Dan,
While I can't figure out how a folding prop can be used to effectively collect regen, their figures support exactly what I said below. Their system is 24V and they quote 3-5 amps from 5kts, followed by a list of reasons why it may not work as well as they suggest. I would be interested to see any data that supports the 5A claim but even so, that would only be 120W. I find three amps more believable. It also shows that sailing your boat at 7kts would get you into the 300-400W range. Unfortunately, most 30 sailboats have a top speed of 6-6.5kts and that is with everything as clean and streamlined as possible. Attempting regen will make those speed targets even harder to sustain.
Many of the conversions here use reduction units, mostly to get the motor speed up for cooling and continuous power rating while keeping the prop speed lower for efficiency. In practice that does not seem to increase the amount of energy that can be extracted from a boat propellor.
I am very interested in regen, but I have yet to hear any reports of significant regen in our type of boats (30' displacement) from anyone not trying to sell me something.
Fair winds,
Eric
Marina del Rey, CA
--- In electricboats@yahoogroups.com, Daniel Michaels <nov32394@...> wrote:
>
> This is an interesting site, and I think the motor is about the same as a E Teck.
>
> http://www.ozmarine.se/OZecoDrive/Eng/IndexOZecoDriveEng.html
>
> That is with direct drive. If you have a PSRU you could be going only 3 knots and turning the motor 6.
>
> Dan
>
> --- On Fri, 8/6/10, Eric <ewdysar@...> wrote:
>
> From: Eric <ewdysar@...>
> Subject: [Electric Boats] Re: Re The Bigger Picture
> To: electricboats@yahoogroups.com
> Date: Friday, August 6, 2010, 5:29 PM
>
> Regen under sail does sound good, but the only real success stories have come from multihulls and large boats. This is because of their extra speed capabilities. I don't know of any verified claims of generating more than 100W (2A @ 48V) at 5kts or less. Since the act of regen slows the boat down, a displacement type 30' boat will have to be pushed pretty hard to stay above 5kts and even then, the energy collected won't put very much back. Here's a scenario, you head out of your slip and spend 15 minutes at 4-5kts getting away to clear water. If you've averaged 3000W, you've used 750Wh. Averaging 5kts under sail, you're generating 100W. 4 hours later, you've put back a little more than 1/2 the energy that you used up front. Even running slower under power, like 1500W, for every 4 minutes under power, you need an hour of sailing at 5kts to break even. Of course, like you said, many drive systems already include this capability, so any collected energy is essentially "free".....
>
> Fair winds,
>
> Eric
>
> Marina del Rey, CA
>
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