Hi John,
I agree with your sentiment, but I have to ask, when was the last time that you motored your boat anywhere at 2 knots? In comparison, at 51 years old, I can swim 1.5 nm in about an hour and my average paddling speed in the 17' ocean kayak that I built is between 3 and 3.5 kts.
For most of our boats, there's a big difference between hull speed and 2 knots. I have found that 3 knots takes very little energy for my 10,200 lb, 30' ketch (right around 500 watts) and at that speed, my 200 lb, 8kWh Li battery pack has a usable range of more than 12 hours.
For me, motoring at 3 kts seems barely more than drifting and I find that 4 kts is a comfortable slow speed. 4 kts works out to 1000W and my batteries will cover that for more than 6 hours without any input.
While my electric drive can push my boat 1/2 kt faster than the diesel that I removed, the only time that I've motored at 6 kts (5200W) was during performance testing. I would guess that about 80% of my electric motoring has been around 4.5 kts.
But like other members have noted, many of our boats are sailboats. When I was putting my conversion together, I was worried about the limited range that an electric drive would represent. But I have found those worries to be unfounded. Since converting my boat 2 years ago, I haven't ever discharged the batteries more than 30%, except for during performance tests.
So I agree, it pays to slow down with electric, but you don't have to resign yourself to a fast drift. Seriously, if you tell regular boat people that an electric boat should only be operated slower than 3 kts, then most boaters will think that electric drive is just a novelty and not a viable replacement for IC engines. So be careful how you represent the electric boat community, most regular boaters are quick to grab onto any excuse to dismiss our technology.
Fair winds,
Eric
1964 Bermuda 30 ketch, 5.5kW Propulsion Marine drive, 8Kwh LiFePO4 batteries
Marina del Rey, CA
PS. Don't hold your breath for better batteries, historically they're pretty slow coming and we've already got batteries that support the auxilary job really well.
--- In electricboats@yahoogroups.com, John Francis <surv69@...> wrote:
>
> ... Today(and in the future), it will be electric with virtually no
> infrastructure for a while, then when a viable infrastructure(and better batteries), exist, electric will be the way to go.
>
> I say today . . . and work with what works and what's available.
> I say slow sustainable speed under power( maybe about 2 knots or so)....
>
> BUT . . . of course . . . NO ONE really want's to go "slow" in a sailboat under power and EVERYTHING is valued at maintain hull speed or near HULL SPEED.
>
> You got to say goodbye to HULL SPEED being the determining "value" of an acceptable speed.
>
> LEARN TO SAIL and learn to live a more leisurely life(style) . . . THEN electric will be worth it.
>
> John Francis
>
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