New Grand Prix Rule

Hi everybody.

I just got the latest edition of Seahorse through the post and noticed a very interesting article by Robert Laine about the proposed new Grand Prix Rule for offshore sailing. The official Rule Working Party have been looking at producing a rule which, although it does not use a VPP directly to assess a yachts performance, still uses a VPP to derive the formulae used in the rule. Many designers and sailors feel that this could introduce an inherent weakness to a new rule, and so are instead suggesting a simple box rule of fixed maximum and minimum parameters. Different boxes would be created at different sizes. But one of the problem with this approach is that in areas where there are insufficient numbers of boats within the same box, your racing options are limited to using a rule your boat is not designed for (the catch all IRC or PHRF). A couple of months ago when the RWP announced their plan, I began thinking about a different approach. It seems that there is a need to be able to allow different sized boats to race together, whilst also allowing boxes derived from the same formulae to be implemented at different sizes to allow level rating racing.

My initial thoughts were that a formula based rule would work well, with a simple formula designed in such a way as to encourage fast, fun and stable boats, whilst leaving out anything which might complicate matters or be open to exploitation. The base factor to be used in the formula would be L, the absolute length of the hull (so no daft girth measurements or other dodges around a 'rated L'). Different values of L would produce different results from the formula, which would provide a basis for a Time Multiplication Factor curve covering a range of sizes. Thus boats of different sizes could race together on handicap, whilst specific L vales could be chosen at, say, 25, 30, 35, 40, 50 and other sizes for level rating. This approach is somewhat similar to IOR, only that rule used an overly complex formula to derive a theoretical value for L, which lead to bumps, creases and the like. Other areas of complexity would similarly be removed.

Having said all that, it seems that Robert Laine has similar but much more developed ideas along the same lines and so I'll email him and see if he might be willing to put his ideas up in this forum. I think a place like this to discuss these ideas is perfect for anyone who might have some opinions on the topic - owners, designers and sailors alike, so lets have some ideas!!!

There are many other things to consider, such as to allow innovations such as canting keels and so on. I quite like the idea of being able to be free with non dimensional aspects like this - if a canting keel and daggerboards makes you faster than the guy without, then lets have it with no penalty. That, after all, is the true nature of development. Again, anyone got any suggestions?

Andy

 

Hello to all,
I am here to answer any question on the proposal I made in SeaHorse, and to include any good idea in it.

 

Great to have you here Robert! (I should point out to those who don't know that Robert is also the author of Sailcut and Carene shareware and open source software).Do you have your seahorse text and diagrams available to post here, just in case anybody who is interested doesn't subscribe to seahorse?

Andy

 

At the risk of being instantly labelled a misogynistic old curmudgeon (by those who haven't already figured it out...) I'll wade in with the old cry of "Oh, Heck! Not another frikkin' Rule". I would love to see something along the lines o the Open Rules adopted for smaller boats. Length overall is the only limit on design, with some allowance for poles. Stability limits are a must, measured empirically (yes, you'll get wet) to _prove_ the numbers. It is all too easy for a designer to say "Yes, it's stable, look at this graph" when the graph in question is not for the sailing condition. Having to measure the stupid boat to determine if this is so just leads to more chaos.
Tip the thing over, measure it's length if it returns to an upright condition, and race.

Well, that's my two penn-orth.

Steve

 

bumps and creases...

You gotta remember tho, Andy, that all those complications about girths and stuff were only put in there because of earlier equivalents to bumps and creases that simpler rules led to. As soon as you have a rating rule rather than a box rule its got to get complicated 'cos boat design is complicated, and its got to have some kind of element of VPP about it. About all you could do would be to have a series of boxes, and then use an empirical system to produce tmf factors between the boxes. And the trouble with a box rule is that it is inevitably type forming as designers work out which part of the design box is favoured.

The big trouble is that designing boats to exploit loopholes in rules is a whole heap easier than designing rules without loopholes.

 

LOL!
It's also a lot easier to design a boat to fit through a loophole than to design one that really IS faster than the competition.

 

hello folks,
I think that once you have the files of the proposed rule your worries will go away. In the days I was sitting at councilor for France at the Offshore Racing Council I fought for simplification of the IOR... and lost and the IMS went deeper in the wrong direction under the pressure of technical advisors who where interested in working out the 2sd or 3rd decimal when the problem was with the first digit.... Being an engineer myself I recognized the syndrom by to no avail. Anyway time has past and the IRC took the right approach to keep it simple. What I propose is an open box rule reusing the best of the IOR (its way of combining L, D, S) and changing the various weighting factors to encourage lighter and faster boat with NO restriction to stability and shape. Every body knows that a stiff boat is faster and safer to sail than a tender one. I put some limits to the length to beam ratio to avoid the surf board design which are potentially unsafe when knock down. The other limit is on the mast height and maximum size of main and jib, again to avoid e extrem designs. I have asked Andy who started the thread to find a way to post the rule text. Meanwhile anyone interested can write to me and ask for a copy.

 

Already some interesting comments! Firstly, Steve, Robert states in his article that "To encourage a stiff and fast boat, there is no stability factor". Makes sense to me - boats which fall over don't sail fast. I would guess that your inclining test should be included to ensure reasonable standards of offshore safety, but that the stability should play no part in the rating itself. You might then run into problems with very light construction narrow waterline boats and heavy bulbs, but adherence to the ABS standards with additional safety factors stipulated could alleviate this?

A simple box would be a nice idea, but what do you do when there are no other Open 40's around? Get clobbered under an unsuitable handicap system? This is why I believe that a new racing rule will need to allow handicap racing as well as level rating within that system, and for level rating the boats should not have to meet any further limits (as happened with the ILC40's) in order that they can be competitive under one configuration for both level rating and handicap racing. Playing a bit with the formulae of a rule, one can type form the Open boat type Steve wants whilst still allowing a certain amount of trade offs. This way, each boat fits into a flexible box (the rating), where you can alter one variable and compensate in another whilst keeping the same rating.

gggGuest makes some nice observations about rules and VPP's. Yes all handicap systems have an element of velocity prediction about them, but the purposes of IMS and what I'm suggesting are quite different. IMS and other such rules seek to fairly assess and rate every feature of a boat in respect to its performance. That way, revolutionary ideas do not outclass the rest of the fleet, but this complication has its (very visible) price...
I propose a system which uses the bare minimum of carefully chosen dimensionless formulae (so that the numbers can relate different sizes of boat to each other) to determine a base rating, which can be used to compare other boats using the same simple formulae. These formulae would be tailored to creating light displacement, fast boats with lots of sail whilst being offshore suitable for the reasons mentioned earlier. Hard limits to the amount of variation allowed in any parameter can easily be factored in, again with simple formulas (see Roberts Seahorse article!). By keeping the rule simple, it will be full of loopholes but then thats how the boats will develop. So whilst IRC/IMS etc may slap penalties on you for having a swinging keel, by ignoring stability (except safety regs) you can have what you want, as long as it falls within the rule draft formula, with no effect on the rating. In other words, this is a free development rule, rather than an assessment driven handicapping rule. On the other hand, simple restrictions (stating only what IS allowed - anything else prohibited) could also work just as well - see Roberts article. Canting keels were banned from IOR, but if everyone had them you wouldn't need to rate them...

gggGuest also suggests that "...all those complications about girths and stuff were only put in there because of earlier equivalents to bumps and creases that simpler rules led to". This is because historically L was never the full hull length - it was always a complicated computation based on overhangs and the like, and big girths there improved displaced length when heeled and so the maths got tricky. By calling L the extreme length of the hull, all of this is eliminated. Prismatic and LCB should not be accounted for, as again the designer should be able to choose what is most appropriate based on the basics of Length, Sail area and stability he has chosen. Draft should be controlled for practicality, and aside from a few other non performance related issues that should be it.

Andy

 

Here are Robert's rule texts...I quite like them (a few minor tweaks perhaps...)

Andy

 

Forgot to say Robert - not sure that the boat in the diagram is the fastest thing ever designed....!!!!

Andy

 

Some additional comments on the proposed rule:
The forward triangle of the box limit looks awfull it is there to avoid boats with a wide pram bow. Such pram bow would not be 100% eliminated they would necessitate to a much longer L to fit in the triangle. Pram bow are OK on lakes but at sea... I would not like to be on board going upwind in 30knt wind.

The risk of having narrow boat is limited since the narrower they get the deeper the hull would have to be for a given measured weight, they have a shorter waterline when heeled over and also the narrower they get the less effective the crew on the rail gets. If some are deeply concerned we could put a limit to the Length over Beam ratio. In any case narrow boat are not necessarily bad to sail, actually they are easier on the wind.

As for the canting keels, essentially they are expensive and it is very difficult to compare them with the robustness of a fixed keel. I would propose to separate the fleet in those with and those without until we know better.

Fitting existing boat in a new rule is always tricky. Everybody has tried and failed. The only practical solution is some sort of grand-father clause with a discount on th TCF. Note that I took data from the old IOR to ensure that reasonable hull will fit.

If you have tweak to propose send them by E-mail to me and I will integrate them in an update.

 

Hi Robert -

I think the draft limit is too low - the coefficient of 0.15 leads to a depth of 2.3m for a 12m L - maybe a coefficient of 0.18 - 0.20 would be more representative of modern designs?

I also think that an upper limit on displacement should be applied to try to keep everyone sailing light fast boats. On the other hand, the sail area limits indirectly encourage light (enough) displacement with acceptable stability - try to go for a heavy boat and the sail area to displacement ratio suffers. But it could still prevent someone trying a narrow, low resistance but heavy boat (AC style...).

More thought as I have them,

Andy

 

To encourage the lighter displacement I reduced the factor on Sail area over Displacement compared to the IOR

Increasing the draft is a problem for boat sailing in relatively shallow waters, I already increased it from the IOR. O.18 gives a lot of draft why not?

 

I haven't yet read Robert's article, but I agree with Andy and Robert that a straightforward way to handicap boats is needed for both level and handicap racing. I haven't been following the recent specifics of IRC, CHS, Americap, Volvo 70, Transpac 52 and 40, Mount Gay 30, MaxZ86, how they compare with older yardsticks including IMS, MORC, Portsmouth Yardstick, CCA, Universal Rule, etc, but the current batch all seem to be producing reasonable boats and racing.

If I were to start from scratch, here's how I'd approach handicapping: Sail area tends to track stability, so I don't see any need to penalize stability if we penalize sail area. I think one can overpenalize length, resulting in boats that are too stubby relative to their other dimensions. I also don't agree that limiting LOA is the only reasonable approach. Taking one or more waterlines a bit above DWL, as the IACC rule does, is not a bad way to go. My understanding of the IMS rule is that it effectively combined this with considering the longitudinal I at that waterplane. This could be simplified to eliminate the odd bows of recent IACC boats by employing a caliper to take widths just aft of the forward end of any measured waterline.

Besides length, the critical predictive value is sail area to displacement ratio (if one assumes sail area goes hand-in-hand with the stability to carry it). Deep canting bulb keels, movable ballast, etc are all ways of increasing this ratio.

I'd calculate the SA/Displ ratio in a nonstandard way, taking the sail area times the sum of the hoists, all over displacement. By the sum of the hoists I mean "P" plus the average of "I" and the height of the spinnaker sheave above the deck. Where there are two masts the longest hoist plus the average of the second and third longest would be used, and the rest ignored (except as they figure into the sail area calculation). I'd take displacement by equipping a travellift with a scale and physically weighing the boats before a regatta.

My formula would read:
Vp = [m * L^0.5 * (SA*SUM(hoists))^x / Displacement^z] - [n*w*Freeboard/Draft]

w = the percentage of a race consisting of windward work.

I'd start by finding a boat the existing ratings of which put it's typical speed around the course at a speed/length ratio of about 1.00 (Fn=0.30). I'd assume initially that x and z both equal 0.333 and I'd calculate a first approximation of m and n. Then I'd assume that x=z and work them together to fit the performance data, PHRF ratings, and/or the output of a credible VPP. I'd iterate everything a few times. As a final adjustment I'd allow x and z to be varied seperately to fit the data on the theory that this might help account for the greater apparent wind generated by faster boats, and other scale effects.

I think performance data for boats with canting keels and other novel features should be included in the data, but I'm against comparing performance data from light racing boats to data from heavy cruising boats. Raceboats should be compared to other raceboats; then every factor need not be taken into account. If one can identify the major trends and do a good job of quantifying them and accounting for the way they scale, it should be enough.

Finally, like Olin Stephens, I believe there should be a scantling rule.

 

I've now read RL's proposal. Sounds pretty good, but I'm not clear whether it scales in a way that's useful in handicapping boats of different sizes. If it's a type forming rule like Volvo 70, Transpac 52 and 40, and Mount Gay 30, with its primary application being level racing, what advantages does it offer over those rules currently in use (shorthanded "open" classes as well as those mentioned)?

The problem I see currently is that there are too many rules, and none of them do a good job of:

• Allowing the latest 30 meter canting keel mega-racers and other mega-sailers to compete within a reasonable framework, either against each other or on handicap.

• Allowing the many one designs out there to compete against each other within a fair handicap system.

• Permitting innovation, including water ballast and canting keels, but handicapping boats with innovative features fairly without resort to ad hoc penalties.

I'm for development classes, but I'm for one-design too. Most of us do not have time and resources to be shipping our boats around the world in search of comparable boats to compete against. Is this a system that would allow all the racers on Long Island Sound to compete against each other in one big regatta?

I think emphasizing sail area/displacement has a potential upside. Canting keels, water ballast, big crews, and deep bulb keels have the effect of increasing sail area to displacement ratio. If a handicapper were dilligent in tweaking the constants and exponents to fit the performance data generated by boats that employ such features it's possible they could be handicapped fairly without resorting to ad-hoc measures that penalize innovation.

On the subject of crew weight I think it's fairer to women and small people in general to limit crew size entirely by weight, not by number of individuals. But again, this may not be necessary if sail area to displacement ratio IS emphasized.