VMG

Originally posted by Rupert .As for the weed...

You haven't been smoking it have you?

Originally posted by Daniel Holman Sorry meant that last one for the handicap final solution mein kampf by adolf fuller thread! fair bit of crossover between these threads though

Holman? You're not from Poland I hope.

Originally posted by iGRF So, are these 'polars' available for different boats, when was that one issued for the RS100? Where can I order one for the Alto and the EPS? Then the next question (blindingly obvious even to an idiot) if there are such things, that are calculated on fact rather than anarchic fiction like club returns, why is it so difficult to have a given boat a permanent handicap calculated for it?

Hi Graeme,

I generated that one for the 100. To create theoretical polars you need three things:
1. The drag of the hull
2. The power from the rig
3. Other stuff
The drag of a dinghy hull is severly impacted by incorrect trim, waves etc. I used the measured values from a towed 59er and tweaked it by crude judgement to suit the shorter, lighter 100.
The power from the rig can be estimated using standard aero calcs, provided you have reasonable lift and drag coefficent estimates. There are a number of ways of getting these, but getting accurate numbers requires money.
The other stuff covers things like crew weight, mast height, sail roach, daggerboard length etc, which affect the righting moment and hence power available.
So there are quite a few inputs, which you can either guess, estimate, measure or calculate. The more precise these numbers, the better the answer. To get numbers good enough to calculate a PY (becasue yes, you could, in theory use polars to calculate PY) would require a decent level of accuracy. Nice job though!
Having said that, PYs to 4 decimal places is overkill anyway.   

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.

Originally posted by iGRF 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.

BOOM! Knowingly (or unknowingly) you have just stumbled upon the biggest can of worms in the none one design sailing world.