Profile for jakob

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Name	jakob
Email Address	jakob@sailport.se
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Posts	364
...one of the guys behind the game...

2011-06-06 06:56:28

Re: IMSYC 2011

Board » General Discussion

You people are fantastic! What enthusiasm and engagement!!! I will try to get some students to this thread.
...one of the guys behind the game...
2011-05-02 06:35:10

Re: IMSYC / SOLstice Cup

Board » General Discussion

You find them in Homework set 5 and 6.
...one of the guys behind the game...
2011-05-02 06:08:28

Re: IMSYC / SOLstice Cup

Board » General Discussion

...and if you want to play around with hull shapes etc to investigate effects on CP, trim, stability etc you might want to try the msy_hydrostatics-code that I put on the same web-page. The code lets you import hull shapes and then stretch them in various ways
...one of the guys behind the game...
2011-05-01 18:35:20

Re: IMSYC / SOLstice Cup

Board » General Discussion

Regarding IMSYC: If you are interested in the rule for the IMSYC race 2011 you can find it here http://www.kth.se/polopoly_fs/1.47075!IMSYC-66%20rule.pdf
I have about ten students designing boats for the race )

/Jakob
...one of the guys behind the game...
2011-01-15 12:33:46

Re: Leg 2 IMOCA Global

Board » Flag Officers » Races

Hi

As always in SOL: Changing course, maps etc in the middle of a race is generally a bad idea. Main reasons are:
1) the communication problem. How do we make sure that we reach all boats with the info?
2) We have very little control over when the changes become visible in the clients. Often, a clear-cache is needed (or long time).

I vote for not changing courses etc unless absolutely vital.

/Jakob
...one of the guys behind the game...
2010-12-06 19:48:24

Re: NOAA vs SOL weather

Board » Technical Support

...well you should be careful with those softwares... especially when there is a Sailplanner available for free
...one of the guys behind the game...
2010-12-05 20:58:26

Re: NOAA vs SOL weather

Board » Technical Support

Hi all,

You are basically all correct I am the first to admit that there are many ways of doing this and that we did not spend weeks of thinking when choosing algorithm - but it works. Also (Hubert) the game winds will only correspond exactly with the GFS-forecasts when the time is exactly the time of a certain forecast frame and the point of the "observation" is exactly that of a forecast nodal point. Thus, colour coding would not be of any use at all...

Why this attention? Is it just curiosity or weather-rounting ?

Regards
Jakob
...one of the guys behind the game...
2010-12-03 16:17:40

Re: NOAA vs SOL weather

Board » Technical Support

Hi

So, about the interpolation of weather in time and space Maybe some out there is longing for a short one-liner as explanation but I am afraid there is a little more to it… Here is in short the steps we take to get an "observation" (as we call it) at an arbitrary time (called t) and location based on forecasts.

1) Find the two forecast time steps (here called t1 and t2) surrounding the time t.
2) In space we simply use linear interpolation (in the 2 dimensions lat/long) of the forecast-data in the 4 closest forecast-nodes in the grib-file. Since the forecast has separate fields, one for northerly wind and one for easily wind we need to treat these entities separately, in our case by using complex notation. We also need to do this for both frames t1 and t2 from step 1 which thus gives us a set of two complex-valued space-interpolated wind speeds, one at t1 and one at t2.
3) Now we need to interpolate in time as smoothly as we can. We chose to do this using simple shape functions ensuring continuous wind speed and actually in our case continuous time derivatives.

Now, there are naturally many ways of doing this. One draw-back of this kind of interpolation is that we loose energy. Imagine the situation with constant wind speed but rotating wind direction so that at t1 the wind is due easily and at t2 it is due westly. In our interpolation we would (falsely) get that the wind speed at the time (t1+t2)/2 would be zero.

Also note that we do not always use the GFS model from NOAA. In particular around Sweden we have more detailed forecasts.

Hope this helped a little.

Regards
Jakob
...one of the guys behind the game...
2010-09-19 15:00:56

Re: OCTOBER 2010 - draft calendar

Board » Flag Officers » Race Calendar

Hi.

We all remember the Irish-rock episode. The problem that time was the unauthorized use of protected brand names. From that point in time SOL has been, and will continue to be, careful and considerate in terms of naming races. However SOL is not by any means scared of racing between locations in the geography where others, IRL or virtually, also race. Until proven wrong SOL is of the opinion that it is totally ok for anyone to race "similar time-similar route" as IRL-races. No-one has ever raised any legal aspects regarding this. However I do want to point out that if SOL administrators (Godesses etc) do not see that a certain race fits the calendar it is up to the community to argue and be sugary ) Happy sailing /Jakob
...one of the guys behind the game...
2010-06-28 14:46:05

Re: Rename boat

Board » Technical Support

Done
...one of the guys behind the game...

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We extend a warm welcome to the 5th leg of the RTW challenge, a thrilling journey from Ushuaia in the Land of Fire to Nassau in the Caribbean. It also marks the October edition of our esteemed Ocean Race Championship. Covering a distance of 6300 nautical miles, this leg is anticipated to span approximately 29 days. Join us for an unforgettable adventure on the high seas, where skill, strategy, and camaraderie converge in the pursuit of victory. We look forward to seeing you at the starting line! Fair winds and following seas.
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And now it’s Autumn in the Arctic, the sun is permanently below the horizon, but during the day, from c 0900 to c 1700 local time, there is some twilight – nautical twilight, not to be confused with civil twilight which is brighter. Having receded all summer, ice is starting to return to the numerous straits and bays of Canada’s North West Passage. High time then to set off on our last leg of the High Latitudes Series from Halifax in Nova Scotia to Alaska’s Hooper Bay. It’s 3850nm and we need to hurry, so we’ll take the Pelagic 77!
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