Friday, May 21, 2010

Re: [Electric Boats] Re: Potentially a new project.

 

My personal feeling is that everyone wants to "overpower" their boats.
 
I have no doubt that the majority of IC engines built into boats are already overpowered, and that virtually no one actually(or habitually) produce the RPM's to achieve the rated power. Besides, when a person hits about 2/3 the hull-speed, the power-waste increases considerably for a displacement hull.
 
SO, my feeeling is that most boats are already overpowered.
 
WHEN one goes to electric, the torque realized at the top-end of an IC engine, are realized at a much lower RPM.
 
Two different worlds.  We always try to achieve(with electric), what an IC engine is "capable" of. 
 
To me, this turns electricifation into a much more theoretic endeavor. 
 
For sailboats, I don't understand this, cause sailboaters, I think, have a much larger margin of error available to them than powerboaters do.  While powerboaters "power" their boats, sailors generally "sail" their boats. The use of the engine/motor means something completely different in each.
 
When I placed my 32 lb thrust MinnKota on my 25' Macgregor(my 7hp engine was stolen), I never expected much cause it was so totally underpowered.
 
That son-of-a-gun pushed me into winds that were quite formidable and drug my butttt back to dock for about 5-6 miles on a battery that was near-dead when I started.
 
That motor helped me realize how little power I really needed to get my boat out and back into dock.
 
On my pearson 26, I have a 12-volt Motorguide 55 lb thrust engine and the prop is a typical "trolling" prop(on Lake Erie).  Even with this outfit, I can send a substantial wash across the dock to the other dock.  The 9.9 engine would have to be reved to more than the speed I prefer(for docking), to do this and would send even more wash with higher revs.  BUT those higher revs were at a level I've never used the motor at . . . except just to see how the boat would move.  My buddy also borrowed this engine(Motorguide) and used it for moving his Paceship 23(I think he said 23), a few miles from his dock on Lake Saint Mary(in Ohio) to another place for haul-out.  He was very satisfied and impressed. 
 
The only change I'm looking at this year is to get a 24 volt MinnKota and a Kipawa propeller . . . an improved motor and an improved propeller.
 
I will sit at the dock, turn the motor on and see how much "power"(wash) is emitted for the apparatus.  If I like what I see, I'll use it and learn what I don't like.  With this, I will begin increasing my battery package and next year will decide(by trial and error), if I need any further upgrading.  The cost of the MinnKota will be comparatively cheap and can be re-sold if I want still more power.  I suspect there will be a considerable improvement over the Motorguide.
 
As far as those "emergency" situations . . . well, it chancy, but it's chancy with a more conservative engine too.
 
I like to preplan my ideas, but I also like in-the-dirt, trial and error too.
 
 
John Francis
Pearson 26
Port Clinton, Ohio

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