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Effect of split point on bar trim

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Peter_Frank
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Re: Effect of split point on bar trim

Postby Peter_Frank » Mon Jan 16, 2017 4:35 pm

knotwindy wrote:That seems backwards to me. As you move the V down towards the bar the front lines get effectively shorter, right?
It is correct, when the given is (from the O.P.) that you measure your rear lines up against your front lines when pulled out along each other, and secure they are equal length.

Doing so, the setup with V closer towards the bar will have effectively longer frontlines.

But IMO it is not important at all, because everybody trim their kites by flying and feeling where it is spot on, and NOT by measuring (which is something beginners might have to if they dont have anyone to help trim their kite) :D

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Re: Effect of split point on bar trim

Postby Peter_Frank » Mon Jan 16, 2017 4:37 pm

dracop wrote: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.
Spot on - this says it all, no effect really on most kites (bridled kites), but can have both good and bad effects moving the V point a lot, on C kites and 5 line Cs :thumb:

8) Peter

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Re: Effect of split point on bar trim

Postby merl » Mon Jan 16, 2017 7:40 pm

knotwindy wrote:That seems backwards to me. As you move the V down towards the bar the front lines get effectively shorter, right?
Nope. If you want a bit of string to go a long way you need to keep it as straight as possible.

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Re: Effect of split point on bar trim

Postby merl » Mon Jan 16, 2017 7:46 pm

Peter_Frank wrote:
knotwindy wrote:That seems backwards to me. As you move the V down towards the bar the front lines get effectively shorter, right?
But IMO it is not important at all, because everybody trim their kites by flying and feeling where it is spot on
It can absolutely be important - but not necessarily to you with your setup. In my case I lost part of the trimming range that I needed when flying at the high end of the kite. This would not have been a problem if my personal preference was different, or if the range on the trimmer had been more than a measly 12cm or so.

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Re: Effect of split point on bar trim

Postby Peter_Frank » Mon Jan 16, 2017 8:32 pm

merl wrote:
Peter_Frank wrote:
knotwindy wrote:That seems backwards to me. As you move the V down towards the bar the front lines get effectively shorter, right?
But IMO it is not important at all, because everybody trim their kites by flying and feeling where it is spot on
It can absolutely be important - but not necessarily to you with your setup. In my case I lost part of the trimming range that I needed when flying at the high end of the kite. This would not have been a problem if my personal preference was different, or if the range on the trimmer had been more than a measly 12cm or so.
Does not make sense :roll:

You just add pigtails to your front or rear lines or kite, or move to other knots at the leaderlines, like everybody does ?

So no, IMO it has absolutely no importance, as every kite has to be trimmed for your personal liking anyways (pigtails/leaderlines), so you got the full trim range for your riding :naughty:

8) Peter

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Re: Effect of split point on bar trim

Postby Sandras » Mon Jan 16, 2017 10:00 pm

merl wrote: 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.
I'm afraid I have to ask you to explain it more... I do not understand.
La can't be 0, since b is constant 1.5 Look at the drawing, it's just not possible.
Moreover pythagorean theorem needs a right triangle, the one you propose is not a right one.
La+Lb is the total length of the front lines and if trimmed as most manufacturers suggest are also equal to the back lines and therefore the right delta measurement.

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Re: Effect of split point on bar trim

Postby lovethepirk » Mon Jan 16, 2017 11:19 pm

Sandras,

On a non-pure C kite the steering lines shoot out wider than the center lines, effectively reducing the overall reduction in trim, no?

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Re: Effect of split point on bar trim

Postby merl » Tue Jan 17, 2017 3:23 pm

Peter_Frank wrote:
merl wrote:
Peter_Frank wrote: Like everybody does.
If you add pigtails so that the kite feels right for you then I agree it is not an issue. Like everybody does? Hmm, not that I have seen.
Most people just connect the lines and go. The message is simply that you should expect to have to make an adjustment if you change the Y point. The amount is in the region of 1-7cm. Do you really think this info would not be helpful to one or two people...?

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Re: Effect of split point on bar trim

Postby merl » Tue Jan 17, 2017 3:33 pm

Sandras wrote:
merl wrote: 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.
I'm afraid I have to ask you to explain it more... I do not understand.
Sorry, I realise that you are calculating something else with the delta (what is it good for?). I was thinking what is the difference in front line length relative to back lines between high Y and lowest possible Y (a V). It translates to the pigtail length you need to add to the back lines to get back to the factory trim* if you move from Y to V. Your delta is something else.

* Accepting that factory trim is uninteresting if you prefer to always add your own pigtails and adjust by personal feel accordingly.

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Re: Effect of split point on bar trim

Postby Jan:) » Tue Jan 17, 2017 4:56 pm

The difference between V and low Y (4m) is less than one cm.
Between V and high Y (11m like on older North bars) is less than 4cm.

I bet 95% of the bars that are in use, are off by more than that simply by line shrinking.
But yes, if your bar is perfectly calibrated, you do not use pigtails, you do not have multiple knots on your kite to attach the lines, your adjuster is very short and you have no other of compensating for that tiny 4cm bar movement, you will feel a difference.

The other 99.9% of the people out there will not.


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