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1. Preface
a. Purpose. The purpose of this rating is to enable multihulls of various classes to race together. To keep
development under control but making research possible.
b. Validity. These rating regulations are applicable at all races where various classes partake together,
but one racing result is desired.
2. Rule adminstration
a. Authority. The rule is published under authority of the KNWV. This is done on the website:
www.texelrating.knwv.nl
b. Development. The KNWV has the right to amend the regulations if necessary.
c. Interpretation. The measurer has the right during the season to give an interpretation of any part of
the text or on any innovation.
d. Reference text. The english version of the text has priority above any translation.
e. The spirit of the rule. In case of doubt about any part of the text of the rules the meaning, that is to
say, the spirit of the rule counts, not the letter.
3. Rating
a. Determination
a.1. Basics
Ratings will be determined for all types of multihulls on measurable data, guaranteed by the class
organization, the builder, using formulas, verifiable by anyone. A Texel Rating (TR) is calculated,
with the formula given in appendix 5, using normal rules of rounding.
a.2. Abbreviations, formulas and calculations used :
Hulls
AOC = aft overhang component
FOC = forward overhang component
LOA = length overall
RL = rated length LOA - AOC - FOC
Weight
RW = rated weight WC + WS
WC = weight crew
WE = weight declared equipment
WM = weight boat without equipment
WS = weight complete boat WE + WM
Sails
EG = efficiency percentage genoa (jib)
EM = efficiency percentage mainsail
MSAG = measured area jib (genoa)
MSAM = measured area mainsail
RSA = rated sailarea RSAM + RSAG + RSAS
RSAG = EG * MSAG * 0.01
RSAM = EM * MSAM * 0.01
RSAS = MSAS * 0.11 (for open multihulls)
RSAS = MSAS * 0.07 (for cabin multihulls)
VLM = vertical projection of luff of main
VLG = vertical projection of the luff or leech of the jib/genoa. It will be measured alongside the
mast. In practice :
VLG = luff * 0.94
SMG = distance between middle of luff and leech of the spinnaker.
SF = length foot of the spinnaker
SL1 = length luff of the spinnaker.
SL2 = length leech of the spinnaker
a.3. Determination of WC, Weight Crew For calculation purposes : weight each crew
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LOA boat <= 4.00 m:
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65kg
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LOA boat <= 4.80 m:
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70 kg
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LOA boat <=4.80 m:
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75 kg
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If the total sailarea >= 11 m2, than for crew one-man boats always take 75 kg.
b. Centerboards
The rating for boats not having an efficient centerboard is calculated by raising the unrounded
ratingnumber with 3 %. Afterwards the ratingnumber will be rounded as described in appendix 5.
4. Attribution
a. Competence
The ratingnumbers for small open multihulls used to determine racing results will be issued by the
National Authority.
b. Responsibility of classes/builders.
For each new class and after any substantial modification of existing classes, the class organizations
and/or the builders, or importers are responsible for offering facilities to the National Authority to
make it possible for them to let a measurer check and verify boats and equipment, to aid in
determining a rating.
c. Modified types
Each modified boat of a design which is a commercial property, or has been built according to a model
which is a trademark, will be permitted to race only when and after the following written agreements
can be produced.
c.1. Agreement of the owner of the plans with the modifications made. (designer, classorganization,
builder, importer).
c.2. Listed on the Texelrating website or A rating certificate issued by the National Authority
5. Validity
The tables with ratings issued by the National Authority will be valid from the first of March of the year in
which they are brought out.
a. Modifications of ratings during the sailing season
a.1. Based on reports of the measurer and after further advice from the rating committee the National
Authority can change (that means inmost cases lower) the rating of any type of multihull, when
the dimensions of the design deviate substantially from the original measurements. The results
of the remeasurements will be published on the website.
a.2. Deviations from the maximum and minimum dimensions in one direction or another from the
values given on the official lists never will lead to a reduction of the rating. (a higher number).
b. New classes
For new classes, appearing during a season for the first time, ratings will be published on the web site:
www.texelrating.knwv.nl as soon as a rating has been determined. If less than 3 boats of a class have
been measured, or one boat only, of a new or modified design, the catamaran is marked in a column
with **, signifying a one-off.
6. Inspection during races
During the season the rating committee of the National Authority may inspect boats on the measure-
ments and weights used in the formulas.
7. Weights
a. WS = weight of the boat
a.1. The measured weight has to be equal or higher than the weight used in the calculations for the
rating.
a.2. Extra weight can be necessary to bring WS in agreement with the WS used in the formula.
a.3. Extra weight has to be dry, has to be fixed to the boat, but must be demountable, to admit
checking. It may not exceed 4 % of WS.
a.4. If extra weight is permitted than the character and weight of the additional weight(s) must be
recorded in the certificate.
b. WC = weight of the crew
c. RW = WS + WC
d. Minimum weight of boat and crew must be in agreement with the class rules.
8. Responsibility of the owners
a. Conformity
It is the owners resposibility to keep the boat in agreement with the specifications (maxima and
minima) given on the published lists.
b. Class regulations
Boats need to be in agreement with classregulations, if available.Â
9. Definitions and ways of measuring
All dimensions will be given in mm., m., m2, and kg.
a. WS = weight of the boat including all sailing equipment
a.1. Sailing equipment
Sails, spars, rudders, centreboards if present, normal fittings, hulls.
a.2. Safety equipment
a.2.1.With one or both hulls flooded the boat shall lengthwise float evenly while supporting a dead
weight of 70 kg. on the trampoline.
a.2.2. A measurer or race organizer may demand a floatation test to be carried out.
b. Weighing regulations
The boat need to be dry and clean when being weighed. How the weight will be determined is
described in appendix. 2.
c. Length : How the length overall (LOA) and the rated length (RL) will be determined is described in
appendix 3.
d. Sailarea : How the sailarea (main, jib and mast) will be determined is described in appendix 1.
- MSAG = Area genoa or jib
- MSAM = Area mainsail including mast when swivelling
- VLM = Vertical projection luff mainsail. That is the distance measured along the mast in a straight
line between the highest point of the sail normally hoisted and the lowest point reached when the
downhaul is used.
- VLG = Projection luff genoa or jib. That is the vertical projection of the luff or leech of the jib/genoa.
That is the distance between the horizontals on the mast, taken from the highest point of the
jib/genoa towards the lowest point of luff or leech whatever. It will be measured alongside the
mast. In practice : VLG = luff * 0.94
10. Spinnaker and spinnakerboom
a. Definition of a spinnaker
Each triangle sail not being a mainsail or genoa is a spinnaker. The condition is that SMG, the length
measured along the rounding at half height >= 75 % of footlength SF.
b. Stiffening systems
It is forbidden to stiffen the spinnaker by leechlines or battens.
c. MSAS = area spinnaker or reacher
- Calculation area spinnaker MSAS. The regulations including how to measure and calculate the
spinnaker area will be described in appendix 4.
d. Ratingnumber applied when using a spinnaker.
The lowering of the rating when a spinnaker is used will be described in appendix 4.
Texel regulations, Appendix 1
Determination of the sailarea
The real sailarea is determined by one of the usual methods.
Calculation of MSAM and MSAG, area mainsail, area jib respectively. From both data RSA, the effective area, will be calculated by using an efficiency percentage. That requires the determination of the aspect ratio A. This A is the result of the calculation : Vertical height of the sail (VLM for the main and VLG for the jib/genoa) squared, divided by the area. formula :
A = VLM * VLM / measured area
If a mast is used which is swivelling, with a section which is not a circle then the area of the mast is added to that of the main, before the factor A is determined.
Area mast = 0.5 * maximum circumference * VLM
eff. % = 40.1 + 18.31 * A - 2.016 * A 2 + 0.07472 * A 3
RSA = real sailarea * eff. % * 0.01
Translation of some of the texts given in the drawings.
Dimensions P1, P2 and P3 can be positive a well as negative.
With OM is meant the complete circumference of the mast at the point with the maximum circumference.
TEXEL REGULATIONS , Appendix 2
Determination of the boat weight
1.0. Standard equipment
Boats have to be weighed with the complete standard equipment on board.
standard equipment means a.o.
centreboards, rudders and rudder equipment
jib, jibsheets and barberhaulers
main, mainsheet and tack downhaul
helm and joystick
No part of the equipment is:
Anchor
spinnaker and spinnaker equipment 1)
towing line
(Boats which have standard a spinnaker still have to be weighed without the spinnaker and all spinnaker equipment, in order to
calculate the rating in the same way as for all boats that use an optional spinnaker.)
2.0. Method of weighing
Boats have to be weighed in dry condition. Hulls have to be dry inside and out and free from sand.
Weighing can be done in the following ways:
1. Hoist them on a weightbeam. In that case it is important to have the boat hoisted horizontal and the
windage as small as possible. It is recommended to have the mast lowered.
2. Place the boat on three (3) weighing scales. The boatweight is the sum of what the scales measure.
The process has to be done 3 times, changing the position of the scales each time.The average
weight of the
3. measurements is the correct weight. It is important to keep the boat horizontal, have the scales on
a hard stand and the windage influence a small as possible. Like in case 1, it is recommended to
have the mast lowered.
TEXEL REGULATIONS , Appendix 3
Determination of the rated length
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1.0. LOA, Length Over All
The length over-all is the horizontal distance from the most forward point to the farthest point at the
stern of the hull. Lines through these points have to be measured both from vertical positions.
Rudders and rudderequipment not to be included in LOA.
1.1. FOC, Forward Overhang Component
That is the difference at the bow between the most forward point and the forward end of the rated
length. If the bow is vertical or hanging backward than FOC = 0
1.2. AOC, After Overhang Component
That is the difference at the stern between the most afterward point of the stern and the aft end of the
rated length. If the stern is vertical or leaning forward than AOC = 0
2.0. RL, Rated Length
The rated length is the horizontal distance measured as a straight line at two/third (2/3) of the height
of the hull at the location of the sidestay (shroud) or the mastbeam, whatever gives the highest value
Horizontal here means parallel to the deckline.
RL = LOA - AOC - FOC
TEXEL REGULATIONS , Appendix 4
Determination of the spinnakerarea 
For boats up to 22 ft. (6.71 m.) provided with a spinnaker the rating will be lowered with 4 points, if the
spinnaker area and the spinnaker boom satisfy the following conditions.
1. Maximum spinnaker area.
Boats up to 16 ft <4.87 m.: 17 m2
from 16 up to 19 ft. >4.87 m. <= 5.80 m.: 21 m2
from 19 up to 22 ft. >5.8 m. <= 6.71 m.: 25 m2
For boats with a length of more than 22 ft. (6.71 m.) depending on the spinnaker area a ratingnumber
will be calculated, using 11% of the area for RSAS.
Spinnakers have to be measured and calculated as described in the articles 3,4,5 and 6 of the ISAF
publication Measurement and Calculation of sail area.
2. SMG > 75 % SF. SF is the width of the spinnaker at the foot and SMG the width at the midgirth.
A spinnakerboom may not be longer than the longest distance between the fixing point on mast or
mastbeam and the theoretical uttermost end of the boat, + 80 cm. Contrary to ISAF rule 64.2 it is
allowed to fix the spinnakerboom to the forward beam.
 Measuring and calculating the spinnaker area.
The following dimensions have to be measured along the sides, these sides stretched normally.
- SL 1 = luff
- SL 2 = leech
- SF = foot
- SMG = straight line connecting the middle of luff and leech.
The area is calculated as follows :
- MSAS = SF * (SL1 + SL2)/4 + (SMG - SF/2) * (SL1 + SL2)/3
- SMG >= 75 % of SF
- RSAS=0.11 * MSAS
- RSAS is used for boats with a length > 22 ft (6.71 m) and for cats in case MSAM > maximum area allowed.
All spinnakers have to be measured by a measurer acknowledged by the KNWV and has to be stamped by the measurer with the following information :
- date of measuring
- spinnaker area
- name and/or nr. of the measurer
- paraph of the measurer
TEXEL REGULATIONS , Appendix 5
Rating formula
TR rating = 100 / (0.99 * RL 0.3 * RSA 0.4/ RW 0.3)
The rating number is rounded to an integer of two or three digits, using the normal rules for rounding. The rating number for a design not using efficient centerboards will be calculated by raising the number before rounding with the correction percentage of 3. Then the number is rounded in the way described before.
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