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Effect of split point on bar trim

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sarc
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Re: Effect of split point on bar trim

Postby sarc » Sat Nov 05, 2016 4:38 am

All I can say is that my 2012 and 2014 rebels (5, 8, 12m) work awesome with the Y as low as possible (same hi end, more low end, bigger jumps). I put the Y at 7m from the bar (more than enough to depower my 12m Rebel when going to 5th). I posted on this a while back, you can search it

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Re: Effect of split point on bar trim

Postby Peter_Frank » Sat Nov 05, 2016 8:28 am

Pinching can have an effect, both ways kite flying better or worse, a bit different.
This is not the topic of this thread though, as I understand it ?

But not looking at the pinching but only the lines, sensitivity is not changed whatsoever.

One could also say, that the difference in "length" that is calculated is only present if you make a bar yourself and measure the lines for equal length (wrong), but this will not be an issue on existing bars :wink:

Whereas the pinching effect, what it "does" for the kite, might be solely isolated to each individual kite so no common guidelines IMO.

Personally I have never trimmed any bar/kite on "equal" line length, as I find the kites and my personal preferences are of much bigger magnitude :naughty:

8) Peter

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Re: Effect of split point on bar trim

Postby Sandras » Sat Nov 05, 2016 10:12 am

Sandras wrote:
What I say / mean as sensitivity is that if you move the V from 2 to 3 meters trim changes very little, but if you move the V from 14 to 15 meters the trim changes significantly ( so much that you may not be able to adjust it). Check the matrix

Therefore, bars with a high Y are more "sensitive". i.e. can get de-adjusted (with line extensions, stretch etc) more easily.
Peter,
I defined sensitivity in my previous post. I have the impression that you are commenting on another sensitivity. Are we singing from the same book?

Peter_Frank wrote: Personally I have never trimmed any bar/kite on "equal" line length, as I find the kites and my personal preferences are of much bigger magnitude :naughty:
Most people if/when they trim, they do as all manufactures suggest = Equal lines length. This is where the calculation is based and it's clearly stated.
If you do an alternative adjusted tuning, of-course you accommodate the "sensitivity" effect.
This calculation more or less proves that hat you re doing is the right thing (If you've mixed bars, tuning the bars on equal weights is not necessarily what your manufacturer suggested). Substantially we agree.

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Re: Effect of split point on bar trim

Postby davedej » Mon Jan 02, 2017 8:47 pm

It all gets quite confusing. What would you advice a good friend when he wants to use his low V bar on his North kite....?
vote on it!
http://poll.fm/5q9ap
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Re: Effect of split point on bar trim

Postby kiterocky » Mon Jan 02, 2017 9:02 pm

I use a 5 line bar with V line(25m line) close to the depower line.. On 14 m rebel.... I think its more fast and Direct feeling.. But maybe a bit more bar pressure..

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Re: Effect of split point on bar trim

Postby dracop » Mon Jan 02, 2017 10:23 pm

great thread.

I like setting my Naish Torch Bar so that all lines are equal when 2 inches above the QR head. This means the final 2 inches cause oversheeting, which has interesting flight charactersitics on a Naish Torch. For other kites, I tend to prefer leaving only 1/2" at full power above the QR or even setting it to fully sheeted in being all lines equal.

FOcusing on the pinching of the kite, especially when playing with direct connect C kites that are only attached to the corners of the wingtip and a fifth in the middle, the effects are very apparent. Less so on bridled kites that distribute the load across the LE.

Overall I would expect kites that have a more distributed load on the LE (from the bridles) or from a mega thick/heavy/reinforced LE to be less sensitive to the high Y vs low V split issue. I am thinking of a Slingshot Fuel vs a Naish Torch here (two extremes,e specially with the optional bridle on the Fuel; the Torch runs a high Y or low V and the Fuel runs a low V). For bridled kites, you would have to look at how the bridle spreads the load.

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Re: Effect of split point on bar trim

Postby nick14 » Tue Jan 03, 2017 7:04 am

I was actually fortunate enough to have a malfunction when I was testing a new North Evo and click bar. I had an 8m out in 15-20knt with a twintip 75kg. I was using the settings that were given to me off this forum which was on the lower red "Y" split as the lines were 22m. I found on this setting the kite didn't feel like it would pull me but it did. It was very light bar pressure and boosted amazingly well. Then I looped it and the plastic connection loop that you set the "Y" position with snapped so it went to the lowest "V" position. All of a sudden the bar pressure was heavier as I guess the front of the kite was further away from the bar and the kite sat further back in the window. It still flew well and for that lighter wind session I actually preferred the lower V.
I ended up buying an 11 and 8 Evo but with the 22m trust bar and 2m extensions. I am interested to see how these extensions change the characterisyics of the kites (or if 2m extensions will do anything at all). I was on pivots before these.

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Re: Effect of split point on bar trim

Postby merl » Mon Jan 16, 2017 2:28 pm

Just did some similar calculations to this to work out why I was not getting enough trim range on a North Dice with a low V bar. You set b at 1.5. I was guessing at 2.5. I think I need to measure that!


EDIT: Your delta calculation is wrong. The shortening delta is not relative to La + Lb, but SQRT((La+Lb)^2 - b^2). I.e. Just use the same formula with La = 0.

In any case we can summarise this as: if you move the V closer to to the bar from the manufacturers spec, you need to lengthen the rear pigtails (or shorten the front pigtails) to compensate and get back the original trim range of the kite. I think many people forget to take this into account when comparing the behaviour of kites across different bars.

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Re: Effect of split point on bar trim

Postby knotwindy » Mon Jan 16, 2017 4:10 pm

That seems backwards to me. As you move the V down towards the bar the front lines get effectively shorter, right?

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Re: Effect of split point on bar trim

Postby grigorib » Mon Jan 16, 2017 4:30 pm

I think the line length affected by geometry change is neglectible and could be trimmed.

The only major plus I'm aware of for high-Y setup is ability to get wider view from the line-mounted camera and it will catch way less by rear lines when looping or back/front rolling.

The negatives are more serious:
- proprietary line lengths (center and brake lines are not same length) if you have to replace your lines (but even Slingshot is guilty of same with low-Y bars)
- a major safety loss of not being able to flag your kite on any front line, but only on one. Self landing I need to be able to yank on top center line (having kite on one or another side of the wind window) but high-Y allows you to do it only on one side and you just cannon grab the other center line.


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