I got a surprise today. I set speed genie to 27kts for speed instead of the normal for alphas at 10kts.
My understanding is that speed genie needs to be set to less than the minimum gybe speed, for an alpha to be calculated. So I was extremely surprised to see alpha results appearing, most of them less than 20kts.
Has anybody else seen this?

Have I had it wrong the whole time? Bit embarrassing if I have!

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decrepit said..
I got a surprise today. I set speed genie to 27kts for speed instead of the normal for alphas at 10kts.
My understanding is that speed genie needs to be set to less than the minimum gybe speed, for an alpha to be calculated. So I was extremely surprised to see alpha results appearing, most of them less than 20kts.
Has anybody else seen this?

Have I had it wrong the whole time? Bit embarrassing if I have!

Yes, I have seen this. Most of the time, no alphas are shown with normal (high) speed genie speeds. But every now and then, it will show a number.
On my watch, the alphas that the watch shows even when min speed is very low seem somewhat random. Alphas shown by GPSLogit are usually closer to what I see when I analyze the tracks at home.

Alphas rarely show up on my watch. I rely on GPS Results when i get home.

Mike, I've experienced the same, but they are only the odd random result and never any plus 20kt.
You haven't got it wrong. The only way to get consistent alpha results is to set your speed genie less than your lowest speed in the alpha

Mike, I've experienced the same, but they are only the odd random result and never any plus 20kt.
You haven't got it wrong. The only way to get consistent alpha results is to set your speed genie less than your lowest speed in the alpha

Mike, I've experienced the same, but they are only the odd random result and never any plus 20kt.
You haven't got it wrong. The only way to get consistent alpha results is to set your speed genie less than your lowest speed in the alpha

I have seen the same thing with the speed genie set at 25 kts ,the odd alpha perhaps only one or two per session will be displayed on the watch, usually around 18-20 kt alphas.

Also I have had a few cases even with the speed genie set to 10 kts when the watch fails to record an alpha. But they are later recognized by realspeed and KA72.

However the alphas that the watch does display are typically within 0.1 kt of the calculated results in Realspeed/KA72

Had an 8.28 knot alpha today on the watch with speed genie set to 12 knots. I think that was the only alpha the watch showed for the session. Actual best alpha was 13.47 knots (longboard session in marginal winds). FW V 1.2A0314B

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tbwonder said..
Also I have had a few cases even with the speed genie set to 10 kts when the watch fails to record an alpha. But they are later recognized by realspeed and KA72.

This is normal due to the differences between the way the watch calculates alphas and everybody else.

For a start, due to processing limitations, the watch can't do alphas under 300m, whereas other software has, 100m or 50m minimums.

Also due to a difference of opinion between Tom Chalko/Locosys and everybody else. the watch uses doppler to calculate the 50m separation, whereas the other systems use trackpoints to calculate the 50m separation. I've seen up to 5m difference between the two methods, and can be in either direction. So the watch can give you a PB alpha that isn't recognised by other methods, or vice versa, the watch won't show an alpha that other methods do.

Then of course there's always the chance your min speed dropped below the speed genie setting.

Most of the time, my watch display agrees with processed results. I don't remember any other anomalies with alphas.

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John340 said..
Mike, I've experienced the same, but they are only the odd random result and never any plus 20kt.
You haven't got it wrong. The only way to get consistent alpha results is to set your speed genie less than your lowest speed in the alpha

Thanks John, I guess this isn't a big issue then, probably not worth reporting to locosys

I just got around to checking, I have Speed Genie set to 22 knots. Is the thinking that if I set it to 10 it will give me a better idea of how my corners are going while I'm on the water? I generally don't have a problem making the radius so I could try going a little wider.

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Agrid said..
I just got around to checking, I have Speed Genie set to 22 knots. Is the thinking that if I set it to 10 it will give me a better idea of how my corners are going while I'm on the water? I generally don't have a problem making the radius so I could try going a little wider.

As Said, it supposedly only records an alpha when speed genie is under the min speed. So if you can gybe without going below 22kts, it'll work for you. Otherwise look at your alphas and see what min speed is worth recording. You can still get a 20+ alpha with min speed down to 8kts, if you go in and out fast enough.
I started off with mine set to 12, but found there were still alphas I was interested in down to 9.
And yes it's a good way of tuning you alphas, just remember what I said about the 50m calculation difference.

But with speed genie set low, the display will recycle very soon after you gybe, so if you want to check your speed runs back at the start, you need to reset it, so that it's over your upwind speed, but below your downwind speed.

Forgive me if I digress, but I remember an amusing incidence, a friend had been trying to crack 30kts for ages, when he eventually did it, he came in very pleased but also perplexed. He said, "my GPS has gone crazy, the numbers keep changing!"
He'd had speed genie set to 30kts and had never seen the speed genie scroll before.

Ok, I'm trying 10kt Speed Genie setting. All of my decent gybes had me no lower than 12. I just need more speed going in. I reckon I start losing speed as soon as I set up for the gybe.

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Agrid said..
Ok, I'm trying 10kt Speed Genie setting. All of my decent gybes had me no lower than 12. I just need more speed going in. I reckon I start losing speed as soon as I set up for the gybe.

That's odd, I normally accelerate into it, my peak alpha speed is normally entering the gybe.




25kts in and out but 30kts into the gybe

Yep, I speed up as I go into the gybe too. I think I am slacking off a couple of hundred metres out. Sometimes I do a gybe that feels really good through the turn but the @500 is lame because I was only doing 23 knots at the start of the track. I reckon getting more feedback on the water will be a help, and hopefully the lower Speed Genie setting will have some more show up. I'm learning the speed sailing is about the wind, the water, the equipment, the technique as well as strategy. I guess that's why i'm enjoying it so much.

Strop tries to be bearing off flat out when he hits the start, then carry as much speed slightly upwind as he can for 225m, gybe and come out slightly downwind to get good acceleration, before heading back to the 50m separation point. He can judge distance really well, I need alpha markers to do this.

Hey! When did Strop read my play book!??

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sailquik said..
Hey! When did Strop read my play book!??

Did you leave it lying around somewhere?

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decrepit said..

sailquik said..
Hey! When did Strop read my play book!??

Did you leave it lying around somewhere?

Hello, does anyone know how to set the speed to be constant. that does not mean jumping up and down so fast. With the Velocitek speed puck you can enter a delay in the measurement, can you do that with the GW 60 too ?, thank you for your answer. regards

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SUPER10 said..
Hello, does anyone know how to set the speed to be constant. that does not mean jumping up and down so fast. With the Velocitek speed puck you can enter a delay in the measurement, can you do that with the GW 60 too ?, thank you for your answer. regards

I'm not sure I understand what you mean, are you after an average reading of a few seconds instead of the instantaneous?

If so I don't believe the GW60 is configured to do this. I suspect the display is updated about once a second with the 5hz average.

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decrepit said..

SUPER10 said..
Hello, does anyone know how to set the speed to be constant. that does not mean jumping up and down so fast. With the Velocitek speed puck you can enter a delay in the measurement, can you do that with the GW 60 too ?, thank you for your answer. regards

I'm not sure I understand what you mean, are you after an average reading of a few seconds instead of the instantaneous?

If so I don't believe the GW60 is configured to do this. I suspect the display is updated about once a second with the 5hz average.

Set your display on 10 sec ave and that should do the trick

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John340 said..
Set your display on 10 sec ave and that should do the trick

Ah so "action speed" is what you're talking about? Set to NSEC or MSEC, so you can pick what average you want.
Hmm must try that, I think I'll go with NSEC at 2seconds for a start. Not sure I want a 10s delay, I think that would make it too hard to adjust trim.

Thanks John.

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decrepit said..
. I suspect the display is updated about once a second with the 5hz average.

Well I got this wrong, if action speed is set to speed, (like I normally have it) it's showing the 200ms average, no wonder it's changing so fast.

I'm planning on getting back into GPS sailing, is the GW60 available from a friendly shop in Perth or is on line the go ?

I'm pretty good at breaking things and after reading some of the reviews would prefer to have the back up of a local retailer.

I've got a GT31 but it's in a box somewhere

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paulyNOR said..
I'm planning on getting back into GPS sailing, is the GW60 available from a friendly shop in Perth or is on line the go ?

I'm pretty good at breaking things and after reading some of the reviews would prefer to have the back up of a local retailer.

I've got a GT31 but it's in a box somewhere

Surf Sail Australia www.surfsailaustralia.com.au/product/locosys-gw-60-gps#surf-sail-clothing-hardware

Thanks for that Firie,
That's just down the road from me, and they're on special :)