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Author Topic: Prussic Knot Adjustments ?  (Read 1309 times)
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Kitemac
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« on: October 17, 2009, 05:24 AM »

Okay just when I thought I understood when to adjust this knot for wind conditions my Acrobatx gave me a twist.  There is a three knot system by the upper spreader which is to be adjusted for wind conditions.  So.. when do I adjust the prussic knot on the bridle?  It seems like I would adjust it only to maintain the original measurements for the bridle but not for wind conditions.  Is that true?

Thanks,

Tom
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fidelio
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« Reply #1 on: October 17, 2009, 03:07 PM »

if you're saying you have a pigtail near the upper spreader with knots on it, and the prussik knot you're referring to is down by the towpoint where you attach the lines the answer is;

it's possible to adjust either for wind conditions, but if you're only trying to adjust the forward drive of the kite when you pump the lines when the wind is light, or to the reverse, get the kite to stall more easily when the wind picks up then use the adjustment with the knots near the upper spreader. the effect of the adjustment is tipping the nose of the kite forward or backward (lengthening or shortening the upper outhaul leg).

you can change the length of the upper outhaul leg using the prussik knot but by doing so, you're also changing the length of another leg. based on how your bridle is built it could be the lower outhaul, or inhaul.

so by adjusting the prussik knot you're adjusting other flight characteristics (width of towpoints) in addition to angle of attack (windspeed adjustment), where by using the knot system you isolate the angle of attack adjustment.

i'm certainly no expert when it comes to bridles and have never seen an acrobatix bridle but since you had no replies am offering some general ideas. if anyone has experience with your particular setup, hopefully they'll comment.
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Fdeli
Kitemac
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« Reply #2 on: October 17, 2009, 03:48 PM »


so by adjusting the prussik knot you're adjusting other flight characteristics (width of towpoints) in addition to angle of attack (windspeed adjustment), where by using the knot system you isolate the angle of attack adjustment.


Thanks for the reply.  Could you explain what other flight characteristics are being changed?  The only mod I was aware of was moving the nose of the kite up or down.
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fidelio
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« Reply #3 on: October 17, 2009, 07:22 PM »

as you move the tow point away from the spine and towards the wingtip (in a horizontal axis) the kite will require larger inputs from the pilot, in effect making the kite turn less for the same arm motion. you can sometimes use this to reduce oversteer in a kite or make a twitchy kite easier to fly, or help a kite track better in a straight line across the sky. but in the reverse you can use it to make a slow reacting kite react more quickly to the pilots input, to an extent.

however, by adjusting the same knot you're also affecting the vertical location of the tow point, so it's a balancing act and a constant trade off between characteristics.

i feel a bit out of my league explaining bridle workings so should anyone feel like commenting to clarify or add information, i'd politely invite them to do so.

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Fdeli
KiteFace
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« Reply #4 on: October 17, 2009, 08:08 PM »

I personally don't feel experienced enough to offer any explanation but here are some links that I hope will help.

http://www.ian.ourshack.org/kitedesign/bridling.html

http://wardley.org/kites/bridle/index.html

Peace,
Petey.
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