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Mozzy 
Far too distracted from work 
Joined: 21 Apr 20 Online Status: Offline Posts: 209 |
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 Topic: Training aid ideaPosted: 27 Aug 20 at 9:09am |
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VMG toward a mark or waypoint is pretty useless for upwind tuning. The long tack will always show as better VMG. The nearer you get to the layline, the worse your VMG reading will be.
You need velocity in the direction of the true wind over water (i.e. how fast are you doing upwind). Whether you want to follow the number real time or do post sailing analysis then the data needs to be pretty high resolution (1 sec interval or less) and you'll need to adapt your target numbers for wind speed too. This is something most racing yachts will have and be doing if they are good. But I don't think it's possible to recreate it on a dinghy with only a GPS.
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Sam.Spoons
Really should get out more 
Joined: 07 Mar 12 Location: Manchester UK Online Status: Offline Posts: 3401 |
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Posted: 27 Aug 20 at 10:33am |
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Thanks Mozzy, I did try it yesterday and was not able to get it to work satisfactorily. I just want to get a feel for the differences between pointing and footing really so a waypoint a couple of miles upwind would keep me in the middle of the window for a few hundred metres. The Garmin I'm using updates once per second.
Edited by Sam.Spoons - 27 Aug 20 at 10:34am |
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Spice 346 "Flat Broke"
Blaze 671 "supersonic soap dish" |
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Mozzy
Far too distracted from work
Joined: 21 Apr 20 Online Status: Offline Posts: 209 |
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Posted: 27 Aug 20 at 11:57am |
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What would be easier (albeit rough), is to consider what sort of speed increase you need to make a 5 degree foot worth it.
Do 5 tacks recording the tacking angle on your compass. Try not to tack on shifts when doing this. Look at your GPS post sailing to get an idea of your average 'steady state' upwind speed. Run the maths to ascertain how much faster you need to go when you foot 5 degrees to make it a better VMG. Then play around on the water watching your speed as you foot and pinch to see if you can achieve the required speed increase. I think that would be the only realistic way to approach the problem with the tools you have. Of course gusts and shifts wreck all this, even for instantaneous readings. And tide makes these GPS speeds meaningless. I guess this is why, despite advancements in technology, a tuning partner to see relatives against is very valuable.
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Mozzy
Far too distracted from work
Joined: 21 Apr 20 Online Status: Offline Posts: 209 |
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Posted: 27 Aug 20 at 12:01pm |
I'd set it about 50km away. It's only a waypoint. The further away it is, the less susceptible it is to wind shifts and skew as you sail out to one side.
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Sam.Spoons
Really should get out more
Joined: 07 Mar 12 Location: Manchester UK Online Status: Offline Posts: 3401 |
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Posted: 27 Aug 20 at 1:11pm |
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Spice 346 "Flat Broke"
Blaze 671 "supersonic soap dish" |
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