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New class PY numbers?

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PeterG View Drop Down
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Post Options Post Options   Quote PeterG Quote  Post ReplyReply Direct Link To This Post Topic: New class PY numbers?
    Posted: 17 Feb 17 at 5:09pm
Or you could fashion a formula based on boat length, weight, sail size, displacement, etc 

My initial response to that is that it would not be a bad way to generate initial PYs, that could then be updated in the usual way.

However, the danger with that approach is that designers of new boats could end up designing to handicap, in the way IOR boats were (and no doubt others still are). That would tend to push new designs into a limited range of hull shapes etc. And I'd hope we would all agree that those sort of rule based distortions are best avoided if designers are going to concentrate on designing the "best" boat for whatever niche they are targeting.
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Sam.Spoons View Drop Down
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Post Options Post Options   Quote Sam.Spoons Quote  Post ReplyReply Direct Link To This Post Posted: 17 Feb 17 at 6:45pm
Originally posted by RS400atC

The 400 is a bit longer, but the bow is probably raked more? So LWL is not hugely different.
The alleged 85kg of the 400 is bare hull. On the water I suspect heavier than some Merlins.
The claimed weight of the Spice is the same.
LWL does not seem to affect I14's too badly, their upwind sail area is only another 2 or 3 sqm.
LWL is good at low speed for sure. But you need a narrow waterline and and a couple of decades of Merlin knowledge to get the best out of it.
At higher speeds you don't want a round bilge at the blunt end.
There are certain hull shapes that had to be tried in the last 25 years, just to prove they really were a bad idea.

I don't know why you started this thread, with a reference to a dead class like the Spice.
Do you have a CA? Classs rules? Any actual data?
 You are only ever going to get a number dredged out of the past or some personal performance based nonsense like the cruisers have for NHC.
Either stick a GPS on it and take it out in a proper breeze and come back with pictures of 20 knots, or we'll sort out a suburban roundabout and some geraniums.


I started the thread out of curiosity, the Spice is simply my own reference point. I know there is no possibility of there ever being a 'proper' handicap for it, (see above) and I'm perfectly happy for their to be no further mention of it in this thread.

But, how handicaps are arrived at is something that interests me and rather than take the H2 thread even further off topic I decided to start this one (not that it helped mind you). I understand how PY numbers for established classes are calculated, I'm sometimes surprised at where the numbers end up. Musing over the factors that affect them seems a reasonable way to spend a quiet afternoon.
 

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iGRF View Drop Down
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Post Options Post Options   Quote iGRF Quote  Post ReplyReply Direct Link To This Post Posted: 17 Feb 17 at 7:57pm
Originally posted by PeterG

<span style="font-family: "Helvetica Neue", "Lucida Grande", "Segoe UI", Arial, Helvetica, Verdana, sans-serif; : rgb251, 251, 253;">Or you could fashion a formula based on boat length, weight, sail size, displacement, etc </span>

<span style="font-family: "Helvetica Neue", "Lucida Grande", "Segoe UI", Arial, Helvetica, Verdana, sans-serif; : rgb251, 251, 253;"></span>
<span style="font-family: "Helvetica Neue", "Lucida Grande", "Segoe UI", Arial, Helvetica, Verdana, sans-serif; : rgb251, 251, 253;">My initial response to that is that it would not be a bad way to generate initial PYs, that could then be updated in the usual way.</span>
<span style="font-family: "Helvetica Neue", "Lucida Grande", "Segoe UI", Arial, Helvetica, Verdana, sans-serif; : rgb251, 251, 253;"></span>
<span style="font-family: "Helvetica Neue", "Lucida Grande", "Segoe UI", Arial, Helvetica, Verdana, sans-serif; : rgb251, 251, 253;">However, the danger with that approach is that designers of new boats could end up designing to handicap, in the way IOR boats were (and no doubt others still are). That would tend to push new designs into a limited range of hull shapes etc. And I'd hope we would all agree that those sort of rule based distortions are best avoided if designers are going to concentrate on designing the "best" boat for whatever niche they are targeting.</span>



Well that depends on the formula, but better i would have thought than the current scenario where old designs get given a makeover, in light stiff construction and marketed as racing Bandits. Wayfarer being the current example.
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Post Options Post Options   Quote Sam.Spoons Quote  Post ReplyReply Direct Link To This Post Posted: 17 Feb 17 at 8:05pm
Wasn't weight as it affects PN discussed on here recently? If GRFs formula would stifle dinghy development (which I agree it probably would) it should still be possible to create a formula which gave a reasonable correction factor for changes in hull/sailing weight, increased sail area and other changes to an established class. Sailing a two hander solo, with or without trapeze and/or kite should also be fairly easy to cater for. Of course things like a new hull shape in a development class couldn't be so easily guessed at but I guess that is built into the PN for those boats.
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Post Options Post Options   Quote davidyacht Quote  Post ReplyReply Direct Link To This Post Posted: 18 Feb 17 at 9:01am
I would have thought that a formula could give a reasonable stab at an old style 2/3 digit PY number, even for different development class shapes, since the differences in designs are in seconds rather than minutes.

Some kind of rise of floor or prismatic coefficient factor could deal with skinny unstable but fast boats c/w boats of similar dimensions but fatter and more stable.

Would the formula be secret like IRC?  Which would leave room for the conspiracy theorists to suggest that builder's are in cahoots with the handicappers.

What any handicap formula would not deal with unless the RO had some subjective input, is the relative performances of different types of boat in different conditions and varying wind conditions; i.e. Some classes excel on beat and running courses, others in light winds, others when it is blowing dogs off chains.

Ultimately people might conclude that pulling numbers out of a hat in a committee room might work better.

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Post Options Post Options   Quote Sam.Spoons Quote  Post ReplyReply Direct Link To This Post Posted: 18 Feb 17 at 9:52am
Originally posted by PeterG

Or you could fashion a formula based on boat length, weight, sail size, displacement, etc 

My initial response to that is that it would not be a bad way to generate initial PYs, that could then be updated in the usual way.

However, the danger with that approach is that designers of new boats could end up designing to handicap, in the way IOR boats were (and no doubt others still are). That would tend to push new designs into a limited range of hull shapes etc. And I'd hope we would all agree that those sort of rule based distortions are best avoided if designers are going to concentrate on designing the "best" boat for whatever niche they are targeting.

Just a thought, if designers knew that the numbers would be adjusted to represent the 'real world' performance of the boat within a couple of years would that not remove the incentive to design to the rule?
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Post Options Post Options   Quote Rupert Quote  Post ReplyReply Direct Link To This Post Posted: 18 Feb 17 at 10:50am
2 years of making hay while the numbers are kind? I can see a builder taking that, and hoping there are enough for one design racing at the end of it. If there aren't, then cut loses and bring out another one.
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Post Options Post Options   Quote KazRob Quote  Post ReplyReply Direct Link To This Post Posted: 18 Feb 17 at 11:22am
It's worth reading "Yacht Rating" if you can get a copy (https://www.amazon.co.uk/Yacht-Rating-Success-Failure-Competitors/dp/0952947803) to see the futility of trying to predict sailing boat performance by a rule, how the law of unintended consequences seems to arise every time and mostly the fact that it's all been tried before.
If it works "well enough" that's probably the best you can hope for
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Post Options Post Options   Quote iGRF Quote  Post ReplyReply Direct Link To This Post Posted: 18 Feb 17 at 11:30am
The thing is, it's basic physics that defines a boat performance and it is quantifiable, What isn't necessarily quantifiable is the variable performance across wind strengths, but then like now, that's the same for everyone.

What is wrong with the current system is for the sake of argument lets call it indifference, and the focus on a few particular classes and the others get to go hang.

I believe that the boat 'Performance Quotient' for sake of a better term should be fixed once defined and only altered if there are physical changes. Sailors change, they have good days, bad days, make mistakes, the weather has windy years, calm years, there are shifts in volumes of performance types, there are any number of 'chaos' factors that get applied to the current system, which fair enough if that style of handicapping is what's preferred all well and good, but out of the gate the boats themselves should be compared like for like first as a point of reference..

A boat with a given length, volume, a particular sail size with a particular crew weight will perform to a particular speed compared with another with different statistics, big sails go faster than small sails, big volume boats support more crew weight than low volume boats these factors are particularly apparent on fresh water and so they are quantifiable. If you really go into it hull types rounded v flat planing etc can all be formulated if there were the desire for it.

But all the time the luddites are happy to tolerate the status quo then it's not going to happen really is it?

Edited by iGRF - 18 Feb 17 at 11:35am
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Post Options Post Options   Quote Dougaldog Quote  Post ReplyReply Direct Link To This Post Posted: 18 Feb 17 at 1:50pm
Again, I think Graeme has 'fingered' one of the problems facing any builder thinking of launching either an all new boat or a fettled version of an old classic. Where I don't agree is in his solution (if he'll excuse the pun).

With modern tracking devices it should be an easy matter to have a 'sailor boy stig' ( or a whole school of SB Stigs) - so as to match boat and a range of crew weights and sail it over a pre determined course and then compare the results with a known factor. And yes, that could well be the L*ser as in theory the boat itself will not change. I know that the people at Sail Racer were quite happy to do some demos on this (and that may still happen). Then, when Mike at 'Circus' (name changed to avoid conflict with that well know sailing club seen at the winter events) launches his next new single hander project a day/weekend spent with the people from Sail Racer could well spit out a number that is an honest and defendable trial number.

I can only see one problem! You'd have meaningful data on a few boats - but that then questions the rest of the sh*t numbers that are out there!

Could be - should be - done!
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