It will be interesting now to learn about efficient gybe itself.Suppose that we do not longer need to meet 50 m or any at all.
Just a smoothest , fastest gybe without worry about exit point.
Just a gybe and flip sail, even if than complete bear off down the wind after gybe.


What will be then speed drop on optimized for speed gybe? From 30 ktn ? to 20? 25 ??
from 35? to 25?

That could be even new GPS competition one day!! The highest entry speed and the lowest drop !!Similar to alpa 500 but without any 50m requirements .

I admire Izaak ( and anybody else) ability to commit into full gybe at 35Ktn BTW.
Then means at L?deritz one may do a gybe at the bottom and sail back all the way !!

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Macroscien said..>>>>
Then means at L?deritz one may do a gybe at the bottom and sail back all the way !!

Don't think so, if you can sail back the way you came you're not bearing off enough.

Somewhere I've got a 29Kt NM with a gybe in it, that was a full on downwind to downwind gybe. I'll see if I can find it. You've got me wondering now what the min speed was.

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decrepit said..

Macroscien said..>>>>
Then means at L?deritz one may do a gybe at the bottom and sail back all the way !!

Don't think so, if you can sail back the way you came you're not bearing off enough.

Somewhere I've got a 29Kt NM with a gybe in it, that was a full on downwind to downwind gybe. I'll see if I can find it. You've got me wondering now what the min speed was.

right, but maybe one day Lauderitz curators could dig another channel below to allow sailors come back sailing ? returnig channel , not for speed but to travel back? but I think that will not be possible on such speed gear back up wind that much. That could save on transportation costs, and allow you to make more runs.

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decrepit said..

Somewhere I've got a 29Kt NM with a gybe in it, that was a full on downwind to downwind gybe. I'll see if I can find it. You've got me wondering now what the min speed was.

Yep, that is interesting question.
BTW that is quite a commitment to make full gybe down wind well above 30 ktn we could split down wind gybes into two categories: with duck gybe as the second option yep can't chicken but duck to make gybe at 30+ ktn.
Interesting will be to know if full speed duck gybe isn't more efficient then typical flip. Typical flip require you to loose wind power for a moment.Properly done duck gybe could keep you powered near 100% of the time during down wind gybe .

www.ka72.com/Track/t/462883 here is a foil alpha. Can anyone have a look at min speed etc ??
www.ka72.com/Track/t/458121

here you go, min speed 17.8kts max 29.5 you only just made the 50m but

and second one, not quite as good. But similar min speed. Daryl, GPSSpeedreader is only "beer money", then you can do this yourself

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Macroscien said..
It will be interesting now to learn about efficient gybe itself.Suppose that we do not longer need to meet 50 m or any at all.
Just a smoothest , fastest gybe without worry about exit point.
Just a gybe and flip sail, even if than complete bear off down the wind after gybe.


What will be then speed drop on optimized for speed gybe? From 30 ktn ? to 20? 25 ??
from 35? to 25?

That could be even new GPS competition one day!! The highest entry speed and the lowest drop !!Similar to alpa 500 but without any 50m requirements .

I admire Izaak ( and anybody else) ability to commit into full gybe at 35Ktn BTW.
Then means at L?deritz one may do a gybe at the bottom and sail back all the way !!

It's not as high as you might think in moderate winds.
This year the winds were generally light at LG, often in the 15-20 knots range. It was still lots of fun doing bearaways in the glassy smooth, and it was amazing the top speeds compared with actual true wind speed. We were often more than doubling true wind speed in around 15-17 knots of wind with top speeds in the low to mid 30's.

On many of those runs I simply went straight into a gybe at the end of the run. But the big issue with this is getting backwinded by the sail. It's literally putting the air brake on! One has to slow down to wind speed or below before you can flip the sail. Hence, most of my bottom speeds still looked like this. I am guessing this run was in about 15-17 knots of true wind and so I had to drop below that speed before I could filp the rig. Then you will inevitably slow a little more before the sail gets flow and power again, hence the bottom speed on this one at 14.5 knots




Of course, on stronger winds, the rig flip can be done at higher speed, but the bottom speed will be limited by the true wind speed.

Duck gybing won't help much either, as we rely on the drop to almost zero apparent wind so we can throw the rig over the head.

I had a look for my 29kt NM with gybe at Lilacs, couldn't find it, no idea where it's gone

Thats a shame. I went looking for some runs where I gybed at the end of runs and it hard to filter though all the sessions and videos! Still looking........

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sailquik said..

Macroscien said..
It will be interesting now to learn about efficient gybe itself.Suppose that we do not longer need to meet 50 m or any at all.
Just a smoothest , fastest gybe without worry about exit point.
Just a gybe and flip sail, even if than complete bear off down the wind after gybe.


What will be then speed drop on optimized for speed gybe? From 30 ktn ? to 20? 25 ??
from 35? to 25?

That could be even new GPS competition one day!! The highest entry speed and the lowest drop !!Similar to alpa 500 but without any 50m requirements .

I admire Izaak ( and anybody else) ability to commit into full gybe at 35Ktn BTW.
Then means at L?deritz one may do a gybe at the bottom and sail back all the way !!

It's not as high as you might think in moderate winds.
This year the winds were generally light at LG, often in the 15-20 knots range. It was still lots of fun doing bearaways in the glassy smooth, and it was amazing the top speeds compared with actual true wind speed. We were often more than doubling true wind speed in around 15-17 knots of wind with top speeds in the low to mid 30's.

On many of those runs I simply went straight into a gybe at the end of the run. But the big issue with this is getting backwinded by the sail. It's literally putting the air brake on! One has to slow down to wind speed or below before you can flip the sail. Hence, most of my bottom speeds still looked like this. I am guessing this run was in about 15-17 knots of true wind and so I had to drop below that speed before I could filp the rig. Then you will inevitably slow a little more before the sail gets flow and power again, hence the bottom speed on this one at 14.5 knots




Of course, on stronger winds, the rig flip can be done at higher speed, but the bottom speed will be limited by the true wind speed.

Duck gybing won't help much either, as we rely on the drop to almost zero apparent wind so we can throw the rig over the head.

You absolutely right,
and I didn't thought about this.We are going faster then wind, twice as much!
Then during the gybe and sail flip we are going faster then wind and flipping is not possible !
Unless we do tack flip at 30 ktn !!
So factor limiting our minimum , bottom speed will be wind speed.
We need 30 -35 ktn wind to make gybe without falling below 30 ktn speed. (?)
Is it right?
Now I could recall in my memory those aggressive gybes when suddenly sail pushed me back.
Thanks to you all makes sense and clear now.
Here on GC with plenty of wind holes from sky scrapers, few meters could make a difference between good gybe and failed due to stagnate wind or even whirlpooling in opposite direction.

BTW.That brings us also to the necessity of inventing new type of powering rigs, sails, wings!
Such that allow you to make turns at vessel speeds 2 , 3x time wind speed without the need of slowing down.
Specifically important for Americas Cup races .It seems that wings could do the job possible. If we could now invent wing type sail rig installed on the short mast or leash then new type of speed sailing craft could be born. I wonder how long it takes to see now wings beating speed records at Lauderitz ?
If we could extend considerations further, we could see that as some point wings lift exceed available weight of craft + crew.
Fin doesn't help here so only hope in REVERSE FOIL !!!
Yep .
Foil which allow us to grip to the water, now with unlimited upper speed and power from wing sail !! Foil need to push us down , against lifting force of the wing !!

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Macroscien said..
Foil which allow us to grip to the water, now with unlimited upper speed and power from wing sail !! Foil need to push us down , against lifting force of the wing !!

Done already. Refer to Sailrocket 2.

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Macroscien said..
So factor limiting our minimum , bottom speed will be wind speed.
We need 30 -35 ktn wind to make gybe without falling below 30 ktn speed. (?)
Is it right?

Perhaps. But there are a lot of other factors to consider in wind speeds of 30-35 knots.
First, we would probably be still be going significantly faster than the windspeed. In great flatwater conditions at the best angle it is common to go 40-45+ in that wind range. So there would still be a potential problem with backwinding if the turn-in starts too aggressively.
Second, is is very rare that there would be water flat enough to hammer straight into a gybe at those tops speeds. I have seen it once at Lake George, but the last thing on my mind was gybing after a 45 knot peak.
At Sandy Point, and any other places behind a sand bar, the water would be dangerously rough at the and of the speed run just after top speed. It's bad enough just trying to stop in one piece.
Third, even a speed board would be very tricky, to tip into a gybe at that speed.

I am sure we could find someone who was willing to try it, but I probably won't be me! Over to you Macro.

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sailquik said..

I am sure we could find someone who was willing to try it, but I probably won't be me! Over to you Macro.

My lifetime plan is to get 25ktn alpha! and 30 NM maybe too.300km/24h?
But if you look at Trimmer doing jetski alpha at >100km/h finishing 43.3ktn not sure if safety circuits prevent him one day to try similar on the speed board
We could arrange next topic on SB - the fastest speed gybe ever made!!!

When it comes to analysing Alphas (JKs in America's Cup terminology) you guys are still a fair way behind Mozzie sails.

ETNZ enters the JK at 42 knots, dropping to a minimum of 24.5 knots.

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Ian K said..
When it comes to analysing Alphas (JKs in America's Cup terminology) you guys are still a fair way behind Mozzie sails.

ETNZ enters the JK at 42 knots, dropping to a minimum of 24.5 knots.

Well of course they can blow us off for an Alpha. Especially a Tack Alpha Why would anyone think they couldn't when they can do 50 knots in around 12 knots of wind?

So what WAS the AC75's (Tack) Alpha Ian

Well they probably wouldn't have closed up the 50 metre proximity within 500 metres, but the minimum speed in the tack sort of indicates what they could do if they set about trying. The gybe Alpha would have a higher minimum speed but I think having to corner wider they'd have even less chance of getting back to the proximity circle. All the data is there for every race on the www.Americascup.com website virtual eye if you really wanted to see if they'd officially qualify for a good Alpha.

Do you reckon there's potential for a good tack Alpha by a young co-ordinated wind foiler? Technicalities aside , If a slowdown on the turn is inevitable a tack makes more sense to maintain height for the return run.

At 1.40 Balz shows the potential for a neat duck under the clew tack.

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Ian K said..
Well they probably wouldn't have closed up the 50 metre proximity within 500 metres, but the minimum speed in the tack sort of indicates what they could do if they set about trying. The gybe Alpha would have a higher minimum speed but I think having to corner wider they'd have even less chance of getting back to the proximity circle. All the data is there for every race on the www.Americascup.com website virtual eye if you really wanted to see if they'd officially qualify for a good Alpha.

Do you reckon there's potential for a good tack Alpha by a young co-ordinated wind foiler? Technicalities aside , If a slowdown on the turn is inevitable a tack makes more sense to maintain height for the return run.

At 1.40 Balz shows the potential for a neat duck under the clew tack.

A big difference between windsurfing and foiling is that the relative upwind speed on the foil is a lot higher. Here's an example polar plot:

That means an AC75 board could do a very wide jibe, and then go back upwind at a pretty steep angle while still doing 40 knots. A 40 knot alpha seems possible for the top boats (quite incredible for those of us who struggle to reach high 30s top speed!).

For windfoiling, the "old school" duck tack Balz shows would be the way to go for a tack alpha. The problem with it is that you duck the sail against the apparent wind. That's doable for a good freestyler with a freestyle sail, and when foiling at moderate speeds. The move would be much harder with a cambered sail, which can't be switched off for the duck. It is possible to keep almost the same speed into the wind during a tack as in a jibe while foiling. With 25 knot true wind speed and 20 knot board speed, you'd have to duck a sail in 45 knots apparent wind. That would be a huge challenge even for Balz.

The fin freestylers often duck in very high wind, for example in Fuerteventura. But that's a "new school" duck that's typically done slightly off the wind, so the apparent wind is not as crazy. I can do the ducks on in light wind, and I find the new school duck a lot easier to do with any consistency. It does not require nearly the same level of accuracy when moving the sail.

I think someone should put a GPS on Balz and tell him to work on alphas on the foil - both jibes and tacks. And perhaps on on Amado and tell him that you think he can't beat Balz .

The following is the track and speed over time graph for a 21.273 kt foiling alpha completed by Tony Knight at the Train on 20/1/21. I downloaded and analyzed his file from KA72. His top 2 sec for the day was 24.975 which was very close to his max entry and exit speeds. His minimum speed was around 13 kts.

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elmo said..
50m String line

Yep, put a float on it and let it blow down wind.

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GasHazard said..>>>>>>Yep, put a float on it and let it blow down wind.

UUMmmmmmm. The markers need to be directly across the wind. Downwind would be useless

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decrepit said..

GasHazard said..>>>>>>Yep, put a float on it and let it blow down wind.

UUMmmmmmm. The markers need to be directly across the wind. Downwind would be useless

I am thinking you mean the 200-250m length. He means the Proximity gate.

Of course, silly old fart time here

Here's my best windsurfing alpha from Lake George (28.195 knots, with a minimum speed of 17.903 knots) and below that my best foiling alpha (21.522 knots, with a minimum speed of 14.423 knots) - still trying to get the hang of them! Certainly easier to keep the speed during the gybe while foiling and quicker to accelerate back up to full speed.





Also just noticed that Boardsurfr mentioned the Speedreader software shows both minimum speed and percent of entry speed kept at the bottom of the results table - these are mine for slalom (top) and foil (bottom), so as high as 60% for slalom and quite a bit higher (over 70%) for foil (for those two sessions):

I suspect right back at day one of the Alpha there was a bug in the program that slipped by until it was too late to correct it.
An alpha should only be legitimate if it clears the upwind side of the proximity circle. Not anywhere inside the proximity circle. It should really be called it an Uncle. (This of course would favour the foilers)

Thats a truly outstanding Alpha Dave! Thanks for posting it.

It is very interesting because your out-run top speed was higher than your in-run. Do you remember if the in-run was tighter angle to the wind than the out-run?

And the bottom speed is exceptional too!

What board were you on?

I just released that the first one looks like a 1Hz GT-31, and the Foiling one looks like a 5 or 10Hz device.

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Ian K said..
I suspect right back at day one of the Alpha there was a bug in the program that slipped by until it was too late to correct it.
An alpha should only be legitimate if it clears the upwind side of the proximity circle. Not anywhere inside the proximity circle. It should really be called it an Uncle. (This of course would favour the foilers)

When Mal Wright invented and defined the 'Alpha', I think he did actually envisage that it would be common to cross ones own track on the return. We quickly realised this would not be the case for fast ones, but the naming concept was so nice it stuck.

At the very beginning, Mal was convinced that some fast Alphas might be done in the waves as well, where people gybed on a wave face, and used the wave for acceleration out of the Gybe, but most wave sailors don't wear GPS's and ride relatively slow boards anyhow.

A perhaps little known fact is that Mal included 250m, 500m and 1000m Alphas in RealSpeed right at the start. He said he was not sure which of the distances would 'stick'. I think that the A500m inclusion in GPSTC cemented it, although it was probably already becoming the most popular Alpha distance. GPS-Results and GPSAR-Pro also include calculations for the 3 Alpha distances.

Perhaps another little known Alpha fact is that you can make your own custom parameters for distance and proximity circle in RealSpeed, and just Proximity circle in both of GPS-Results and GPSAR-Pro.

I've been trying to get decent alphas for years. I did some good ones ( for me ) in 2015 but even though knew my gybing was better then back then I consistently went too wide.
Andrew's datafields made a hell of a difference and I finally learnt how to do them using his alpha one on the Garmin.

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sboardcrazy said..
I've been trying to get decent alphas for years. I did some good ones ( for me ) in 2015 but even though knew my gybing was better then back then I consistently went too wide.
Andrew's datafields made a hell of a difference and I finally learnt how to do them using his alpha one on the Garmin.

I assume you mean you were often too wide at the proximity circle?? You wouldn't be alone in that. Thats why we have been talking about markers and ways to judge the proximity distance.