Hi Greg,
I'm another one that takes a portable generator along for trips that exceed the range of my batteries, just in case. Running my Yamaha 2000 generator through my battery changer, I can motor at 4.4kts without any input from the batteries as long as the gasoline holds out. Using my battery pack and the generator, I can run at 5kts for seven hours from a full charge. If I don't need the extra range or power, the 50lb generator stays packed in a lazerette and for day sails, it stays at the dock.
However, I agree that optimizing your drive is preferable. But before you start spending money, you need to evaluate just how much you might be able to gain, how much room do you have to improve. I assume that you have an idea of your "watts to knots" numbers with your current setup. If your 4kt power drain is 1200W-1700W, then how much better do you think that is can be? My 5 ton ketch uses 1200W at 4kts, I can't imagine that there is much opportunity to use less than the 1.6hp that I'm at already.
Which brings us back to the other conversation that I've been trying to manage. Is there an accurate way to calculate how much power needs to be applied to a prop to drive a given hull? We now know that the widely accepted Gerr formulas aren't applicable for our boats at our speeds.
Feel free to contact me offline to discuss some of the specifics about your boat and drive if you like.
Fair winds,
Eric
Marina del Rey, CA
--- In electricboats@yahoogroups.com, "Greg Martin" <ffmagellan@...> wrote:
>
> Thanks Mike. I agree, EP allows for many different philosophies and I too have thought of EP as a backup to my sails. Sails only work when there's wind though and last weekend was the first time I've ever seen in Okinawa where we had zero wind all day despite the forecast which called for a light steady breeze.
>
> Personally, I'm all about optimizing my system now and I really want to figure out how to extend my range and make my system most efficient now. Next up: better propeller and possibly better batteries.
>
> -Greg
>
> Greg Martin
> s/v Intrepid
> Bristol 32e
> Okinawa, Japan
>
> www.ElectricSeas.org
>
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