PART 8

DABCHICK BUILDING NOTES

NOTES ON PROCEDURES


 These building notes are designed for the person who has never built a 
 Dabchick before, but may have useful tips for the experienced builder. 

 It is recommended that the first time builders have a careful look at
 competitive Dabchicks and talk to the owners of these boats with 
 reference to any good or bad pointers, and to do this frequently while 
 building their boat. 

 We suggest you study the sketch carefully.
 Preferably print it to a large scale while you read the notes.

 1.  MEASUREMENTS AND MATERIALS
  
 1.1  All measurements on the plan have a 15mm tolerance on either side,
      except where a maximum or minimum is stated. The wood sizes are only
      recommendations.

 1.2  4mm Plywood is recommended to keep the weight down, but 6mm plywood 
      may also be used with fewer stringers.

 1.3  ABE Epidermix 372 and 365 are recommended for the glueing work. 372 on
      stringers and 365 on the ply edges and surfaces.

 1.4  ABE Epidermix 389 is recommended for painting of inside of hull and 
      underside of deck.

 1.5  Material Requirements 

      a) Sheets of Marine Ply.               2440 x 1200 - 4 1/2 sheets

      b) Meranti centre board framing        15 x 12 x  900 - 4 of reqd.
      c)   "     forward spine framing       12 x 12 x 1500 - 4 of  " 
      d)   "     aft      "     "            12 x 12 x 1750 - 4 of  " 
      e)   "     edge stringers              12 x 12 x 3500 - 4 of  "

      f) Juluton bottom stringers            18 x 12 x 3800 - 4 of  " 
      g)   "       "       "                 18 x 12 x 2750 - 2 of  " 
      h)   "     top       "                 12 x 12 x 3650 - 4 of  " 
      i)   "      "        "                 12 x 12 x 2650 - 2 of  " 
      j)   "     seating stringers           12 x 12 x 1100 - 8 of  " 

      k) Formica                             600 x  600 - 1 of  " 
         ( suggested lining to centre board case) 

      l) Jig                               3700 long x 1100 wide
         with positions of bulkheads, A,A1,B,C,D,E and bow located in relation 
         to transom. A number of clamping devices are required to keep spine
         straight and flat on jig as well as maintaining cross frames in
         position.

         N.B. Ensure that jig has adequate strength to take heavy loading 
         from bricks/sand bags when fixing underside and deck to frames.

      It is recommended that the sheets of ply are weighed before purchase, 
      as their mass can vary considerably. A mass of less than 5kg per 3mm
      sheet is desirable. 

2.   PREPARATION

 2.1  Cutting wood for framing and stringers :

      If you have access to a radial-arm or circular saw and wish to cut the
      wood yourself, it is recommended that you save by buying rough wood in
      the size 30 x 150 x 3850 mm which can be cut down easily. 

 2.2  Plywood and cutting lines for the bulkheads : 

      4mm plywood is used for the bulkheads because it is lighter and easier
      to use accurately. Draw all the bulkheads on a sheet of plywood as shown
      on the plans.  4mm should be subtracted from the bulkhead measurements
      for bulkheads A,B,C,D,E and Transom to allow for the sides, deck and
      bottom skins. 8mm should be subtracted from the bulkhead measurement for
      bulkhead A1, to allow for butt joint backing plus sides, deck and 
      bottom skins. 

 2.3  Centreboard case :

      Varnish the inside of the centreboard case before you glue the two
      halves together. Formica glued to the centreboard ply can be used as an
      alternative to varnishing as it is maintenance free and provides added
      strength to centre board case.

      Glue top and bottom stringers to both sides of centreboard case
      allowing end projections to form joint with forward and aft spine.
      The stop-ends to centreboard case should be grooved to allow the ply 
      forward and aft spines to be securely glued to them.

      The two halves of the centreboard case plus the stop-ends are glued
      together. Ensure that the inside of the centreboard case is not twisted 
      when you glue the two halves together.

 2.4  Forward and Aft Spines :

      Use 4mm ply for the spines and frame the top and bottom with Meranti
      stringers. Provide semi-circular cut-outs for bulkheads. (These are 
      positioned at the measurement stations). Provide lightening holes taking
      into account the positions of the mast step strengthening and 
      jib attachment fixing blocks. 

 2.5  Bulkheads : 

      12x12 Framing strips should be glued to bottom of bulkheads to increase 
      the glueing surface with the bottom.

      a)  Cut the slots for the top and bottom stringers, side stringers, and 
          spine.

      b)  Cut holes in each bulkhead for about 40% of its area to reduce its
          mass. 

      c)  A 12x12 Jelutong framing strip should be glued round the edge of
          the transom to increase the glueing area. The strip should overhang 
          the ply and be sanded to correct angle to suit incoming angles of 
          sides and bottom. When putting in the stringers you should only cut 
          grooves in the Jelutong and not the ply.

      d)  Fit a central hardwood block on the transom for the rudder pintles
          or gudions. This should be slotted to provide for the fitting and 
          glueing of the aft spine to the transom.

     NB.  Extreme care should be exercised when forming this connection as
          the forces on pintles and gudions are very high!! 

          It is suggested that only the best pintles and gudions are used for 
          the rudder as cheap varieties are prone to failure. 

 3.  FITTING THE FIRST PARTS OF THE BOAT ON THE JIG

      Contact your Association to try to borrow a jig, otherwise make one.

 3.1  Ensure that the jig is level. 

 3.2  Glue the forward and aft spines to the centre board case and fix this 
      assembly to the jig,  ensuring that the top of the spine is straight. 

 3.3  Glue the bulkheads into the spine, then attach the bulkheads to the jig.
      Check that bulkheads are upside down and that the larger side of centre 
      board case is in front. 

 3.4  Glue the transom hardwood block to the aft spine and fix the transom
      into position on the jig. 

      NB. Ensure that bulkheads are at correct measurement stations and that
      the edge height of frames above jig are identical on either side. 

 4.  FITTING THE BOW TO THE JIG

 4.1  The Bow is made by laminating strips of 4 x 4mm ply = (16mm) together.
      The grain of the bow strips must be vertical to enable one to bend them 
      sufficiently. Adequate retaining stop blocks should be fixed to jig so
      as to ensure correct curvature of bow.

 4.2  Laminate the bow strips into position allowing outside ply to pass aft
      of the bulkhead E and the 3 inside plys to stop at bulkhead E.
      Half the perimeter of the bow is 637mm (maximum length allowed),
      measured around the outside edge, from 3300mm from transom (bulkhead E) 
      to the front centre of the bow. Screw front centre to spine. Screw
      through bulkhead E into the 3 ply layer that has stopped short. 

 5.   ATTACHING THE STRINGERS

 5.1  Stringers should be flush with bulkheads except that stringers at the A1
      bulkhead stick out by 4mm.

 5.2  Work from the inside out so as to prevent buckling of bulkheads.

 5.3  Use wire as a clamp to hold the stringers in place when glueing them. 

 5.4  Stringers aft of bulkhead A1 and forward of bulkhead D are tapered to 
      approximately half thickness so as to reduce weight.

 5.5  Hold the stringers at the bow in place with a strip of wood over the
      stringers, at about 90 degrees to the stringers, held in place by a 
      clamp.

 5.6  Recess stringers by 4mm at frame A1 and use 4mm ply backing for supports
      for the bottom and side.

 5.7  Check the measurements of the bulkhead widths.

 6.  ATTACHING THE SIDES

 6.1  Chain plates are bolted to hardwood backing strips between top and
      bottom side stringers and are fitted before sides are glued into
      position. This positions the chain plates inboard of side ply.

 6.2  Glue the sides to the side stringers and bulkheads. 
      Clothes pegs can be used as clamps while glueing on the sides.

 7.0 PREPARING THE FRAME FOR THE BOTTOM SHEETS OF PLY

 7.1  a)  Cut the sides down to the level of the bulkheads at each
          bulkhead/side joint.

      b)  Shape the sides with an even curve. 

      c)  Shape the stringers level with the sides. 

      d)  Shape the keelson level with the stringers and the side.

 7.2  (DO NOT FORGET!)  Cut the water grooves in the bulkheads. 
      These are positioned on the high side and directly adjacent to the
      stringers. The grooves should be 5mm deep. Grooves should also be cut 
      behind bulkhead C from the side to the centre line. 

 7.3  Check the measurements of the bulkheads.

 8.  FITTING THE BOTTOM

 8.1  Cut the front bottom and back half sheet of ply down the centre.

      Short screws through some scrap ply has been found to be very successful
      in holding the edges of the ply down. Weights, bricks, sand bags are
      used in the middle of the ply.
      The screws are removed when the glue is dry and the holes are filled. 
  
 8.2  Glue on one complete side of the bottom, when dry, plane the overhang at
      the keelson down level with the keelson.

 8.3  Glue on the other half of the bottom. 

 8.4  When dry trim all ply overhang back and cut the centre board slot out.

 9.   |Mast step and forestay notes.|

      The boat is detached from the jig and turned right-way-up for these 
      fittings. 

      a) Two chain plates are recommended for the forestay on either side of
         spine ply. 

      b) 8mm thick hardwood fixing blocks between top and bottom framing of 
         spine are used for fixing jib forestay.

      c) The holes for the bolts for fixing the chain plates in place should
         be drilled before glueing the blocks in place. 

      d) A strong mast step is recommended - 10mm hardwood blocks between 
         top and bottom framing of spine. 

10.  TOP STRINGER and BACKING BLOCKS

      The top stringers are fixed as per bottom stringers.
      Backing blocks (3x4mm ply) should be fixed for jib fairleads, toe 
      straps  and cleats. 

      NB. Fully measure and record positions of backing blocks so that once 
      deck is glued on these positions can easily be found. 

 11.  |Varnishing the interior|

      ABE Epidermix 389 is suggested as it not only strengthens the wood but
      is compatible with ABE Epidermix 372 and therefore simplifies the 
      glueing of the deck sheets as no marking of deck is required. Care
      should be taken not to paint top of stringers especially if ABE 
      Epidermix 389 is not used!. 

 12.  THE DECK

 12.1 Attaching the deck and varnishing the interior of the deck. 
      (If ABE Epidermix 389 and ABE Epidermix 372 are not used) 

      Two or more people are needed for this as the glue sets quickly.

      a) The boat, especially the transom, must be supported so that it will
         not twist when the weights are put on the deck.

      b) Spread glue on the surfaces of stringers and bulkheads to which the
         deck will be glued.

      c) Put a deck ply sheet in position to make a print, remove it then 
         varnish between the glue marks.

      d) Re-glue the surfaces when the varnish is dry and place the ply in
         position and secure it with weights while the glue sets. 

      e) Drill a hole where the hatch cover is to be, as a breather hole. 

 12.2 Attaching Deck. 
      (If ABE Epidermix 389 and ABE Epidermix 372 are used) 

      a)  The boat, especially the transom, must be supported so that it will 
          not twist when the weights are put on the deck. 

      b)  Paint the interior of the decks with Epidermix 389 and before the
          paint dries completely :-

      c) Spread glue on stringers and place deck into position and secure it
         with weights.

 13.  Fibreglass (Optional Extra) 

      a) Fibreglass over all the corner plywood joints is an optional extra.

      b) All the edges are rounded, except the transom which doesn't get
         fibreglass.

      c) The fibreglass matting, 50mm wide, should be inlayed less than one 
         veneer of plywood or about 1mm.

      d) The fibreglass should be filled and sanded until it is level with
         the plywood. Resin, Epidermix or car body filler can be used.

 14.  Painting

      a) It is recommended to sand out the bumps in the plywood before any
         painting. It is suggested that the edges be sanded round, except for 
         the keel/side edge from the transom forward 2/3 of the boat's length.

      b) Glatex 8 or equivalent good (polyurethane or polyacrathane) yacht
         paint should be used.

      c) One should aim to put on at least four layers of paint.

      d) After two coats of paint first 220 then 400 waterpaper should be 
         used to sand the boat. After the third coat 400 and 600 waterpaper 
         should be used. The final coat on the bottom should be sanded with 
         400, but mainly with 800.

 15.  Fittings

      a) It is recommended to put silicon marine sealer/varnish in with the 
         screws when putting on the fittings. Stainless steel selftapping 
         screws should be used. 

      b) For the hatch cover you should only make a small hole first then 
         make it bigger to fit the cover when you know the position of the
         stringers, because you do no want to cut a stringer. 

      c) Two strips of sail cloth, 40mm wide, should be glued under the 
         centreboard case to prevent water from spraying up the centre board
         case. Commercially obtainable centre board gasket is available 
         which could be used as an alternative. 

 16.  Centre Board and Rudder

      a) Make plywood templates of the shapes shown in the plan.

      b) The laminated centre board should be about 27mm thick: it is then
         sanded down to the thickness of the centre board case, less 1,5mm
         for the paint. It should be made longer, then cut to size when 
         shaped to allow for error. 

      c) Only shape the underwater parts of the centre board and rudder.
         If possible have hardwood for the leading and trailing edges.

      d) If you can use a radial or circular saw, draw the template shape on
         the bottom of the centre board or rudder, then line the saw blade
         depth with the depth of the template shape. Cut four slots as
         guides of the depths on both sides then shape down (I use a coarse 
         plastic sanding disk) to the template shape. 

      e) When fitting the similarly laminated rudder, ensure that it is 
         positioned on the centre line of the transom as well as vertically 
         to the deck. 

 17.  Mast and Boom

      a) A straight mast section as shown on the plans is recommended. This 
         section can be tapered at the top or purchased ready-made from a 
         commercial supplier. 

      b) The thinner tube section with a track riveted onto it can be used
         but it has been found to be too weak.
 
FITTINGS

 Hull

 Rudder pintles                           2 
 Rudder retainer clip                     1 
 Pulleys for aft-sheeting                 2 
 Saddles for aft-sheeting                 2 
 Mainsheet block                          1 
 Swivelling cleat for fixing
 main sheet block to deck                 1 
 Toe straps                               2 x 800mm 
 Toe strap plates                         4 
 Jib fairleads                            2 
 Adjustment cleats                        7 
 Pulleys for adjustments                  11 
 (Kicker 2, outhaul 4, cunningham 
 3, jib cunningham 2) 
 Saddles for adjustments pulleys          1 
 Cleats for adjustments                   7 
 Mast step                                1 
 Chain-plates                             6 
 Hatch covers                             2 
 Bung plug                                1 
 Centre board gasket                      0.9m
  
 Boom 
  
 Hangers & shackles for mainsheet pulleys 2 
 Attachment for fixing kicker             1 
 Mainsheet pulleys                        2
 Recessed outhaul pulleys (Metal)         2 
 Monal pop rivets 40x5mm x 13mm 
  
 Mast
  
 Gooseneck                                1 
 Mast heal                                1 
 Halyard pulley  (metal)                  1 
 Halyard lock (toothed rack)              1 
 Monal pop rivets                         40 x 5mm x 13mm
 Burgee holder                            1 
  
 Rudder & Centreboard|  
 Rudder gudions                           2 
 Tiller extension                         1,1mm x 16mm tubing 
 Centreboard retaining rope               1m  x  3mm
 Eye for retaining rope                   1 
  
Rigging
  
 Aft-sheeting bridle                      2m   x 3mm
 Mainsheet                                5,5m x 8mm
 Jibsheet                                 7m   x 6 or 8 mm
 Adjustment rope (Kicker,outhaul, 
 cunningham, jib cunningham)              9m   x 6mm
 Kicking strap lever                      1 
 Outhaul rope in boom                     3m   x 3mm
 Strop in boom                            1.5mm x 2.5mm 
 Halyard strop                            4,2m  x 2,5mm (for internal halyard)
 Halyard rope                             4,5m  x 2mm   (for internal halyard)
 Stays with chain plates                  2,94m x 2,5mm (2 of reqd) 
 Levers for fixing stays to deck          2