Henk wrote: ↑Mon Apr 23, 2018 2:57 pm
Foilholio, I have a few questions with respect to B limited depower and your Z-mod.
- If B limits the depower after the SPL has shrunk, is it not possible to increase depower range by changing the front/rear line ratio
On the kites I have seen NO. This is a limit imposed by the mixer, stand on your front line at the mixer and pull on B, it stops and the rear line is slack. Extend the rear lines past this point will just make them more slack, observed as a bow or arc in the air. When you have some bow or arc in your rear lines you have no more depower at the bar. When you have a bow or arc in the B gallery of bridles you have reached the limit of depower for that kite ( without altering the sewn shape).
How do you know if your B is limiting your depower? Quite easy if when depowering your rear lines are slack but you B bridles are not
. Now there also seems vary levels of slack, what might be slack at the windows edge may not be in the middle of the window. Best consult a line plan to understand the correct amount but you can tune it by feel. Z extended by what I did in the picture seems a good amount for shrunk pulley lines on flysurfers.
These methods of course only apply to foils that fly solely on A, but for kites that fly off A and B the AB limit is still important of course in fact more important as overextending it will cause collapses particularly inversions.
Henk wrote: ↑Mon Apr 23, 2018 2:57 pm
- Your Z-mode changes the point where C pully attaches Z-main. Is it therefore needed to adjust front lines accordingly?
Yes it will move your bar position, there is a wonderful thing call a trimmer to fix that
It will also change the sheet range/position of the kite, for that you may need to adjust your line lengths. The best way to trim lines is use the trimmer, adjust the lines when you are running out of trimmer. Advanced foil flying needs backstall so having that available with the trimmer is a must, even lines is kooky
Henk wrote: ↑Mon Apr 23, 2018 2:57 pm
- To tune a used foil, what are the best steps to follow? Maybe next sequence:
1. Measure A/B difference and do the Z mod with the deviation from 25 cm
2. Mixer level, if needed extend C if not enough SPL available (or swap SPL, or would that mean you swap the SPL way earlier then normal wear would require?)
3. Long mixer test to level cord-wise bridle shrink (where Z is typically shrinking most and A the least)
4. If the kite has many flying hours, span-wise shrinkage might result in too short wing tip bridles. Compensate by comparing wing tip bridles with line plan and make extension loops from LCL bridle material to be placed between kite and bridle.
We get the 25cm from 1/4 of the factory 100cm C SPL, factor in some shrink of B in the upper bridles say 2cm and you have 27cm.
Do the mixer test, then measure the AB difference. Use Z-mod to get that up to 25 or 27cm with another mixer test. There is an explanation and excel sheet on the first page but I guess it's too complicated. If you measure say 23cm there is 4cm to get to 27cm you will need to extend Z 4x that 4cm so 16cm. If you want to get to 25cm that's 4x 2cm so extend Z 8cm.
Swap your SPL when they are worn not for shrink.
I have never (maybe once or twice a long time ago
) done a long mixer test I prefer to adjust kites to my liking a little from session to session etc( or switch setting with the Zmod). The shrink cord wise is usually in ratio so then there is no real need to correct it. The benefit most people would see from the LMT is an improvement of the AB limit. Same reason you see users like Mossy shout out changing pulley lines made such a difference, it's the improvement to the AB limit.
For Span wise shrink I have found restretching the bridles best. I have tried measuring and adjusting every bridle(with loops), many times and I have found it a waste of time. One of the fundamental problems with measuring bridles is the force used to measure them accurately (5kg) is enough to restretch them and in some cases as low 1 to 2kg will start restretching a bridle. You end up with measurements all over the place as 15-30kg is needed to fully stretch a bridle.
There is no doubt though making extensions to bridles to alter the span wise shape of a kite can have a dramatic effect on it, as I have seen with the Pansh Genesis and Aurora 1. Doing such you would think you would need to take all sorts of measurements and be really precise. but there actually seems quite a margin for error and you can really tweak here or there. Just changing the Z gallery on the Genesis was amazing. What seems important is symmetry, and that is what I emphasize when restretching. If you were considering altering the bridle I would try and probably stop at Z, it shrinks the most and seems to have the most effect on the kite, so largest benefit can be obtained altering it.