Ditto here…and it's been 11 ½ years since I've taken that data on my boat, but here's what I measured then:
Speed | Power (Pbatt) | Speed/Power (range/energy) |
2.5 kt | 0.69 kw | 3.62 n-mi/kw-h |
2.9 | 0.97 | 3.00 |
3.5 | 1.33 | 2.64 |
4.0 | 1.73 | 2.31 |
4.2 | 2.14 | 1.96 |
4.5 | 2.85 | 1.58 |
4.9 | 3.52 | 1.39 |
5.2 | 4.20 | 1.24 |
5.6 | 4.97 | 1.13 |
5.75 | 5.79 | 0.99 |
6.0 | 7.29 | 0.82 |
Graphically:
It's wiggly, and the power data assumes constant battery voltage of 36v as battery current was measured. Speed was measured using a "knotstick". This data taken in 2004…you can see the power roughly doubling with speed in knots.
Your mileage may vary-
-Myles
From: electricboats@yahoogroups.com [mailto:electricboats@yahoogroups.com]
Sent: Friday, November 20, 2015 1:39 PM
To: electricboats@yahoogroups.com
Subject: [Electric Boats] Re: Electric conversion
Quite Agree,
I've been preaching that for years, Not that anyone listens 
.
Eric SV Meander
---In electricboats@yahoogroups.com, <moriartybob@...> wrote :
Just a very general statement about hull speed; it takes twice the energy to motor at 6 knots vs. 5 knots on a ~33 foot LOA (26.4 LWL) displacement sailboat. So, don't think about going hull speed (1.34 X square root of LWL in feet). Think instead about a sweet spot of around 1 X square root of LWL. This puts my boat's ideal speed under power at around 5.1 knots instead of 6.0. It's just a general guideline. I could go even further at 4 knots. What's the hurry?
Thanks to James Lambden for this concept.
Cheers,
--Bob M
Ox C&C 33-1
Jax, FL
Posted by: "Myles Twete" <matwete@comcast.net>
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