Power Kite Forum - adjusting brakes for lift

adjusting brakes for lift

rando - 23-9-2009 at 07:26 PM

Hi,

I saw a youtube video (can't find it again) that mentioned tightening the brake lines to make more "pocket". does anyone know what this means?

If anyone could breakdown what effect on lift and power adjusting the breaks has on a kite, that would be super.

I'm asking cause I might try it on the 7m beamer and the 6m panshm if that's important.

Thanks.

-Randy

kitejumper - 23-9-2009 at 08:00 PM

this is just my preference, but i like little to no brakes when jumping--to me, its safer

acampbell - 24-9-2009 at 05:33 AM

Four-line biased kites will benefit from the proper brake tension. An example is the Peter Lynn Reactor; get it cruising and the right goose on the brakes will give you a surge.

The new Beamer IV's will benefit from the right touch on the brakes as well.

Brakes add drag, but also affect camber and can add lift. The right touch on the right kite can add more lift than drag.

BeamerBob - 24-9-2009 at 05:49 AM

In addition, the Beamers are designed to not have significant lift (upward) until you get above the recommended wind range. I had some time with several Aces and owned a 6m. It hated any brake input, so use them only to assist turns and to land unless they've had a major design change in the last 18 months.

kitejumper - 24-9-2009 at 07:57 AM

i agree with the above comments,i usually only jump with blades and as lifty as they are ,very little if any braking is required......i would say if there wasnt much wind,you could tighten up the brakes for some jumping,but i like more wind--so very loose brake lines

soccerflyer - 24-9-2009 at 08:22 AM

Quote:

Originally posted by acampbell
Four-line biased kites will benefit from the proper brake tension. An example is the Peter Lynn Reactor; get it cruising and the right goose on the brakes will give you a surge.

The new Beamer IV's will benefit from the right touch on the brakes as well.

Brakes add drag, but also affect camber and can add lift. The right touch on the right kite can add more lift than drag.

What would be a list of kites that this would work on?
Beamer IV's . . . . any others?

One of my plans down the road is to get around a 7 meter high aspect ratio kite to fly on low wind days and get the Ozone turbo bar to fly it on.

Mostly cause this vid looks cool ---> http://www.youtube.com/watch?v=Cn29IP_hCgQ

My plan was to get a big Blade and try this out on this bar. but Kitejumper says they don't like brake input either?

snobdr - 24-9-2009 at 08:35 AM

Your really adding more drag then lift. You will get a surge with the kite moving at speed with a jab on the brakes, but that is soon lost by the loss in speed of the kite. The camber change is only at the rear of the kite, like a flap on an airplane. You will get the most out of a kite by letting the kite build speed, more speed more power.

acampbell - 24-9-2009 at 08:52 AM

Quote:

Originally posted by snobdr
Your really adding more drag then lift. You will get a surge with the kite moving at speed with a jab on the brakes, but that is soon lost by the loss in speed of the kite. The camber change is only at the rear of the kite, like a flap on an airplane. You will get the most out of a kite by letting the kite build speed, more speed more power.

Largely true for front-line biased kites but not an absolute.

The Crossfire II in the low-lift setting is another example of kite that actually requires some brake tension to stay powered up and inside the window. For this reason it not recommended for a bar, but a Turbo Bar should work well with it as it did on my Reactor.

Soccerflyer, the Blade would be fine on the Turbo Bar since you can control the brake tension dynamically, as you can with handles. On this bar you can turn a kite so tight on a bridle point that the inside tip will fly backwards for a moment and tuck.

BeamerBob - 24-9-2009 at 09:44 AM

Quote:

My reactors would give you an increase in power that was sustainable if the kite was powered. PL actually sells this function as an ability to add usable range to the kite. I've also buggied with the reactors and NOT applied any pressure to the brakes in order to keep the power muted if I was a little overpowered. But this isn't a temporary explosion of power but more like a turbo boost that pulls harder as long as you keep that pressure on. I'm not sure there is a significant drop back in the window either.

snobdr - 24-9-2009 at 11:08 AM

If the kite were sitting further back in the window it would be why you have more pull.

rando - 24-9-2009 at 05:02 PM

th

BeamerBob - 24-9-2009 at 06:32 PM

Quote:

Originally posted by snobdr
If the kite were sitting further back in the window it would be why you have more pull.

I disagree but that is my observation. We can leave it at that.

furbowski - 25-9-2009 at 01:26 AM

aces don't like brake input, so yes the broke boost is useless on aces.

it varies a lot from kite to kite.

the brake boost effect is better when riding something than when jumping static.

I haven't played with it much since for static jumping keeping the kite moving fast is best and safest. Also it's kinda hard to maintain an even and controlled brake line tension while jumping static, much easier in a buggy, maybe that's why the brake boost is better then?

power rings add to the boost, at least they did on an old u-turn (a 6m, oxigen?) I flew once. I tried it both ways while setting it up for its new owner, a guy I know from the beach. I think the different angle adds curve, doesn't just pull down the back edge of the kite?

snobdr - 25-9-2009 at 06:06 AM

Are we talking about adding a boost of power or addind consistant power?

furbowski - 25-9-2009 at 06:26 AM

both. boost the brakes hard and you can get a fair bit of extra pull flying static, but it risks a stall, it worked better on the u-turn than any other kite I've flown. I can feel the boost with my blade, but it's nowhere near as good a pull and so far it's been better flying it fast.

i imagine in a buggy you'd be in a better position to get a consistent pull with even tension on the brake lines, so that's when consistent power would be happening.

it's nowhere near as good a boost as a yank on a depower bar, tho.

snobdr - 25-9-2009 at 06:32 AM

BB how much increase would you say percentage wise?

BeamerBob - 25-9-2009 at 07:46 AM

Maybe 15-25% depending on the wind speed and direction relative to travel. It requires a delicate touch to just cup the trailing edge without actually slowing the kite down and dropping it back in the window. I understand that it would be difficult to believe/understand if you had not flown a kite in a buggy that had this characteristic, but it is undeniable when you feel the boost (sustained) in power. Like I said earlier, I also use this to have less power at times by flying with the brake lines untentioned if I'm on the edge of being overpowered.

snobdr - 25-9-2009 at 07:50 AM

Understandable but the terms had me confused.
Boost( tempoary)
Increase(sustained)

awindofchange - 25-9-2009 at 09:24 AM

I would kind of agree with Snobdr on this one. A stalled kite has no power. By applying the brake lines to your fixed bridled kite you will stall the kite out and eventually, kill all the power (depower is something totally different because increasing pressure on the brake lines will actually change the curvature of the sail). With some designs you can benefit from a finesse of the brake lines - managed tension but once you go past that magical point, the kite will stall and you will kill the power from it. Even the Blade will suffer from this.

Different kites are designed for different types of controls. Some kites are designed to fly strictly from the front or top bridles, others are designed to utilize the rear bridles to help form the air foil shape and would require a slight amount of tension on them.

As Snobdr posted, speed on any kite is power. The more speed you can get the more power you will produce. This is from the apparent wind the wing creates as it flies through the air.

The position the kite is at while in the wind window will also effect the amount of power it is capable of producing - but it still needs speed. If you are sending the kite overhead hard or out to the extreme edge of the window, then by pulling in the brake lines you will change the angle of attack of the kite so that it can catch more air - thus giving a sudden but very short increase in power. If you continue to do this without redirecting the kite then you will stall the kite out (very quickly) and the kite will collapse (if at the edge) or fall straight down (if at zenith). The increased boost of power is not sustainable without redirection and constant movement where you are able to keep up the speed. If the speed of the kite starts to decrease, power will decrease proportionately.

Both sides of this discussion may be about the same thing - just viewed differently in each others eyes as to what each person perceives as power or increase of power.

Hope that helps.

BeamerBob - 25-9-2009 at 09:36 AM

AWOC I presume you are disagreeing with me on this. While I have great respect for your knowledge and opinions, it seems there is a gap in our observations here. I won't restate my views I've noted before but will add that at times when I've felt I was going a little too fast for conditions, I have released the tension on the brake lines and felt a reduction in power from the kite. IMO this indicates that the "boost" I felt when tensioning the brake lines just right was indeed being sustained.

snobdr - 25-9-2009 at 09:39 AM

awindofchange That would be how i understand it.
I do believe BB may be correct also. On some kites it may be possible to add a little brake pressure thus adding a little bit of camber and increase the lift of the kite without increasing drag to a point.
On some kites this may not do anything as the kite might already be in its optimum shape, any increase in brake immediately increases drag. Whereas other kites might not be in their optimum shape and an increase in brake pressure brings the kite to this optimum point. This "sweet spot" might have a feel to it in the handles were its easy to find and hold this position, in turn increasing the power of the kite without stalling it.
On most kites there is some give and take of performance and stability. Each kite can be tuned to fly more on the "edge" of the performance envelope but may become less friendly or more of a handfull to fly.

acampbell - 25-9-2009 at 10:07 AM

I had near-laboratory conditions to observe this last night although I would not hazard a guess at any percentage point of boost.

I broke out the 5.5 Reactor II on Jekyll island late yesterday with dead steady winds at 13 mph and 20- 25 degrees off of dead-on-shore, depending on what stretch I was on. Upwind slog to the north and deep broad reach to the south. I rode till sunset at 7:20 and with few pedestrians on the beach I could ride for miles and just stare at the kite if I wanted to.

I was riding the upwind legs with strop and harness (no one died) so my fingers were free to tease the brakes any way I wanted and study the effect. The RII has an almost permanent crease about 15% forward of the trailing edge, even with brakes pretty loose. This is more pronounced that with the R I for sure. Tweaking the brakes just right with just a little tension, I could see the added cupping of the trailing edge and not just feel a boost but clearly see the kite advance a few degrees forward and stay there. Just a bit too much and of course the kite would drop back further into the window. And I am not talking about stalling the kite, just changing the L/D profile. I reserved stalling the kite for the downwind runs ;-).

Winds were steady enough that I could tell the difference between the effects of minor wind speed changes and the effects of messing with the shape of the kite. Plus, I had numerous runs of several miles to repeat the experiments.

I will have to say that the RII goes upwind quite well. I have a tell-tale mounted on my headstock and on my upwind runs, the apparent wind was but a few degrees off of dead ahead. On down wind runs, the kite was docile enough for me to work it in any direction I needed to keep it flying in a deep reach without having to harden up into the surf.

krumly - 25-9-2009 at 01:40 PM

You're going to have the potential for maximum sustained power with the kite flying at its maximum lift-to-drag ratio. We kiters tend to confuse power with force - power is force x distance/time. Not the same as line tension or lift. I think that is what everyone is getting at in some way or another.

I see no reason why a kite couldn't be designed to fly at very low drag but not at it's maximum lift to drag ratio with the brakes completely slack. This might even be affected by your line length and line weight - it doesn't take much in light winds to pre-brake the kite. This kite could have its profile changed a bit with minimal brake input to bring it up to it's maximum lift-to-drag.

Try this out as a thought experiment: Fly your kite static directly overhead. Play with the brakes or bar position to see where the kite sits highest at the zenith - where it gives you the greatest line angle off the kite bridle relative to the ground. That is at the kites max lift-to-drag.

krumly

awindofchange - 25-9-2009 at 02:36 PM

Beamerbob - I am not disagreeing with you at all, in fact if you re-read my post you will find that I actually commented on what you have said in your post about the Reactor II. Some kites such as the Blade, Radsails, Crossfires and the Reactors I and II (plus many others) do benefit with an increase in performance from a fine finesse of tension on the brake lines. The problem is that if you pull the brakes in to far, you will start to stall the kite out - stalled kite means less power. Just as you mentioned in your post about the RII - if you pulled in too much the RII would start to back up in the window a little. Pull a little more and the kite would stall and if held in that position, you would eventually come to a stop (unless you changed your tack angle and/or the wind increased).

I do agree that some models do require a little brake tension to maximize performance, but there are other models on the market that don't require any brake tension to fly at maximum performance - and applying brakes to those models, even in the slightest will decrease the overall power output.

Every kite is different which makes it difficult to state that "this way" or "that way" will give you a boost in power or not.

Hope that helps clarify my comments.

awindofchange - 25-9-2009 at 02:37 PM

Ok - My bad - I just realized that Angus posted about the RII, not BBob. Still, I hope my last post helps clarify things a bit more.

BeamerBob - 25-9-2009 at 03:31 PM

yes it did. I've flown a crossfire II and its personality with the brakes is different still. Brakes on it are a matter of survival instead of added performance. It will charge at the window edge and you have to be prepared to turn before it gets there or use some brake tension to actually stall it a little to pull it back. The reactor doesn't require the brakes but has some added performance if the skilled pilot does so in the right quantity.