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upwind difference?

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platslagarn
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upwind difference?

Postby platslagarn » Mon Jan 11, 2016 10:22 pm

how big is the difference in upwind between foilkites and tubkite in winds over 20 knots? both good kites.....

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Re: upwind difference?

Postby plummet » Mon Jan 11, 2016 11:28 pm

The actual difference is small side by side if you compare a ozone edge to a chrono V1. Chrono V2 and Edge are exactly the same upwind.....

But over a long distance it can be significant.

But as the wind builds the extra efficiency of the foil is offset by less depowerability. I'm sure there's a point where the gust managability of a high aspect lei surpases the efficiency of a foil.

I'm not sure what that point is. I'm guessing 30+ knots? or maybe its more a gusty/lull differential as apposed to wind speed.

I've compared 13 edge to 12 chrono V1 and 10 edge to 9 chrono V2 and 6 reo to 5 chrono v1.

The 5 chrono 6 reo comparison was interesting as it was a stupid hell gusty day. 5-35 knots on one day and 25-45 the next day. The 5 chrono was faster and better upwind. But not by much at all. My top speed was something like 71kph and my buddies 72.3kph. I came away thinking that had I been on an edge I would have had the upper hand on those 2 stupidly gusty days. Reo is Ozones worst upwinding kite!...

Side note. Those comparisons are in the kitebuggy on land. Its actaully a very precise comparison Comparing 2 kites as the surface is the same and the wheels/tyres on each buggy are the same. The only change is the kite. On there water you are unlikely to have 2 boards exactly the same and the changable water conditions can also interupt a direct comparison.

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Re: upwind difference?

Postby Mossy 757 » Tue Jan 12, 2016 12:35 pm

Tube kites will get you around the course, but are not competitive in anything but the most amateurish levels of racing. I'd reckon that there's a 15 to 20 degree difference in upwind angle and 10 to 15 degrees downwind, advantage ram airs.

If you're considering a kite for racing only, ram air all day.

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Re: upwind difference?

Postby Starsky » Tue Jan 12, 2016 1:54 pm

15-20 degree difference! That's a shit load.

Easy low tech way to get an idea would be on snow.

same rider, same skis/board, same day.

Pick a start point and ride pointing as high as possible.

Start at same point and do it again after swapping kites.

Compare tracks....

Or use a GPS and include speed in the comparison.

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Re: upwind difference?

Postby Mossy 757 » Tue Jan 12, 2016 5:02 pm

Starsky wrote:15-20 degree difference! That's a shit load.

Easy low tech way to get an idea would be on snow.

same rider, same skis/board, same day.

Pick a start point and ride pointing as high as possible.

Start at same point and do it again after swapping kites.

Compare tracks....

Or use a GPS and include speed in the comparison.
I should be more specific with that claim.

The most relevant performance metric in my mind is the split time at mark roundings between racers on a fixed length course. Given that measurement, tube kites are not competitive by a wide time margin, my guess is that equates to 15-20 degrees difference overall throughout a race given what I've seen in my admittedly limited experience over the last 2 years. This is the Kitracer section of the forum, so I'm assuming this is not a generic freeride "quiver builder" question.

There is absolutely no question about this within the Gold Cup, a Diablo will stomp all over an Edge on every point of sail except a close reach.

platslagarn
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Re: upwind difference?

Postby platslagarn » Tue Jan 12, 2016 10:10 pm

Starsky wrote:15-20 degree difference! That's a shit load.

Easy low tech way to get an idea would be on snow.

same rider, same skis/board, same day.

Pick a start point and ride pointing as high as possible.

Start at same point and do it again after swapping kites.

Compare tracks....

Or use a GPS and include speed in the comparison.
I made this way. I felt or saw no difference in height. that was why I asked. I will try more. but I do not think it differs much on ice with skis.i have à chrono 11 v2 and à best TS 17 ..

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edt
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Re: upwind difference?

Postby edt » Tue Jan 12, 2016 10:34 pm

Mossy 757 wrote: is that equates to 15-20 degrees difference overall throughout a race given what I've seen in my admittedly limited experience over the last 2 years.
this is actually not a very good way of thinking. It's not the degrees you count in a race but VMG or velocity made good. For instance if you are going 20 knots at a 45 degree angle upwind towards a mark directly upwind that's 14 knots VMG. If you are going 36 knots at 23 degrees upwind you are about 10-20 degrees lower but the VMG is exactly 14 knots.

what's better, going 20 knots at 45 degrees or 36 knots at 23 degrees? No difference you get to the mark at exactly the same time. 45 degrees is 12 degrees higher than 23 degrees but it means nothing without specifying how fast you do it in.

What you need to do is look at the polar diagram then you figure out what the best upwind angle is for VMG, and then you can calculate how much faster the foil kite is to the mark. The foil kite can go faster at a higher upwind angle than the tube kite can at the a lower angle. How much exactly? In a race one or two percent difference is enormous.

looking back at the formula results, 2015 everyone was on foils but i see in 2014 someone was on an rrd race kite they finished next to last.

so . . . maybe 5% faster? 5% is about the difference you expect from 1st in the race to the last finisher. 5% is a lot in race.

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Re: upwind difference?

Postby Mossy 757 » Tue Jan 12, 2016 11:05 pm

edt wrote:
Mossy 757 wrote: is that equates to 15-20 degrees difference overall throughout a race given what I've seen in my admittedly limited experience over the last 2 years.
this is actually not a very good way of thinking. It's not the degrees you count in a race but VMG or velocity made good. For instance if you are going 20 knots at a 45 degree angle upwind towards a mark directly upwind that's 14 knots VMG. If you are going 36 knots at 23 degrees upwind you are about 10-20 degrees lower but the VMG is exactly 14 knots.

what's better, going 20 knots at 45 degrees or 36 knots at 23 degrees? No difference you get to the mark at exactly the same time. 45 degrees is 12 degrees higher than 23 degrees but it means nothing without specifying how fast you do it in.

What you need to do is look at the polar diagram then you figure out what the best upwind angle is for VMG, and then you can calculate how much faster the foil kite is to the mark. The foil kite can go faster at a higher upwind angle than the tube kite can at the a lower angle. How much exactly? In a race one or two percent difference is enormous.

looking back at the formula results, 2015 everyone was on foils but i see in 2014 someone was on an rrd race kite they finished next to last.

so . . . maybe 5% faster? 5% is about the difference you expect from 1st in the race to the last finisher. 5% is a lot in race.
edt, if we were standing face to face discussing this we'd be on the same page, I know what you're saying and I think I just explained my position wrong. I know all about VMG, been sailing for 25 years. At the end of the day, inflatables aren't winning races and that's very easily measurable with just a stopwatch. I'm not sure why that is, it seems like you could make a fast inflatable if you wanted to...I wonder if there will ever be a "next generation" racing LEI to supplant the current dominance of paragliding inspired ram airs. I for one would love to see that

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Re: upwind difference?

Postby edt » Wed Jan 13, 2016 2:19 am

didnt mean to sound patronizing just trying to explain it to others so they understand what is going on. very easy to understand why inflatables are worse, they have more drag, that's it. foils have a better wing shape.

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Re: upwind difference?

Postby SaulOhio » Mon Feb 01, 2016 5:04 pm

I was at the 2015 WISSA championships, and did pretty well among the inflated kites, but nobody could keep up with the foils. Have a look at the final results. I added in an F or an I next to the racer's sail number, and you can see that almost all of the foils are ahead of the inflated kites.

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