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Re: Request for GPS Data [Re: TEH] #186539
07/30/09 09:25 AM
07/30/09 09:25 AM
Joined: May 2006
Posts: 96
Budapest, Hungary, Europe
CatSailingHu Offline
journeyman
CatSailingHu  Offline
journeyman

Joined: May 2006
Posts: 96
Budapest, Hungary, Europe
A year ago I also tried to make some tracklog analysis in excel.
[Linked Image]

What I found:

1. It toke a lot of time until my boat reached the speed she had before the tack. t = 60 sec.

2. the acceleration is not continuous, poor helming...

3. My speed went down dramatically (21km/h --> 4km/h)ds = 17km/h = 4.7 m/s

4. This tack cost me (measure the blue area, just approximately ) ds x t / 2 = 4.7 m/s * 60 s / 2 = +- 140m.

5. So If I make an unwind leg with 5 tack instead only 3, it cost me nearly 300m. So I really need a good reason to do this.


Of course all of this depend on the wind/wave conditions, and just one tack is not representative. Based my practice the loosing should be much less. I hope...






Sanyi
Nacra Infusion
www.catsailing.hu
-- Have You Seen This? --
Re: Request for GPS Data [Re: CatSailingHu] #186544
07/30/09 10:45 AM
07/30/09 10:45 AM
Joined: Dec 2008
Posts: 329
Chicago, Illinois USA
TEH Offline OP
enthusiast
TEH  Offline OP
enthusiast

Joined: Dec 2008
Posts: 329
Chicago, Illinois USA
Interesting. I will add some charting to my program.

I identify when the tack has begun (combination of drop in average speed and/or change in lat/long) to when the tack "ends" (increase in average speed). Two of my metrics are time to reduce speed or decelerate and time to accelerate.

Given your input, I think I will add distance covered on tack as well. Maybe I can work the math to show angle or arc of the tack as well.

Given comments on this board, I have begun doing more wide tacks. This increases deceleration time, but reduces acceleration time.


Blade F16 USA 725
Re: Request for GPS Data [Re: TEH] #186545
07/30/09 11:06 AM
07/30/09 11:06 AM
Joined: Jan 2009
Posts: 5,525
pgp Offline
Carpal Tunnel
pgp  Offline
Carpal Tunnel

Joined: Jan 2009
Posts: 5,525
My guess is you will find technique even more important on the lighter boat. It is awfully easy to make an atrocious tack. Don't ask me how I know.


Pete Pollard
Blade 702

'When you have a lot of things to do, it's best to get your nap out of the way first.

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