The question was asked in another thread about what speeds one need to do on the in-run, out-run and min speed to get a 25 knots Alpha.
It would be good to see and share some examples, so here are a few I grabbed from a few of my sessions a Lake George this year. Most were done in very flat water. All in around 20-25 knots of wind and all on my 2017 Isonic 80 (59cm wide) with 20cm Atomic Nuclear weed fin Prototype and 2021 5.7m KA Speed sail. All using mini Motion @10Hz in my helmet.
Here is a pretty classic one at 25.4 Kts. I managed to get back pretty much just inside the 50m proximity circle and had fairly even speed in but a bit slower out. This one has a slight bearaway just before the gybe which I normally try to avoid as much as possible, and good accelleration out with a min speed around 13 knots.
Here is a better one IMHO, at 25.6 where I got better accelleration out and a better shaped Gybe: I recon there was a bit left on the table at the start and the end here, but one of the hard things is to judge distance. One way is to get to what you think is max speed and count to 10 seconds before the Gybe. Then count another 10 after the Gybe.
Note that I am trying to run-in exactly square to the wind (cross wind), and come back the same.
I have experimented with going in slightly upwind as it is often easier to hold a high speed by building up slightly off the wind and then tightening up for the run-in. The advantage of this is that you can come out on a slightly broader angle to the wind and get better accerationa and out-run speed.
Again at LG. Carbon Art 100 litre, MUF (old school) Delta 22cm
Similar entry speed to Sailquik of around 32 kt and a minimum of 13kt. Result 25.6 kts
Looks like I could have not pointed quite as high on the exit, but I knew it was a good one and didn't want to end up outside the 50.
For comparison here is a 20 kt Alpha, from a foil session.
Entry speed around 22 minimum similar at 13.
Select to expand quotetbwonder said..
For comparison here is a 20 kt Alpha, from a foil session.
Entry speed around 22 minimum similar at 13.
Nice Andrew. What device is that recorded with?
A sightly faster one - 26.2. THIS is what I am trying to do, but it seldom works out this well. 
Select to expand quotetbwonder said..
For comparison here is a 20 kt Alpha, from a foil session.
Entry speed around 22 minimum similar at 13.
A fair bit more potential for foilers I'd think if they really decided to go for it.
Be interesting to run the Alpha program over the AC75 tracks. Either the "JK" or the "Chicago" manoeuvres should give good results. American Magic was undertaking a Chicago when she came to grief.
Most people agree that one of the most difficult aspects of doing an Alpha is judging the 50m Proximity circle on the return run.
In some places, like at Sandy Point on an Easterly, there is a bank you sail behind and a channel marker bouy which helps get some distance perspective. In other places there can be markers or bouys, but where there is none, on a large flat expanse of water like Lake George, Primbee, L Budgiewoi, Fangy's. Liptons, Frenchmans Bay etc, it can be hard to judge your distance and angles for the return.
One technique I have used a lot in the last few years is to run in square across the wind and line up some feature in the distance in front of me as a reference. Halfway along the run-in, I look back and line up my wake with another feature in the distance behind. It is often a slight hill or tree on the horizon. When I gybe, I try to head straight back towards that feature. I can even check behind to see if my wake is lined up with what I was heading for on the run-in, but that one can be a bit deceptive.
Here is a nice Alpha if did recently where you can see me look behind for the line up on the in-run:
Walking through the thick weed with a tape measure is not practical. 
I have a foiling one here from last Wednesday 10th to share
Gusty 20kt+ SSE at the train so didn't quite get the timing right and tended to sail out of the gust before finishing up, still lots of fun,
I think for me a flat 22 on the foil is possible if the stars align
Here is a screen shot
File can be found on KA72
NB- low tide at the train and I am between two sand banks, so bearing off further is a catapult on a foil
Cheers
TK
Select to expand quote>>>>> I have not quite solved yet is how to place them accurately 50m apart. I have a rangefinder, but it's not water proof! Walking through the thick weed with a tape measure is not practical.
When we did the fist ones in alpha land, I used the GT31. But 50m may be a bit to far apart given the 1.5mX2, accuracy of the alpha calculation. If you skim the markers with a 50cm board you're alpha could be invalid.
Select to expand quotetonyk said..
I have a foiling one here from last Wednesday 10th to share
Gusty 20kt+ SSE at the train so didn't quite get the timing right and tended to sail out of the gust before finishing up, still lots of fun,
I think for me a flat 22 on the foil is possible if the stars align
Here is a screen shot
File can be found on KA72
NB- low tide at the train and I am between two sand banks, so bearing off further is a catapult on a foil
Cheers
TK
fascinating, because minimal speed during turn never dropped below 17 ktn!
I saw few gybes made on fin with very high minimum speed , but that is very rare indeed.
Select to expand quotesailquik said..
Most people agree that one of the most difficult aspects of doing an Alpha is judging the 50m Proximity circle on the return run.
In some places, like at Sandy Point on an Easterly, there is a bank you sail behind and a channel marker bouy which helps get some distance perspective. In other places there can be markers or bouys, but where there is none, on a large flat expanse of water like Lake George, Primbee, L Budgiewoi, Fangy's. Liptons, Frenchmans Bay etc, it can be hard to judge your distance and angles for the return.
One technique I have used a lot in the last few years is to run in square across the wind and line up some feature in the distance in front of me as a reference. Halfway along the run-in, I look back and line up my wake with another feature in the distance behind. It is often a slight hill or tree on the horizon. When I gybe, I try to head straight back towards that feature. I can even check behind to see if my wake is lined up with what I was heading for on the run-in, but that one can be a bit deceptive.
Here is a nice Alpha if did recently where you can see me look behind for the line up on the in-run:
I noticed a couple of years ago that the guys at Fangy's had put in a couple of Alpha marker posts. Thats a great idea where you have a dominant wind direction and a spot were you can consistently expect good wind and water conditions.
I have been toying with the idea of making up a couple of flags on fibreglass stakes (the type they sell to farmers for electric fences) to stick into the mud at Lake George in a good flat spot, but the issue I have not quite solved yet is how to place them accurately 50m apart. I have a rangefinder, but it's not water proof! Walking through the thick weed with a tape measure is not practical.
absolutely fantastic video! I wish we have this gybe recorded from distance or even better - drone. Few angles slow motion , so we could see and learn all details. Feets works, , hands on boom, sail flip, angle of the board carving in the water. I still have some doubts how much angle is needed for fast carve. Very deep carve (as adviced by Nico)looks good on video but may be eventually slower then shallow and flat board . The question could be how much during fast gybe depend on board rails and how much on fin. ? I think then fin component will be more efficient the rail . ?
that last thought brought me idea that for really fast alpha we could rather use oversized fin. ?
Since top speed is not so important, bigger fin could allow us to keep board flat , don t need to dig rails.
Did somebody such experiment? Same d
board, sail, wind and water but using two different size fins?
May not be very practical for LG to swap fins in the mud, ....
Top speed is quite important I think Macro. But top speed is not just dependant on fin size. The whole package of sailor, board, sail and fin for the given wind must be in the right balance for top reaching speeds, but then also add acceleration and how much the board digs in and slows in the turn.
Generally, Slalom boards are specifically designed to accelerate fast and carry speed though a Gybe well.
Quite a few years ago I was experimenting with Alphas in quite strong winds. I found that on my older 2008/9 IS87, once I was over about 32-33 knots on the reach it was very hard to tip into the turn aggressively. There was so much pressure under the board it was really hard to sink the rail to start a gybe, At the time I had a CA50 (large speed board) with narrower tail. When I tried that I could often reach a higher speed on the run-in and it was very easy to initiate the carve, but the speed bled off far too much in the turn because of the narrower tail and lack of area. It felt great but I was always slower out of the gybes and the Alphas were never as good as on the bigger, wider board.
One big difference with my newer 2017 IS80 is that even at 33-34 knots it is far easier to tip into a gybe, and then it still holds speed through the turn and out just as well, or better than, the older IS87. I would be surprised if the other newer, top brand slalom boards of similar size were any different in this regard.
Seeing my slalom Alpha gybe from the side might not help you much and may actually confuse you as I do many things atypical of most slalom racers who have different set of considerations in a typical slalom race.
Here is an example of what I mean taken many years ago in bigger kit in lighter winds. (IS110, 6.6m Koncept - 15-17 knots of wind) This kind of Gybe is very efficient on smaller kit and flat water, but not so well suited to rough water and using overpowered large sails as one does in a slalom race. My current Alpha and gybing technique is very similar in essence to this. I freely admit I am now very much a flat water Prima Donna, and rarely sail when I would need a sail larger than 6.3m.
Select to expand quotesailquik said..
Top speed is quite important I think Macro. But top speed is not just dependant on fin size. The whole package of sailor, board, sail and fin for the given wind must be in the right balance for top reaching speeds, but then also add acceleration and how much the board digs in and slows in the turn.
Generally, Slalom boards are specifically designed to accelerate fast and carry speed though a Gybe well.
Quite a few years ago I was experimenting with Alphas in quite strong winds. I found that on my older 2008/9 IS87, once I was over about 32-33 knots on the reach it was very hard to tip into the turn aggressively. There was so much pressure under the board it was really hard to sink the rail to start a gybe, At the time I had a CA50 (large speed board) with narrower tail. When I tried that I could often reach a higher speed on the run-in and it was very easy to initiate the carve, but the speed bled off far too much in the turn because of the narrower tail and lack of area. It felt great but I was always slower out of the gybes and the Alphas were never as good as on the bigger, wider board.
One big difference with my newer 2017 IS80 is that even at 33-34 knots it is far easier to tip into a gybe, and then it still holds speed through the turn and out just as well, or better than, the older IS87. I would be surprised if the other newer, top brand slalom boards of similar size were any different in this regard.
Seeing my slalom Alpha gybe from the side might not help you much and may actually confuse you as I do many things atypical of most slalom racers who have different set of considerations in a typical slalom race.
Here is an example of what I mean taken many years ago in bigger kit in lighter winds. (IS110, 6.6m Koncept - 15-17 knots of wind) This kind of Gybe is very efficient on smaller kit and flat water, but not so well suited to rough water and using overpowered large sails as one does in a slalom race. My current Alpha and gybing technique is very similar in essence to this. I freely admit I am now very much a flat water Prima Donna, and rarely sail when I would need a sail larger than 6.3m.
It looks for me that this video confirm my suspicion above.
That key to fast gybe is relatively flat board keeping ,not aggressive digging rails in the water. Very smooth turn, fluid motions.If we look at Nico Prien it may looks very spectacular turn and most likely efficient in slalom.
But I doubt that eventual total result on alpha 500 will that great at all.
To much waste on water frothling IMO.
Select to expand quoteelmo said..
50m String line
Wot?
You've all got a GPS on your arm.
It tells you distance as well as speed.
That last Gybe would definitly have made a great Alpha! 
That is probably the smoothest and fastest step gybe I have ever seen!
There was an excellent video I saw of Izaak Perkins doing a Step Gybe Alpha a few years ago. Very fast!!
Select to expand quoteTe Hau said..elmo said..
50m String line
Wot?
You've all got a GPS on your arm.
It tells you distance as well as speed.
The issue at LG is, that in the best places, it is almost impossible to walk through the weed to carry a tape or step out a measurement. Your right though. I could probably find a distance screen on the old GT-31 to zero and measure roughly 50m. 
. But even one flag for a rference point would be very useful.
In my experience, it is important to start a Alpha Gybe quite aggressively (turn-in), but also very important to progessively flatten the board after the initial turn-in to keep speed and maintain a constant arc. That is, as the board slows quickly during the turn, it sinks deeper into the water and the arc tends to tighten very quickly. This is why many gybe attempts end up 'overturning', where it feels you suddenly round up into the wind as you complete the turn. But ths is also amplified if you are too slow in and start to drop off the plane, or loose too much speed in the turn.
If you hold a constant board angle through the turn, it will tighten the arc and overturn, killing exit speed and rounding you up into the wind at the end.
You can clearly see the tight turn-in and widening of the arc on exit in Andrew Haigs slapper and foiling gybes above, where he turns-in with a tight arc and then widens the arc through the second half of the turn.
The very first one I posted is the opposite and not a great one. I am turing in less aggressively and tightening up on the second half. A good example of leaving a lot on the table.
Select to expand quoteelmo said..
50m String line
That would work if I went out with a helper on SUP's on a calm day. But of course, one has to anticipate the wind direction and best place. Probably not impossible.
Thats why I reckon just one marker is probably the best compromise and works with changing wind directions. Start about 20m high of the marker, count to 10, gybe, aim for about 20m low of marker. 10m margin of error still requires judgement, but better than no marker. Currently, I just look for an object on the horizon and my wake, as you describe sailquick. When Fangland had weed I'd use a weed burg as my marker. At Liptons, I try to use a boat channel marker. At Lilacs, you are a bit compressed against the shore, which I think helps avoid going wide. I actually brought a pvc pipe marker Post and float with me last trip down to Lilacs, but of course forgot all about that as soon as I hit the water 
Select to expand quoteIan K said. Be interesting to run the Alpha program over the AC75 tracks. Either the "JK" or the "Chicago" manoeuvres should give good results. American Magic was undertaking a Chicago when she came to grief.
Hey Ian, do you think you could 'reverse engineer' the GPS data for that off the replay video. All the numbers are on the virtual eye video looks like.
I would be very surprised if they hit the 50m Proximity circle though.
Here is an interesting 25.34 from yesterday which shows it's entirely possible to do a decent Alpha in reverse. By that I mean pinching upwind a bit before the gybe and coming out a bit broader. In this one I was reaching when I felt a small squall start, so I pinched a bit to gybe and then came out building speed for a bearaway speed run. So it is the reverse of most I do where the in-run speed is faster. On this one the out-run is much faster and acceleration faster.
I think there may be an adavantage in deliberately applying this strategy so some extent, to get better and faster accelleration for the out run, but I have not really explored it yet. Bottom speed is 14.1 in this one which is slightly above average for me.
Now for a little bit of fun there is our experiment made in Burrum two years ago.
Alpha 500m - 43.3 ktn !!!
I could not locate the gps file, now , but will be interesting to see the graph actor -Trimmer
Some nice alphas here. For windsurfing, the minimum speed is typically just below 50% of the maximum entry speed (which is a darn good jibe). On slalom/speed gear, I often struggle to keep 40% of my entry speed in the jibe. Staying above 60% is rare; above 70% on winddsurf gear is usually only seen on slower gear when timing a wave right (at least for me).
But when foiling, keeping 60%-70% is reasonably easy, even with a light touchdown. Good foilers routinely keep 70 to 75% of their entry speeds. GPS Speedreader shows both minimum speed and percent of entry speed kept at the bottom of the results table:
The number in the +/- column is the percent of entry speed (maximum within 50 meters before the turn) kept. GPSAR reports this as "score", but I think it calculates it a bit differently (using the speed exactly 50 meters before the turn, not the maximum entry speed, I think).
I'd love to look at the numbers for America's cup races. Are the GPS tracks available for downloading somewhere?
Here's one of mine with a roll in speed at 31.1 kts , a low of 16.9 and an exit of 27.6. Not my best but close to my best lowest speed which I think is the key to a fast Alpha.
Gybing is a battle of balancing drag and distance in the underpowered part of the curve. Turn tight too much drag, turn wide too much distance. Drag times distance wipes off kinetic energy so you should really square your output speed and divide by the square of your input speed. Kato retained 29.5 % of his ingoing kinetic energy in that super slick gybe above.
Select to expand quoteMacroscien said..
Here is one of the Izaak Perkins alpha totaling 28,6 !!
Alphas by far my favourite category! Can be frustrating to miss that radius! But a very fun challenge to snag a good one. Dad and I have always loved the alphas. And tried many different ways to achieve it. Having any type of reference points help judging distances too. I think some things that definitely consist to a fast one. Is by far exit speed! If you can get back in the straps, locked in. Driving that board accelerating as close as you can or think that radius is. Building up exit speed anywhere near as close as your entry speed. You'll get a good one. Min speed in the turn has a bit to do with it. But not always the key. The way I see it. (Being on a 45cm speed board myself) The faster you're entering. The harder it is to get a tighter arc in giving you more angle to stay square or even bear off a little in that 250m exit out.
I've had a look at my best alphas, and they vary, none of them are optimum, where I've got high in and out speeds I have a lower minimum, (13 kts) where I've got a higher minimum (16kts) the in and or out speeds are lower.
here's my best at 26.4 location Pt Grey. Curve tightens a bit too much causing lower min speed, but runs are fairly square, and 50m is very good max gybe width 61m, (thought I'd taken this screen shot with this showing, senior moment again).
And here's my 5th best at 25.4kts, location Lilacs
The 60m+ gybe width is fairly typical for the best 5.
I didn't judge the 50m as well here, bit too upwind on the way back. This also has a more even gybe curve resulting in a higher min speed.
One of these days I may get all the stars to align
