I have difficulty in aligning sail with board center line to close the gap.
With my 8m cam sail I could feel sudden acceleration when in strong winds this two align close - bottom of the sail along the board. But usually there are quite apart and at the wider angle.
I suspect that my harness lines could be to long ?
or
changing boom heights my help ?
If I am using waist harness not a sit could effect it too?

If you have successfully built a time machine and gone back in time 15 years then maybe this would be an issue... but windsurfing has moved well beyond closing the gap.

Go be feel not what an out of date text book says.

If your comfortable (not wrestling the rig) then it will be faster than when you fighting everything trying to get perfect alignment.

I can only sheet in hard, close to the centreline, in a gust if I try to go upwind, otherwise it feels like i am losing power. But I also see better sailors than me 'closing the gap', maybe the technique is not totally dead, just has a different name ?

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aus301 said..
If you have successfully built a time machine .......

Don't encourage him

if your sail is on the centreline of the board then you have oversheeted.

Illustration "borrowed" from near by topic on our forum " speed windsurfing"


"





#t=89

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Mark _australia said..

aus301 said..
If you have successfully built a time machine .......

Don't encourage him

you saw what I did there

stop it boys..... !!

seriously Macro I got the advice from A² in person : go to the gym and pull on that back hand....

Every one going quick on a slalom sail ive seen always has the sail slammed down hard . when bearing off a little bit less but up wind and across wind its pretty much on the top of the board . I dont think its about pushing the sail down as much as it just goes there on its own when everything else is working . I find if im not locked in with the sail low the board just slaps the waves instead of flying over them . It could be how the sail is rigged or maybe the fin choice if the fin is to small it will just spin out when you push it to hard , also if you dont have enough down haul the center of the power is higher and to far back once its leaned over and that can also make it spin out or not want to close the gap .

How long are your harness lines , i change mine between 26 and 34 depending on angle and wind strength having them rite makes a big difference in comfort an getting it all to balance . A waist harness could be alot to do with it too , i find without a super low hook i cant get that locked in balanced position thats probably the biggest issue , go buy a seat harness .

During a race i was stuggling to go upwind on a rsx in 18knots. Spin outs backwind pressure and slow uncomfortable overpowered feeling. I was advised to increase down haul to move draught down and forward. The effect was to alter the balance point between centre of effort (sail) and centre of lateral resistance (fin). Next race the sail closed the gap without me trying spin outs stopped back wind pressure disappeared board speed and angle improved and overpowerd feeling went away. Lesson for me that day was tuning is everything

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Macroscien said..

Illustration "borrowed" from near by topic on our forum " speed windsurfing"


"

He's not actually closing the gap to the board but rather closer to the water.
personally I sailed a little back handed especially for going of the wind this prevents you from over sheeting to much.
works for me anyway

Some of the local gurus call this "decking the sail". I've only learnt to do it this season. Since cracking the straps a few years ago, my speed mates weren't explaining the concept properly, so for a few years I was trying to deck the sail by pulling the sail down with arms which was totally wrong. As Sean said, it's pretty much sheeting in with the back hand and then using the harness (which will end up having the majority of load force) to pull the sail towards you. I looked down one session a few months ago and discovered I was doing it (and going a few knots faster ). A local speed guru explained to me the board/water becomes an extension of the sail and stops wind slipping under it (I suppose it's the same principle as winglets on modern air liners ? - ie: stops the wind falling off the wings and therefore improves lift efficiency).

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Gestalt said..

if your sail is on the centreline of the board then you have oversheeted.

Yup

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Macroscien said..

I have difficulty in aligning sail with board center line to close the gap.

Have a squiz at en.wikipedia.org/wiki/Forces_on_sails Macro

I reckon there's more important / influential techniques to work on

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paddymac said..

Gestalt said..

if your sail is on the centreline of the board then you have oversheeted.

Yup

Macroscien said..

I have difficulty in aligning sail with board center line to close the gap.

Have a squiz at en.wikipedia.org/wiki/Forces_on_sails Macro

I reckon there's more important / influential techniques to work on

Virtual wind will eventually straighten your sail to the centerline, and smaller contact patch will tilt it back?
Wikipedia bores you with formulae but then chucks them all away:
"Without going into calculations, the faster the boat moves, the more the surface area intercepted increases, the vessel has more energy per unit of time, it goes even faster. If the boat is faster, the area intercepted is even greater. It gets even more energy. It goes even faster than before. The boat then enters a virtuous cycle. If the apparent wind increased indefinitely. with no heeling problem and hull resistance, the boat would accelerate indefinitely."
He he, striving for that virtuous circle, here.

Macro,
I'm not an expert. But here's my take on it...

1. Aligning the sail with the board centreline usually depends on two things for me:
- Direction of travel vs wind
- Speed
The sail will end up aligned with the board when speed is high enough and I'm sailing the right angle. Let this happen naturally. If you force to align the sail, you'll find the sail loses drive.

2. Closing the gap. For me this depends on 3 things. Direction/speed as above plus sail design. Some sails will not like the gap closed and will be slower if forced to. Guy Cribb has a good article on this, and recommends for best power/speed recommends the mast as vertical as possible, ie gap open. When I find that I'm sailing with the gap closed, it's not something I've done consciously, it's happened because that's where the sail feels the best.

I've at times forced it aligned and closed after watching faster sailors, it felt wrong and I've lost speed. It happens for me when all 3 factors above kick in. On the other hand, there's also been times when I needed to rake the sail back more and found that it's already on the deck had and no where to go.

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Macroscien said..

I have difficulty in aligning sail with board center line to close the gap.
With my 8m cam sail I could feel sudden acceleration when in strong winds this two align close - bottom of the sail along the board. But usually there are quite apart and at the wider angle.
I suspect that my harness lines could be to long ?

If your arms are slightly bent gripping the boom shoulder width when hooked in, then I'd say you're in the ball park with the length. It could be the harness line location, further back will tend to sheet in more, closing the angle.

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Macroscien said..
or
changing boom heights my help ?
If I am using waist harness not a sit could effect it too?

If the boom sits between shoulder and chin height when horizontal, then I'd again say no major changes will be required.
I personally don't think harness style makes that much difference, whatever feels good for you.

I personally only close the gap when I'm completely getting overpowered or going upwind hard. On a broad range / speed run I never close the gap as that easily causes me to oversheet.

I crank them down low and close the gap on light wind & flat water & they stay there alot- mast foot position is a big part of it - that is closely linked to the board, strap position & fin. I moved from a seat harness to a waist, 2 years ago when I was having sore back probs - waist harness totally fixed my back by the way!! Has changed my life! - i used to hang out on v long harness lines straight arms ,totally differnt style like you see formula - now I seem to be much closer to the sail - I am on short harness lines, with very bent arms, sheeted hard in. - I think the rig is more leaned to windward now, takes longer to load up the weight on the rig but faster over all when you get into the sweet spot - It took a while to adjust actually, it is micro stuff macro, really small incremental adjustments in things + time = a new style - my back lets me sail as often as I like now!