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The PY system |
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Late starter 
Far too distracted from work 
Joined: 24 Feb 07 Online Status: Offline Posts: 481 |
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 Topic: The PY systemPosted: 17 Mar 13 at 10:32pm |
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I think the PY scheme as administered by the RYA is probably as good as it can be, given all the variables inherent within it. However, what I really don't like is seeing clubs using local adjustments based on 1 or 2 boats in a class, hence they're really running personal handicap racing. A club I know has increased the handicap of a class by 5% because the guys sailing weren't capable of flying it's spinny !!
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Medway Maniac
Really should get out more 
Joined: 13 May 05 Location: United Kingdom Online Status: Offline Posts: 2788 |
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Posted: 17 Mar 13 at 10:57pm |
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I guess a good rule of thumb might be not to amend locally unless the "confidence factor" is 0.7 or greater. Ours are 0.1 at best, so definitely a bad idea to make local adjustments!
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sargesail
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Joined: 14 Jan 06 Location: United Kingdom Online Status: Offline Posts: 1459 |
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Posted: 18 Mar 13 at 1:03am |
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Love the proximity of these last two posts. The first shows up a glaring abuse of the system (but one which is potentially ideally supported by the data.
And the second shows the down side of a blinkered statiscal approach - confidence factor is good so it must be OK!
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rb_stretch
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Joined: 23 Aug 10 Online Status: Offline Posts: 742 |
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Posted: 18 Mar 13 at 8:34am |
In theory I agree. In practice I can see some need to break it. For example, where there is a factor (eg. tide, current) that can be applied to all boats in a methodical way then I think adjusting all classes even if there is only 1 boat is the fair and right thing to do. The fact the adjustment is applied in a methodical way should hopefully remove the crew skill factor. The other issue I can think of is when a crew is so light that they can't sail the boat above force 4. If they only sail the light wind races they effectively have a better handicap. The point for me is that there must be a clear reason for the change which isn't crew skill factor. |
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Rupert
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Joined: 11 Aug 04 Location: Whitefriars sc Online Status: Offline Posts: 8956 |
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Posted: 18 Mar 13 at 9:14am |
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In the case of a boat which should have a spinnaker, but in a particular example doesn't (ie, there is no rigging even for it) you could say that to get fair racing, the handicap should be adjusted to allow for this. In effect, the boat has become a different class. I guess an example of this would be an original Fireball. No trap, no spinnaker. Be daft to send it off the same PY, wouldn't it? And by extension, a more modern Fireball converted to how they once were, too. You would then start the "new boat" process to get a fair rating.
On the other hand, just because someone is crap at using a spinnaker, it shouldn't be a reason for change. |
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Firefly 2324, Puffin 229, Minisail 3446 Mirror 70686
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Medway Maniac
Really should get out more
Joined: 13 May 05 Location: United Kingdom Online Status: Offline Posts: 2788 |
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Posted: 18 Mar 13 at 10:40am |
What alternative rule of thumb would you use, then? Or would you simply not make local adjustments in order to avoid any possibility of a "glaring abuse"? Given how hard it must be to reach a confidence factor of 0.7 (judging by our experience of just 0.0 or 0.1 after 3 years of returns to the website), I would imagine that glaring abuses would be pretty much ruled out by my suggestion. Certainly the single boat of the example would not get above 0.0. If the boat absolutely never used the kite than any return should maybe be for a spinnakerless boat: the RYA stress that they want returns to include details of the boats as sailed, such as (2|S|A||) after the class name.
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AlexM
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Joined: 10 Jan 06 Online Status: Offline Posts: 857 |
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Posted: 18 Mar 13 at 12:00pm |
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Medway Maniac
Here's an extract of the kinds of data required to get high c.f. (If the data is stable) 
What we do when we've only got small c.f. is apply a % of the change. Here's the table i use CF % 0.0 0% use RYA number 0.1 20% 0.2 40% 0.3 60% 0.4 80% 0.5 100% Alex Edited by AlexM - 18 Mar 13 at 12:00pm |
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RS400atC
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Joined: 04 Dec 08 Online Status: Offline Posts: 3011 |
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Posted: 18 Mar 13 at 12:51pm |
Does only applying a fraction of the change just mean that next time the PY is recalculated, another fraction of the correction is applied? So the same number results in the end, it just gets there asymptotically? e.g 1/2 the change, 3/4, 7/8 etc?
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AlexM
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Joined: 10 Jan 06 Online Status: Offline Posts: 857 |
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Posted: 18 Mar 13 at 12:57pm |
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Yes, so in the case of the 100 (0.1 c.f) We'd only use 20% of the change (996-981= 15*20% -3 PY = 993 . So nothing really.
Once you get to about 0.5 c.f. the pdf file gets a stamp of authority from RYA Alex Edited by AlexM - 18 Mar 13 at 12:58pm |
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Medway Maniac
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Joined: 13 May 05 Location: United Kingdom Online Status: Offline Posts: 2788 |
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Posted: 18 Mar 13 at 2:02pm |
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I see the logic in that, and if WSC was peopled by Swedes or others dedicated to reasonableness at all costs then I might propose doing it.
As it is, an 0.7 cut-off makes a good excuse not to change anything and not to upset absolutely everybody. We decided to use the RYA recommendations to establish PN's for classes that didn't have any, like the Alto and V3000, but even then it caused upset (and frankly I am upset that my V3k h'cap is in reality a group-personal handicap), loss of confidence in the system and, I believe, a fall-off in turn-out. Maybe if club members studied the system thoroughly they might accept some tinkering, but they don't and won't. We avoided introducing a set of tidally-adjusted PN's for the same reason, despite highly plausible maths and a clear desirability.
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