Funky bars being occasionally an interest to me, I was wondering, has anyone made one like this?
If so, what is it good for?
How would it compare to a "normal" 2:1 bar in practice?

To me it seems the advantage might be a shorter depower throw, but an easier to reach trim strap, compared to the normal pulley bar.
For example, if you were racing, and trying to keep your stance good,
maybe you would have less worries about getting into a bad stance when you needed depower or trim adjustment?
Would this give unbearable bar pressure?
Or could it be balanced well against the frontlines with the right mixing bridle up top?
Would this be a new idea, or just something forgotten from the past? I wonder....

I assume you got thinking about this from the discussion on:

viewtopic.php?t=2362627&p=637059

My post incorrectly analyzed the relationship of "throw" and "bar pressure", and pdkite stated what I believe to be the correct analysis of this relationship.

I have never seen this use of pulleys on the rear line system in any set-up from the past. Has anyone seen this before? I like to see inventors credited for their innovations.

From what pdkite noted, it looks like the system would be an advantage to a very strong kiter with a need to quickly and extensively power and depower a NORMAL kite... Now if a kite was designed to work specifically with such a control system...hmmmmm! Maybe it is a racer's secret weapon, and they don't want us to know.

edit: my mistake, more like 4:1 and more heavier bar.


winds

In racing they seem to have to adopt a very uncomfortable stance with the bar pushed a long way from their spreader bar.

It seems to be a depower issue rather than a steering issue.

If so, they may end up having a new system for lengthening and shortening the centreline on some sort of ratcheted reel, or extensions on the ends of the bar, so you can hold the extensions without bending forward.

Well, if i did see a picture of some secretive pro, with a strange bar, it might not have shown all the details, so above is my speculation, or idea.
But the idea, to me, is to work with a big kite with long depower.
Most of the time you will need to ride it mostly depowered for pointing, top end, and the reserve aility to power up if wind drops.
With 1:1 you are in monkey stance all the time, probably also playing with the trim. 2:1 gets you out of monkey part of the time, but this 3:1 may make good stance easier.
It reduces throw and will make more bar pressure, but mainly when you sheet all the way in.
And since you will probably be riding a powerful 14m+ kite, you are not going to sheet it all the way in that much, I would think even in light wind you can accelerate quickly and then sheet out some.
As for the turning, I would think it would be similar to 2:1, since it has the same number of pulleys on the bar.
It seems like the benefit might be to tune the bar to be ergonomic for good stance, and well balanced with medium pressure over the range you would normally call 60-90% depower. But it would also depend on the kite and bridles up top....

Something just did not seem right with any of the analysis dealing with the pulley arrangement and the power advantage and length of throw, sooo...

I just rigged up a bar with the pulley arrangement in the above diagram...and guess what?

I was surprised by the results, but not too surprised...because I ran into the same situation a few years ago when I tried to analyse the "cruse control" bar made by Windwing. My intuition was wrong in that case and it looks like it was wrong in this case, also.

Here is what happens: When you pull the bar (as shown in the diagram) 6 inches toward the rider, as you would to power up the kite, the back line going to the kite (attaching to the top pulley), gets pulled toward the rider.......only 8 inches......not 24 inches as would be the case by a 1:4 advantage......and not even 12 inches as in a 1:2 advantage..... but a mere 2 inches more than the "throw" of the bar, which amounts to a 1:1.3 advantage. WHAT?

But, it gets weirder (at least from an intuitive analysis)...because, I then clamped off the top pulley, so that the system acted like the classic Cabrinha 2:1 pulley bar, and guess what the result was?

I pulled the bar down the same 6 inches, and it pulled in on the the rear line 10 inches, not the 12 inches one would expect intuitively from a 2:1 pulley bar. So, unless I have missed the mark with my experiment, it looks like the 2:1 pulley bar really is only a 2/1.2 ratio.

I would be interested in others (preferably someone with a trigonometry or physics background) analysis of this bar, but from my possibly flawed analysis, it looks like this type of bar would increase the bar pressure only about 8/6 (4/3) or in other words, by about 1/4 the force above that needed to sheet in a "normal" 1:1 ratio bar...and, actually requires less force to sheet in this odd bar than to sheet in the classic "2:1" bar.

So, again, if all of this is accurate, then, the question to ask is: Why would a kiteboard racer what a control bar which has a bar pressure, which is MIDWAY between that of a standard 1:1 ratio bar and a classic "2:1" bar? And other questions follow about (1) turning speed (2) bar "throw", and other factors.

First, I hope someone will study the above possibly flawed analysis, maybe repeating the experiment...and confirm or correct my data and assumptions.

I also just thought of something to complicate the analysis even more....It may that the force needed to pull in the rear line )in order to power up a kite) is not linearly related to the amount of line that is pulled in. By that I mean that, for example, pulling in 6 inches of line (by pulling the bar toward the rider, to power up the kite), may not take twice the force that it would take to pull in three inches of line. The force may be related to the amount of line pulled in...on a logarithmic scale, and it may, for instance, take 4 times the force to pull in twice the amount of line.

Ow, this is making my head hurt!....discuss amongst yourselves...

True. Depends on the kite.
tuned to be the way he wants it?
I guess he likes it that way. Not trying to be a smart ass, just another aspect of tuning I guess...
Thanks for figuring out the mech. advantage -I kinda skipped that part I'm afraid.

An answer to kitezilla's question regarding Cabrinha 2:1 bars: The reason it is not completely 2:1, is that the end of the steering lines are attached to the center lines, hence creating an angle offset between the line going in and the line going out of the pulley. This prohibits the 2:1 effect of the pulley. Put in a different way, when you pull in on the bar, the steering line from the pulley to the centerline attachment is rotated around the centerline attachment point, which decreases the amount of steering line that goes through the pulley by a factor of cosine of the angle offset. This will also apply to the "3:1" bar that started this... If the end of the steering lines where somehow placed with no angle offset, the actual effect of that bar would be 3:1...

Regards.

You nailed it!

Of course, the "inner child" in me will not let you off the hook that easily, and forces me to respond by asking: "WHY?" ...and since I am not ashamed of my bad habit of talking to myself, I will attempt to answer the question,... or at least present some arguable ideas, that may stimulate other participants on this forum to venture opinions on "Why?".

But first, I suggest we go here to gain a basic understanding of the concept of "mechanical advantage" of a conventional series of pulleys and line, known as a "block and tackle".

http://en.wikipedia.org/wiki/Pulley

You can see from the diagrams, that the pulley and line set-up used on the classic 2:1 kite bar and the kite bar in the above diagram (3:1 bar may not be an accurate label for this bar), do not conform to the classic "block and tackle" device...mainly because the force (supplied by the kiter's arms) does not pull on a rope, as would be the case with a classic block and tackle device...instead the force is applied to the bar, and the full length of the rope does not change in length, as the force is applied to the back line of the kite. The kiter does not reel in line, and does not have a coil of slack line, hanging down, each time the kiter applies force to the back line of the kite. This fact creates the first point of confusion, when the analysis of this bar system is approached with the false assumption that the classic "block and tackle" can explain the relationship between "force" and "rear kite line length".

With a classic "block and tackle" arrangement of pulleys and rope, there exists a direct relationship between the "length of rope that is pulled in" and "the force needed to pull in that length of line". For example, if 5 pounds of force is needed to pull in one foot of rope, in order to lift a 10 pound weight, you are working with a system that has a mechanical advantage of 2:1. The "1" in the "2:1" designation refers to two elements in the system: first, the 5 pounds of force and second, the 6 inches of movement of the weight. Likewise, the "2" in the "2:1" designation refers to: first, the 10 pounds of weight (2x5 pounds), and second, the one foot of rope (2x6 inches) movement needed to move the weight. The calculation being: 2x6 inches=one foot, and 2x5pounds=10 pounds.

The same basic relationship exists with a "block and tackle" arrangement, which has a 3:1 mechanical advantage, and so on...4:1...5:1...etc. In each case the ratio of how much rope must be pulled in and how many units of force must be applied is expressed by the mechanical advantage designation.

In the case of the kite bars, you can see that no rope is "pulled in", but that the full length of rope running through the pulleys, stays within the system. The kite bar moves, and along with the kite bar,the one pulley which is fastened to the bar, moves with the kitebar. Of the 2 anchor points of the rope, only the one on the bar moves, along with the bar. The other anchor point attached to the front kiteline remains fixed in one place and does not move. The kiteline going to the rear kite pigtail moves, as it exerts force on the kite pigtail. These are factors which make the analysis of our kite bar systems much more complicated that the analysis of a classic "block and tackle" device.

This is why I said that the "2:1" and "3:1" designation for the classic Cabrinha bar and the above illustrated bar may not be accurate labeling. The labeling of the bars might more accurately be: "one pulley bar" (classic Cabrinha bar) or "two pulley bar" (the above illustrated bar). I think that some more testing would be needed, involving the actual measurement of applied forces over measured distances, by moving the kite bar...and the resultant force applied to the rear line of the kite and the actual distance that the kite pigtail moves.

If anyone has a simpler (as long as it is accurate) way of explaining this whole situation, then, I would like to hear it.

Here is the picture of a block and tackle that most closely relates to our 3:1 kitebar.

If you turn it up-side-down and pretend that the arrow at the end of the rope is the anchor point where the line attaches to the front lines, and that the weight is the kite line going to the rear line pigtail, and that the dark line is the kite bar, then, the drawing relates quite well to the diagram of the 3:1 kitebar.

It would seem that the red line with the arrow on it, would be equivalent to the line in a classic "block and tackle", upon which force is exerted, and which normally would then be the loose coil of rope, that we would be pulling on in the classic "block and tackle". It would follow that the distance that the weight, in our case, the rear line pigtail, attached to the kite...would move, and that, that distance would be related directly to the final distance between the anchor point of the red line on the front lines, and the pulley attached to the kite bar. It would seem that the initial and reactive forces would be related to these two distances.

But, what we really want to know is the relationship between the force and distance needed to pull on the bar, related to the resultant force and distance experienced by the rear line pig tail.

Ow, this just made my head hurt again....