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Pointless PY Pondering

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Noah View Drop Down
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Post Options Post Options   Quote Noah Quote  Post ReplyReply Direct Link To This Post Topic: Pointless PY Pondering
    Posted: 22 Nov 20 at 6:35pm
Tidal is not quite that black and white. Estuary and harbour tides (Chichester harbour - HISC, Itchenor, Salcombe, Exe) are very different from the open channel venues (Shoreham, Lancing, Mounts Bay.
It’s a minefield.
Nick
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423zero View Drop Down
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Post Options Post Options   Quote 423zero Quote  Post ReplyReply Direct Link To This Post Posted: 22 Nov 20 at 6:42pm
Formula to apply for these two boats over first three courses, plus, the tidal estuaries, add in very light wind and a howler. You would be very popular.
Robert
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Rupert View Drop Down
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Post Options Post Options   Quote Rupert Quote  Post ReplyReply Direct Link To This Post Posted: 22 Nov 20 at 8:19pm
Noah, tidal may be different in a variety of venues, but wouldn't an average tidal yardstick be better than one including all the non tidal venues? If you really sail somewhere that out on a limb, then the only option would be club numbers.
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Grumpycat View Drop Down
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Post Options Post Options   Quote Grumpycat Quote  Post ReplyReply Direct Link To This Post Posted: 22 Nov 20 at 8:59pm
Originally posted by Sussex Lad

Originally posted by 423zero

There's no problem with thoughtful discussions regarding anything, problem is when posters not only infer fiddling but actually state it's happening.


I guess you're refering to IGRF's post of earlier in the thread. If you are then it might be more constructive to call that post and IGRF (or anyone else) out specifically as and when you think he's being unhelpful. Don't use inference  and innuendo to point it out.

.....and Grumpy cat don't use your disapproval of one post to try and control and shut down a discussion that scares you by using ridicule and scorn.......if you think the discussion is pointless then don't participate. By the way I'm guessing you sail on a pond or lake?

The world is now changing at an alarming rate and the conservatism in the sport is holding it back. The fear of new ideas, new ways of doing things and an aversion to people saying "what if? is not doing the sport any favours right now. "The status quo"  "it's how it's been done for 70 yrs"........  surely this forum deserves better than that"



Yes I sail on a lake and yes the py works at my current club as it has worked at every inland club I have ever sailed at at . As it does for the vast majority of sailors across the country. 
I totally understand it works less well on the sea . But the ability to change the numbers is in the clubs hands and plenty of sea clubs do change them to suit local conditions. 
In no way does anything on this forum scare me . It’s just half a dozen people expelling hot air. Sometimes it’s fun and interesting and sometimes it isn’t.
At no point have ridiculed or pored scorn on anyone other than grf, and he gives it out and expects it back . All I have done is point people asking questions to the the correct people to answer the question . 
It’s a discussion and I have given my point of view . In no way has this closed down this thread judging by the amount of posts on this thread after your post ,on a weekend .
I suggest you follow grf advice except people have views different to your own or scroll on by . 
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Post Options Post Options   Quote Sam.Spoons Quote  Post ReplyReply Direct Link To This Post Posted: 22 Nov 20 at 9:30pm
Originally posted by 423zero

On a 20 acre lake would a 'Enterprise' be faster in real time, than, say a '505'?
Same boats, 'Rutland water'?
Same boats, big range, Sea course?
This is the problem with using PY without local adjustment.
Ent' would win first race, both have top crews.

My point exactly. Not trying to 'improve' the accuracy of the numbers, just to eliminate one of the reasons why many clubs don't apply the recommended adjustments.
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Sussex Lad View Drop Down
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Post Options Post Options   Quote Sussex Lad Quote  Post ReplyReply Direct Link To This Post Posted: 22 Nov 20 at 9:59pm
Originally posted by Noah

Tidal is not quite that black and white. Estuary and harbour tides (Chichester harbour - HISC, Itchenor, Salcombe, Exe) are very different from the open channel venues (Shoreham, Lancing, Mounts Bay.
It’s a minefield.


So what would be be better?


3 or 4 sets of numbers that span most venue types.

or

1 set of numbers that sit up one end of the spectrum.
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Post Options Post Options   Quote Guests Quote  Post ReplyReply Direct Link To This Post Posted: 22 Nov 20 at 10:04pm
Originally posted by Sussex Lad


So what would be be better?3 or 4 sets of numbers that span most venue types.or1 set of numbers that sit up one end of the spectrum.

Probabilistic PYs.
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Rupert View Drop Down
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Post Options Post Options   Quote Rupert Quote  Post ReplyReply Direct Link To This Post Posted: 22 Nov 20 at 10:11pm
Originally posted by Peaky

Originally posted by Sussex Lad


So what would be be better?3 or 4 sets of numbers that span most venue types.or1 set of numbers that sit up one end of the spectrum.

Probabilistic PYs.


I do remember this, but need reminding of the premise, as in my head it has turned into something Douglas Adams would have been proud of!
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423zero View Drop Down
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Post Options Post Options   Quote 423zero Quote  Post ReplyReply Direct Link To This Post Posted: 22 Nov 20 at 10:40pm
What about a length of legs handicap? Long legs suit fast boats, short legs suit slow boats.
Robert
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Post Options Post Options   Quote Guests Quote  Post ReplyReply Direct Link To This Post Posted: 22 Nov 20 at 10:51pm
Haha!

1. Accept that no class PY will ever be perfectly known. Small sample, tidal effects, etc etc.
2. Therefore accept that there is uncertainty in what PY should be used.
3. Therefore accept that the Laser PY (for example) is not precisely (or consistently) 1100.
4. We can be reasonably (95%) confident that it is somewhere between 1080 and 1110.
5. An OK (PY1104) will have a bigger 95% confidence spread due to fewer boats and more uncertainty e.g. 1070 to 1130
6. Currently if a Laser and OK finish at exactly the same time the OK wins and scores 1 point and the Laser 2.
7. But the OK may actually be quicker (if a fairer PY is actually 1095) and so there is a chance it shouldn’t have won.
8. Instead, calculate the corrected time for the range of PYs and weight the result.
9. e.g. if there is a 90% chance of being 1st and 10% chance of 2nd, score 1.1 points. If there is a 50/50 chance of first or second score 1.5 points.
10. The further ahead you finish the more likely that you actually deserved the win (rather than being gifted it due to dodgy PY) and so the lower you will score.

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