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10 June 2007 @ 07:53 pm
more ultra-low-energy boat R&D  
The little pontoon inflatable I bought recently will be a good winter boat for slower rivers. And, the kayak I bought late last summer will be my main human-powered summer craft.

But I decided I also want to know just how fuel-efficient a moderate-speed motor boat can be. I define moderate as fast enough to overcome all non-whitewater currents in the Midwest.

I am the first person in the universe to really investigate this! Or, if it has ever been investigated, the investigator(s) never recorded his/their findings.


Well, just realize how little ultra-low energy land transportation has REALLY been studied. And it is probably 100 times as important as water travel.

The good news is the physics to properly study low-energy motorboating was hashed out and published in the 20th century, beginning with the Wright Brothers research on sea planes at the same stretch of the Great Miami where I did my research yesterday and today, and ending with the paper written by a naval engineer named Savitsky in 1964.

Professor Savitsky still teaches in New Jersey and he sent a copy of his 1964 paper to a man in Colorado.

I contacted that man last week and he sent me a .pdf of the 1964 paper.

I have 14 years of experience investigating watercraft and a strong background in mechanical engineering including fluid dynamics.

So, I digested Savitsky's formulas very fast and learned they predicted a total weight of about 225 pounds could indeed be easily propelled to "planing" speed with a tiny 2 HP motor.

And, I know the new Honda motor I just bought holds the world's record for mpg in a boat (128) but this was at low speeds, not moderate (planing) speed.

I determined the large flat wetted area and low draft and tiny weight of an $80 4' x 8' inflatable raft would make it a very good but not ideal test boat.

So I bought one Friday at Dick's Sporting Goods, and I equipped it with a home-made rigid floor/engine mount assembly.

Today, I believe I was achieving semi-planing for several hours and I believe the tiny 28 pound motor was using very little gasoline.

I am hoping I will achieve full planing this week if I lower the engine mount 2".

Even at the semi-planing speed I was driving at today, I think I was meeting my definition of moderate speed.

It's too early to get excited until I really know my best efficient speed and until I have fuel consumption data from my future tests.

But, my intuitive sense today was that this is going very well and I actually felt very comfortable driving the little $80 boat for several hours. (Usually comfort is the last thing you expect in these rafts but this little setup was a joy.)

When this research is done, whatever the results, I'll be sure to share it on the internet.

And, hopefully I'll have gained a third tiny useful boat, one ideal for summer journeys from my Scioto property that will allow me to go farther per hour than my kayak but that will also use very little gas.

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