New mixed class "Racing formula 100R"

I’d like to introduce an idea that ClaudioD has been thinking about for a while following his observation that RC sailing classes are thinning out which also makes it also difficult for new modern classes like IACC 120 to make any headway in Europe or the U.S. and we would like your opinion on an idea ?

Basically, the concept is to introduce a mixed class rating formula (similar to large boats) that would allow different RC sailing classes to come together & sail competitively against each other using a basic rating. It’s a concept and not too far from the old “10R” just redefined to increase the scope to allow different RC sailing boats to fit into the formula.

The initial idea is to have different boats in the 110-130 cm LOA length range, to be able to compete together with a simple formula! Not to mention more guys with common passion, having a beer together at end of the day. One could also allow for new boat designs developments later if worthwhile.

Claudio has called it “100R” so those old school sailors familiar with the 10R formula can identify its origins.

The formula (open for discussion) works as follows:

[ LWL(cm) x SA(cm²)] / 8000 = 100 (metric system) with examples of how it would work.

Class M: 125cm x 6400cm² / 8000 = 100.00 here normally the max SA should be 7200cm² for rig A, but bulbs and weights are free.

AC 120: 100cm x 8000cm² / 8000 = 100.00 would be the maximum allowed but with FIN/BULB of 3000g out of 4500g minimum weight - most of the time would sail with 7800cm²

Comparing these two examples, the class M will have smaller sail area (noting that this class uses already 6 different rigs) and would benefit from its longer LWL against a AC 120 that would benefit from max SA that would be offset by its shorter LWL and keel/bulb weight which are governed by the boats own class rules.

The formula works together with basic box rule where ANY class boat that fits within the dimensions of 275 cm x 130 cm. would eligible for racing. The box is split into two parameters to define the only rules with maximum limit for the mast height (200 cm) and the max draft (72cm) from the deck line. Sail rigs maximum 2 … everything else totally free !

It is just a concept open to discussion at this stage, the formula can be modified (I’m sure Claudio is fine tuning it now) to ensure widest range of class fit fairly into the formula.

Would really appreciate your comments and/or suggestions if in your opinion there would be interest using this mixed class using racing formula 100R ?

Cheers Alan

I think this is going in the wrong direction. The problem is not that ‘classes are thinning out’. The problem is ‘too many classes’, fragmenting the sport. And now a suggestion of one more class.

The other problem is that the format you suggest gives the win to the boat that fits the conditions of the day. . .a windy day and the long boat/smaller sail wins. . . a light day and the shorter boat/bigger sail wins. So it is the conditions that determine the winner and not the skill of the sailor.

A major factor in the reduced popularity of the M and 10R (in my opinion) was the lack of a max draft spec in the class rules. That allowed boats to gain stability with a very deep fin and lighter ballast. The downside of that is that those boats cannot sail on many ponds due to lack of water depth. To be competitive you had to go that route, but many dropped out and switched to other classes to be able to sail on the available sites.


I John,

In my opinion and many class M sailors says the same thing, the loss of interest on Class M is mainly due to economic costs . At the time when this class was very famous, the prices started to grows unreasonably and was no rare to spend 4800/5000€ for a complete M with 6 rigs.
At that cost level most of modelers could not afford anymore and turned to some others models like IOM being reasonably cheaper. Today also the IOM are getting expensives and modelers turns to RG65. If the RG65 would become expensive, the Footy are ready too.
An interesting point is to check the Class member subscriptions trend at National level in the last 5 years !

Most of the experimented sailors never use 66cm long Fin simply because the increased Wet Surface was a serious handicap in terms of wet area.
My Class M are satisfied with 54cm and less, including bulb, from the hull bottom when the gain on wet area is reduced by about 240cm² .
Certainly pond deep and weeds are a problem , but avoided with better choices including sea side.

The above formula is initially developed to permit two or more classes to race together and getting more boats in the water at once !

In the specific case we told that class M could race with the AC120, thats all !

The 100R is now adjusted to use the LOA instead of LWL since more simpler and read as :

( LOA x SA ) / 9000 = 100

This experiment was already carried out in Italy with another formula a little bit more complicated where Beam and Wights were included.

This formula was called “SAFALERO RATING”

[(SA + LOA - Beam ) x 0.2 ] - ( Pb + Ps ) / ( Pb - Ps ) = 31 <> 34 and probably better if limited to 32<>33

SA = Sail Area in dm²
Beam = max deck in cm
Pb = Bulb weight in kg
Ps = Boat weight without Fin/ Bulb


Both international M and 10R’s have max depth limits. They are quite deep and there are ponds that will not support racing at max depth. US M class does not have a max depth, but once you get beyond the international M limit you are in an area of minimal returns.

Personally I would not measure depth of the keel from the deck. Much easier to measure from the bottom of the hull.

What I think would really help a class grow would be having a limit on the amount of ballast ratio. Most classes dont have such a rule and are thus chasing lighter hulls, deeper keels to get better performance. It would be better to set this at the start to avoid an arms race. Possibly set a balance point on the keel, ie set the keel/boat on a block and see if it tips off. If it does, add weight to the hull until it doesnt.
Another thing would be to limit the fin thickness to 6 or 8% to allow easier home building. IOM’s did not do this and now are using 4% foils which need to be made out of CNC cut molds to be competitive.

Hi John,

No suggestion for new class at all, as you say classes are fragmenting, using a rating formula (as big boats do) the idea is to help bring some of those fragments, without changing the boats original class rules so they can compete together as closely as possible.

Getting the formula as close of possible is the ultimate goal, if possible …any suggestions ?

Cheers Alan


The ‘Basic Idea’ is to put together differents classes for racing and get more fun .

I tend to agree with some points you mention and will be good idea if every one interested could offer his idea and figures !

Could you please propose a Rating Formula or common parameters of existing classes, where boats of LOA from 110 cm to 130cm could race together ?

I’m ready to change my BOX Rules to reduce Fin/Bulb Lenght to 48cm for instance from hull bottom and the total mast height being at 200 cm.
Good idea to limit the fin thickness to 8mm minimum and 10mm minimum for the rudder.

A parameter, most of the times negletted is the Bulb/Boat Ratio. This figure give the idea about lateral stability.
A good design figure should be above 65% and better if above 70%. America Cup Boats go up to 83% , class M are around 72% and RG65 are often at 65%.

Racing for the highest bulb weight can be discouraged by the total weight that the sails can push, It may be possible to introduce the minimum total weight to 4200g and max Sail Area to 7500cm² and using the BOX as Rules


PS : BOX Rules Changed

All I was suggesting is to get more boats is to fix the ratio so that there is no need to make super light hulls. There are lots of older M’s that are heavier and by limiting the righting moment they have the potential to be more competitive. More like the IOM where you have to have a set bulb fin weight. Although that has become misplaced as well since now you can add corrector weights down low, so it is an advantage to have a light hull and add corrector weights. Should have had to add the correctors at the top of the deck.

As I have several 10R’s and M’s all of which would not qualify I dont really have much interest in another class. Just adding my $.02 on where I see other classes going wrong and fueling an arms race.


The ‘Basic Idea’ is to put together differents classes for racing and get more fun .

I tend to agree with some points you mention and will be good idea if every one interested could offer his idea and figures !

A parameter, most of the times negletted is the Bulb/Boat Ratio. This figure give the idea about lateral stability.
A good design figure should be above 65% and better if above 70%. America Cup Boats go up to 83% , class M are around 72% and RG65 are often at 65%.

Racing for the highest bulb weight can be discouraged by the total weight that the sails can push, It may be possible to introduce the minimum total weight to 4200g and max Sail Area to 7500cm² and using the BOX as Rules

If one were to do a search, I had/have offered several times to create a Portsmouth rating for class or size of boats. Unfortunately - in order to handicap, one needs some accurate, reliable data on the performance of class, the wind strength (measured) and the finishing time of first/last boat in order to even start a set of handicap numbers. Unfortunately, it wound up as all talk and no action - since each class would have had to record several regatta results (too much work) so just like the “Speed Trials” often discussed - that is all that has happened - just discussion (with exception of the Footy Class) who actually put together a good model for speed times. Won’t work too well for larger boats needing longer courses.

Some of these discussions went back as far as late 1990’s and early 2000. Just an FYI for those looking to reinvent the wheel. Is an IOM really faster than a US1Meter? Is a 36/600 faster than a CR914 ? M class vs. 10 R ? How about an M/10R vs. a Mini40/F48 multihull? How competitive is the new crop of “plastic boats” - and who tracks modifications, when even the classes themselves have trouble having/measuring/checking rules?

A few thoughts - good luck coming up with answers that everyone will buy into. Cheers.

Hi Dick,

The below Safalero Formula is indeed an “Handicap” Rating Rule used in Italy until some years ago for models of the America Cup in scale 1:20 :

At that time, models with differents Sail Areas, Beams, Overall Lenghts and Weights could race together since each boat was Certified with an “Handicap Rating”.

The Handicap was limited within rating from 31 to 34.
Personally I would like to widen the range from 31 to 35

Some calculations can be made to prove the consistency.

One example : …GENERAL Specifcations

Boat LOA 120cm max
Bmax 18cm …( range 16 to 25 cm )
BF 3.00kg …(range 2.90. to 3.10 kg )
HR 1.30kg …(Free)
SA 78.0 dm²…(Rig 1 72dm² to 80 dm² and Rig 2 66 to 72 dm²)
BF+HR…(minimum 4.00 kg)
Draft …(48cm max from hull bottom)
Mast height…(175.0cm)
Fin thickness…(8% min.)
Rudder…(10% min.)

Rating with above parameters : [(120 + 78 - 18) x 0.2)] - (3.00 + 1.30) / (3.00 / 1.30) = 34.14

by reducing the SA to 75dm² we get a lower Rating as :

… [(120 + 75 - 18) x 0.2)] - (3.00 + 1.30) / (3.00 / 1.30) = 33.54


what about a PHRF rating of some sort… or the Portsmought yardstick or the IRC, IMS, or ORC

the hard part will be determining the rating. obviously for a one design class it would be much easier. for a developmental class, you would have to take an “average” rating of some of the boats. or have a formula…

the hard part again. how to determine the handicap…

Hi Marc,
if you make some calculations with the above rating, you will find out. The boat Rating is between 31 and 34.

The Rating of the boat obtained is added to the racing points for the final ranking .

So having too high Rating will penalise the score ! This is the Handicap !!

I ignore totally the Rating Rules you mention and I will be glad to knows them , hoping are not demanding complex calculations.

The Nice of the Safalero is that it is very simple while considering all aspects as Sail Area, Bulb weight , Boat weight, total Lenght and Beam


I don’t know much about the ratings systems I mentioned either… I was juts offering up an idea to use systems that are already in place. IE don’t reinvent the wheel.

how would you classify a boat that doesn’t have a bulb. LIke A soling 1 meter, or a full keel Ec12 or J? or someone who has a bulb that is mounted permanently on the fin. with no way to measure the weight separately?

Hi Marc,
I went searching on the net the warious rating,
None is applicable to our models since no data are recorded in quantity to establish an average.

The question about the fixed keel is included in the Safalero Rules, see attachment.

By changing the parameters, this Rating Rule can be also adapted to others models that are self Designed / constructed and not pertaining to a monotype design.



I am having trouble figuring out how the Salafero formula would work in a regatta. Say we have five boats that have ratings between 31 and 34. Before the first race, I assume the boats would be ranked 1 to 5 in ascending order of their ratings. They race and the ranked boats finish in this order (for example), 2,3,1,5,4. So, the highest ranked boat finished 3rd, the 2nd highest rank finished 1st, etc. Here are my questions:

  1. How does the ranking and points come into the scoring?
  2. Does the ranking in race 2 change based on the race 1 results?
  3. What is the Classification calculation used for?

I am trying to figure out how to actually run and score an event. In my experience with full-scale systems like ORC and PHRF, the differences between ratings are corrected with time adjustments. This system is obviously not using time but points. A simple example of a few races would be very helpful. Perhaps there is a spreadsheet scoring template in use?

This rating formula sound interesting, in that it does the same thing as the PHRF, IRC, ORC, and other rating formulas do for full scale boats through the rating part. I think the ranking part takes driver skill into the equation. Members of my club have been talking about this very idea for a while now, and we were thinking of going down the empirical path with lots of data collection. That is a huge task, while this formula approach is much easier to implement. Of course, we will probably have disagreements about the “fairness” of individual ratings.


Hi Eric,
So far I knows there are several Rating methods used for real boats as you mentioned and all demanding a lot of statistical sailing capability evaluations as such that each boat get is rating value after several years of observations and reporting. Often this value is updated too.
There is also another Rating method based on boat “dimensions measurements” : like lenght, weight, bulb, sail area, beam, etc

Each boat receive his Rating Certificate according to the formula expressed above. This rating is represented by a numerical value from 31.00 up to 34.00 as mentioned above.

At the end of the race each boat get a certain number of points based on their ranking. These points are “summed” with the boat’s Rating.
If you arrive first because your boat is lighter for instance, the added Rating Value may put your boat at the second or third place depending on the Rating of the other boats.

The funny of that, is that after many many races, one boat will be identified as the best of his category and not because is winning all the times, but more because is always well ranked, among the capacity of the skipper.
The ability consist of course to make the right parameters choices in conjuction with the personal skipper skill.
With the variability allowed by the Rules, at a certain moments all the boats will copy the retained best and they will end up with the same Rating !!! This phenomen will be the way to obtain a “monotype” issue after the events and with the assurance that this boat will offer the best performances achievables with that design in terms of weight, sail area, etc…
Hope , Eric to have been of any help !

AMYA is currently governed by US Sailing, which is governed by ISAF, which is (I believe) the holder of the Portsmouth handicap numbers. I tried through US Sailing to ask for someone to allow me to have/use the numbers and formulas to begin a rating system for R/C boats - and obviously I didn’t even get a response (no surprise) so if someone wants to “press” the issue, I suggest pushing it to the AMYA Board - especially considering the number of new boats/classes showing up each year, which will either need to be included or excluded and only a limited number of recognized classes. Back when I was volunteer for Model Yachting publishing group, I think it was pointed out the US (by far) had the most number of recognized classes when compared to other countries. In some countries, only 3 or 4 classes are officially recognized.

So big question - does a county’s “authority” want to reduce, maintain or increase the number of classes ----- which in turn would answer how do all classes race together?

Just need some volunteers to work to get ISAF to provide (or allow) a handicap system to be developed with 'their" knowledge and assistance.

Hi Dick,
I suspect that will be “mission impossible” for RC models because too many variables in each single class and too few races together.
How to compare a class M of 4.7kg racing in California with another M of 4.6kg racing in New Jersey with another M of 4.2kg racing in Missoury ?
With an enormous effort collecting racing data from “Close Rules” model like IOM may be still possible after several years, similarly with monotype hull models where only sail area may change.

The dimensional rating is much easier within the same class and not only as far is dimensionally similar.
Certainly, a class M could not compete with the RG65, but rather with a ac120.

The exposed Safalero Rating formula worked very well in Italy for some years until was applied :

major significant data are :

  • higher the bulb weight > higher Rating figure…because it provide better righting moment
  • less beam width > higher the Rating figure…because reduce the main immersed section area and drag
  • higher sail area > higher the Rating figure…because offer more propulsion power
  • lower hull/rig weight > higher the Rating figure…because increases the overall sail area /weight ratio

summarising :
a boat with the highest permitted bulb weight , the minimum hull+rig weight and the maximum sail area and narrower beam, will produce the highest Rating figure .

The highest Rating figure added to the Ranking points will induce the “penalities” application of the Rating and the loss of ranking positions.

To remark that all the favourables parameters combinations will produce an OUT Rating.
assuming an ac120 with :
LOA… = 120cm… the max LOA (fixed for ac120)
SA… = 80 dm²… the max Sail Area
Bulb&Fin. = 3.2kg… the max bulb & fin weight
Hull&Rig… = 1.0kg… the lowest hull & rig weight
Beam… = 16cm… the narrower beam

we obtain :

1st part of the formula : 120 (LOA) + 80 (SA) - 16 (beam) x 0.2 = 36.8
2nd part of the formula : (3.2 + 1.0) / (3.2:1.0) = 1.31
Rating = 36.8 - 1.31 = 35.49 This boat could not race even with a Rating widen to 35

parameter’s variability for an ac120-CE :

Sail area… from 60 dm² to 80 dm²
Bulb&Fin… from 2.9kg to 3.1 kg
Hull & Rig… from 1.0 kg to 1.5kg - (this is a free parameter depending on the skill of the builder and material used)
Beam width… from 16cm to 25cm
LOA… from 115 cm to 129 cm - (as per ac120 and class M limits)
LWL… not included (yet) - but ac120 LWL maximum lenght compulsory

Up to the skipper to find the parameter’s compromise to stay inside the Rating figure range .

This approach will avoid to design boats too differents each other and pretending racing under the same Ranking system.

Assuming that the best boat is in the hands of the best skipper, there is no need to make a racing campaign ! the winner will be known before the start !!!

This is what I can see so far, practical calculations are demonstrating the full feasibility, nevertheless I’m ready to condider others formulas so far can be easily implemented as the above one !

Actually, I’m thinking that a wider range from 31 to 35, instead of 31 - 34 , will cope better with the “variability” of the parameters including Class M and AC120-CE and the points allocated to the ranking positions may need some considerations too.



Hello Claudio,

Thank you for the explanation on how the ratings work in a regatta. I was trying to make it way more complicated than it really is - typical for me :slight_smile:


btw Eric, as Alan remarked , the Rating formula is applied only to fleet races. The selected finalists for Match Races are using the normal system, first arrived get 1 point .

Good question Dick ! Excuse my ignorance on this point if I have it wrong, but outside the U.S I’m not aware of any other countries having an “authority” ??

Here lays the heart of our problem (outside U.S) no-one coordinating different classes in same country to initiate these ideas ! it is left up to individual crusaders like Claudio !

Cheers Alan