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Board » General Discussion » Jubilant Fastnet Campaign Qualifying Races - POLAR needed

Posted by NZL_Scotsman Posts 251 Registered at 2008-10-04 07:59:40	2013-04-24 07:07:25 - Re: Jubilant Fastnet Campaign Qualifying Races - POLAR needed
	I would think you are faster under small spinnaker or gulling than with a genny in heavy conditions. Therefore the first one. --- Last Edited by NZL Scotsman at 2013-04-24 07:08:20 ---
Posted by javakeda Posts 73 Registered at 2013-03-01 03:18:22	2013-04-25 15:45:57 - Re: Jubilant Fastnet Campaign Qualifying Races - POLAR needed
	Initial thoughts: [Forgive me it I state the obvious.] 1) Having different polars for different sail configurations [and/or weather conditions] is fairly common for IRL routing. So the choice between 'a" and 'b' is not absolute. 2) Shape is more important than scale. It is a lot easier to scale a shape than vice versa. 3) In SOL we get used to having detailed polar values for every TWA degree and TWS nm. IRL, it may be more constructive to think in terms of Points of Sail. I would test values for being on a: -- beat -- close reach -- beam reach [TWA = 90, NOT AWA = 90] -- broad reach -- run [tacking downwind] -- DDW [wing and wing] with particular attention to finding "maxVMG" points for the -- upwind sweet-spot -- downwind sweet-spot. [Helmsman needs to make the call here. Mark the time when the helmsman is happy. Use post-sail log analysis to determine values. Feedback corrections can apply to the polar, the helmsman, or both ... but it is normally easier to correct the polar, and make the helmsman aware of the change.] 4) For empirical polars, it is a whole lot easier to think in terms of a sparse polar that is wind-line based ... as opposed to one that has values for almost any wind angle and wind speed. I would try for a sparse polar first [like the one for the J30 attached] and let software fill in the details later. Certainly a sparse polar is easier to revise. Again, these are just initial thoughts based on my experience in validating the polar for a Beneteau First 47.7 [cruising rig]. --- Last Edited by javakeda at 2013-04-25 15:51:08 --- --- Last Edited by javakeda at 2013-04-26 15:27:51 --- --- Last Edited by javakeda at 2013-04-26 15:28:35 --- Attachments J30.txt (684 bytes)
Posted by ALL_4_Aaron Posts 5 Registered at 2012-09-22 11:10:08	2013-04-26 15:04:06 - Re: Jubilant Fastnet Campaign Qualifying Races - POLAR needed
	quote: Feedback corrections can apply to the polar, the helmsman, or both ... but it is normally easier to correct the polar, and make the helmsman aware of the change.] LOL
Posted by ybw_mjm Posts 20 Registered at 2009-11-12 21:48:35	2013-04-26 17:15:10 - Re: Jubilant Fastnet Campaign Qualifying Races - POLAR needed
	After having sailed the Moody s38 for a number of years, the _b polar is looking like a good match in terms of shape and speed. My only comment is that since we are a little heavier we might need a little more wind to get us going. Virtual sailors might do better than us in real life if the winds are light. We will record our speed/wind data in real life and see then what improvements can be made.
Posted by RainbowChaser Posts 2656 Registered at 2009-06-14 09:44:50	2013-04-26 17:49:39 - Re: Jubilant Fastnet Campaign Qualifying Races - POLAR needed
	mjm - OKies Jubilant_b it shall be. In reality you will have the benefit of tide? or current? so maybe the fact that SOLers will grab the wind swifter will be offset a little?
Posted by ybw_mjm Posts 20 Registered at 2009-11-12 21:48:35	2013-04-27 00:36:03 - Re: Jubilant Fastnet Campaign Qualifying Races - POLAR needed
	Tide.. Good thinking.. Although I think in the first race (4th May) we will be against a weak tide IRL for the first hour or so...then crossing the English Channel, the tide will be across our course.. so it should all even out in the end.
Posted by ybw_mjm Posts 20 Registered at 2009-11-12 21:48:35	2013-04-27 00:37:41 - Re: Jubilant Fastnet Campaign Qualifying Races - POLAR needed
	With the race to The Rock - IRL the tide will be with us for six hours and then against us for six hours. It will be like this all along the south coast so should even out with the virtual yachts.
Posted by 76Trombones Posts 362 Registered at 2009-08-03 18:04:56	2013-04-27 00:43:46 - Re: Jubilant Fastnet Campaign Qualifying Races - POLAR needed
	SOL takes a pretty big hit vs irl on nearshore winds, so it's all probably a bit moot. Looking forward to seeing you guys out on the water!
Posted by ybw_mjm Posts 20 Registered at 2009-11-12 21:48:35	2013-04-27 01:51:01 - Re: Jubilant Fastnet Campaign Qualifying Races - POLAR needed
	So are we! It's going to be interesting...

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