The major secret in getting the natural curve lies in:
a) the solid, soft Meranti nose cone……It starts off as a square bloc. 8″ x 8″ x 3″ thick (200mm x 200mm x 76 mm )
b) The shape of the sides….Once you have them the rest just fit together…
I would use 4mm – 5mm marine plywood for the bulkheads and the rest of the ski, you can use 4mm – 5mm marine plywood.
4mm- 5mm 2,440mtrs x 1.220 Mtrs Marine plywood ONLY
*Sides: 2 x sheets end, butt joined……
*Bulk Heads: Off-cuts from above…
*Top Deck: 2 x sheets Loose and not joined.
*Bottom Deck: 2 x sheets, end butt joined.
Battens: 15mm x 15 mm Meranti ONLY. ( 25 x 4.20 ) lengths
* 13 mm Meranti quadrant: 10 x 4.1 mtr lengths
* 15 mm Meranti quadrant: 4 x 4.1 mtr lengths
Screws: 2 x 100 boxes – 20mm x No6 Stainless screws with PosiDrive heads for electric screwdrivers…Flat heads are OUT! and will only take much longer and hurt your hands!
Epoxy Glue: 2-Pack Epoxy glue: 4 x 300 ml
Masking tape: 1 x roll x 50 mm
Tools: 1 x electric screw driver with PosiDrive heads, Japanese “Pull-push” Dozuki / Dovetail saw, At least 10 x small wood clamps and 6 x large wood clamps.
1 x set very sharp wood chisels ( 10 mm, 15mm, 25mm and 40mm ) Electric orbital sander plus sanding pads….60 Grit and 80 Grit.
Hand drill with a set if drill bits + 1 x Countersink head.
White school chalk, HB woodwork pencils, 600mm Steel rule preferably with an adjustable stop, 5.0 mtr measuring tape, large builders marking square, marking gauge, set square
Saw horses / stands: 1.00 Mtr wide x 95cm to 1.00 mtr high
Tie-downs: x 2 sets no less than 3.00 mtr long x 30 mm wide
The best way to do this is to
1) Measure and draw a set of bulkheads and transom onto a sheet of 3mm marine plywood.
2) Cut those out and then take 15mm x 15mm Meranti batten material and epoxy glue ( Epidermix 372 made by ABE ) that around the entire perimeter of each bulk head…..I used an airgun stapler with 8mm aluminium / stainless, if you can get them staples which finishes that job in quick time.
3) A standard Crocker used to be 12ft 8″ ( 3.86 mtr ) long by 4 feet ( 1.20 mtr ) at the widest point at about 1/3rd from the transom.
4) As marine plywood is only made in sheets of 8ft x 4 ft ( 2.44 mtrs x 1.22 mtrs ) we joined two sheets lengthways…..* You butt-join them and place a 4″ ( 100 mm ) strip of the same thickness across the entire width of the join. Staple right through and bend the tips over with a small hammer when dry.
* 4mm or 5 mm Marine ply is OK for the sides, bottom and top deck…I would rather use addition battens rather than thicker plywood.
5) Take a number of pieces of thick cardboard and stick them together with wide packaging tape on both sides, to make a sheet approximately 2ft ( 600 mm ) wide by about 14ft ( 4.3 mtrs )
6) Lay this flat and mark two lines at 8″ (200 mm)n intervals along the length….You now have three equal sections marked off. Mark the lower most line as “A”. The next one up is “B”…Mark both ends with the same letters.
7) Mark, with heavy black marker pen, a length of 12ft 8″ (3.86 mtr) from the one end of the cardboard and draw the line across the width of the cardboard.
8) Procure about ten heavy concrete building blocks and place them in easy reach of the flat surface where you will be marking out the curve of the ski. Place a concrete building block
9) Take the joined plywood ( You need a few sets of hands for this ) and stand it on its side edge on the cardboard, with the ends of the plywood and cardboard in line with each other.
10) Place the end of the plywood on the end of line “A” and place a block either side to hold it in place . ( With the joined cover strip on the inside of the curve….
11) Bend the plywood so the bottom curve just touches the bottom of the cardboard and place two blocks either side of the plywood to hold it in place, while bending the free end of the play to a spot somewhere between line “B” and the centre line of the cardboard…
* This is the basic curve of the ski and by moving the blocks you can position the curve a little further towards the transom side which should be on your left…..By manoeuvring the second set of blocks you should try to get the natural, lowest point of the curve to about 1/3rd from the transom….
It may well be more difficult to do the bending and you should stop before distorting a natural curve…..This is trial an error, but you are aiming at about 1/3rd being the lowest point without forcing any bend.
The front ( Right hand side) should end up about on the line marked “B”….If the curve looks too radical, drop the point so there is just a hint of a curve to line “b”. Place two blocks to hold the right hand side in place.
12) Once you are satisfied, mark the curve on the cardboard with a felt tipped marker pen and remove the plywood and blocks.
13) Cut the bottom curve of the cardboard out ONLY.
14) Place the cardboard on edge so you can see the “rocker” curve ….(This is what the bottom of the ski will look like) on a dead flat surface of the floor, and gauge the lift at the transom as opposed to the lift in the nose and place a block in the front to fix the kick-up of the nose. Place two blocks in the centre either side to grip the cardboard template so it stands on edge.
* You have five open areas between the transom and nose cone. These are defined and separate by each bulkhead. * NOTE: Each bulkhead has a different depth.
15) Take a builders marking square with the long leg of the square being the vertical. Place the marking square against the transom and mark of the vertical line with the marker pen. This is repeated to create five equal spaces between the bulkheads.
16) You now have a curved piece of cardboard, marked with parallel vertical lines. Transfer these same lines onto both piece of plywood making sure that the lines are drawn the full depth, as these are the lines which the bulkheads will be matched to and provide the vertical alignmnet for each bulk head.
* Each bulkhead is a different depth, so for the sake of the initial template for the sides, I would mark the depth of each corresponding bulkhead in its position along the length…BUT remember that the curve now runs in two dimensions and the actual side ply of the ski will measure slightly wider than the depth of each bulkhead……..
17) Starting with the transom measure the depth of the transom PLUS 70 mm and mark the point where it cuts the vertical line which you marked with the builders square. The next bulkhead is a little deeper than the transom. Measure than and add you extra 70 mm and mark that off against the vertical line which you made using the builder’s square……..You add a consistent 70 mm to each bulkhead depth right through to the nose cone.
18) Bring back the plywood and place the edge of the plywood on each mark as if it would be the top deck of the ski. Just like you would draw a natural curve graph and then mark with the felt tipped pen.* If you would like a small lip on the top deck ( They are very handy and strongly recommended because they save all kinds of stuff washing off the deck) allow a freeboard of about 20 mm as you will use 15 mm quadrant to sit in between the top deck and side sking and this gets fitted after the deck has been finally fitted )
19) Cut the top curve with scissors and place that template onto the joined plywood. Mark two identical shapes and cut them out on a band saw. Bring both together and clamp with wood clamps while you sand both template edges together.* Simply flipping one piece over will give the other side of the ski.
20) Start by “Dry” screwing the back of the sides onto each side of the transom and work forward. ( *Just let the screw go in half way and just enough to hold the pieces together. Do not fully screw them in….Position the screws approximately 35mm in from the top and bottom of the ends to make way for the deck chines…..That is the batten which sits against the sides running fore and aft)
Provided the dimensions of the bulkheads were correct you should get the sides to be a perfect natural curve and at the same time making the “rocker” of the ski. Just us two screws put end of each bulk head to start. * Bulkheads may be moved forwards or backwards to fit snugly. ** DO NOT position screws at extreme ends of bulkheads as there are deck chines with will be added in the final assembly
21) The nose cone is left for the last. By this time the sides should give you the line where they meet the nose cone. Draw a pencil line to divide the nose cone in half and mark it on all four faces using a set-square.
22) Place the nose cone underneath and make sure the centre line which you marked on the nose cone is dead in line with the centre line of the ski length. Mark the shape where the sides will sit along.
23) Take the nose cone, and keeping it on the same plane without flipping it, now place it on top of the ends of the sides and mark the lines where the side meet.
24) By looking at a three-dimensional view of the nose cone you will see the top and bottom curves and the angles of the shoulders. These should now be cut with a band saw………You will not do the perfectly the first fit and have to keep shaving until you have shaped the nose cone to fit snugly.
25) Once the ski is sitting well, in a symmetrical balance, with the bulkheads all sitting in a vertical plane, and all areas are fitting relatively well, you mark the top deck level with the top of the bulkheads.
26) MARK every piece with a number and name with white chalk so you can reassemble the kit again……..
27) Unscrew everything and lay it out in order and not in one big pile!!!
28) Lay the plywood along the top marked sides and drawn the curve of the top deck using the play to join the dots. Place both sides together and clamp. Then sand together giving an identical shape for both.
29) Reassemble the entire ski and make sure all is sitting true and not distorted.
30) Take a short 2.00 mtr odd batten and lay it on the top deck to mark out where you want the hatch. Mark with felt tipped marker making sure the hatch sits exactly in the centre. DO NOT USE a tape measure….Rather use a piece of batten cut to 110 mm in length, as a template on one side and then flip the same piece of batten to the other side to give layout.
31) To mark the batten positions, Take a straight batten and lay it fore/aft either side of the hatch using spacing templates only….(Batten pacing should be no more than 110 mm apart) and mark out the top deck with a felt tip marker. These will later be “notched out” and each batten will fit snugly into each notch.
Directly under each “notch” where battens will be inlaid into bulk heads, fix a +/- 25 mm off-cut of batten material. This creates a “ledge effect” and adds support for each batten.
32) Having laid out the batten positions and the hatch positions, be sure to mark the hatch position with additional white chalk over the felt tipped markings.
33) Flip the ski over and layout the bottom deck battens.
34) Dismantle everything being sure to have marked everything and placed it carefully to avoid mixing parts.
35) Notch out all batten positions by using the Japanese Dove-tail saw and a sharp wood chisel to cut through the plywood leaving a snug “notch into which each batten sits.
36) Re-enforcing 15mm x 15mm ( Same as deck ) battens are then fixed to the bulkheads for the hatch. Once that glue has dried, remove the inner portion of the bulkhead which makes the space for the hatch.
37) Re-assemble the ski, still using only two screws at the ends of the bulkheads ….But this time add the glue just on the ends of the bulkheads. *Do not tighten the screws until the entire ski is sitting true, on an even keel and is symmetrical. Once you have that, then tight the screws fully….DO NOT OVER TIGHTEN SCREWS as this will split battens etc…..If you do happen to split a batten, ease it open and insert some glue with a thin sliver of wood, then close the gap with a clamp and allow to cure over-night.
* ONE THE MAIN FRAME AND SIDES ARE GLUED, ALLOW THE CARCAS TO CURE OVERNIGHT WHILE SITTING ABSOLUTELY TRUE.
38) Fit all deck battens and top and bottom chines ( Extreme ends top and bottom of the bulkheads, with glue. * Make sure that you either use a pneumatic nailer with one aluminium / stainless nail or if you use screws, make sure to drill pilot holes first.
39) Drainage is a simple set of parallel notches running either side of the hatch from front to aft and out through drain plugs in the transom.( * DO NOT drain the hatch through the bulkheads otherwise the ski will smell of fish forever and will have a tendency to rot.) This has its own, through-deck drain hole in the bottom of the hatch. You simply glue a block of wood the thickness of the drain plug and fit the drain plug so it is flush with the bottom of the hull.
40) Dry-fit the bottom deck by flipping the carcass of the ski upside down and screwing the butt joined plywood. The plywood is simply clamped into position with no screws.
Flip it back and then trace every batten and bulkhead onto the inside of the bottom skin with a pencil….Do not miss anything!
41) Use the Japanese Douzuki / Dovetail saw to cut the outer shape of the bottom deck.* Keep all off-cuts as they are very useful as glue mixing boards and for patching.
42) Remove bottom deck skin. Using the electric drill with the correct drill-bit for the 20mm x No6 screws, drill pilot holes inside the marked areas where the bulkheads are…..It is not necessary to drill any areas on the battens as they should fit snugly and at the end when you apply the final glue, they should stick perfectly.
43) Remove and lightly sand the inside of the deck to smooth any ply slivers which have become raised or rough to ensure absolutely smooth fitting. Sand all the edges which should already be quite smooth as the Japanese Dovetail saws give a very clean cut.
44) Re-install the bottom deck using screws, lightly screwing.
45) Take a piece of plywood and place it into position for the side of the hatch. The may be clamped into position while you trace the outline of the bulkheads and battens. Do this for both side of the hatch. Then unclamp and cut to size using the Japanese Dovetail saw. Sand the edges smooth and drill pilot holes.
46) Re-assemble the bottom deck and hatch DRY…. Screwed but NO glue.
47) The top deck is done as two separate sections. Front and Aft. They have to join on a bulkhead which has been re-enforced both sides to give it some anchoring purchase.
48) Stirrups are a must and once you have selected a position for each set, the underside of the stirrup should be re-enforced by means of gluing in a separate block on each side of the foot, a pilot hole drilled from the outside and a motor car seat belt used as the strap. Plastic screw mounts to protect the screw head are used and the belt/stirrup is mounted after the ski is finally painted.
49) Once you are satisfied that all components fit, the bottom deck and hatch are fitted using screws and a generous amount of glue….It is desirable that all seams will pull up nice and tight leaving glue oozing out all around. This should be carefully “Finger-smeared ) which serves two purposes…It seals totally waterproof and ensures full joint adhesion. The carcass should again sit true…If not, the occasional strategically placed concrete block wrapped in newspaper for protection, may be applied so the glue will cure in the correct position.
50) Quadrant is now fixed into all internal corners of the hatch and along the top combing / edge of the hatch.* Separate dry hatches may be sectioned off or added to suit. Hatch lids should be removable for washing and secured with robust reefer truck cantilever catches with rubber seals to insure dryness.
* The surf ski manufacturers sell plastic sealed compartments which can easily be incorporated into paddle skis…..Just not that they should be mounted on top of the hatch so they don’t get wet when opening and closing. These are sealed with Marine silicone.
51) The drainage holes are all checked to see that they are big enough, all seams checked for complete glue squeeze and fingered smeared well. The entire inside of the hull including drain hones etc is painted with either a Glatex 8 or waterproof Poly Urethane. I would put at least 2 coats to ensure a total waterproof seal. I like white as it shows all unpainted areas clearly. Do not use a dark colour.
52) Lightly sand any surface which will be receiving glue in the next stage.
53) Your top decks by now should have been prepared and pilot holes drilled ready to assemble. All the contact points to battens, chines and bulkheads should be clearly marked before the bottom deck had been fitted.
54) Carefully paint between all the batten, chine and bulkhead contact points and ensure that there is total 100% waterproof coverage. Allow to dry and set hard.
55) Assemble the top deck using ample glue and as many screws as possible ensuring 100% adhesion and sealing.
56) Fit top deck quadrant around the deck perimeter and quadrant to other finishing areas as required. Sand when cured.
56) Build the hatch lids to suit and sand everything for painting.
57) Paint the bottom deck first. Then flip and paint top deck. Then bottom again and then top again. A third coat can be applied if the paint has not yet totally sealed.
58) OPTIONAL: Anti-skid patches may be marked off and given a coat of finishing paint and immediately a layer of sieved beach sand or fine sawdust are applied and allowed to cure for no less than 24 hrs. The area must be wire brushed clean.
58) Fit only stainless steel hardware or seat belt material as grab handles and stirrups. Plastic drain pugs are available at all boating shops.