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The 2000 "SideWinder" HPB

For 2000, I decided to replace the fiberglass superstructure with aluminum, and to straighten out the chain path to the gear box. These changes were to improve the durability of the frame, to make it easier to modify, and to quiet the drivetrain. Bill Murphy spent a couple hours welding together the 1" aluminum framework for me. I used 1" square aluminum tubing that I obtained at the hardware store for all the new frame components. While Bill TIG welded them, we noticed that some joints welded a lot better than others. We attributed that to the "mystery" alloy. Personally I think the better joints were on aluminum from recycled Coors cans, and the bad joints were probably recycled Miller cans... I added some upright handlebars, as it helps to have something to hold onto while flailing wildly on the pedals during sprints. The new superstructure bolts to the hulls using the same mounting holes that the previous superstructure used. Though it seems to cruise nicely, this was a major rebuild, and the bugs are still not worked out.

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The chain line goes straight from the 52 tooth chainring, to the 13 tooth drive cog. Because the drive shaft at the drive box is now mounted parallel to the surface of the water, I had to use a U-joint to redirect the driveshaft at about a 15 degree angle, down into the water. In the picture below, you can see the drive box, which was made of commonly available aluminum L-section, and round tube hardware, and was pop-riveted together. The driveshaft is 3/8" steel rod. Bearings are also of the hardware store variety. Behind the drive box (toward the top of the picture below) you can see the U-joint. Also in the picture below, is the idler wheel. I may change this to a spring loaded idler for next year, as I have found that a solidly mounted idler does not compensate for minor irregularities and changes in torque very well, which can allow the chain to pop off at inopportune moments...

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The next picture shows the drive box from the bottom. A combination of a straight chain path, and beveling the teeth on the 13 tooth drive cog to a chisel profile cured the chain noise problems I had been plagued with in previous years. This was the first year that I actually had a quiet drive train. Amazing... The u-joint is a little cheesy. I may have to find one that actually has bearings as I'm sure this one is pretty lossy.

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The propeller stay was a 1-1/8" aluminum tube, that I had faired to allow the water to pass around it efficiently.  This large object in front of the prop was a mistake as I think it slowed the boat down by disturbing the water flow. Also the boat did not turn well this year. The prop stay acted like a rudder, and wanted to make the boat go straight.  Pictured is the 20x16 fiberglass APC prop, which worked well with the 4x drive ratio. It cost aout $50. Unfortunately, I broke an inch off one end of the prop on a sandbar at the Sparta, Wi.  HPB races, and had to trim the other end to match. Apparently those tips are there for a reason because it felt slower after the tips were gone.

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For the Hydrobowl, I added a boom for the rudder to try to improve the turning situation, faired the prop stay more to try to make it faster, and switched back to the $13 16x16 prop, with a 68T chainring. (Thanks R.D.!) It helped a little, but I'm thinking now that the single beefy chainstay is a mistake, and next year I will return to the "V" shaped prop stay that I was using on the previous version of the drivetrain. I think that this will improve the turning as well as the prop efficiency.

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I ended up in 4th place in this year's Hydrobowl, due to the fact that my chain popped off once during the drag race, and again while trying to pass Bill Murphy during the 2K race. As can be seen in the picture below, these hulls have plenty of floatation, probably enough for two people. I'm thinking about cutting them down some to make them faster. Fortunately the single layer of fiberglass peels off of the foam fairly hulls easily.

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This years modifications have greatly improved the boat's ability to be easily taken apart and stored in a small area, as well as making it a quieter, more refined vehicle. Next year's task will be to make it fast too. The most amount of work will be in reshaping the hulls. I'd like to make the hulls look more like the drawings below. In 1995, When I started building my first HPB hulls, I was pretty clueless about what a good hull shape was. In 1997 when I built my second set of hulls, (the hulls in the picture above) I at least had a clue. After 5 years of observing which boats go fast, I hope now I have a pretty good idea of what will go fast.

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Updating the hull shape, along with making the modifications to the drivetrain mentioned above, should make the Sidewinder much faster. It will need to be. As interest in this sport grows, the competition gets tougher. People now have the option of buying a fast HPB that they didn't have before. Now to find the time...

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