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Board » Technical Discussion » Performance loss

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Posted by dtayls Posts 29 Registered at 2014-06-23 03:34:16	2014-11-19 01:38:23 - Re: Performance loss
	There are some really interesting ideas in the pipeline and there is a great team of people working on it. Physical (kinetic) performance loss certainly exists but it's probably not a significant issue in an ocean race. Crew fatigue, on the other hand, is probably much more important. Lots of manoevres (tacks/gybes) will take a big toll on the crew. And doing these in high winds or at night is going to have an even greater impact. So, perhaps double at night; a sliding scale from x1 to x5 from 20 to 50 kts; and a no-go-zone from 50kts+ where you can't tack or gybe at all because the crew is simply refusing to get up on deck. --- Last Edited by dtayls at 2014-11-19 01:56:30 ---
Posted by Rod Posts 392 Registered at 2010-06-24 22:30:48	2014-11-22 18:02:52 - Re: Performance loss
	I do like the last bit--"the crew is simply refusing to get up on deck."--0r in our case "get out of bed". Obviously we need much more versatile DC nomenclature...... If it breaks, it's not strong enough--if it doesn't, it's too heavy.
Posted by RCLASER27 Posts 2 Registered at 2015-06-06 11:16:15	2015-08-10 18:25:55 - Re: Performance loss-Eureka!!!! ????
	It seems to me that the subject of Performance Loss has the highest number of posts with the most controversy and many are still unclear as to how it works and whether it is fair. It is also clear to me that for those that are 'clever' there is an opportunity to 'cheat'. I know you are trying to design a realistic sailing simulator but surely the Performance Losses for an AC72 (foiling cat) are considerably different from a monohull. My point is why have it at all? What 'harm' would that cause to your drive for 'realism'? If indeed you need a 'penalty' why not apply a standard one across the board of 50% boat speed reduction for 2 minutes. This would stop the short tacking zigger-zaggers. This would only apply to tacks not gybes. Of course a penalty such as that is totally unrealistic in the sailing world but at least everyone would understand it rather than having something that is almost subjective and seems to vary at random and cannot easily be understood. I await your comments.
Posted by kroppyer Posts 346 Registered at 2010-02-05 15:25:55	2015-08-10 19:23:50 - Re: Performance loss
	Simple solutions like this have crossed our minds. I reject some of them because they do not satisfy a couple of requirements. For example, I'd like to have two consecutive manoeuvres twa 45 -> 50 -> 55, to result in a distance loss that is no less than the loss resulting from a single manoeuvre twa 45 -> 55. At the least both losses need to be comparable. So we can't really penalise a manoeuvre regardless of the change in angle. Of course the easiest way to get a minimum of realism into the performance loss model would be to handle a change of tack differently. Another, more important, requirement is that every manoeuvre that crosses a cavity in the polar (polar hopping, including tacking/gybing), needs to be penalised by a significant amount. This is to prevent "infinite" manoeuvring (tacking/gybing/hopping) along a shoreline or lane of high pressure. Your suggestion of penalising only tacks a̶n̶d̶ ̶g̶y̶b̶e̶s̶ does not satisfy this requirement. These requirements are not really worked out or well discussed. I welcome any critique or additions on them. I do fully agree with your idea of having a model that anyone understands. It makes the game more fair when everyone understands the rules. So we need a model that is either simple (easy to understand), or very realistic (sailors will quickly understand). Of course the second option is much harder to realise, but also a lot more rewarding. --- Last Edited by kroppyer at 2015-08-10 20:00:27 ---
Posted by RCLASER27 Posts 2 Registered at 2015-06-06 11:16:15	2015-08-10 19:55:03 - Re: Performance loss
	Just to clarify my earlier post there is NO penalty for gybing, only Tacking
Posted by JB Posts 305 Registered at 2013-03-07 08:54:34	2015-08-26 11:52:04 - Re: Performance loss
	Viva All. Recap on this: 1 - One of SOL goals is to approach as much as possible the real boats behaviour. 2 - This one is pacific - gybing a “barge” is not the same as gybing a foiling boat. 3 - A real example: an AC72 don’t lose Performance during foiling gybes and doesn’t take more than 30 minutes to recover from any maneuver made (tack or gybe). 4 - So, “zero” Loss of Performance (LP) as a rule for all boats during/after gybing doesn’t seem to me correct. 5 - LP should be, namely, boat dependent and not only on the BS/TWA couple previously obtained to the boat maneuvers (small/large turning or making a full tack/gybe). 6 - More important than the LP value (boat dependent, namely, or not) is the Recovering Time to reach again the 100% P; 7 - Exception made to slower boats (barge, fixed keel 30 ft cruisers, not racers) and for all boats in special “blue” conditions (TWS / BS < 5 - 6 Kts) the SOL LP is almost irrelevant. 8 - The big problem comes on the remaining boats/Wind conditions, being the AC72 the extreme paradigm of this issue. Sail Fair.
Posted by Rod Posts 392 Registered at 2010-06-24 22:30:48	2015-10-27 01:35:30 - Re: Performance loss
	I hate to butt into a tech argument that I have contributed to in the past--to a level that is long past my pay-grade!! -----but surely some programmer for one of the many other sailing sites has solved this problem some time ago---and might be invited/paid to do a little modification to OUR perf loss problem?????? If it breaks, it's not strong enough--if it doesn't, it's too heavy.
Posted by bonknhoot Posts 97 Registered at 2013-08-06 21:35:15	2016-05-06 16:01:13 - Re: Performance loss
	As long as we can't change it, best we live with it on an equal footing. This might have seen the light of day when we went ice yachting on Winnebago, but then we switched PL off altogether (another solution!). I am not guaranteeing anything written in the attached is the best way of "evading" usurious PL, just stuff that works for me (if I get it right). Clipping along Attachments PERFLOSS2.docx (23.0 KB)
Posted by Capt.D.P. Posts 66 Registered at 2009-10-27 01:51:32	2016-11-24 14:04:40 - Re: Performance loss
	I went little bit through this topic and to tell you the truth I did not know about 93% rule in loss performance.Years ago maybe 7-8, I spent a lot of time to find out how to reduce that annoying performance loss.I surely went through that 93% but did not notice big difference but noticed that performance could be down even to 82%,when gybing with big speed several times in fast continuation. We all know that smaller the change of course less performance loss but there is an exception in that rule. There is a situation when you change the course for 1 degree only and you have performance loss of 90%.I found it while trying to gyb step by step and coming to 179.5 deg. and to -179.5 deg. and at once performance loss for one degree which use to be only cca 99.8% jumped down to 90%. As the perf. loss is minor when tacking I even tried that to go in desired direction but found out that more ground is lost than the gain in performance loss. Ciao Damir
Posted by kroppyer Posts 346 Registered at 2010-02-05 15:25:55	2016-11-24 16:00:39 - Re: Performance loss
	Yes, when you change tack, the degrees you turn is irrelevant, but the new boatspeed is relevant. So when turning from 179.5 to -179.5 you will be penalised proportional to your new boatspeed. When going upwind, you generally have less boatspeed, so changing tack is less costly. See a complete breakdown of performance loss here. This is bound to change at some point though (not sure when, could be years, but I'm hoping less).

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