August 2005 - ?
Some time over the summer I decided I needed a new kiteboard. When I learned my friend Gene was building his own board, well, I immediately got jealous and decided to build rather than buy. 6 weeks later I have built 4 boards, broken 3 of them, and I'm firmly hooked on a new hobby! It's fascinating trying to engineer a board that has good riding characteristics plus light weight and durability. Starting with board #2, each one has tested a new concept or idea as I learn more about composites and construction. My head has not stopped spinning since I started and I will have to build many more boards before every idea has been tested and evaluated.
I have leaned heavily on the experience and ideas of other builders, notably local builder Trent Hink of Anomaly, former local builder and pro rider Nick Bowers, and the websites of DC Kiteboards, Custom Kite Boards, and the Yahoo board building forum. Thanks everyone for sharing your experience and technical know-how!
The first 4 boards have all come off the same rocker table. The rocker is basically flat between the footpads, rising about 4.5 cm beyond that. The concave is concentrated between the footpads and flattens out beyond that. I built the table out of 3/4 inch mdf board (particle/sawdust-type board). I cut out a flat piece 16" x 60" and took a powerful sander and made the middle convex. Then I cut the main rocker into 2 2x6's and forced the table into this curve. The table turned out to be slightly porous so I have to bag the entire thing to get a good vacuum. But I don't mind this and I think the bleeding through the table helps reduce dry spots on the board bottom. The last 2 boards have been one-shot layups, all of the layers are laminated at once. This makes the most sense to me and I think all my future boards will use this technique.
The board breakage has been very educational. Boards 1 and 2 broke on the top, compression failures running across the board directly under the footbeds. To help strengthen the mid section, board #3 has 4 wet-layup fiberglass stringers running about 70% of the length of the board. This strengthened the board significantly, but the board ultimately broke on the bottom, a compression failure in the exact center. I now realize the loads on a kiteboard are more complex than they seem. The bottom has compression loads between the footbeds and tension loads beyond the footbeds. The top has tension loads between the footbeds and compression loads beyond. The length of the board will effect the proportion and intensity of the loads inside and outside of the footpads.
All of the breaks have been width-wise. It seems to me that 50/50 weaves are a real waste of weight, until I see a board break along the length axis I will be stealing from the weft and adding to the warp. My next order of fiber includes some carbon and s-glass unidirectional cloth as well as warp-bias E-glass, can't wait to try them out!
Board #1, model Che, laid up Aug 29. 135 x 38, 4.5cm rocker, 3.5 mm concave, extruded poly core. Click here for building details and pics .
Board #2, model Amaru, laid up Sep 2. 125 x 38, 4.0 cm rocker, 3.5 cm concave, extruded poly core. Deck: 9oz bi x 2, bottom 5.6oz kev + 6oz gl, wrapped rails. Click here for details/pics.
Board #3, Amaru Des Nudo, laid up Sep 19. 120 x 38, 3.8 cm rocker, 3.5 mm concave, extruded poly core, 3.5 lbs fully rigged. top: 19 oz tri, bottom: 5oz kevlar + 6 oz E. 4 oz internal stringers. fully wrapped rails. Click here for details/pics.
Board #4, Amaru Negro, laid up Sep 21. 125 x 38, 4.0 cm rocker, 3.5 mm concave, H80 divinycell core, 5.5 lbs fully rigged. top: 5oz carbon x 2 + 6 oz E, bottom: 5oz kevlar + 6 oz E. 9 oz bi heel reinforcement, fully wrapped rails. Click here for details/pics.
My friend Chris Butzen spent last Saturday testing out boards 3 & 4, he had very kind words to say about them. The boards seem to have plenty of pop, Chris really wowed us with some great moves on a gusty day in Sheboygan. Thanks for your feedback, Chris!
So far in my riding I have found the concave contributes greatly to the edge-holding power without making the board track too tightly. You can flick to toe-side on mind-power alone, yet all of the boards go screaming up wind. Plus it throws up great sheets of water when you carve a transition! The 125 x 38 proportion works well with our gusty Lake Michigan winds, there is enough width to glide through lulls. But you need to have tight footstraps to survive the puffs, otherwise it can be dicey keeping the board on an angle. The rocker is just about perfect, it finds it's way over waves without any effort, yet it still goes fast. As expected, the square corners make losing the edge very sudden, but for advanced riders this seems to be an acceptable trade-off. The super-light boards (both 2 & 3 were well under 4 lbs rigged) feel magical to ride, I really want to come up with a formula for a durable board in this weight class.
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