Jve said..
I ask again, how would longer lines increase power? Longer lines with a kite increase power by a completely different mechanism that isn't relevant to parawings.

I'm not an engineer, but I would think that a flatter high aspect canopy profile like the Pocket rockets might need a bit longer lines to be stable, but the PR is really not known for it's good low end power. If the lines were shorter the canopy would either have to be more C-shaped (giving lower power for the AR) or the angle of the bridles to the canopy would be sharper, which I'd guess would make it less stable. My thinking is that line length thus has more to do with what kind of canopy you can design, not really in itself contributing to power. The medium AR parawings like D-wing or Frigate seem to have more low end despite shorter lines than the PR. Can anyone give a convincing explanation of the opposite?

Apparent wind creates power and the longer the lines the more potential time the wing is accelerating. Its exactly like a kite. The same calculations just the ratios aren't as great. As also pointed out height and the ability to change height also get the wing moving around.

On the subject of range the longer lines the more the wing can move forward and back more in the gusts to generate more apparent wind. It also allows the wing to fly further forward on the front lines.

Very important also is the fact you can pump the crap out of the ozone to get up and line length is again is part of that success. The wing is allowed to move around and recover from the pull as it again races forward for longer.

Isn't the pt skin 5.4 the best low end pw?

Jve said..

AnyBoard said..

Jve said..
I ask again, how would longer lines increase power? Longer lines with a kite increase power by a completely different mechanism that isn't relevant to parawings.

I'm not an engineer, but I would think that a flatter high aspect canopy profile like the Pocket rockets might need a bit longer lines to be stable, but the PR is really not known for it's good low end power. If the lines were shorter the canopy would either have to be more C-shaped (giving lower power for the AR) or the angle of the bridles to the canopy would be sharper, which I'd guess would make it less stable. My thinking is that line length thus has more to do with what kind of canopy you can design, not really in itself contributing to power. The medium AR parawings like D-wing or Frigate seem to have more low end despite shorter lines than the PR. Can anyone give a convincing explanation of the opposite?

Apparent wind creates power and the longer the lines the more potential time the wing is accelerating. Its exactly like a kite. The same calculations just the ratios aren't as great. As also pointed out height and the ability to change height also get the wing moving around.

On the subject of range the longer lines the more the wing can move forward and back more in the gusts to generate more apparent wind. It also allows the wing to fly further forward on the front lines.

Very important also is the fact you can pump the crap out of the ozone to get up and line length is again is part of that success. The wing is allowed to move around and recover from the pull as it again races forward for longer.

I'm not convinced. Apparent wind is relevant for kites as they are moved around, if you hold a kite steady at a given height over the water a 5 m kite has the same pull with 12m or 22m lines, it's only when it's moving that the power will be increased. When getting started with the parawing you don't move it around, do you? Most hold it steady, perhaps pump it.

Regarding the wind gradient, you hold the parawing with such a slight angle upwards that the wind gradient barely changes with 20 cm longer lines.

How far forward it sits is a consequence of the canopy profile (though, as I argued in the previous post, longer lines might be needed for stability in a flat high aspect design that likes to sit far forward). Longer lines, all else being equal, increases drag, thus making it sit deeper.

It might be that longer lines allows better pumping, I have no idea.

My best argument is empirical; the parawings that are getting the best reviews for low end doesn't necessarily have long lines. For example the 4m 777 PT skin supposedly has a much better low end than the Pocket rocket, despite very short lines for the size. The Pocket rockets best attributes is the very good upwind and being rock solid in its high end, not low end power. On the other hand Flysurfer POW has a very good low end and long lines, but it also has a pulley greatly affecting the camber in the profile, which I believe plays a bigger role in the low end.

I think that we should see long lines mostly as a compromise that might be necessary for some canopy profiles, not in itself helping with low end more than perhaps minimally.

Not low end as that is different again but light wind success is all about the power developed through the apparent wind that is made possible with the pump. The pump flies the wing back and forward through the window. Its the equivalent of sining a kite. When you pull the wing toward you, you accelerate the board but nearly stall the wing deep in the window and as the board accelerates forward it also contributes to positioning the wing deep in the window by leaving it behind so to speak. The wing again can now accelerate forward generating apparent wind and consequently power as it races forward again. Longer lines, super stable canopy and higher aspect really take advantage of this technique to get off the water and ozone has done it best from what I see and experience.

Without what is going on in this technique you just have a dw handkerchief that needs near 20 knots and lots of canopy. The bar pressure in this circumstance is too often taken as power to get going but it's not.
Standing on your board with the wing barely flying waiting for that 12 knot gust and then trying to make the most of what it gives you will quickly dial in you appreciation for a wing like the ozone with its line lengths. not just high end but ozone does it all with the exception of having longer lines to pack up. For some applications that maybe be too much of an inconvenience. It was always predicted that ozone would do a good job and they did. It's not perfect but probably the best at most things

Sheps, so you are actually whipping the Ka'a back and forth across the window to get up? I will try that!

Bar tuning has a lot to do with how a Pwing handles. I learned this on the v1 Malikos. I have since updated my bars, but on the original bars, I used the BRM harness line velcro thingies to attach my A and B lines. This made it really easy to slide A and B positions on the fly and find what worked best for me. I get great upwind angles, easy light wind handling, choice of flying deep in the window or at the edge with simple bar input, fast turning, no fluttering or collapsing when really powered up and flying mostly of the A lines.

On my Ka'a 3.6 I moved the A line attachment on the bar about 1 inch further forward in order to gain a little more purchase when sheeting out. Only tried it on skateboard so don't know for sure if it will work when powered up, but it seems to fly further forward towards the edge of the window similar to the Kanaha (in other words, easier light wind handling).

My guess as to why I have an easy time going upwind on the Ka'a is that I learned to kiteboard in year 2000 on two-line kites with no depower. Then I rode fixed four-line kites until 2006 (also no depower). So it feels natural to just edge hard and control my speed in order to point upwind. People who only know how to sheet out in order to control power are not going to like the Ka'a. But for those who learn how to fly it, it does have its advantages. I have only done this once, but it felt amazing in side-on conditions, going down the line on a swell, down wind, and turning the Pwing with each turn of the board, one handed, hardly any pull. I know this goes against the whole purpose of a Pwing, which is making it dissapear, but still it just felt so amazing to do something that you could not do with a kite or wing. Felt natural.