I've done some experiments on different boats in reference to drag, consistently the lighter the boat the drag affect goes up, tremendously. I started with my old San Juan 21, a light little boat that will give you a response on anything. My pretend propeller and nozzle would take nearly 2 knots off the speed when dragging. On a friends boat weighing 16000, we couldn't see much at all, I mean 1/4 to 1/2 knot and that was a guess as the wind wasn't that steady and under power it was closer to 1/4 knot. So using that as a bench mark the boat itself makes a big part of the equation..
Dave K
From: Steamboat Willie <stmbtwle@yahoo.com>
To: electricboats@yahoogroups.com
Sent: Mon, November 29, 2010 8:34:17 AM
Subject: Re: [Electric Boats] Re: Converting an Albin 27
I think you're on the right track... Normally the prop is chosen for the best compromise for the engine, drag, and friction. A bigger prop will give you more thrust for a given HP and also will intercept more water flow for regen; however it'll also create more drag under sail. How much you're willing to accept is the kicker.
--- On Mon, 11/29/10, Dave Kellogg <inganear1@yahoo.com> wrote:
From: Dave Kellogg <inganear1@yahoo.com>
Subject: Re: [Electric Boats] Re: Converting an Albin 27
To: electricboats@yahoogroups.com
Date: Monday, November 29, 2010, 8:16 AM
Mike,
Won't think of giving up, just going a different route.... Starting at the root, not the back end in the controller. The prop and the efficiency of that system is my starting place, when I have that in my grasps at 2 knots.....(I hear some faint chuckles out there) that's the speed that almost all sailors can get... the beat goes on, but it starts with the prop.. Dave K
From: Mike <biankablog@verizon.net>
To: electricboats@yahoogroups.com
Sent: Mon, November 29, 2010 7:59:46 AM
Subject: Re: [Electric Boats] Re: Converting an Albin 27
David: You should absolutely not give up on regen. I was able to get my regen working this past season after two years of trying. Though I was moving along at about six + knots at the time. So I know it works but, one is not always going that speed (at least I am not). Also I think my controller may have a programming issue as when I put the throttle into the regen detent position I get a current draw of -4 amps. I'm thinking that the controller is setup to be used as an "electric brake" and not set up for the type of regen from a propeller turning in the water. I may get around to looking at this issue at some point. But, my electric propulsion system is working great for my cruising needs and I don't depend on regen for charging. Plus when I'm moving along at regen speeds I concentrating more on sailing than keeping an eye on the current meter. So the urgency to get in there and mess around with programming the controller is not high on my list. I'm a "if it ain't broke, don't fix it type of sailor" but, that does not mean I don't encourage others to experiment and tweak their systems if they want too. Capt. Mike
|
|
No comments:
Post a Comment