| Mike, sounds like your at the limit now and as far as extending the shaft I don't think that would be a good idea, any out of balance on the prop would take out the cutlass bearing. I don't know of any program for calculating the best prop for speed and power, Gerr's book on propellers is a great read. I have run into the same issues with diameters myself, only so much room. My second boat, an Island Trader 37 ketch has quite a bit more room and I"ll probably go up to a 22/23 inch prop, should help on the Regen also?? don't know, need to experiment.... there was an article a couple of years ago about a guy that was running a diesel but spinning his prop with a big alternator, he had a power hungry boat and needed all the juice he could get... he had an adjustable prop and through changing the pitch he was able to get reasonable results... as he wrote later that same setting was the best setting for efficiency in cruise mode... his prop was around a 20 inch, boat somewhere in the 40 ft range...?? don't remember exactly. I wouldn't get on the Regen band wagon, lots of people here think it's just not worth the effort, I personally think there is a good change that it can happen to a big advantage.... but who am I, just a shade tree inganear... haha
Dave K --- On Mon, 1/4/10, Mike <biankablog@verizon.net> wrote:
From: Mike <biankablog@verizon.net>
Subject: Re: [Electric Boats] Prop issue?
To: electricboats@yahoogroups.com
Date: Monday, January 4, 2010, 9:11 PM
Dave: I checked the boat today. I have exactly two inches from the tip of the prop blade to the hull. So I'm not sure I can go with a larger prop in the current position. I suppose I could extend the shaft but, then I am worrying about the clearance between the rear of the prop strut and the prop. Currently there is about an inch of clearance. I'm not sure if it's a good idea to extend it much further. Any comments on that? Also does anyone know if there is any program that can calculate the best prop diameter and pitch for an electrically propelled boat? Would like to see what kind of an improvement (if any) I might be able to get if I were to change the prop and see if it would be worth the cost of making the change. Capt. Mike
From: Dave Kellogg <inganear1@yahoo.com>
Subject: Re: [Electric Boats] Prop issue?
To: electricboats@yahoogroups.com
Date: Sunday, January 3, 2010, 11:49 PM
Mike, I don't believe prop pitch will do what you want, how much larger can you go with prop diameter...? Dave K
--- On Sun, 1/3/10, Mike <biankablog@verizon. net> wrote:
From: Mike <biankablog@verizon. net>
Subject: Re: [Electric Boats] Prop issue?
To: electricboats@ yahoogroups. com
Date: Sunday, January 3, 2010, 6:30 PM
| Hi Dave: Well I am not really worried about achieving regen though it would be nice. I too am more interested in low speed efficiency when motoring at say three to five knots. In the tests I've done so far I can use the Honda 2000 powering the Zivan NG-1 charger to move the boat about 2.8 knots in calm conditions without drawing any current from the battery bank. I'd like to see if I can get that over three and was wondering if changing the prop pitch might help. As I said I'm very happy now I was just wondering if some tweaking of the prop might improve things. Though I'm not sure how to figure what is the best prop size and pitch for my boat. Capt. Mike
From: Dave Kellogg <inganear1@yahoo. com>
Subject: Re: [Electric Boats] Prop issue?
To: electricboats@ yahoogroups. com
Date: Sunday, January 3, 2010, 8:32 PM
Mike, it's not uncommon to re-stamp a new pitch number when refurbishing. As far as Regen capabilities, I don't believe the inch change in pitch will do anything and unless your prop efficiency and boat speed are 6+ knots your possibilities are pretty slim on Regen... I don't know your setup so it's hard to make any determination. . The more efficient you can make your prop you can better that speed by a couple of knots, but less than 3 knots you will not get anything... I'm still working on the lower speed efficiency Dave K
--- On Sun, 1/3/10, Mike <biankablog@verizon. net> wrote:
From: Mike <biankablog@verizon. net>
Subject: [Electric Boats] Prop issue?
To: "ELECTRIC BOATS" <electricboats@ yahoogroups. com>
Date: Sunday, January 3, 2010, 2:31 PM
| I originally spec'd out my 30 foot 8 ton sailboat with it's current 3 bladed prop. Which I thought from the documentation was a 16 inch diameter, right handed prop with a 14" pitch. When I was polishing the prop last spring I came across some of the stampings on the prop which lead me to believe I have something different than I thought. You can see the markings I uncovered in the second photo located here: It appears to me that the original 14" pitch was stamped over and 13 is stamped in it's place. I've been happy with the performance of the prop (except no regen) with my electric system but, I am wondering if I would get better performance with a 14" pitch as I thought I had. Can anyone shed some light on this issue and what I things I might want to change. As I said I have been happy with the performance as is but, I am wondering if I can make it better. Capt. Mike |
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