Different Sailing Boats at the same Regatta By ClaudioD

Introduction :

The World of Sailing Boat Racing is often a complicated matter.

National and International Rules has been established and all dealing with Rating.

I was fortunate and happy when racing with my vintage wooden Dragon with 300kg excess of weight, most of the time finishing before last. Rating was an unknown word since all Dragons where coming out from the same moulds except mine and nobody care.

Today, when different Sailing Boats like to participate to the same Regatta at the same time, there is the need to establish a form of ‘handicap’ for each participating boat in order to reach a final Standing Classification.

Rules has been published were, not only the Boat itself was Rated, but also the capability / skill of the single skipper as well the full crew.

Monotype Boat Races do not need a predefined Rating, the first arrived is the winner or at least until now since also there one could suggest that the Crew Skill could be Rated !

Is not only matter of Prestige with a Cup in the hands, but also a lot of money is involved.

For those interested, here below a short list of Documents addresses, all dealing with Racing Boat Rating :

1. https://en.wikipedia.org/wiki/Performance_Handicap_Racing_Fleet

2. https://en.wikipedia.org/wiki/International_Measurement_System

3. https://www.ircrating.org/technical-a-certification/rule-a-definitions

4. http://www.orc.org/index.asp?id=1

5. http://classicratingformula.com/crf-mkii-formulae/

Many more can be found on the Web starting with the:

https://en.wikipedia.org/wiki/Universal_rule

For those interested many books are available about Classic Yachts

Check on the Web and Amazon

What about RC Sailing Models ?

RC Sailing Models World is a bit different, most of the time regattas are organised around the same boat category.

Class M with M, Class IOM with IOM, RG65 with RG65, etc.

Under these conditions the word RATING has no meaning.

Difficult today to imagine that the multi-world champion would receive a compensatory “Rating” or “Handicap” in order to give others skippers the opportunity to win a race.

Most of the RC Sailing Boats are governed by Rules.

The most ancient rating, 100 years old, is still used for the 10R Sailing Model:

R = LWL(mt) x S (m²) x 8

R shall be less or equal to 10

In Italy several years ago a Model Club was developing scale RC Models of the America Cup.

Since not all America Cup boats were using the same dimensions and Sail Areas, the Club designed a Formula called:

Safalero Cup Rating

Rating = [(SA + LOA- Beam) x 0.2] – (Bulb +Hull) / (Bulb /Hull)

Rating accepted by the AC120

From 31 to 34

Where:

• Bulb Weight in Kg

• Hull weight without Bulb in Kg

• LOA in cm

• Beam in cm

• SA in dm²

In this formula the Hull Draft is not taken into account.

The Safalero Rating Formula was developed for earlier IACC RC Scale Models.

At the present, with the new AC120 models Rules, the Safalero Rating method is dismissed since the New AC120 Class Rules introduced detailed parameters more close to a monotype.

I’m of the opinion that the Safalero Rating could be modified by adding the missed parameter like de Draft as well introducing the need to remove the ballast momentarily in order to measure the separated weights of Hull and Ballast.

In this case the New Safalero Rating formula could read:

Rating = [(SA + LOA + Draft – Beam) x 0.2] – (Bulb +Hull) / (Bulb / Hull)

PROPOSAL

New Rating Formulas for Vintage / Classic RC Sailing Models

Assuming to organise a “Vintage” RC Sailing Model regatta, one could start by checking what was already done until now.

A Rating Rules shall be as simple as possible where no argumentations can be introduced including the Age of the Skipper …!

The Vintage RC Sailing Models can be of various nature according to the time they where developed.

So far some simple elements are defined like the LWL and Sail Area as well the Displacement, all the rest being of minor importance at Scale Model level.

It is common sense that the SA and DSPL for a Sailing Boat are the major parameters. The fastest boat will be the lightest with the greatest sail area.

This is true up to a certain point, particularly under low wind conditions.

For instance one of the major difficulties met by the Measurers is to check the LWL that cannot be performed without a water basin.

Thus one could decide to use the LOA at the condition that the overhangs are mandatory in the general Racing Rules to characterize the Vintage Model Boat.

In this case all the Classic Boats with Long keel like: J-Class, 15mt Class, 12 Metres Class, 8mt Class, Dragon, Star, etc, could be considered candidates to race together under a dedicated Rating Formula.

Rating values will be added to the Regatta Final Score to establish the Final Standing as was the case for the Safalero Cup Rating.

The simplest Rating Rule so far identified is the one used for the 10R Class.

With a simple modification this Rule can be recalled 100R and can be used for the RC Vintage/Classic Models in the length range from 100 to 120cm and 6000cm² to 8000cm² of Sail Area :

R = LOA x SA / 8500 = 100

Where :

• LOA in cm

• SA in cm²

Displacement not considered since intrinsic to the Scale Factor used. If necessary scale could be modified

A discussion about Rating started some years ago with my proposal in 2012 on Forum:

www.rcsailing.net

See tread:

http://www.rcsailing.net/forum1/showthread.php?6560-New-mixed-class-quot-Racing-formula-100R-quot/page2&highlight=100R

At that time, the discussion was mainly concerning the AC120 Models Old and New and others of similar lengths.

At that time was considered also the substitution of 10R formula with the 100R formula, I believe, that 100R is still the simplest formula to define a useful scale taking into account the LOA instead of LWL and Sail Area only

Modified Safalero Rating containing the Draft and the 100R formula are potential candidates to organize races with different RC Models within similar size.

By checking with Scaled Model’s drawings and Scale Factors will can demonstrated the feasibility.

At RC Sailing Model Clubs

An RC Sailing Model Club whishing to renew or introduce a new Model Class in his Fleet shall consider various aspects.

The Classic Model Class is composed of various options from Gaff Rig to Cutter Rig.

The Classic or Vintage requires particular attention since their construction demand more skill and are heavier than most of modern sailing models of the same length.

This is due to the Long Keel and Rigging most of the times made with wood.

Decks are also often made with wood.

Before any Model size choice a detailed weight Budget shall be established including the Bulb/Boat ratio above 62-65%.

Today with the introduction of Carbon Square Tubes, one could make a Mast covering the Carbon Square Tube with wood stripes. The result will be a lighter and stronger Mast. Similarly could be done for the Booms.

The marked is actually offering wooden plates for Decks with alternate stripes clear and dark of 1.6mm thick and 47g for 7cmx100cm.

As a guess a Hull Displacement of 4.5kg for120cm long Hull should be considered.

Expert modeller can build a 120cm long Classic Model with less as shown below:

Above budget may appear optimistic and this is why 4.5kg are considered as reference point.

Important:

When scaling from real dimensions it is important to bare in mind the Scale Effect that is often forgotten:

• Linear dimensions as per Scale Factor

• Surface dimensions as per Square of the Scale factor

• Volume dimensions as per Cube of the scale factor

1. To avoid design deformations of the Hull in order to maintain the sailing beauty and performances is recommended to modify the Hull Volume Shape to the minimum.

2. Another contradictory aspect concern the Hull Draft that shall favour the righting moment or lateral stability. Most of the time the lateral immersed profile is modified in order to lower the Ballast position inside the Keel.

3. Care shall be taken since the Profile modification is going to modify the Total immersed Volume – DSPL . Therefore the Scale may be a little different as shown later.

4. Verification shall be carried out to check the Static Stability against wind force using the Bernoulli formula.

5. Other may use a so-called removable Prosthesis, a sort of Add-On Fin with a Bulb.

This option allows a scaled model with the original lines.

Add-on Fin and Bulb are used only for the races.

Observations about Scale Effects:

1. Vintage long keel Models are generally suffering of an excessive heeling and this because of the limited Draft. Care shall be taken to ensure adequate Ballast/Boat Ratio.

2. Before going any further in the next page there is a Table used as an example showing the ‘Scale Effect’ from a real Boat to a Scale Model.

3. For the purpose all Models have a Hull length of 115cm.

4. Interesting to see the bottom line indicating the ratio of Sail Area versus Weight.

5. From above “Scale Effect’ table” it can be seen that Tuiga is the heaviest model if the 115cm long hull is maintained, while the Dragon is the lowest.

6. Another observation shows that the 12Meter Columbia has a bit more sail area per gram.

Out of these first observations, personally I would modify the Tuiga Hull Scale in order to reduce the excessive Sail Area

The Tuiga scale modification will reduce the Sail Area to be closer to the Columbia Model.

J Class Enterprise is suffering of Hull length and Sail Area per gram.

JClass Scale should be modified.

Dragon is the lowest in all domains therefore not competitive, if retained to be part of a Fleet will accuse an important handicap.

Practical applications

Here below some examples of Rating formula application to Vintage Models with

Long Keel and Overhangs.

Here the 100R applied to the Tuiga Model:

Scaled down to 1: 20.5 to obtain a LOA of 113cm

R = 113 x 8809/ 8500 = 110.6

Obviously the above Rating is to high and out of limits therefore the designer shall adjust the parameters to enter in the Rating of 100 by reducing Sail Area or shortening the Hull Length.

Here with a reduced SA

R = 113 x 7522 / 8500 = 100.00

(Simple to find out: 100×8500/LOA = Sail Area or 100×8500/SA = LOA)

Scale 1 : 20.5 produce a DSPL of 4.52kg

°°°°°°°°°°°°°°°

Here the 100R applied to the Columbia Model

R = 121 x 7025 / 8500 = 100.00

Reducing the LOA in order to increase the Sail Area will produce a lower Displacement.

It may be necessary to simply increase instead the Sail Area

Tuiga has large Sail Area compared to Columbia, this late will have better lateral stability. Tuiga has interest to achieve the same performance by reducing the Sail Area

Total Tuiga length 133cm including bowsprit and total Columbia length 121cm

Scale factors Verification with Tuiga 15mtJI

The modeller will have a choice according to his skill to select the scale that provides a comfortable DSPL. The scale 1.21 offers 4.20kg. Sail Area may require a reduction to satisfy the lateral stability.

Tuiga with 113cm hull length (LOA)

Sail Area is too large as expected

Here the scale is 1:20.5. The SA of 8809cm² is too large to ensure a good Lateral Stability. SA shall be reduced as indicated before

Similar exercise is depicted with another Model like the Columbia 12mtSI.

Columbia 12mJI Scale factors:

Possible choice for the Columbia 1958 12mtJI with scale 1:17.5

Rating: 121 x 7025/ 8500 = 100.00

Columbia is offering an easier Rig construction.

The SA may need to be increased for both Main and Jib include longer LOA

Possible choice for the Columbia 1958 12mtJI with scale 1:17.5

Rating: 120 x 7084/ 8500 = 100.00

Columbia is offering an easier Rig construction.

From previous drawings it is evident that Columbia Scaled Model misses some Sail Area and Tuiga has too much Sail Area typical of those classes.

88dm² against 58dm².

Displacements remain the same at 4.5kg for both Models.

Modified Safalero Rating application

Here I’m going to apply he Modified Safalero Formula to the above illustrated Plans:

Rating = [(SA + LOA + Draft – Beam) x 0.2] – (Bulb +Hull) / (Bulb / Hull)

When applied to Tuiga of 113cm LOA

R = (88 +113+14.5– 20) x 0.2 – (2.8kg +1.7kg) / (2.8kg / 1.7kg)

R = 39.10 – 2.74 = 36.36

When applied to Columbia with 121cm LOA and increased Sail Area :

R = (62 +121 +15.5 – 21) x 0.2 – (2.8kg +1.7kg) / (2.8kg / 1.7kg)

R = 35.50 – 2.74 = 32.76

Redrawing the Tuiga Sail Plans down to less than 69dm² we get

R = (68.7 +113+14.5 -21) x 0.2 – 2.8kg +1.7kg / (2.8kg / 1.7kg)

R = 35.04 – 2.74 = 32.30

Trial with Sail Area of 68dm² for Tuiga:

Here the reduction of the Tuiga Sail Plan to 68.7dm² .

May be that Columbia do not need to increase her Sail Plan

Remark : From aesthetic point of view is very acceptable even without the Top Jib.

Increased Draft depicted in light blue.

Conclusions

Two Rating formulas used for comparison:

1. Modified Safalero Rating previously used for AC Models

2. 100R created for the purpose and derived from the 10R Rules

Observing the ‘Scale Effect Table’ at page 7, the LOA is 115cm for all models,

Can be observed that:

Model LOA cm SA cm² DSPL kg SA/DSPL

Tuiga 115 9250 4.87 1.89cm²/g

Columbia 115 8461 4.20 2.01cm²/g

Enterprise 115 6835 3.87 1.76cm²/g

Dragon 115 3620 3.62 1.17cm²/g

1. Tuiga shall reduce the Sail Area by reducing the scale to reach 4.5kg.

2. Columbia could increase the LOA and probably the Sail Area by changing scale.

3. Enterprise could increase the LOA as well the DSPL by changing scale.

4. Dragon is too far from the above models in term of dimensions.

Two models analysed: Tuiga and Columbia.

• With Modified Safalero Rating and with the introduction of modifications, mainly on the Tuiga SA, we get two values rather close each other:

32.76 for Columbia and 32.30 for Tuiga.

Rating range could be widen from 32.00 to 34.00

• With the 100R formula

Tuiga with : LOA 113cm and SA 7522cm²

Columbia with : LOA 120cm and SA 7084cm²

This is the privilege or the 100R Formula where one can choose the LOA versus SA , but very careful because the choice have a direct impact to the DSPL.

Some potential Classic Yachts for Vintage RC Models :

15M JI : Tuiga, Viola, Lady Anne, Pesa, etc.

12M JI : Columbia, Vim, Vanity V, Valiant, Trivia, , Seven Seas, Cintra, American Eagle,

10M JI : Tonino, etc.

JClass : Enterprise, Velsheda, Shamrock, Endeavour, etc.

and many others including Ketches

My conclusion:

• The Modified Safalero Rating is rather tolerant from 32 to 34.

• The 100R is more demanding since has direct impact on DSPL