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This kiteboard snapped after a few sessions!
Fully powered up, I slapped headlong into
the face of a wave and the nose
cracked under the front foot plate. I am in the process of making another plyboard, this
time wrapped in glass, not a ply-glass-ply sandwich.
Having used my kiteboard for about six months, mostly at the weekends, I still have tons of trouble trying to go up wind. I removed the fins which made the board skatier and more fun, but didn't change the up wind ability at all.
I talked to some of the guys at the beach about this and they were surprised that I couldn't go up wind especially with a kiteboard with so much volume. The only real difference between their boards and mine was the rail thickness.
Anyway, I lost my job and I was keen for a new board so I tried my hand at a ply board.
One sheet of 6' x 8' x 6mm ply (yes - feet and millimeters - plywood has a crazy measuring system), not marine ply or anything special. I cut two rectangles out of it, each one 40cm x 160cm.
Scored one side of each with a knife so the resin would take to it better. Resined the scored side of both bits of ply, put a layer of 6 ounce glasfiber cloth between the two sheets of ply (making sure the glass was thoroughly wet with resin). Then stuck them together.
Here are a couple of photos of the setting process:
I chocked up the nose and tail to give the board a little bit of rocker (I imagine this to be negligible) but I don't think rocker is really needed in a kiteboard. Just a little nose kick to get through the chop.
Most of the weight was from some lead roofing I found (this was *heavy*) at my dad's.
I left this for two days to set (it was winter and approx. 0-5'C) in fathers garage. When the resin had gone off I took the weights off the board and to my utter astonishment then rocker stayed put, I imagined the board to flex back to its original shape.
Next was cutting the board shape from the 'blank'. I measured and drew lines through the centers of length and width. I took 4 small nails, hammered one in at the center of the board at the correct width, for a 38cm wide board, the first nail was 38/2 = 19cm out from the center. I put another nail 10cm further down the rail and also 19cm from the center line. This will give me a 20cm 'flat' spot in the middle of the rail, this is to give me a nice smooth transition from nose to tail. If you take the curve to the center you get a little notch where the nose curve joins the tail curve.
This is the point in the explination where I get confused about 'nose' and 'tail' cos I'm making a symetrical twintip.
Now 1/4 of the board shape is done. What you *should* do now is cut this 1/4 out, then use it to make a template. Place a sheet of paper or some card under the cut out section, and draw around the edge of the board. Then cut along the line to make a template, use this template to shape the other 3 quarters.
I was too lazy to make a template so I took measurements of width every 10 cm down the curve and transfered these widths to the other 3 corners.
Cut out the final board shape. Then used a belt sander to round off the corners and make the rail thinner and smoother. The board was really flexi at this stage. I wonder if it'll go?
Slapped a layer of varnish over the top and bottom, let it dry then added another layer.
I then drilled holes through the center line for the 't' nuts and bolts. The distance between the bindings was exactly 30cm.
You can clearly see the rocker in the above picture.
Apart from the heaviery than average weight (which I don't think will effect my riding in any way at all) the board is great! It will hold the rail better than my legs, they started to shake during the gusts.
For a total of 10 pounds for the ply and 6 for the nuts and bolts (and 100 for the bindings which I already had) the board is WIN!
I used the board with my 640 Arc today in a nice 15 - 20 mph (underpowered) I was flying upwind in the strong spells and keeping ground while sining the Arc. I managed a bit of toe side and a couple of little transition jumps. I think I could have made the board a little thinner, it flexed a little bit but not as much as I thought it would.
I really think I could go with less than 12mm (2 x 6mm) of ply, maybe a single sheet of 9-10mm with the glass on the bottom, this would be also be easier to make. If you went shorter than the 160cm (which is quite long) maybe 140 - 130cm you could definitly get away with a thinner board. Sauls boards, are made from 9mm ply with a glassed bottom, and he uses normal cloth instead of glassfiber which makes his boards cheaper again (and waaay more colourful!)
Because of its simple construction (I swear I've spent more time on this web page than making the board) a lot of design iterations are possible.
My final ideas
You could drill some holes in the top sheet of ply, some in the middle and a lot at the tips. This would make the construction more flexible at this point, giving the tips good flex.
'Pickle fork'-ing the shape would also make the tips more flexible. Flex is aparently good for jumps :-)
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