Introduction: Hollow Wooden Kitesurfboard
This is how to make a hollow wooden kiteboard from marine plywood. The design and construction of this board has been simplified as much as possible to facilitate quick, cheap construction with out specialised tools.
The board consists of three layers of wood laminated together to form the core of the board. The centre lamination is not solid in order to reduce the weight of the board without compromising the strength too much.
This style of board is known as a directional , it is designed to be ridden in one direction only and must be gybed or tacked similar to a windsurf board in order to go in the opposite direction. This requires practice and is not best suited to a beginner. The benefits of this style of board is that it does not require any design compromises, you can have huge fin area at one end (for pointing up wind and loading up for jump)s and plenty of nose rocker in the other end for riding in choppy or surf conditions.
Step 1: Acquire Your Tools and Materials
1 8' x 4' sheet of 6mm thick marine plywood
250ml of epoxy resin
4 x stainless steel self tapping screw for attaching footstraps
4 x stainless steel washers
4 x Future Fins Fin boxes (side type)
4 x Future fins
2 x Footstraps
Marine plywood is preferred but good external construction plywood will work fine
Epoxy resin is used to join the laminations together as well as seal the board from the elements as an alternative the laminations may be glued with water proof polyurethane glue as this is easier to use (1 part) and the ply can be sealed with varnish once the board is finished instead
Future fins are preferred over FCS as they are stronger and easier to install correctly
Footstraps any hard ware is optional as the board may be waxed and ridden like a surfboard instead.
3mm Drill bit
12mm Drill bit
A handsaw is better for cutting plywood than a powered saw as it tends to cut a smoother less wandering line and does not splinter the wood as much.
Step 2: Draw Out the Template
Lay out the sheet of plywood .
Draw a centreline for the board, 150cm long 24cm from the edge of the longest edge of the plywood (this ensure the grain of the outside layer of wood is running in the correct direction).
This centreline is the most important reference mark for all subsequent measurements so make sure it is very clear.
Clearly mark the tail width(28cm) at one end (14cm either side of the centre line).
Clearly mark the widest point (48cm wide, 24cm either side of the centre line) of the board (measured from the tail this shouldbe +/- 95-100cm from the tail) .
Draw one side of the template connecting the tail, wide point and nose in a nice flowing curve , use a flexible piece of timber to get a smooth curve.
To ensure the board is symmetrical you can now meaure more offset points and transfer to the other side of the centre line to create a mirror image.
Mark the fin locations as per attached photo.
Mark the foot strap mount holes as per the attached photo
Step 3: Cut Out the Template
Once the outline has been drawn out on the sheet of plywood it is time to cut it out.
This first cut out will be the bottom lamination of the board, its important to cut this accurately as it will be used as the template for cutting out the middle and top sheets.
Cutting a large sheet of plywood can be difficult if you do not have a large work bench, I found it easiest to cut out with the wood resting on the ground and use a small wooden block to support the panel immediately adjacent to where I was cutting.
I cut out the template using a handsaw, this is less prone to wandering (cuts straighter) and does not splinter the wood as much as a jigsaw. However it does not like to follow tight curves and it is necessary to make multiple angled cuts then smooth off with a hand plane later .
Ensure that you cut "oversize" as it is easy to plane back the wood to the line after the rough cut has been performed.
Once the rough cut has been made use the block plane and sand paper to fine tune the outline .
Step 4: Cut Out Top and Centre Laminations
Use the bottom lamination as the master template for cutting out the top and centre laminations.
The centre lamination is not one continuous panel and is made up of multiple segments that will be glued together when the board is laminated.
As can be seen in the picture I ve left the tail area solid as this is where the fins and rear footstraps will be installed , ive also left it solid under the area where the front footstarp will be installed.
If you were concerned about the weight of the board you could easily further reduce the amount of timber in the centre lamination as most of the stress is taken by the top and bottom sheets. One option would be to drill out weight saving holes in the timber to make a honey comb effect (too much trouble for me!)
Step 5: Glue the Laminations Together
Before mixing any glue its important to prepare the area that you intend to do the gluing and assemble all the required materials.
You will need a flat hard surface to glue the board on (im using a concrete slab in the picture).
Lay down some plastic sheeting to capture any excess glue.
Acquire the wooden blocking necessary to raise the nose end by 90mm and the tail end by 30mm and lay in position.
Gather a bunch of weighting material with which to press the laminations together and form the rocker of the board while the glue sets (im using gym weights but bags of sand or buckets of water will work as well.
Also do a trial fit up and any final trimming before the glue gets near the work. its a good idea to mark up exactly where the centre lamination will sit on the bottom lamination to allow accurate glue/epoxy placement.
Lay down the bottom lamination resting on the wooden blocking (tip of nose raise 90mm , tail of board raised 30mm).
Apply glue /epoxy to the bottom lamination.
Lay down the middle lamination segments and apply lots of glue / epoxy to the top surface of them as well as the butt joints between pieces.
Lay down the top lamination.
If you have some clamps it is a good idea to install a few of these around the nose end of the board to hold the pieces in place while the weights are applied (see photo). Only install clamps on one end as the sheets must be able to slide relative to each other when the weights are applied and the board forms a curve.
Stack up the weights on the board, concentrate most of the weight over the planned footstrap positions, this ensurethe correct distribution of rocker between the nose and tail. Apply sufficient weight to the board such that the belly of the board is pressed hard against the ground.
With all of the weight applied walk around the outside of the board and check that the sheets have not been displaced side ways, a tap with a hammer is easiestto adjust any misalignment.
Allow glue to set for 24hr before removing weights.
Step 6: Final Shaping
Once the laminations are glued together remove all of the weights.
You will find that the sheets will not be perfectly aligned due to slippage while gluing and it will be necessary to do some tidying up of the outline using the block plane to achieve a smooth template outline.
To avoid errors sneaking in use the bottom sheet as the reference point and trim back the middle and top lamination to match the bottom sheet.
Once the outline is fair it is necessary to shape the rails of the board. This is best achieved using the block plane and sand paper.
for a directional board you will want hard turned down rails for the back 13 rd of the board , shape the front 1/3rd of the board as 50/50 rails and then transition between the two for the middle 1/3rd of the board . See my hand drawn illustration of rail shape on the plan.
Step 7: Cut Out the Holes to Receive the Fin Boxes
On wooden surfboards (which are thicker than kiteboards) ive made the recess for the fin box would be chiselled out from one side only however as a kite board is a lot thinner and plywood is a pain to chisel its easier to just cut the hole for the fin box completely through the board.
Mark the centre line location of the fin boxes (see hand drawn plan in step 1) .
Use a 3mm drill bit to drill multiple holes through the board along the planned line.
Use a 12mm drill bit and open up the 3mm half way from one side then all the way from the other (yhis avoids too much splintering of the plywood).
Work the drill bit against the sides of the holes to create a slot.
Use a hole saw and are raps to tidy up the slot that has been created.
Install the fin box into the slot (on th bottom side of the board) and draw around the top flange of the fin box.
Use a chisel to create a recess to receive the top flange of the fin box so that it sits flush when installed.
Step 8: Drill Hole for Footstraps.
Refering to the Hand drawn plan in step 1, mark the position of the footstrap holes.
Using a 3mm drill bit drill the holes to receive the self tapping screws for receiving the footstraps.
Only drill 2/3rd of the way through the board.
Use a countersink bit to tidy up the top of the hole and prevent splintering the timber when the screw is installed.
Step 9: Decorate the Board
Before sealing the board with epoxy or varnish you can decorate the board.
My daughter used water based kids poster paint to draw up a nice surfing dogs picture for me.
Step 10: Epoxy/seal the Board
Mix up some epoxy and roll it on the bottom of the board to seal the wood.
Concentrate on getting good coverage in the slots for the fin boxes, footstrap holes and around the rails.
With the epoxy still wet install the fin boxes and push firmly n place.
Allow to dry then repeat for the top side of the board.
Pour some excess epoxy in the gaps around the fin boxes to seal up the slot.