T-Pain Is On A Boat: Re: [Electric Boats] Any larger electric boat owners out there?

Sunday, May 24, 2009

Re: [Electric Boats] Any larger electric boat owners out there?

James,

HP is HP, whatever the prime mover. The continuous (not max or peak) power rating of your motor is the number to use.

The battery bank is the real power constraint anyway, not the motor. You want to consider speed and range. Not much sense setting up an E boat that will go fast but drain the batteries flat in 5 or 10 minutes. Start the design process by defining the speed and range you require, select a possible motor/battery system, evaluate cost, weight, performance. Repeat until you are confident you have the best compromise.

Get Dave Gerr's "Propeller Handbook" to figure the prop size and rpm best suited to your boat.

Google the "Peukert Effect" to see how rapid discharge affects battery capacity.

You will be removing around 2500 - 3000 lbs from the boat. You new installation needs to maintain the original center of gravity or the boat won't float level and if it floats bow down maybe hard to steer.

Good luck.

Denny Wolfe
www.wolfEboats.com

----- Original Message -----
From: James Sizemore
To: electricboats@yahoogroups.com
Sent: Sunday, May 24, 2009 3:25 AM
Subject: [Electric Boats] Any larger electric boat owners out there?

I see a lot of traffic on this list for smaller conversions replacing
A4's and such on 20-30 foot sail boats. Are there any folks that have
replaced larger motors on cruisers/trawlers?
I will be replacing two 427 fords (350hp gas engines) on a 41 foot
Chris-Craft. This if for a number of reasons including not wanting
the ongoing expense of buying gas, second I really hate the monstrous
complexity of combustion engines. I have a computer science/
electrical background so I am much much more knowledgeable and
comfortable with electrical systems. And not to mention the smell and
noise of combustion engines. The knowledge I lack right now is boat
related: prop size pitch ...etc...etc. I don't need the boat to plane
at 17 knots or anything like that, although if it does all the better.

My current thinking is to replace the fords with a pair of (Netgain
Warp 11'' or Transwarp 11'')'s. The part I can not rap my head
around is if I go direct drive with the Transwarp's will they spin the
props to fast? Or should I keep the transmissions that the fords are
bolt to now and go with the Warp's. I would prefer not to have the
extra complexity of the transmissions. The Netgains can move a large
truck at freeway speeds 70+ MPH. My understanding of the conversion of
electrical hp to combustion hp is at 144v these motors should be about
the equivalent of a 150-200 hp gas motors with considerable more
torque at the low end.

The boat will soon have a fairly large solar array and already has
7.5 KWH generator. So keeping the battery bank feed should not be a
problem. I know finding a solar charger/inverter for a 144v battery
pack will be a real challenge. Any recommendations are welcome. I
would also be very curious of other conversions of larger plaining
hull boats, and what motors you use and performance you get now. Also
any recommendations on motors/charges/controllers or kits for boats
this size would be most welcome.

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