Laser 140101 Tynemouth |
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Laser 28 - Excellent example of this great design Hamble le rice |
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Rossiter Pintail Mortagne sur Gironde, near Bordeaux |
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List classes of boat for sale |
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transient ![]() Really should get out more ![]() Joined: 21 Aug 12 Online Status: Offline Posts: 715 |
![]() ![]() ![]() ![]() Posted: 06 Sep 13 at 9:50am |
Polars are available for a few boats. Few and far between though. How applicable are they in a real race?
http://100races.blogspot.co.uk/p/polars.html Quote: "Bear in mind these are numbers are essentially theory, having been collected in ideal flat water conditions. In practice, laser performances are affected by kinetics, waves upwind, surfing waves down wind and sailing by the lee."
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2547 ![]() Really should get out more ![]() Joined: 11 Aug 11 Online Status: Offline Posts: 1151 |
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You are quite right; if you sail with your phone & a GPS watch you risk disqualification. These items are not permitted by almost every class. Same applies to GoPros etc ... all effectively banned. Some classes however are quite progressive on these matters such as the Musto Skiff who's class rule I have posted below. But I know your are not very keen on the Musto. C.5 PORTABLE EQUIPMENT C.5.1 FOR USE (a) OPTIONAL (1) Electronic or mechanical timing devices. (2) One magnetic or electronic compass showing only information relating to heading speed, VMG, bearing, current or elapsed time. (3) Maps charts and means of recording courses and compass headings. (4) Items on deck which functions are storage of food, drink, clothing, safety or relevant tools. (5) Mobile phone, solely for emergency communications. (6) Video and / or still cameras. (7) GPS device showing only information relating to heading, speed, VMG, bearing, current or elapsed time. Edited by 2547 - 06 Sep 13 at 9:51am |
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Fearful ![]() Newbie ![]() Joined: 30 Jul 12 Location: Kent Online Status: Offline Posts: 19 |
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To create proper polars you are also going to need to know what wind the boat is experiencing at that time.
Edited by Fearful - 06 Sep 13 at 9:57am |
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transient ![]() Really should get out more ![]() Joined: 21 Aug 12 Online Status: Offline Posts: 715 |
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Too many variables. A possible scenario for the future though could be a simulator. Maybe (fantasy) the designer could submit a bang on accurate 3d model to a PY com who then run the model on a sophisticated simulator that uses all the known variables to calculate a number......effectively a same helm same conditions comparison with other boats |
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alstorer ![]() Really should get out more ![]() ![]() Joined: 02 Aug 07 Location: Cambridge Online Status: Offline Posts: 2899 |
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Al |
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iGRF ![]() Really should get out more ![]() ![]() Joined: 07 Mar 11 Location: Hythe Online Status: Offline Posts: 6499 |
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None of which would be beyond the wit of man, should he wish to correctly assess a mean boat speed in given controlled circumstances to be applied to all craft as the basis point within which to construct a fair handicap system devoid of the 'anarchy' of bumbling buffers and egregious event number driven organisers.
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Fearful ![]() Newbie ![]() Joined: 30 Jul 12 Location: Kent Online Status: Offline Posts: 19 |
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BOOM! Knowingly (or unknowingly) you have just stumbled upon the biggest can of worms in the none one design sailing world. |
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JimC ![]() Really should get out more ![]() ![]() Joined: 17 May 04 Location: United Kingdom Online Status: Offline Posts: 6662 |
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I'm not aware of reliable polars for any dinghy class in the UK. The problem with that sort of thing is that it needs a small team of people and a huge amount of time and boring effort to setup, and most people would rather go sailing. Also, as mentioned above, you need the instrumentation to be able to establish true wind speed and direction (lets not even get into tides).
The only people who have really done much of it to my knowledge are the Bethwaites, and that seems to be because father, son and daughter comprised their own team of sailing 'anoraks' who lived near each other and were prepared to put the effort in. For example I've tried to set up tow testing in a development class and failed, because no-one else near enough to me for it to be practical was really interested enough... And even I am not so interested in this stuff that, for example, I'd be prepared to drive 50 or 60 miles for umpteen weekends in a row to go and spend days sitting in a motor boat reading off measurements on a spring balance. Edited by JimC - 06 Sep 13 at 11:38am |
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Daniel Holman ![]() Really should get out more ![]() Joined: 17 Nov 08 Online Status: Offline Posts: 997 |
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Physical testing of dinghies "in the field" would be impossible to do in a scientific and meaningful manner whereby you could quantify every aspect of the aero and hydro characteristics accurately enough.
Big boat IMS (and I believe subsequently IRC) handicapping sought to handicap the boats based on their VPPs - i.e velocity prediction programmes - maths models of the aerodynamic and hydrodynamic components of the yacht which can resolve the equilibriums for any speed / heading / sail set to effectively produce polar charts from which theoretical times around theoretical (perfect triangle or ww/lw or point to point) courses. Most polars that you get on leadmines to steer and trim to are derived from the VPPs that have been created rather than physical testing (far, far more expensive given that you'd have to do extensive wind tunnel and towtank / CFD analyses to populate all the physical models). There is no reason why you couldn't run every dinghy class through a vpp, apart from effort and expense. Trouble is then, what windspeed would you decide to take the relative handicaps at? Thats a can of worms to start with. Also, the VPP number will have to be given for whatever course config (i.e. ww/lw; specific point to point etc) that has been fed into the computer. I don't need to overstate the disparity in performance between most classes depending on time spent on which leg of the course or wind strength. Then the aspect that could never be simulated in a computational environment, except by means of a massive subjective fudge, is that an empirical scheme like the PY is the only way to capture the differences between how a boat should perform on paper compared to how it performs in practice - how easy it is for the performance to be realised by the crew etc. An RS 100 may be a rocket at VMG running in moderate breezes, easily captured in a maths model for steady state, but how do you quanitify and account for the ballache of raising and hoisting the kite singlehanded on a 70 yard run on a pond? Believe me, as one who has thought about this more than most, PY especially of late with all the effort going into it, is by far the least imperfect way of divining some comparisons between disparate craft in disparate circumstances competing in the sport with the largest set of variables. |
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Daniel Holman ![]() Really should get out more ![]() Joined: 17 Nov 08 Online Status: Offline Posts: 997 |
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Sorry meant that last one for the handicap final solution mein kampf by adolf fuller thread! fair bit of crossover between these threads though
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