Sailing Handicap System
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Sailing Handicap System
Proposed National Keelboat Rating System ? How it works !!
General overview: This is a measurement-based system with the basic hull and sail specifications being obtained from formal measurement systems such as IRC, IMS, ORC International, Naval architect design specifications, sailmakers, and, finally, sales brochures.
Basic hull performance rating:
All data extracted from the above is summarised, reviewed, corrected for any apparent errors and entered into the system.
The system/formula takes the above measures and calculates the upwind and downwind immersed waterline length?s, and applies a derivative of the SA/D (sail area / displacement ratio) to extract a deemed upwind and downwind speed relationship across the full range of yachts. The ?scratch? yacht is the Lavranos-designed L-34 at 1.015 deemed rating.
Once the basic hull performance rating is arrived at, , a range of factors are applied to the rating model to level the perceived ?go-faster? advantages/disadvantages of different yachts - all related to the scratch L-34. The combined adjustment for a normal club cruiser/racer would on average be up to a maximum range of about +/- 1% of the basic measure (excluding propeller adjustment). ?Grand Prix? type yachts would have a higher percentage spread above the base rating of up to 3% to allow for exotic fabrics, ULDB construction and optimised performance sail selections.
These factors include:
*Accelerative performance ? ability to accelerated faster and obtain hull speed in lighter wind conditions. Impacts on ability to surf.
* Off?wind bias ? ability to perform off-wind at closer angles when not flying spinnaker.
* Form and crew stability factors ? ability to carry sail area in stronger and over-powering conditions, includes advantage of bulb type keels.
* Stern profile (relative to hull profile) ? ability to extend waterline when beating, and stiffer profile for off-wind Sailing in stronger conditions
*Rudder efficiency ? rates rudder as to overall hull drag
* Spinnaker bias ? allows for better spinnaker exposure of masthead relative to fractional items.
*General - items such as , fixed blade propellers, roller furlers & heavy UV sail fabric protection.
* ?Grand Prix? - items such as sail fabric(kevlar, carbon, 3DL), carbon spars, Code ?zero?s?, penalty poles/sprits, multiple spreaders, rod / synthetic rigging, runners, exotic materials etc
*Generation factor allowance for age of yacht in design after correction of uprated factors above already included ? i.e. no double counting
A selection of ratings are available for use in regions with different environmental conditions, and which emphasises regional weather conditions:
* ALL WEATHER 10- TO 20 Kts - Achieves hull speed
* INLAND Below 10 kts average - Below hull speed
* OPEN/OFFSHORE Substantially wind average > 20 kts - Exceeds hull speed ? surfs / planing
PHRF / Confidence level
The model is checked against the best results from local W. Cape data, and on average is 99.9% consistent with the majority of the fleet but penalises some of ?faster? yachts and gives credit/advantage to ?slower? yachts on corrected times in some cases.
A ?sanity check? is additionally performed against both IRC #?s (towards the racier/cruiser end of fleet) and USA-PHRF (towards the cruiser/racer - cruiser end of fleet). Further cross references are made to ISC rating ( Island Sailing Club ? Round the Island Race ? Isle of Wight ? 1500+ yacht fleet), CSA rating ( Caribbean Sailing Association) and AMS (Australian Measurement System).
NO ?slower? yachts are worse off?..
The model appears to give a tighter spread of corrected time ratings than current local or imported rating systems.
The system will be in a continuous process of evolution to adjust for any formula bias, but will not be adjusted or manually over-ridden to fix any individual yacht?s performance. Each factor (formula & rating) has been tested to function from lightweight club racers up to heavy crusiers with no ?funny? results or over-rides.
Would be considered on the basis of measurements only.
Proposed National Keelboat Rating System ? How it works !! (part 2)
It is based on similar data extraction as used in IRC or ORC International type ratings. The main difference is in the finer points.
The generic method of calculating yacht speed is hull standing wave for immersed hull upwind and downwind, times a power factor. Upwind, there is little variance between the hull standing wave speeds and actual speed on water as boat is not able to climb over standing wave.
Downwind is where the fun begins. All rating systems attempt to put a power factor onto standing wave to determine how fast the yacht will go. The generic method for speed is standing wave x power factor x contant to get speed in knots.
The power factor in a unlimited downwind range would be standing wave x square root of downwind ( SA/D). This is fine but the faster yachts run out of pressure in a constant true wind speed, so a quick-fix system used over the years has been standing wave x cube root of (SA) divided by quad root of D (displacment). This method speeds up the slower yachts and slows down the faster yachts, but is unfortunately a one size fits all method. It works reasonably well with yachts of different sizes and similar SA/D relationships, but does not work well with heavier yachts of same size. I.a.w. the system has a bias towards the sportier type of yachts and hammers the slower yachts ratings several percentage points!
From a math?s point of view, the cube root of SA is fairly constant in rating effect, but the quad root of mass pushes heavy and light yacht towards a factor of 1 with little difference, so formula become biased towards lighter yachts.
Where the proposed system outperforms the current types is that the model is based on apparent wind pressure downwind, and adjusted individually per boat (by model ? no over-rides) based on SA/D relationship. This has no bias towards any boat in fleet and a steel cruiser can take out an IRC racer, the podium position being based on Sailing skill and calling tactics on water and on board.
How does this compare to the two most popular measurement based systems?
If look at ORC International, the VMG downwind speeds match up close to 100% for boats with moderate SA/D relationships such as First 36.7, 40.7 and X-37, but compute a lot faster for yachts such as A-35 and X-41 than the ORC #?s. The ORC system at 20kts shows a downwind VMG speed of about 11-1/2% faster than hull speed ( factor 1.115) for ALL above yachts,while the faster yachts as described above have performance downwind factors (unrated) in 1.19 to 1.23 range, a nice free unrated factor at 20 kts? The yachts in ?Performance cruiser? range such as Dufour 34, Grand Soleil 37 and Dehler 44 have downwind factors often in range 1.08. These Performance Cruisers are lifted up on tables to a minimum default range of 1.115 with a deemed faster VMG speed than can achieve with existing sail area. No podium places for these type of yachts!
With IRC being a not so secret system, a simple module to get onto podium is to rate with a (9/10 fractional rig) non-overlapping jib, a mainsail/jib (Ms/Ji) relationship of 1.2, a spinnaker/main relationship (Sp/Ms) of 2.2 and divide (Sp/Ms) by (Ms/Ji) to nett out at about 1.8. If have an overlapping genoa, go for (Ms/Ji) 1.1 (Sp/Ms) of 1.85 and divide (Sp/Ms) / (Ms/Ji) to achieve 1.70 and will do well, but not crack the non-overlapping rigs. The proposed rating system has a direct and linear relationship between types of yachts and IRC #. If take the X37 / First 36.7(spinnaker) as median point, then peformance cruisers are about 2%+ slower on average, the IMX40 about 3% faster, the X-41 and J-yachts about 4-1/2% faster, the Beneteau 10R about 5-1/2% faster and the A-35 about 6% faster. These #?s would be in wind range average of 20 kts true wind speed. Again being a secret formula, the major difference between IRC and the proposed system would appear to be that of the difference between calculated downwind speeds (IRC does not show wind speeds on rating certificate), between the flat calculation vs apparent wind speed pressure calculation, the mass bias in system and how well IRC optimised the yacht is. Going by results in the performance cruisers? statistics, it would also appear that IRC do the same as ORC and lift up minimum downwind hull speeds to the 1.115 factor if the yachts SA/D can?t make cruiser/racer threshhold!
The treatment of big asymmetricals also varies between systems. IRC appears to take a % off area of asym?s to equal deemed spinnaker area, while our system has an exponential system to allow for greater asym bias and need to sail wider and longer downwind courses.
The system also copes with the lightweight club racers such a First Class 8 or similar, as the apparent wind calculation works out much better than the quad root of mass used in some systems above!
Anarchist: Bruce Williams
Proposed National Keelboat Rating System ? How it works !! (part 3)
Following on from comments in the S/A Forum.
The system is not a simple regression formula, but a very involved model which looks at every major feature, and which are then inputted into a multi layer structure which allocates a value (weighting) to each component, and the final result is a rating #. There are in excess of 20 material inputs, and these interact against each other in multiple calculations with a check at each level to ensure makes sense??
The initial speed generation model is similar to IMS/ORC where works out a dynamic windward hull speed and downwind VMG hull speed in 20 kts TWS. The course weighting is a combination of a windward/leeward course and an upwind beat/offwind fetch to factor in a portion of offwind usage. Net effect (by distance) is 55% upwind and 45% downwind & offwind. What one would expect to generate from a circular random profile, and to relate to general club racing.
The basic speed numbers are 99% of final model and rest of mix averages out to less than 1% for performance cruisers and club level cruiser/racers, about 2% for racer/cruisers and about 4% for carbon and kevlar kitted out racer/cruisers.
Many of the features compensate or offset each other, such as accelerative ability and low DLR offsets stability factor. But if tick all the performance boxes for a racier rig, then expect to pay in rating #.
The question as to asymmetrical?s refers. If run a spinnaker and asymmetrical, the system charges you for the largest sail and longer of SPL/STL. If run an asymmetrical only, the yacht is rated on the area of sail, the STL measure, and then an adjustment off the total rating for lack of downwind VMG ability. This is adjusted and based on a combination of inputs by a single formula in the model. If put this into a sail area comparative, would allow an average extra 20% more sail area (without rating penalty) for asymmetrical on sprit only, compared to a spinnaker only(no penalty pole). This example would be for a J-120. The sail area calculations are measured at the IRC 0.83 and not IMS/Sailmaker 0.95 factor.
Questions as to immersed waterline and short stern overhangs refer. IRC appear to use an ?overhang? factor of 1.00 for any yacht with a stern less than 5% of static waterline in their computation of combined immersed waterline. This can be expensive for club racer/cruisers and some one designs such as Farr 40 OD which have plumb bows and very little to no stern overhang. If there is insufficient stern overhang (SO) measure, the boat will be overrated on any regression formula by up to 2.5% on speed, and which would be very hard to claw back in competitive racing fleets. The model takes a dynamic 4% of static waterline as first measure for stern overhang, with 40% of difference to max stern overhang for windward waterline. If less than 4% overhang, then rated at actual overhang only. In addition to which, 15% of bow overhang (BO) is added to windward waterline for bow immersion factor when heeled. Downwind Sailing immersed waterline is rated at a flat static waterline plus 100% of SO measure? no bow down IRC tricks here at all!!
Yacht (Displacement) mass is rated empty, with addition of anchor, safety gear and sail?s mass into this measure. Model does not add crew mass, as is a very gray, variable and open to abuse factor used to depress DLR factors of lightweight racer/cruisers with high crew mass percentages and make yacht look much slower in any regression formula. One does question why IRC adds crew mass to displacement but measure the performance of static waterline with crew off the yacht for a shorter waterline and double the advantage! The impact of 1 extra crew on average 34 footer has a speed/rating cost of 0.005 or 3 sec/mile in boat dynamics! Let the skipper call the crew numbers for optimum performance.
The DLR factor in model is also used to rate its wave making ability and how slippery the hull moves in conjunction with its SA/D ratio?s. The model uses a modified version of the generic DLR #, being based on immersed waterline so gives a more honest version of how the boat displaces water when under sail.
A standard measure is taken (as with ORC) to measure maximum beam from stem, and to factor this as a % of LOA. This factor is used to determine cruiser profiles with a lot of rocker in centre of yacht, to a median 65% level for most club cruiser/racers, to racer/cruisers with measures in the 70% to 80% range. This is incorporated in model and factors wide sterns for downwind power and extended inclined waterlines at the high end, to pedestrian performance at the lower end.
The rudders are rated in this system as have a material impact on the yachts performance as actually delivered, unlike IRC which does not rate the rudder at all! This is because old style rudders which pivot on the leading edge end up being more of brake when applied, while spade rudders are more of a foil deflecting water around the blade and have very little drag when used with a balanced sail plan. Carbon rudders also have a huge advantage, as can narrow the foil for a better aspect ratio without having to cope with a large metal tube having to be incorporated into foil dimensions. There is also the aspect of blade drag to be allowed for in that rudders close to keel and inside standing wave have their drag reduced substantially from the disturbed water behind the keel, while transom mounted rudders are in clean water outside the standing wave and pay with 100% comparable drag.
All models and regression formula?s factor in a value for Sailing off-wind at angles too tight for spinnakers or asymmetrical?s, and to allow for huge exposed sail area variance between say a 155% genoa to a 105% jib. This is one of major features on IRC optimised rigs with a known bias towards large fractional mainsails with non-overlapping jibs. This feature is so powerful, that in extremes, a small increase in mainsail area can decrease the rating by such an extent that the extra sail area actually rates lower than the smaller sail. This model has already provided for any such instances. The normal pattern based on PHRF data would suggest a maximum spread of 4.5 percentage points for off-wind legs built into rating to allow for the above, but this does not explain the excessively low ratings of yachts optimised with 105% jibs. When trying to ?crack the code? of IRC ?secret formula? and based on data run through the model, it would appear that IRC take the nett ?off-wind? % factor and times by an equation such as ?1.55/(LPG/J). This very clever equation makes no diffence to all the older yachts (with overlapping genoa?s) whose ratings will remain practically unchanged, but gives a quick fix ?bonus? of 0.005 or 3 sec/mile, or more, if larger multiples of this equation are applied to rigs with non-overlapping rigs.
Finally, the Hull Factor story is not needed at all as the SA/D has already included the stove, bunk cushions etc and if used would be double counting of mass in system. The HF is really only needed where a regression formula has used the power factor (cub root (SA) / quad root (D) ), and which has computed ?silly? rating and needs a fix up over-ride to get ?rating? back into line?
The ?hot? IRC optimisation numbers decribed in part 2 refer. Some fractional rigged yachts which slot into the system and compare very closely to my data are the X-35, A-35 and 1980?s generation Farr 38, and after adjusting for asymmetrical ?discount? are the Beneteau 10R and Marten 49. There are a couple of hot masthead rigs around which have a sweet spot with mainsail/genoa factor at 0.75 to .080 and final factor 3.5 to 4.0 such as Angelo Lavranos designed Holiday 34 and several of the Late Carl Schumacher designs such as Lightwave 395. Even on similar designs such as First 36.7 and 40.7, smaller ?tweaks? make a huge difference on rating #. Both these yachts have the same design with identical SA/D relationships with the 36.7 having a 2.5% better main/genoa relationship while the 40.7 has a 2.5% better spinnaker/mainsail relationship, but the 40.7 eats the 36.7 on rating by extra estimated unrated overall 3% advantage ......mainly due to a much superior DLR advantage on the 40.7.
Bottom line is that this measurement based RATING system gives the closest relationship to USA PHRF #.
Anarchist Bruce Williams
Proposed National Keelboat Rating System ? In Action !! (part 4)
We will now compare two production yachts with similar IRC Ratings and show how the above system looks for the sweet spot:
The two yachts selected are the Archambault A-35 (ORC measures) and Beneteau First 36.7 (ORC measures).
Basic dimensions are: Archambault A35 First 36.7
Mainsail *** 37.26 39.11
Jib *** 30.67 42.49
Spinnaker (0.83) *** 81.84 81.90
Displacement mass **** 4905 5677
LOA ** 10.59 10.64
BO ** .101 0.367
SWL ** 10.144 9.795
SO ** 0.345 0.478
Immersed waterline - upwind ** 10.504 10.276
- downwind ** 10.489 10.273
Dynamic hull speed - upwind * 7.065 6.988
- downwind * 7.060 6.987
Downwind Power Factor # 1.184 1.122
Downwind:Sq.root(SA/D) # .0154 0.144
Basic VMG downwind[wind averaged]
hull speed * 8.35 7.84
Circular random factor (BASE) # 1.079 1.040
Fine Tuning Factors %:
Stern Profile/Beam aspect 1.00 0.20
Main/Jib Bias -0.55 0.64
Accelerative -0.12 0.09
Form Stability -0.10 -0.10
Hull Mass & Crew stability 0.04 0.16
Wave-making HF 0.23 -0.11
Rig factor (spreaders / stays) 1.25 1.00
Aluminium spars (std mass) -0.50
Carbon Spars 1.25
Spinnaker bias 0.14 0.08
Code Zero 0.39
Sail fabric ? aramid 1.00 1.00
Jib battens 0.25
Penalty pole 0.06
Generation Factor ? age allowance 0.20 0.14
Fine tune overall factor 1.0504% 1.0260%
Final factor # (base x fine tune %) 1.133 1.067
IRC # (averages) 1.030 1.035
IRC ?mark-up? 10.0% 3.1%
Comparative performance advantage 6.9% 0.0%
DLR 131 168
Factor * Knots ** Metre ***metres squared **** Kilograms
Reconciliation (From IRC):
IRC ?mark-up? 10.00% 3.10%
Formula mass bias-downwind -0.55% 1.16%
Apparent wind adjustment -0.66% -0.15%
Crew mass adjustment -2.65% -2.06%
Main/jib optimisation # 0.0% 2.00%
Excess jib overlap bias with extra LPG % adjustment x 3 # -0.23% x 3 =-0.69 0.07% x 3 =0.21%
Size adjustment 12M # 0.06% 1.46%
Gross formula comparatives 5.51% 5.72%
Estimated ?IRC? optimisation 0.21%
# See part 6 for explanation
Final factor # 1.133 1.067
IRC # (averages) 1.030 1.035
PHRF # NE #69 #78
While it does not needs the skills of a rocket scientist to revue the above, it is patently obvious to see that the A-35 has a longer effective waterline upwind and downwind, an easy 6.6% greater downwind power factor and much lower [faster] DLR, a quick-fix PHRF estimate would put the A-35 overall about minimum 3% [18 sec/mile] faster than First 36.7 using the most basic PHRF regression formula. But the First 36.7 fleet has a very high level of skipper and crew competence, and similar to Farr 40 OD, will find its PHRF # a bit low [over-rated] on a results driven vs. measurement based system, and may explain the above anomaly.
Also to be noted, and if go back to part 1-3 of proposal, that system offers a TWO NUMBER rating, being all round and light wind. The light wind rating drops the A-35 relative to the F36.7 by about 0.007 / 4 sec/mile due to drop in performance of non-overlapping 103% jib compared to F36.7 147% genoa and adjustment for reduced downwind apparent wind pressure in these conditions!
A-35 F 36.7
Final factor # ?all round? 1.133 1.067
Final factor # ?Light wind range? 1.126 1.067
However, forward to the rating revue:
The three systems are illustrated with rating/performance #
?Faster? Yacht A-35 First 36.7
IRC # (averages) +0.05%
PHRF NE [Base rating] +1.50%
/ less 9 sec/mile
Proposed rating system +6.90%
From an overall review of above data, it can be deduced that yachts with a lighter SA/D do benefit from IRC on the ?Power? factor, and on rating advantage from the ?Main/Jib bias? factor as well. Wide sterns [with increased immersed waterline] receive an un-rated advantage under both IRC and the current PHRF base rating.
Not to be forgotten, is the IRC optimisation factor, and which could make up all the difference on the chart above. The sweet spot in optimisation was found by generating a rating comparison from a database of over 80 yacht designs, and representing over 2000 yachts actually racing, and looking for greatest offset from derived VMG over a course vs. IRC #.
Optimisation #?s A-35 First 36.7
Mainsail/Genoa area ?A? 1.215 0.920
Spinnaker / Mainsail area ?B? 2.196 2.095
Optimisation ?hot-spot? ?B/A? 1.808 2.275
DLR 131 168
It is also important to remember that IRC2000 was based on CHS, and at that time most of yachts racing were ?genuine cruiser/racers? and not the current carbon fibre and aramid pseudo ?cruiser/racer? rigs running huge racing budgets. The then hot combination was the 1.10/1.85/1.70 relationship with a DLR of close to #150 or just below. The current downwind sleds with DLR?s nearer to #120 get some free bonus rating in the power (SA/D) calculation, so can increase factor 2 and 3(to about 2.2) without rating cost for a substantial increase in actual off-wind performance, or keep to the prescribed ratios and with a moderate SA/D relationship enjoy a very favorable IRC #.
A further quick comparative to cross check if your yacht will rate well, is to take a bit of a mix Downwind ?Performance Hull Factor? (sq.root?metric?(SA/D)/?imperial?DLR)*1000 and compare to well documented yachts, as illustrated below:
Ocean Cruiser Elan 434 Oceanis 390
Performance Hull Factor 0.60 0.64
Performance Cruiser Grand Soleil 37 X-34
Performance Hull Factor 0.80 0.75
Performance Cruiser Dufour 34 Perf Dufour 44 std
Performance Hull Factor 0.70 0.70
Cruiser/Racer First 40.7 First 36.7
Performance Hull Factor 1.00 0.86
Cruiser/Racer Dufour 40 Perf
Performance Hull Factor 1.04
Cruiser/Racer X-37 First 34.7
Performance Hull Factor 0.89 0.92
Cruiser/Racer?Add ? age allowance? Lightwave 395 X-332
Performance Hull Factor 0.91 + age 0.88 + age
Cruiser/Racer?Add ? age allowance? Farr 38 (1980?s) J-120 Asym
Performance Hull Factor 1.02 + age 1.14**+age
Racer/Cruiser X-41 A-35
Performance Hull Factor 1.40 1.14
Generally, any yacht with the illustrated factor much below 0.95 / 1.05 (asym?s **) will be out of the IRC silverware, unless has a good slice of ?age allowance? or ?IRC Optimisation? to make good rating #.
It should be noted that the yacht?s selected were extreme examples to each side (10.0%/3.1%) of model, with the bulk of racing yachts ?mark-up? being in range 5.0% to 8.0%.
The point of the above exercise? With some boats having good PHRF data and the arrival of say a new ?one-off? or modified hull into local fleet, how do we split the PHRF number estimation between boat speed potential and skipper ability or lack thereof? It is common cause that a PHRF ?link? to the IRC TOT system gives a very vague result in many cases. The benefit to the fleet with this proposed rating system is that is transparent with no apparent bias of cruiser vs. racer, and local handicapper cannot bend rating # for local politics, show favor or bias, nor build in skipper handicaps. It also prevents the well recorded practice of ?sand bagging? at local events to engineer a ?nice? rating for major events and upping the ?pot hunting? possibilities!
A thought on many USA sailors? minds is why the PHRF adjustment?s are made in 3 sec/mile increments. This equates to a metric 0.5% and is fine for club level racing, but with top level events and normal expectations of first five boats often within 1%, any error in PHRF # is very expensive. An example is have two yachts racing to the wire with small differences not enough to justify 3 sec/mile and each yacht, if rated to opposite extreme, being 6 sec/mile apart on rating?? The problem is PHRF system is ?results driven? and can?t call numbers closer than 0.5% per yacht with any degree of statistical confidence.
Racing needs and deserves in today?s competitive environment a more accurate and transparent rating system. IRC with ratings to 0.001 make the serious racers a lot more confident than committee deliberations trying to call 0.5% based on combination of local conditions, local skipper skills and comparatives and perhaps a huge variation of boat shapes and sizes thrown into local fleet mixture. But IRC is a ?secret formula? and the local fleet may not find the rating # consistent to fleet PHRF data, nor transparent to revue and understand why huge variances occur.
One of many unspoken ?measures? from IRC system is that don?t rate sail fabric. The quantum result of this on PHRF is about a 12 sec/mile [0.020 on TCF rating] un-rated advantage between the same boats with 3DL type sails and those with club level Dacron. This is great for the checkbook sailors, but hammers the ordinary club boat down at the pond as well as one-design?s limited to ?white sail? construction.
The above does not build confidence, and accordingly why there is usually a ?mark-up? from IRC to club PHRF to fix fleet data so entire fleet has a chance at silverware. Even Ireland, a strong supporter of IRC, has the ECHO system to phrf the IRC fleet ratings for club Sailing??.
A final thought! The proposed rating system offers a seamless selection of a TCF[0.001] based on TOT or the option of a TOD #[1sec/mile] comparable to current USA-PHRF!
Anarchist: Bruce Williams
Proposed National Keelboat Rating System ? Special Interest Groups!! ( - Part 5)
Having already covered the displacement keelboat?s, we now look at the planing sportboats and bigger asym rigged sleds, and how to rate them!
These boat?s perform with the same profiles of regular keelboats upwind, but downwind all the rules change. Two issues stand out, the terminal hull speed and secondly the apparent wind pressure issue(s).
The terminal hull speed occurs on sportboats when the planing hull?s resistance equals the opposing driving force of the sail area. In a simple world, one could have just used the power formula times the waterline speed and end up with a residual downwind speed number. Unfortunately, the hull?s resistance rises at an exponential rate, and peaks before the theoretical downwind speed on many sportboats.
The system has therefore used a formula to apply the hull speed against the immersed DLR # to generate an estimate as to when the hull speed will max out! This works very consistently from lightweight day racers through huge asymmetrical rigged sportboats, all of which plane at substantial downwind speeds.
The apparent wind pressure adjustment needs a system formula which accounts for having to sail wider angles on asym?s to keep speed up as the yacht simply runs out of wind. A quick-fix factor such as allowing an extra say 20% ?free? area on asymmetrical vs. spinnakers works in a fashion with moderate sprit yachts such as the yachts in range J-120 / First 10R, but the ULDB?s have so much downwind speed that have a greater downwind tacking angle of about 90*+, and have to sail much further than their ?free? area gives them credit for. Accordingly, the proposed system has an exponential formula which gives an adjustable asymmetrical credit based on the factor by which the downwind residual hull speed exceeds the nominal immersed downwind hull speed.
What performance numbers do the above represent? If rate the hull with full sail area of asymmetrical, then a larger non-planing hull would get a discount of below 2% off its rating, a J-109 about 2.8%, First 10R 3.4%, the said J-105/J-120/J-122 a reduction of about 3.8 to 4.2%, while yachts such as Flying Tiger 10 gets a whopping 6.5% correction off sportboat rating. A couple of the larger cruiser/racer asym rigs such as the Sydney 47CR , as well as some of the latest carbon fibre yachts such as Marten 49 also end up with corrections in the 5.8 to 6.9% range. The TP 52 ends up with a reduction of nearly 11% for asymmetrical use and its IRC # and our system?s are within a relative % or so??.
How do these numbers collate?
The PHRF #?s match up on a circular random course within 1-2 sec/mile to the system generated TCF / sec/mile rating #?s. So no real change, but a very high confidence level ?sanity check?.
When compare the data to IRC Ratings, the J-105/J-120/J-122 have IRC#?s in range to about 4% more favorable than the R/P 45 (-2.5%), with Sydney 47CR, Marten 49 and STP 65 in (-4%/-5%) range.
What is very important are the comparatives as well as the absolute rating #. If compare two similar style and size of yachts, being, for example, the FT10 vs. First 10R. We have a performance based record on PHRF-NE list with FT10 #54 and 10R # 81, a TOD difference of 27 sec/mile relevant to windward/leeward racing. On our model (circular random course) we show the FT10 #44 and 10R #70, both a bit (10-11 sec/mile) faster, but the almost identical 26 sec/mile difference.
It is interesting that the J-109 base PHRF-NE is #69/81 when on this system and rating on circular random course, the J-109 rates at #72. The J-122 matches very closely PHRF with #32 per this system vs. PHRF based on IRC TOT to PHRF TOD as follows: (650/IRC#1.096)-557 = 36 sec/mile and PHRF-NE at #33. See chart 5.5 below!
This PHRF conversion does not always work for sportboats such as FT10 etc, as IRC conversion gives them a conversion at 24 sec/mile [(650/1.118)-557] when race PHRF at around 48 sec/mile. In a similar vein, larger lightweight sleds such as R/P 45 / TP 52 with said IRC/PHRF conversion would have very expensive PHRF overstated by about 30/sec mile. Said conversion [by mistake??] has effect of chasing the real racer/cruisers out of PHRF and letting them sort out their battles on IRC battleground!
With the extreme variances and difficulty in the measure of performance data for this style [asymmetrical rigged] of yacht, we do look for comparisons to other rating systems to provide sanity checks. The model has a derivative formula to ?read? how ?hot? the various yacht?s relate to each other on a comparative basis against the ORC International certificate. Herewith a comparison of some performance yachts to the proposed rating system as well as a cross reference to IRC. Some conventional spinnaker yachts are included as reference points.
Yacht Rating# IRC# ORC # ORC ?check?
FT 10 * 1.175 1.118 574 .341
TP52 * 1.514 1.378 431 est .457
Marten 49 * 1.312 1.255 499 .335
Syd 47CR * 1.238 1.176 515 est .328
R/P 45 * 1.379 1.289 470 est .403
J-122 * 1.203 1.100 577 .300
Dufour40 P 1.121 1.047 621.7 .275
J-109 * 1.098 1.035 616 est .289
J-105 * 1.108 1.015 619 est .296
A-35 sp 1.144 1.030 614 .299
Bav35M sp 1.076 1.043 622 .278
X-35 sp 1.168 1.059 601 .309
First 36.7 sp 1.066 1.035 623 .282
Salona 37 sp 1.096 1.061 616 .279
J-109 Sp 1.088 1.035 626 .284
First 40.7 sp 1.140 1.065 596 .292
X-41 sp 1.235 1.126 564 .318
Sp = Spinnaker * Asymmetrical
From a review of the above data with reference to ORC ?check?, and in common with the larger fleet data base, a reference point below .280 puts any such yacht in negative rating territory for ORC, and below .285 for IRC. Yacht?s [spinnaker] with ?check? factor from about .300 upwards do very well on IRC Ratings.
The asymmetrical ?check? would only quantify decent rating performance if compare boats on a size basis AND against ORC ?check?.
The comparative ?check? # of the Sydney 47CR (.328) and Marten 49 (.335), while appearing quick for a 40 ft yacht, is far too low for asymmetrical yachts in 47/50 ft range and would explain such a low ?mark-up? on IRC Rating.
A comparison of asymmetrical rigged boats follows from part 4, and a further quick comparative to cross check if your yacht will rate (IRC/ORC) well, is to take a bit of a mix Downwind ?Performance Hull Factor? (sq.root?metric?(SA/D)/?imperial?DLR)*1000 and compare to well documented yachts, as illustrated below:
First 10R 0.96
King 40 1.10
Farr 395 1.43
Sydney 36CR 1.07
Sydney 47CR 1.23
R/P 45 2.45
Martin 49 1.46
TP 52 3.76
STP 65 3.55
Generally, any yacht with the above illustrated factor much below 1.10 (asym?s) will be out of the IRC silverware, unless has a good slice of ?age allowance? or ?IRC Optimisation? to make good rating #.
Herewith list of IRC optimisation ratio?s
Main/jib ?A? Asym/main ?B? Check ?B?/?A?
FT10 1.66 2.43 1.46
First 10R-105LP 1.36 3.15 2.32
J-105 1.33 2.77 2.07
J-109 1.18 2.90 2.44
J-122 IRC 1.22 3.04 2.52
Farr 395 1.45 3.06 2.11
King 40 1.30 3.10 2.38
Sydney 36CR 1.31 2.71 2.05
Sydney 47CR 1.39 2.79 2.00
R/P 45 1.41 2.73 1.93
Martin 49 ORC 1.36 3.00 2.19
Martin 49 IRC 1.51 2.96 1.93
TP 52 1.38 2.98 2.14
STP 65 1.51 2.66 1.75
The estimated ?sweet spot? for IRC optimisation is not as obvious as with spinnaker rigs, but with the asym (ratio ?B?) getting a free % somewhere in system, it appears IRC likes to up ratio ?A? above by 20% from optimum 1.20 (Spinnaker rigs) to about 1.44 (Asym?s), but limitations of normal roach (at MHW 0.65 E) constrain optimising to mid 1.35 factor ?A?. Factor ?B? goes from spinnaker [2.20] x 1.20 to asymmetrical [2.65] But the final optimised factor (?B?/?A?) is not the spinnaker optimised # of about 1.85 x 1.20 but only 1.85 x sq.root (1.20), and which is impact on speed at 1.85 x 1.095[=sq.root 1.20] ending up with target 2.03 for final factor. But, with some extremes of downwind SA/D ratio as on TP52, they get an apparent unrated [SA/D]advantage on IRC system, so can up the ?B? [2.98] above and end up with higher factor ?B?/?A? of around 2.14 and remain IRC optimised!!
In a single fleet race, the above numbers would stand, but if race in several close rating/size divisional ranges, then the comparatives of yachts per division would be more relevant, and may be a bit skewed from ideal optimisation ratio?s as slightly heavier yachts with longer waterline?s may find a sweet spot in division. This is noticeable in that some yachts have factor ?B? much past optimum ratio, as need to ensure that factor in chart 5.2 exceed 1.10 in first instance.
In the battle for the 40 ft C/R fleet, there is a serious tussle between the Farr 395, J-122 and new King 40. On paper there is little between them, but the fine tuning and IRC type forming is rearing its ugly head. The first issue is that later fractional designs are setting the mast rearwards [with keel moved to balance sail plan] to enable a longer actual LP measure, and with longer J measure, it enables the rating bias of LP% of 108 or less to be used for maximum IRC Rating advantage with more jib sail area. Beyond the simple mathematics, the longer LP [5.07m] of King 40 compared to LP [4.56m] of Farr 395 give it an absolute % advantage of 11%, but in practice is closer to 20-25% in power as the longer the absolute LP is, the greater power is generated in the ?slot? behind the main as the wind accelerates off the sail [foil] and better laminar flow behind the main increases the overall power of the rig upwind. This is being achieved by a gradual increase in mast height with corresponding greater driving force from greater LL measure, all without extra mass due to latest carbon fibre mast technology of current models. The Farr 395 STL measure is also substantially shorter than J-122 and King 40 measures, which closes the slot behind the main when reaching with asymmetrical?s, and requires over-trimming of the mainsail with cost in speed.
By moving the mast and keel rearwards, the keel mass is more balanced and reduces the bow down tendency upwind [of mast forward rigs] when heeled, with better immersed profile and lower drag, as well as having less tendency to cause the yacht to round up in a gust when flying asym?s. The King 40 stern profile [unmeasured under IRC], is very similar to A-35, both of which generate a lot of ?free? waterline when heeled to windward..?
A final ?riddle? when comparing the above yachts and their phrf?d ?Hull Factor?s?, is that with a spread of 8.8 to 10.0, any ?error? can throw out the rating by a % or so and ruin the rating of any yacht on wrong side of equation. I have seen some crazy numbers where the lightweight prototype hull was given a very highish HF, and when the yacht went into production, this same high HF was carried forward on subsequent ?heavier? production models with very onerous rating impact. On the other side, smart manufacturer?s now rate their first yacht for IRC with a heavy hull build (heavy ?luxury floor boards, upgrade freezer, hot water geyser, grey water tanks, starter and minimum 2 x extra heavy auxillary batteries [in bow compartment to assist bow down static measure & up DLR#] electric windlass, stainless steel winches and wheel, ?cruiser? alloy mast, roller furler, etc) and moderate asym to show a poorer SA/D and DLR relationship, and then once have the ?official? HF#, upgrade [strip out] the yacht and increase power stakes and then say ? how can you now change the HF when the hull is same???? And don?t forget to design yacht with a nice ?bow down? measure for measurement of SO[before crew mass is on board], so the calculation for immersed waterline is tweaked a bit lower as well.
Model HF DLR DLR(Metric) immersed [SO] Stern Overhang
J-122 8.8 166 1.62 0.87
King 40 9.6 177 1.61 1.19
Farr 395 10.0 151 1.58 0.71
Model Proposed Rating IRC # % ?Mark-up? % Current Advantage
J-122 1.203 1.096 9.76 0.71
King 40 1.229 1.126 9.14 0.09
Farr 395 1.229 1.127 9.05 0.00
From a revue of above data, it can be seen that the J-122 HF# is very kind to it?s rating #.
Please find examples of ?J? optimisation per above paragraph:
Yacht ?J?/ LOA
First 10 R 0.368
Sydney 36 C/R 0.385
X-37 Spin 0.362
King 40 0.383
Farr 395 0.357
R/P 45 0.391
X-41 Spin. 0.397
Swan 45OD Spin 0.390
Sydney 47 CR 0.377
Marten 49 0.355
TP 52 0.390
STP 65 0.380
The proposed rating system cleans up this anomaly with a single calculation across entire model, to even up chances and to get a sniff of silverware!
Many of the above asym yachts have a definite advantage under IRC, with their optimised rigs, over the older generation spinnaker rigs.
However with reference to optimised factors of R/P 45, Sydney 47CR and Martin 49, and expensive ratings for owners of these boats, current media interviews in Australia seem to be swinging the story that IRC was designed for 30-40 ft cruiser/racers and larger yachts and sportboats don?t always fit into IRC model so well!
If go back to part 3 with reference as to poor results of many ?performance cruisers?, it would appear that IRC have patterned some of their model on ORC (20 kt wind VMG model) with THE GREATER OF a deemed minimum VMG downwind DYNAMIC hull speed calculation of ?standing wave? hull speed x 1.115 OR ?standing wave? hull speed x linear power factor. This ensures that the racier yachts, on above average, will always beat the performance cruisers in lighter (>SA/D) or stronger (
Having successfully run the TP 52 on this model, it was very interesting to run the comparatives for the STP 65 having regard to comparative press comments about its tough IRC Rating. With the STP65?s having a 13% longer waterline speed vs. the TP52?s equal 13% downwind power advantage, the two yachts nett out with almost identical downwind speeds. The upwind speed advantage would be no more than 5 to 7% nett on rating and on this model netts out overall at 5% between them. The IRC difference has a 10% spread between the two classes and makes little sense unless they have been rated on the basis per the paragraph above with a length bias against the STP65, together with a favorable power bias towards the TP 52, netting out to an overall rating bias of about 5%. This would reconcile to about 2.5% (SA/D) power adjustment, 1.5% dynamic hull speed base level adjustment and the rest an estimate of 1% IRC optimisation!
With the STP 65?s built as ocean racers, and the mini-maxi?s being built as an overnighter/coastal/regatta racer, the mini-maxi?s are a bit lighter (10%) and with their more powerful SA/D have a rating benefit. The effect of lighter mass on rating[speed] would be about 2.7% more, but will achieve a better downwind asymmetrical credit of about 0.7%, netting difference down to about 2.0%. But with a slightly lower SA/D power [formula] factor at 1% advantage over the STP65?s, would end up with the mini-maxi?s shedding a substantial mass with mere 1% assumed rating cost under IRC before IRC optimisation effect?and which could zero out to NIL!! A positioning of STP65 [?B?/?A?] optimisation ratio should put it between Marten 49 [1.93] and TP 52 [2.14] at about 2.04, and which is a long way from present 1.75 ratio?..
The terminal hull speed, referred to in paragraph 3 above, disadvantages a few of the faster cruiser/racers where the rating formula speed is right on the terminal hull speed, and is a bit of speed bump absorbing a lot of power as approach said threshold. Yachts right on this number are the Farr 395 and STP 65, and which would both struggle to achieve rating # downwind whether with this system or IRC in wind ranges close to 20 kts TWS. The TP52?s and mini-maxi?s can power past this threshold?.
A final comment to issues raised in forums as to rating debate. This is not a ?magic formula? regression analysis, but is a quick-fix VPP model for club racing which works out actual boat speeds up and down wind, then fine-tunes by a % or so to adjust for go-faster features. It does offer a general 10/20 kts rating as standard and an extra below 10kt rating as option. It does not have a sweet spot for optimisation at all, and would gladly run any boat-on-boat comparison for S/A members if supply data with IRC or ORCi certificates.
At the end of the day, a much more complex rating system than with spinnaker boats. Readers comments are invited!
Anarchist Bruce Williams
Yacht Handicaps Racing - Global Travel
A selection of post 2000 performance cruisers are listed below which illustrate the ?mark-up? method apparent to ORC and IRC where lift up the downwind speeds to a deemed minimum ?rating? speed even if yacht does not travel this fast!
Performance Cruisers Immersed WL Speed iWL speed x 1.115 True VMG downwind % over-ride
Dufour 34 ?Perf? 6.877 7.67 7.44 3.1
Dufour 34 ?std? 6.877 7.67 7.33 4.6
Bavaria 35M 7.138 7.96 7.84 1.5
Grand Soleil 37 7.249 8.08 7.78 3.8
X-37 7.261 8.10 7.98 1.5
Grand Soleil 43 std 7.764 8.66 7.91 9.5
Dufour 44 std 7.814 8.71 7.90 10.2
Dehler 44 7.923 8.83 8.50 3.8
Swan 45OD 8.020 8.94 8.77 1.9
The other 90+ yachts in sample don?t have this problem!
This does not occur for yachts with a series date of 2000 or earlier, and ensures that older yachts have ?raceable? IRC #. i.e. The Lavranos H-34 (IRC 0.920) and L-34 (IRC 0.966) would rate the same if applied per below!
Performance Cruisers Immersed WL Speed iWL speed x 1.115 True VMG downwind % over-ride
Holiday 34 masthead 6.723 7.50 7.04 6.5 ? not applied
Cruiser / Racer Immersed WL Speed iWL speed x 1.115 True VMG downwind % over-ride
L-34 6.765 7.54 7.71 NIL, VMG>
Proposed National Keelboat Rating System ? Size counts! (Part 6)
Having run the fleet ratings against IRC #?s, there is a trend with the 40 ft yachts creaming it on IRC ?mark-up?. The pattern seems to be IRC plus 5% for most Pre-2001 C/R?s in mid size range 30 to 35ft., with larger 38-42 ft. range in a comfortable 7 to 9%+ mark-up. But then past 43 ft upwards, the mark-up drops sharply back down to 4-5% range unless has radical SA/D relationship such as the TP52 class.
As discussed in previous chapters, most post-2000 models of 34-45 ft Performance Cruisers * already have terrible ?mark-up?s? in range 1 to 2.5% due to ?deemed IMS/IRC speed? being greater than actual achievable with rated SA/D.
If run a normal model, with yachts of different size but similar DLR and SA/D, would expected them to rate with similar relationship, and not fluctuate on size as per IRC mark-up. It is not consistent, and asks the question why is happening? It would require a bit of reverse engineering as slows down the 38/42 ft?ers but speeds up the < 37 ft & > 43 ft + yachts, but goes back to earlier comments that IRC was designed for 30 to 40 ft yachts?..It cannot be to adjust for wind pressure, as proposed rating # already has already allowed for same. Perhaps the reasoning was for the top of [then] fleet with most expensive & prestige yachts with big campaign costs, being guaranteed that would not be taken out of the silverware by a mom & pop 34 ft weekender! Also would help to ensure that big teams pay their certificate and re-validation costs?
What factor would do this, as is ending up with a bell shaped graphical curve? It could be on lines of:
Secret factor (metric) = sqrt ( (Immersed waterline -12)^2)
This would give results per below, and would be likely outcome of said formula if included in rating!
Yacht IRC # New Rating IRC + % ?A? 40 ft % ?B? Recon. % ?C?
Swan 56 1.209 1.269 5.0 4.43 9.43
Marten 49 1.255 1.312 4.5 2.43 6.93
Sydney 47CR 1.176 1.238 5.3 1.67 6.97
R/P 45 Asym 1.289 1.379 7.0 1.67 8.67
Swan 45 OD * 1.192 1.231 3.3 1.53 4.83
J-122 1.096 1.203 9.8 0.18 9.98
X-41 1.126 1.219 8.2 0.19 8.39
Dufour 40 P 1.047 1.121 7.1 0.04 7.14
Farr 40.7 #1 1.065 1.140 7.0 0.37 7.37
L/W 395 1.040 1.125 8.2 0.77 8.97
Farr 38 1.013 1.094 8.0 1.38 9.38
J-109 1.035 1.098 6.1 1.66 7.76
Bavaria35M * 1.043 1.076 3.2 1.28 4.48
Dufour 34 P * 0.986 1.009 2.3 2.37 4.67
X-34 0.998 1.051 5.3 1.95 7.25
Lavranos 34 0.966 1.015 5.0 2.37 7.37
Sunfast 32i 0.985 0.947 4.1 2.78 6.88
½ tonner/30ft .890 .935 5.0 3.84 8.84
? Post 2000 Performance Cruiser
?A? Illustrates how much the performance rating # exceeds its IRC Rating. A high number in 9.0?s would be a ?handicap bandit? and a low number below 5.0 would be an ?also ran?
?B? 1. Illustrates for yachts below 40? how much IRC Rating will
be overstated on smaller yachts relative to 40 ft?ers.
?B? 2. Illustrates for yachts above 40? how are treated as smaller
yachts with correction which has effect of increasing rating to favour 40 ft?ers! A bit of a nonsense!
?C? Illustrates for yachts how ?A? & ?B? rating percentages match up to model/formula detailed above to show likelihood of formula being used by IRC.
But you say, what about much shorter A-35 having a ?killer rating?? Yes, it is true, and revolves around the following ?black box? tweak.
Below is ?normal? A-35 comparative to 40 ft hot spot, and still the best optimised yacht in fleet even with this comparative, but reconciliation ?C? is not as accurate as expected!
Yacht IRC # New Rating IRC + % ?A? 40 ft % ?B? Recon. % ?C?
A-35 1.030 1.144 11.0 1.51 12.51
But then we have ?crack the code? with the ?most-likely? formula:
Secret factor = sqrt (( (Immersed waterline*X/Y) -12)^2))
Where X is ORCi measure of bow (stem) to max beam / LOA, in case of A-35 coming out at 0.74
Where Y is default measure constant: 0.65
[most cruisers are in range 0.60 and cruiser/racers 0.65]
Illustrated as follows:
Yacht IRC # New Rating IRC + % ?A? 40 ft % ?B? Recon. % ?C?
A-35 1.030 1.144 11.0 0.06 11.06
Net result is takes Immersed waterline x .74/.65 and turns effective 35 ft waterline into a yacht with a deemed 12m/40ft waterline, with no penalty for length at all. So can then take on the best of 40 ft?ers and win, and sail down the fleet in lower division as well, and clean up substantially! With reconciliation ?C? now at 10% more than next most optimised rig (J-122), this makes sense for this formula in IRC model, especially having regard to relatively un-rated high aspect deep fin keel on A-35!
Before we go, lets cover how the mainsail/jib optimisation process works.
Secret formula factor = sqrt ((sqrt ((main/jib-1)^2)- 0.2)^2)
Yacht?s Main/jib [area] bias Formula Factor Est. % cost per IRC *
Farr 395 1.45 Sqrt((1.45-1)^2) -0.2 0.25 2.5%
J-122/A-35 1.2 Sqrt((1.2-1)^2) -0.2 0.00 0.0%
Farr 38 1.1 Sqrt((1.1-1)^2) -0.2 0.10 1.0%
IMS 1.0 Sqrt((1.0-1)^2) -0.2 0.20 2.0%
L/W 395 0.8 Sqrt((0.8-1)^2) -0.2 0.00 0.0%
IOR 0.6 Sqrt((0.6-1)^2) -0.2 0.20 2.0%
* Note how this adjustment perfectly balances out the ratio?s in ?C? in table 6.1 for overlapping genoas[7.0] vs jibs [9.0] with special reference to IMS Beneteau 40.7 and Dufour 40 Performance, while upping the rating of Farr 395 relative to J-122/A-35. However, the Farr 395 may be substantially reduced by offset in Table 6.5 [with notes] below.
And don?t forget overlapping secret formula, as discussed previously, with formula: ?1.55/(LPG/J).
Yacht?s Main/jib bias ?F? Offwind bias 4.5% on fleet 155% - 105% ?G? Factor ?H? Estimated advantage(-) [I] Most likely ?J?
Farr 395 108% -1.15 -1.65 -0.50% -1.50
J-122/A-35 108% -0.50 -0.71 -0.21% -0.63
Farr 38 148% -0.15 -0.15 0.00% 0.00
IMS 144% 0.00 ** 0.00 0.00% 0.00
L/W 395 133% 1.63 +1.89 +0.24% +0.72
IOR 155% 3.50 +3.50 0.00% 0.00
** median point for offwind bias.
[G] The average for model to allow for offwind bias of bigger genoa vs
smaller jibs [without spinnaker] is in range 4.5%, with non-overlapping jibs in range -1.0%, with a 150% genoa rig about +3.0%, with model centred on IMS rig at 0.00 median point.
[H] Is the measure [G] above tweaked with formula ?1.55/(LPG/J)?,
which gives an expanded ?bonus? for non-overlapping rigs factored into it?s off wind bias#
[I] Is impact of extra ?bonus? per [H] above, which is anticipated ?tweek? to create non-overlap bias in system.
[J] The estimated ( [I] x 3 ) adjustment to match up IRC data with King 40, J-122 and Farr 395.
A review of table 6.5 would suggest that advantage (-) may be a much higher multiplication [2 to 3 times greater factor] than per above in IRC formula, as is shown by current yachts all with huge non-overlapping jib bias, and when read with table 6.4 shows how some relationships offset each other, but bottom line is that optimisation is very critical!
Funny how the IRC proponents are so good at mocking IOR with it?s rating optimised bumps and pinched sterns, while some of latest IRC optimised hulls are now developing powerboat chine?s to keep maximum beam forward and develop more waterline beam at stern for better immersed waterline advantage and better downwind surfing, all without rating penalty. The more times change, the more things remain just the same!
To quote from the acclaimed novel ?Animal Farm? by George Orwell, and in context of the government of Sailing administration, the quote ?all pigs are equal, but some are more equal than others?, would be good reading for those in authority of yacht rating systems?.
Finally, an absolute tragedy to the sport and ethos of Sailing that a system promoted as the finest measurement system afloat exhibits such latent flaws, and has accordingly disenfranchised so many 100?s if not 1000?s of keen amateur yachtsmen who raced and gave their best never knowing that the system was rigged and that they were literally Sailing the extra mile, until finally withdrawing from the sport and costing Sailing its growth and viability into the future. What multi-national sponsors of yachting?s premier racing events may think can only be imagined?
Anarchist Bruce Williams
Proposed National Keelboat Rating System ?
Non-Spinnaker (Part 7)
Having already covered the nuts and bolts of system, comparasons of other ratings and handicap systems, this section covers the more social and less rating intensive MAJ (main & jib only) social racing events.
The system has incorporated into it?s model a full range of data to generate said information, and does the same with working out [MAJ] upwind and downwind base speeds, and then uses the same fine-tuning data as the full rating model with the exception of spinnaker related adjustments.
A selection of yachts are shown with normal spinnaker rating, the Non-Spinnaker rating and % difference if sail in mixed with/without spinnaker fleets.
Yacht Spin Rating# JAM# % ?discount?
FT 10 1.168 1.118 3.41
Marten 49 1.253 1.255 3.35
A-35 sp 1.132 1.030 2.99
Bav35M sp 1.059 1.043 2.75
X-35 sp 1.153 1.059 3.09
First 36.7 sp 1.066 1.035 2.82
GS 37 sp 1.037 1.043 2.72
First 40.7 sp 1.140 1.065 2.92
X-41 sp 1.219 1.126 3.18
Sp = Spinnaker
From a review of the above data, and in common with the larger fleet data base, the following assumptions can be made:
Downwind VMG > 1.14*hull speed (-)2.5%
Downwind VMG < 1.14*hull speed (-)2%
PLUS: DLR adjustment
High DLR >200 (-)0.5%
Moderate DLR >160 / < 200 0.0%
Light DLR >120 / < 160 (+)0.5%
Ultra Light / Sportboat < 120 (+)3.0%
PLUS: LP Adjustment
< 110% (-)1%
Heavy Cruisers [DLR>320] ?Extra? Flat (-)1% nett
The above is a quick fix for yachts with limited data and based on PHRF ?spinnaker? comparasons. The actual numbers per formula give a more accurate representation of peformance and more relevant for mixed spinnaker and asymmetrical rigged fleets.
Anarchist Bruce Williams
Sailing Handicap System
Yacht Handicaps Racing - Global Travel
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