George, I skimmed over your blog - very interesting. You probably know about the WoodenBoat Forum http://www.woodenboatvb.com/vbulletin/upload/ but if not check it out. Lots of great advice from (some) knowledgeable wooden boat builders.
On your formulas question the answer is "yes" and they are all contained in Dave Gerr's "Propeller Handbook". Well worth the money. Gerr will also guide you through picking the prop dia, pitch and rpm.
Of course if you are going to use an outboard you don't get to pick the prop.
With the waterline length and displacement you can figure the power required vs. speed relationship. Pick a target cruising speed, that amount of power (kw) times range in hours gives useable KW-H required of battery bank. Assuming lead acid batteries I'd figure useable KW-H = 80% of total battery KW-H for Concorde Lifeline AGMs.
Denny Wolfe
----- Original Message -----
From: George FarrellSent: Tuesday, November 24, 2009 9:38 AMSubject: Re: [Electric Boats] Alternative to propellerHi All
I'm in process of building a sailboat. I want to power it electrically.
How do I compute what I need (based on the length of the boat, its
displacement, distance I need to travel to get to open water suitable
for sailing or to get home if the wind should die, on whether I got
after inboard or trolling motor, etc.)? Are there formulas to cover
such questions -- and if so, what are they or where can I find them?
Thanks in advance for your help.- - - - - - Read my sailboat building blog at: http://buildingmysailboatcallednoma Happiness is a tall boat and a breeze to sail her by George F Farrell, Jr.d.blogspot. com/
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