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Speed 3 21m Upwind adjustment

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The Captain
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Speed 3 21m Upwind adjustment

Postby The Captain » Sat Jul 23, 2016 6:21 pm

My Speed 3 21m just doesn't go upwind as well as it should or used too. Sitting deep, pulling like a truck.
(yes, I know how to ride it with 'finesse')
I have stretched out the bridles, that helped with some stability issues that had crept in over the last season or two.
I am now running B +1cm, C +2cm, but am walking a fine line in sacrificing stability (especially noticed on the beach, were it is itching to nose over in light wind if not watched very carefully).
Leading edge is dimpled in the lower wind. Cant really remember if it always did that in light wind, or if it is something that has gotten a little more pronounced over time...I'd be surprised if low pressure from leakage were the issue, it is in good shape and only gently used.

Is there anything else I can try to get my upwind back without turning it into an unpredictable monster?

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Re: Speed 3 21m Upwind adjustment

Postby Regis-de-giens » Sat Jul 23, 2016 9:26 pm

What if you set the mixer test back to the original 0/0 or even -1/-2 ? Indeed your setting brings more power ("truck") but less stability (as you noticed) but also worse drag hence a bit less upwind angle traction.

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Re: Speed 3 21m Upwind adjustment

Postby kitexpert » Sat Jul 23, 2016 9:51 pm

It is a big kite. Your mixer adjustments are very small and they should not threat the stability. There is much bigger problems if 21m kite is very noticeably flying bad.

It is a tough one if your kite sits deep but still unstability is close...

Have you checked pulley lines? I have seen ones 10cm shrinked. LE dimples are normal when depowered, but if too deep kite leaks. Then wingtips start to fold.

To get upwind performance back kite should fly at lower AoA, further in the wind window. Then low camber (original mixer setup) is needed for the stability.

I suggest to do bigger adjustments to get certain feedback from the kite, possibly for one size of the wing at the time. Then if kite starts to turn better that direction (fly faster) and not being unstable corrections are in right direction.

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Re: Speed 3 21m Upwind adjustment

Postby foilholio » Sun Jul 24, 2016 12:50 am

The Captain wrote: Sitting deep, pulling like a truck
viewtopic.php?f=197&t=2392205 Pulley lines have shrunk causing a loss of depower. Measure out AB depower point , it needs to be 25cm(standard)or maybe more to account for upper B bridle shrink, 26-27 is a good guess, too long and you'll get front collapses more easy when fully depowered.
The Captain wrote:I am now running B +1cm, C +2cm
This creates a higher camber which is WORSE for upwind, but gives the kite more lift or pull. It will however improve the depower limiting by your shrunk pulley lines. You need a slight reflex or negative camber for best upwind, so shorten B and C. You could set to b-1 c-2 etc but that would limit the depower even more. Either compensate for adjusting B less with more adjustment in a ZMOD( you read the first link right?), or after you have set the mixer to correct for shrunken pulley lines with a ZMOD move the C pulley line down to the ELC to effectively lengthen Z. Alternately you could move the ZMOD knot or make another knot, but I doubt you'll have room. Doing this all will also alter the trim of your kite to be more powered so you need to pull the trimmer or shorten the front leader. It does this because one making a knot in the rear main shortens it but 2 if you move the pulley attachment down it powers more or up depowers more, both for the same line trim.

If with a reflex profile you lack the umpf to get going or do jumps, you can try using a WAC(hard soft) line or setting the mixer to be a bit less reflex. An alternate to camber the whole wing is just to camber the rear more by delaying C engaging by setting it more loose in the mixer but keeping B the same. This has the benefit of being more stable and high lift.

I think it's all a bit complicated because the FS mixer lacks all of the adjustments to correct for everything and FS themselves band around that this and that isn't needed and the mixer should always be adjusted in a certain way like B for 1 and C for 2 etc, which none of it is correct.

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Re: Speed 3 21m Upwind adjustment

Postby Kamikuza » Sun Jul 24, 2016 4:52 am

Usually a careful "long" line tune sorts it for me...

But last week I snapped an A-main and when I measured it, it was 4cm too long...may be a factor.

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Re: Speed 3 21m Upwind adjustment

Postby foilholio » Sun Jul 24, 2016 7:49 am

Long line tune? is that a long mixer test?

The snapped one was 4 cm too long? how do you measure a snapped line exactly the fibers elongate.

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Re: Speed 3 21m Upwind adjustment

Postby Kamikuza » Sun Jul 24, 2016 1:57 pm

foilholio wrote:Long line tune? is that a long mixer test?

The snapped one was 4 cm too long? how do you measure a snapped line exactly the fibers elongate.
I go up to the end of the pig tails, as they' can be different lengths. But after skimming through one of your posts about lengthening Z, I wondered if going up to the end of the A-/Z-mains might be a good idea...

Wore out at the larks head at the bridle end. It was getting furry and I forgot about it. BTW the kite will loop when they break :o

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Re: Speed 3 21m Upwind adjustment

Postby foilholio » Sun Jul 24, 2016 2:52 pm

You have lost me. Going up to the pigtails for what, mixer test or measuring or...? The length of the pigtails is just line trim.

So it looped, but it didn't loop hard? and of course you could back stall it on to the water or flag it? I would think an A main going would be enough to make it collapse and not be relaunch able. With a short wac line you could probably still fly it.

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Re: Speed 3 21m Upwind adjustment

Postby kitexpert » Sun Jul 24, 2016 8:23 pm

foilholio wrote:You need a slight reflex or negative camber for best upwind
No. Best upwind needs high L/D ratio and enough pull to counter the drag of the kiter. If kite has negative camber and low AoA these values become very low, even 0. Then kite doesn't pull at all. At higher AoA negative camber is not as effective as cambered one.

Apparently you foilholio mess things up when you think mixer adjustments could result "negative camber". It would need huge amounts of adjustment and kite would distort badly. There is no kitesurfing kite which has negative camber and it would be foolish to try to distort kite such by tweaking the bridle. Reflexed airfoils are used, but not always.

Again, lower and upper skins of the kite are correct shaped for only one airfoil, the one which is used. There is easily couple of cms shape differences between low camber and high camber wings for each cell, and that multiplied for example Speeds ca. 40 cells results huge total differency. Differences are both chordwise and spanwise.

In practice best upwind is achieved when kiter takes out maximum pull of the kite when still able to hold the edge. This is very hard work and because of that kiter often has to depower to not to drag downwind. This may give an illusion that depowered and lower cambered kite goes better upwind. Of course kite has to fly far in the window to go well upwind, race kites and Speeds do.

It is much more precise to compare upwind performances on snow/ice, then kiter and board does not have so significant role.

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Re: Speed 3 21m Upwind adjustment

Postby The Captain » Sun Jul 24, 2016 8:58 pm

All good info. I'll try setting B-1,C-2 to start (low hanging fruit first!). If nose over is the symptom of too much camber (extended B/C), what is the symptom of shortening them?

Failing that, I'll dive into giving the mixer a full go-over. I will check the pulley lines quickly as well, to see how much they have shrunk.

Thanks folks!


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