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Building a Sport C Class Outboard Powerboat

This twelve-foot long tunnel boat is being developed and built for racing in the Sport C class. Sport C utilizes the two-cylinder, 40 horsepower Nissan or Tohatsu to achieve speeds approaching 60 mph. At these speeds a tunnel boat can literally fly.

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The Sport C is out of the basement. Predictably, it looks much smaller out in the open. Here it will reside under a tarp for the time being while I work on one of my GT Pros.

Out of the basement at last

August, 2007: Finally back to the Sport C.

Next step is to complete the cockpit in preperation for permanent installation. Here I've sanded down the skim coat of sanding filler.

cockpit freshly sanded

... followed by a fresh coat of epoxy/microballoons sanding filler.

cockpit recoated with sanding filler

I needed some way to trim out the cockpit opening. So why not a few dozen little blocks of wood?

Shaped, filled and sanded.

I've been gathering together hardware, hoping to get as much as possible at least roughed in before installing the cockpit.

The steering wheel is mounted on a quick release hub. On the right side of the wheel will be the trim control; on the left the start button. I might mount the kill switch on the wheel, too. The dash is just too far away to reach, at least if I decide to use restraints.

Finally, a break in the cold, rainy weather allowed me to work outside again. The cockpit and coaming are now installed. I also glued in some blocking then drilled bolt holes for the foot throttle. Next step is the deck.

The port-side deck is installed, including a vent hole required by APBA. An upside-down boat can become stable, floating on air trapped within the hull. Vents cause the hull to sink at the stern, making driver rescue easier.

As always, I try to avoid using screws. I hate filling all those screw holes, and the patches never seem to sand out just right, and may imprint through the finish later on -- from wood shrinkage, perhaps. Only three screws were used for each side of the deck, mostly to assure the plywood was exactly where it was supposed to be, and didn't slide off the boat on a slippery slope of wet epoxy.

I use lead weights as much as possible, and masking tape where the edge of the plywood is accessable. I glued the scarf joint in place, at the same time I glued down the deck.

Transfered to a trailer, ready to put away for the winter. Time to build a new GT Pro. Then I'll finish this project in the spring.

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