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marke View Drop Down
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Posts: 211 		Post Options Post Options   Quote marke Quote  Post ReplyReply Direct Link To This Post Topic: PY Inland vs Sea
    Posted: 21 Oct 14 at 11:31am
I'm going to try one more time.  The PNs produced from the PY scheme are NOT an average across all boats and sailing abilities . . . and never have been.  It was recognised some 50 years ago that the poor performance "tail" of the distribution has a significant impact on the PN.  For that reason there is a poor performance threshold used to exclude any boats whose corrected time is more than about 5% slower than the average corrected time.

This also has the effect of reducing the impact of boats that are sailing with 30 year old sails, and foiling moths sailing in a F1.
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I think everybody knows that the worst and the best results are not used in the calculation.
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Rupert View Drop Down
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Posts: 8956 		Post Options Post Options   Quote Rupert Quote  Post ReplyReply Direct Link To This Post Posted: 21 Oct 14 at 12:02pm
OK Marke - an average of all boats and abilities of the boats that are counted in the calculations. Yes, I know you take the outlier numbers out of it. That wasn't really anything to do with what was being said. I'm pretty sure a fairly well sailed (ie, can get round the course and actually think about tactics) 1950s Merlin will register on the curve that you use, but will distort the figure compared to a new boat.
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Rupert View Drop Down
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Posts: 8956 		Post Options Post Options   Quote Rupert Quote  Post ReplyReply Direct Link To This Post Posted: 21 Oct 14 at 12:03pm
Looking back, I didn't even use the word all - you bunged that in. Odd thing to do.
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Steve411 View Drop Down
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Posts: 705 		Post Options Post Options   Quote Steve411 Quote  Post ReplyReply Direct Link To This Post Posted: 21 Oct 14 at 12:20pm
Originally posted by Rupert

An average across boat ages and sailing ability.

That few new boats race on handicap (really? I suspect more do, especially in winter, than you are making out) means the results are even more skewed in their favour.

The -17 for the GL thing would seem to reflect that more modern boats join in with the big winter events, thats for sure - pro jockeys selling their wares? What does SWS data mean, though?

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marke View Drop Down
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Posts: 211 		Post Options Post Options   Quote marke Quote  Post ReplyReply Direct Link To This Post Posted: 21 Oct 14 at 12:22pm
Hi Rupert

I wasn't referring just to your comment specifically - there were several posts implying it was a simple average.

Depends where that 1950s Merlin was sailing - on a river, light winds you would probably be right; on open water against a reasonable standard fleet of other classes then I doubt it would be included (if sailing of 994 - which of course it shouldn't be given the class association have gone to the trouble of defining old boat handicaps).

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Rupert View Drop Down
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Posts: 8956 		Post Options Post Options   Quote Rupert Quote  Post ReplyReply Direct Link To This Post Posted: 21 Oct 14 at 12:26pm
Does the RYA take into account the age of the boat? Surely what comes back to you these days are elapsed times for a class of dinghy, so how will you know how old the boat is? So if a club is using the Merlin old boat handicap system, how does that info affect the system?

On the river, it is likely that the 1950's boat, if it has a new rig on (again, no way for the returns to tell) will be up with the new boats and mixing with them - after all, some people are deliberately chosing those designs.
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JimC View Drop Down
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Posts: 6662 		Post Options Post Options   Quote JimC Quote  Post ReplyReply Direct Link To This Post Posted: 21 Oct 14 at 12:28pm
Originally posted by Blue One

I think everybody knows that the worst and the best results are not used in the calculation.

I hope not..
The top of the fleet is not excluded in the standard calculations. I have a feeling that the system used on the web based system may exclude a very few results that are really out of line with the rest of the race to catch the "two boats finished before the wind dropped" style situation. Basically though the number reflects very approximately the top two thirds of the active fleet, but this will vary if the performance of the fleet varies. I don't see, for example, vintage Merlins (or low riding Moths unless identified separately) having any impact on the numbers. If a class has a big performance jump old and slow boats will come out of the calculations quite quickly.

Originally posted by Rupert

So if a club is using the Merlin old boat handicap system, how does that info affect the system?

Hopefully most clubs will do what mine does and distinguish older boats. Apart from anything else if you don't most computer results systems will get very confused. My club's Sailwave rating file includes:
PY     Merlin-Rocket     990
PY     Merlin-Rocket 3430-3453     1020
PY     Merlin-Rocket 895-3429     1030
(we don't use the Merlin Association old boat handicaps because they don't seem to relate to the PY the boat had when new, whereas the above do).


Edited by JimC - 21 Oct 14 at 12:55pm
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Blue One View Drop Down
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Posts: 317 		Post Options Post Options   Quote Blue One Quote  Post ReplyReply Direct Link To This Post Posted: 21 Oct 14 at 12:48pm
Originally posted by JimC

Originally posted by Blue One

I think everybody knows that the worst and the best results are not used in the calculation.

I hope not..
The top of the fleet is not excluded in the standard calculations. I have a feeling that the system used on the web based system may exclude a very few results that are really out of line with the rest of the race to catch the "two boats finished before the wind dropped" style situation. Basically though the number reflects very approximately the top two thirds of the active fleet, but this will vary if the performance of the fleet varies. I don't see, for example, vintage Merlins (or low riding Moths unless identified separately) having any impact on the numbers. If a class has a big performance jump old and slow boats will come out of the calculations quite quickly.

Originally posted by Rupert

So if a club is using the Merlin old boat handicap system, how does that info affect the system?

Hopefully most will do what we do and distinguish older boats. Apart from anything else if you don't most computer results systems will get very confused. My club's Sailwave rating file includes:
PY     Merlin-Rocket     990
PY     Merlin-Rocket 3430-3453     1020
PY     Merlin-Rocket 895-3429     1030
(we don't use the Merlin Association old boat handicaps because they don't seem to relate to the PY the boat had when new, whereas the above do).

Thanks for putting me right, Jim. But perhaps you could pass this info onto Chris G as I was only repeating what he sent to me in an e-mail, when I queried the British moth handicap a couple of years ago.
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Rupert View Drop Down
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Posts: 8956 		Post Options Post Options   Quote Rupert Quote  Post ReplyReply Direct Link To This Post Posted: 21 Oct 14 at 1:08pm
o, does that mean the Merlin handicap is a mix of returns from clubs which exclude the older boats by posting the results separately and those which sail/send returns in as a lump?

How do the corrected times for the boats you separate out compare to the handicap bands into which you place them?

And are there enough returns coming in from clubs which separate the boats out to start getting any sort of EN for them?
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