Single vs Double Skin

[Glice227]

Why does my Peak 4m have the same power as a 7m or 8m double skin foil kite? Is it due to different top skin cambers or is there an effect from the lower skin?

[tomtom]

Why does my Peak 4m have the same power as a 7m or 8m double skin foil kite? Is it due to different top skin cambers or is there an effect from the lower skin?

It depends on which double skin kite you have. But there is no physic behind it. Peak 8m is same power than FRS 9m or Soul 8m.
Only thing SS do differently is sitting deeper in WW. So it can be perceived as more power. But its just more downwind pull or grunt

[Peter_Frank]

I dont fully agree Tom.

For the big sizes, yes, it is a perceived impression they have more power, as sitting deeper, but not in reality.

For the smaller sizes though, I think they ARE more powerful.

For two reasons.

Most likely they have a camber with more power, as the goal is not range nor upwind, but ease and okay power and drift capabilities
Even more important though, the small ones are extremely fast turning and light thus accelerate in all directions, down or horizontal or up - which gives LOADS of more power overall, I am not in doubt about this

Peter

[Herman]

Just to be jocular I won’t agree with either! If single skins were more powerful arguably they would be the race kite of choice. Power is a rate of energy per second and is watts needed to win races, bike or kite. However if we are talking pull I think Peter is on the money. This is not a new phenomenon, just ask people who remember the C quad!

[drsurf]

Remember the Peak kites were originally designed as snow kites, pulling you up the mountain. So they are powerful for their size.
Although we've had a wet summer here without as much wind as we usually have, I've only used the 3m and 4m Peak4 kites on my Moses/Sabfoil 679 surf foil and I'm currently 67kg.
Foiling of course means you don't need as much wind, as when I'm out on my 4m foiling, most others are on surfboards or TT's with 10m - 12m inflatable kites. And that's in wind from 10 to 30 knots with the 3m & 4m Peak4's. So much for Peaks having a limited wind range

The characteristics of the Peak kites, instant depower/power, quick turning, sitting deeper in the window, light feel and great drift set them apart from all other kites. And don't forget the original design for pulling you up mountains has made for a kite with great durability.

[Peter_Frank]

Just to be jocular I won’t agree with either! If single skins were more powerful arguably they would be the race kite of choice. Power is a rate of energy per second and is watts needed to win races, bike or kite. However if we are talking pull I think Peter is on the money. This is not a new phenomenon, just ask people who remember the C quad!

You are right, power and pull is not the same.

Although - racekites need to be efficient meaning maximum lift/drag ratio, on cost of agility (turning) which they dont need as they are going with the maximum controllable size in a given wind.
Meaning when I ride a 5 m2 Peak they ride 20 m2 racekites

The ability to give power on demand is extreme for light small kites, this is where many single skin kites excel, if not too big.
But one could make a really powerful/pullkite in double skin with more camber in a small size also, which would not have max L/D for racing, but be able to ride in the lowest possible wind relative to its small size, especially taken into account it need to be flown around so span must not be too high.

Last winter we had a fun example on skates on the ice, in maybe 2-5 knots of wind or something, on the limit where just possible to kite-skate.
I used the 5 m2 Peak4 and it worked perfectly, easy although not much riding speed in this low wind, but fun.
My experienced buddy used his 9 m2 racekite, and he said (and it was easy to see) that it kinda "raced to the side of the window" and lost its pull now, as no speed to generate pull.
Looping constantly did not work well, not fun at least, and would require longer lines.
So at low speed they are not good, compared...

Just an observation, a bit surprised eventhough it makes sense - in a tad more wind (or skate speed) the small racekite would probably work great.

Peter

[tomtom]

You have nothing to compare with - there is almost zero CC kites smaller than 6. And if they exist im almost sure that they exhibit almost same characteristic you describe. "extremely fast turning and light thus accelerate in all directions, down or horizontal or up - which gives LOADS of more power overall"

What im saying is: From two kites CC/SS with comparable profile depth and other parameters - i see no reason for SS to be more powerfull.

And yes maybe for very small Air speed it is possible than quasi SS profile is optimal. - But im not sure...

I dont fully agree Tom.

For the big sizes, yes, it is a perceived impression they have more power, as sitting deeper, but not in reality.

For the smaller sizes though, I think they ARE more powerful.

For two reasons.

Most likely they have a camber with more power, as the goal is not range nor upwind, but ease and okay power and drift capabilities
Even more important though, the small ones are extremely fast turning and light thus accelerate in all directions, down or horizontal or up - which gives LOADS of more power overall, I am not in doubt about this

Peter

[Herman]

Interesting skate story. I think if you were designing a kite for clean ice racing you might need to go for adjustable camber to cope with the enormous apparent wind that can be generated. Ice rigs have or used to have very flexible masts so that they could be bent to remove camber from the sail as speed increased. Trouble is I guess you would need a vast expanse of ice to have enough room to make a race skate kite fun, and the speeds would be crazy dangerous.


PS. Fixed bridle kites tend to feel more “powerful” than the equivalent depower foil for some of the same reasons imho.

[Regis-de-giens]

To explain these power nuances between kite designs, I like to use the analogy with a car gear box ... you "feel" higher power on the first gear (when you start from 0 speed to 30 km/h, that pulls you strong on your seat) , butwhen you swap to second gear after you reached a minimum speed , then the third speed when you enter in a motorway you feel less accelaration at 100 km/h even if pushing the pedal the same), while the power of your engine remains exactly the same ...

The single skins or medium ratio ( called less 'performant' kite) are like the first gear of these car : it give a lot of pull at low speed, feeling a high pull in lower wind;
The race kite are like the second or third speed : you fight to feel power at low speed right after waterstart, but the power transmission is more efficient when you have decent speed and the speed, in the end, will be higher while less "grunt/pull" ...

In both case the power in its physical formula remains "the same" ; power = speed x pull load projection ( in your ride direction) , so :
- Singles skin are deeper in the window = higher pull but lower speed (which is the aim in low wind when no upwind challenge like on a hydrofoil).
- race kite are further in wind window = lower pull but higher speed (which is the aim of race)

So power is approx the same . you just felt different in your legs and also to water start (which requires high pull at low speed), hence SS feel more adapted to start in lower wind, which we "translate" as "more powerfull" in the sense of beeing able to ride with a smaller size.... (bit far less max speed)

The extrem is like Peter said, with fixe bridle power kite , that have a ton of pull but at very low speed (you can be pulled on the sand with very small kites, or climb mountains slowly) .

Hence 'power" is not actually higher for a similar surface, just "transmission lever arm" is changing ...

[Sceotend]

Heavier kite pulls less as some of its power is needed to keep it in the air.