PART 7

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.

 GENERAL

 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.

 HULL MEASUREMENTS

 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.

 HULL MASS

 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.

 EQUIPMENT

 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 GENERAL

 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 
 consulted.

 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.

 Definitions:-

 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 
              necessary.

 Tack point The intersection of the foot and the luff, each extended if 
               necessary.

 Mid foot point The point on the foot equidistant from the tack point and 
                  the clew point

 MAINSAIL

 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.

 JIB

 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 
    clew point.
    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 :-

 RULE

 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 )