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The Full Mixer Test and Psycho 4

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foilholio
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The Full Mixer Test and Psycho 4

Postby foilholio » Sat Apr 06, 2019 10:37 pm

I recently tried out what I would describe as a full mixer test. Measuring out one side of the kite to calculate the differences. How I did it was to anchor all the base of the bridles where the mixer mains end. Then attach a measuring tape to the shortest bridle while detached, just stick the end in the loop. From that I measure each bridle working along the cord then move along the span. It is quite quick. I was very careful to pull gently just enough to pull the "bow" out of the line and not risk stretching the bridle much. I wanted to capture the differences in the bridles in their shrunk state. I also took a measurement for the error introduced by the way I setup to measure. I did this by reconnecting the measuring bridled and measuring it against another bridle near it I had already measured and noting the difference in measurement (I use this error to correct all my numbers in the spreadsheet)

I enter the data in a spread sheet which compares against the factory lengths with calculated differences and then calculates the differences between factory and my bridle. The results were quite normal. A had shrunk more at the tips and Z more in the center. Something I hadn't thought about before is that they tend to cancel each other out.

I then enter in a correction based on a number of LCL loops and mixer adjustment. The spreadsheet calculates the now adjusted differences. Which are now much closer than before.

I apply the LCL loops to AB and C. I ignored Z as I felt it was designed to be shrunk. I didn't adjust the mixer as it's ratio change would correct itself. I basically flattened A and B, increased camber at the center, increase ARC on C and reduced camber at the tips. Which is to say I shortend A and B(less) in the center and C at the tips.

Before the kite was not flying like original, it was due for a restretch I think. The tips were quite unstable a common Psycho4 problem. The Arc had unnoticably to me increased and so had the PA change... After adjustments (LCL loops) the kite had reduced ARC depowered, reduced PA change, but overall flatter ARC and higher PA. It had very stable tips, much higher performance, better L/D and power, but much less stability and a greater tendency to overfly. Jumping it was much better but surfing drift was much worse. It is now I feel much like it was new... And as I remember it after a restretch, the surf drift is not as good and I am not sure I prefer it this way. What I have learned so far is the Psycho4 PA is highly sensitive to bridle changes. Maybe it is more sensitive than other kites? The progression of the bridle to more ARC and flapping tips makes it drift much better and a lot more stable. The differences between a new Psycho 4, or one with a correct bridle and one with a shrunk bridle would quite confuse different people about what the kite is good at.

I will note that I have never had quite this success measuring and adjusting a bridle before. I put that solely down to the measuring force used to get the measurements. Flysurfer says something about 5kg. I have noted before as little as 1to2kg will start to restretch a bridle and as much as 15 to 30+kg is needed to restretch a bridle fully. So if you apply between 1 and 30kg you can alter the length of the bridle... and if you don't use even force measuring you will get uneven temporary stretch and the more you apply the more stretch is produced. The solution is I think quite simple use as little force as possible and focus on differences not total lengths.

If anyone wants the spreadsheet just ask, I will have to add some explanations in it first I think. I could add functions to auto calculate adjustments too, though maybe now right away.

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