MEASUREMENT PROCEDURE FOR DABCHICK CLASS BOATS
Dabchicks shall be measured by a SAS appointed measurer. In order to
achieve consistent and accurate results the Measurers are to follow the
procedure laid down here. The measurement is intended to be made in the order
given on the official measurement form.
The object of these instructions is to ensure that all boats are measured in
exactly the same way.
Equipment needed for the measurement of a Dabchick :-
1) SAS measurers' stamp.
2) A 5 metre tape.
3) Callipers of the outside type.
4) One 1.5 metre straight batten.
5) Weighing machine capable of weighing up to 50kg accurate to 0.1kg.
6) Copy of the class rules and the measurement form.
7) A copy of the plans and the IYRU sail measurement rules may also be useful.
The hull shall be complete when presented for measurement. The Dabchick class
yacht must be built according to the class rules, the object being to ensure
that all yachts in the class shall be as nearly alike as possible.
The measurements shall be taken in accordance with the official rules.
Measurers shall look for variations in measurements from the rules even if
not specifically mentioned in the measurement schedule.
Measurers may ignore normal wear and tear on old boats if, in their opinion,
the basic speed is unaffected.
If the measurer considers that there has been an attempt to depart from the
design measurements, he is to report the matter to the Association. Tolerances
are laid down to allow for errors in building, but intentional variations
within these tolerances are not allowed.
Unless otherwise specified all tolerances shall be within +/-15mm.
To help in expediting the issue of the measurement certificate, the measurer
could assist by requiring the owner and/or builder to rectify any errors
which are outside the permitted tolerances, prior to completing the
measurement schedule and forwarding to SAYRA.
If requested, the sail number may be allocated on completion of the hull
measurements, provided there are no constructional errors.
The measurement must be started with the boat the right way up.
The overall length is measured on the centre line of the boat .
The next item is to mark the beam measurement stations on the deck.
Beam measurements exclude any rubbing strake.
Perimeter of one half of bow is measured round the bow from centreline to a
point 3300mm from the transom. It is a maximum measurement.
HULL UPSIDE DOWN
Mark the positions for measurement on the bottom, making the measurements on
a line parallel to the centre line of the deck, on the centre line and sides.
Use the straight edge batten, as in the diagram. Fibreglass tape over the
joints should be accommodated within the prescribed measurements.
A guaranteed weighing machine should be used. The measurer must ensure that
the hull is dry and free from sand etc. All loose gear, not permanently
attached to the hull, must be removed prior to weighing.
Mass correctors must be fitted adjacent to the mast step.
BOAT ON ITS SIDE
The daggerboard and rudder projections below the hull are measured on a line
at right angles to the deck centreline.
Callipers should be used to check the thickness of the daggerboard and rudder.
When measuring the spars, it should be noted that intentionally bent spars are
prohibited but this does not preclude tapering.
Sails are to be measured in accordance with the IYRU sail measurement rules.
The following notes are obtained from the 1993 version. In the case of doubt,
the latest full instructions should be referred to, or the technical committee
The "sail" shall include headboard, clewboard, reinforcement, bolt ropes.
It shall not include parts of fastening such as cringles, hanks, slides etc.
which are outside the edges of the sail.
When measured a sail shall :-
be dry, not be attached to spars or rigging, have all battens removed,
have just sufficient tension applied to remove wrinkles across the line of
measurement being taken.
Sails shall be made of single ply woven fibre cloth. When a woven ply is torn
it will be possible to separate the fibres without leaving evidence of film.
Reinforcement of sail is permitted only at a corner of the sail and at the
Cunningham. Reinforcement size is measured from the relevant corner
measurement point or Cunningham.
Primary reinforcement ( unrestricted number of additional ply ) for the
Dabchick shall be less than 250mm for all sails. Secondary reinforcement
( not more than two additional ply of the same material as the body of the
sail ) for the Dabchick shall be less than 750mm for all sails.
Head point The intersection of the luff extended if necessary and the line
through the highest point of the sail perpendicular to the luff.
Clew point The intersection of the foot and the leach, each extended if
Tack point The intersection of the foot and the luff, each extended if
Mid foot point The point on the foot equidistant from the tack point and
the clew point
a) The length of the leech for the purpose of measurement shall be the
straight line distance between the head point and clew point of the sail.
Maximum length 3810mm.
b) The midpoint of the luff shall be determined by folding the sail upon
itself, with the head point even with the tack point.
The midpoint of the leech shall be determined with the head point even
with the clew point.
The half height width folded shall be the distance between the midpoints
of the luff and the leech with the sail laid on the floor with just
sufficient tension to remove the wrinkles. The bolt rope shall be
excluded. Maximum measurement 1485mm.
c) The headboard shall be measured square to the mast, excluding bolt rope
and shall not exceed 115mm.
d) Battens shall have a maximum length of 610mm.
e) Dabchick insignia - minimum size 200 x 140 x 30 mm
f) Sail numbers shall be :
clearly visible, legible, and of a single colour which strongly contrasts
with the sail,
capital letters and arabic numerals with line that are continuous,
upright or with a slope of not less than 10:1 (10 vertical to 1 horizontal )
relative to a line through their base.
a) The length of the luff ( maximum 2667mm ) shall be the distance between
the head point and the tack point.
b) The length of the leech ( maximum 2667mm ) shall be the distance between
the head point and the clew point.
c) The length of the foot ( maximum 1473mm ) shall be the distance between
the clewpoint and the tack point.
d) Centre measurement ( foot median )
The foot mid point shall be determined with the tack point even with the
The length of the centre measurement shall be taken as the distance
between the head point and the lowest edge of the sail at the
foot mid point.
This measurement shall not exceed 2720mm.
e) No battens or headboards are allowed.
INTERPRETATIONS by the TECHNICAL COMMITTEE
To aid Measurers the DASA Technical Committee interpretations on various
Class Rules are given below :-
21 The general tolerance of +- 15mm is interpreted to mean 15mm above or
below the measurements stated in the rules, except where a maximum or
minimum measurement is stated. ( 1/96 )
22b For this rule the 'jib attachment' is interpreted as the fitting to
which the jib and forestay are attached to the deck. ( 1/96 )
22f This rule is interpreted as follows, the deck should not deviate in the
vertical plane from a straight edge, if such a straight edge were placed
along the centre line on the deck, from transom to bow, taking into
account the general tolerance allowed. ( 1/96 )
31 The main sheet block, and any fitting that can be removed from the
chain plates that are permanently attached to the boat ( glued, bolted ),
must be removed before the boat is weighed. ( 1/96 )
If the boat mass is to checked ( at an event and not for measurement
certificate purposes ) the boat may be weighed with the main sheet block
as long as due allowance is made for the block mass. ( If the boat is
only 500gm over the allowed mass, then the measurer can ask for the
block to be removed. If the boat is 5Kg over - the block mass is
inconsequential. ) ( 1/96 )
33 As the Class Rules do not specify material of construction - only that
the daggerboard float - wood covered by GRP would be acceptable.( 1/96 )