects more sunlight and keeps the plane "cooler"?
True or bull****?
Planes are painted white to reduce their weight. Dark colors especially black add significant unnecessary weight to the plane. Nothing to do with keeping the plane cool.
Yes CTOz, I can relate to that kind of theory as it’s along the same lines to why a mate of mine brought a red car- they go faster…
Some kites just flap like bastards - Ozone Reo and Catalyst are the worst at flapping in any kite that I've ever flown, but all do it on occasion. Cab Vector was another one, when you sheeted out.
AFAIK there's a line through the trailing edge seam and thicker material there already on all kites, to control the flapping. Some go further and add reinforcing "arrows" of thicker material or even battens. North has added that crenelated layer too.
There are thermal advantages to having a white aircraft - especially when parked on the ground - and apparently some composites require white paint. White doesn't "fade" either.
black is easier to put a sneaky patch on that doesn't show. white or light colors show patches or repairs and get easily stained. Lighter colors look better new, but black looks better longer term. So I avoid white or light color kites. As for UV like everyone says don't leave kite in the sun when not being used, black absorbs more radiation but increased absorption possibly reduces UV degradation as the color dyes will absorb some of the UV.
black is the new black even if it adds a few mg of weight (in an aeronautical sense)
Select to expand quoteCrashTestOZ said..Loftywinds said..
For the same reason jets are black? But then again white planes (passenger planes) are white because white reflects more sunlight and keeps the plane "cooler"?
True or bull****?
Planes are painted white to reduce their weight. Dark colors especially black add significant unnecessary weight to the plane. Nothing to do with keeping the plane cool.
Military aircraft were traditionally painted matt grey when pilots needed to see the enemy to shoot them down, I think it's called 18% grey, it's the most neutral colour to the human eye and blends in well with everything. Probably not an issue with modern aircraft and their technologies and over the horizon radar capabilities, they probably still paint them grey because it looks bad ass.
As far as the trailing edge flapping on a kite, there are only two ways to avoid it, either fly it and put that trailing edge under tension as Hardcarve1 said, or pack it away. Leaving it on the beach allows that trailing edge to flap away and destroy the fabric on the trailing edge at a microscopic level leaving it far more prone to a catastrophic failure.
