Eric,
I know Bill and Cynthia on the DragonFly and have corresponded with them frequently. I was working on the Arc in LaBelle last year when I met them passing thru Florida. They where a real inspiration at the time. That 60hp Yanmar in DF is probably about twice as big as it needs to be for that boat in my opinion but your point is well taken about having the diesel in parallel. I figure I might need to upsize the electric motor a bit if I do convert to a series hybrid but I want to develop a lot of baseline data with the 9hp before I decide anything. I just barely got in two short test cruises before I had to leave last week and I didn't have a DC amprobe so I still don't know that much about how well the boat is operating other than it seem to work very well. I'll be returning with an amprobe and tachometer soon for much more testing.
Since I'm designing the boat specifically to be ditch cruiser I really believe I might just be able to get by with the 9 hp in a series system though for what I'm doing but that definitely has yet to be determined. My intention right now is to virtually never use the diesel unless the motor simply dies, my anchor line breaks, and I'm drifting toward a rocky shore. My hope is to complete the entire great loop on solar power alone. I realize if I decide to go ocean cruising in it, 9hp will be sorely inadequate. For the several brief open water excursion along the loop I'll just have to be careful and time the weather right. Many people have made the passage on far less seaworthy boats than the Arc.
Also, if I do get rid of the old diesel I could eliminate 4 bearings, two universal joints and the V-drive from my driveline and that might offer another 5-10% of power at the prop. Plus, it will give me room and ballast credit to add another battery bank in the aft engine room. But, like I said, a lot more data will have to be generated before I can make an informed decision. However, given the performance I experienced from the 9hp, I'm thinking I might be able to go water skiing with 20 kW.
I'm not sure if we're talking about the same autoprop here. The one I have was "supposedly" custom designed for this boat specifically to enhance the performance of the diesel propulsion and according to the previous owner it did a good job of it. It does not fold up and doesn't look like it would reduce drag any to me. But I don't know that much about it, since it came with the boat.
You mentioned "most of our sailboats with similar hulls" and I was wondering who else had a twin keeled bilge boat with a very shallow draft. I'd like to talk with them. This boat was custom crafted and totally hand made by a naval architect that really knew what he was doing from what I can tell. I've seen some similar bilge keel boats, I think Colvic makes one in England, but they are quite a bit different than the Arc. It really does have a very unique hull shape. I've never seen anything like it in my 30 years on the water and I believe it might give it measurably superior hydrodynamics. It's pretty tricked out in some other ways too with nearly 500 gallons of water storage, 500 gallons of fuel tanks,(which I no longer need btw) and a 75 gallon waste tank. You have to fill and empty the port and starboard tanks evenly or you get a noticeable list if one is completely empty and the other full.
I will post more data as I generate it and we will see how it does.
Carter
From: Eric <ewdysar@yahoo.com>
To: electricboats@yahoogroups.com
Sent: Tuesday, March 27, 2012 2:58 PM
Subject: [Electric Boats] Re: Introducing the 'Arc'himedes
To: electricboats@yahoogroups.com
Sent: Tuesday, March 27, 2012 2:58 PM
Subject: [Electric Boats] Re: Introducing the 'Arc'himedes
Hi Carter,
While you might not use the diesel engine much, I would not replace it with a diesel generator. That would turn your boat into a serial hybrid rather than the parallel hybrid system that you have now. See what the owners of Dragonfly (slowboatcruise.com) did for their great loop trip. Given your small motor, you won't have the power to deal with adverse conditions like heavy crosswinds or strong currents. Your current setup should be ok for most days, but I would hate to see you stuck or worse because you misjudged your power output needs.
I was going to comment earlier that your small motor seems ok as long as you've got a diesel driveline to fire up in emergencies. The whole 1kW per ton guideline is geared to provide enough power to deal with most situations (not Coast Guard rescue boat type conditions) and to keep our electric only boats safe. If you do go serial, you should upgrade your electric motor to something more appropriate.
The only real reason to run an Autoprop is for less drag while sailing. Since you can't sail, a fixed prop will be fine (notice that no power boats use autoprops or similar). You will be able to go much more aggressive in pitch and E.A.R. (expanded area ratio)with the electric motor, but you'll have to temper that with your diesel driveline capabilities. Again, if you go serial, you should be able to improve your electric efficiency by optimizing your prop.
If you get up to 5kW of solar collection, you should be able to collect more than 20kWh per day. That works out to about 8 hours at 2500W, give or take. Most of our sailboats with similar hull shapes can hit 5kts with 2500W. If you get a chance, can you perform some controlled speed trials (multiple passes over a set course in opposite directions) to figure out what your watts to knots performance number are? Without your rig, you'll have less wind resistance, but your stock driveline will suck up more power than you think. I'm really interested how your numbers will turn out.
Fair winds and smooth seas,
Eric
Marina del Rey, CA
--- In electricboats@yahoogroups.com, Carter Quillen <twowheelinguy@...> wrote:
>
> Tim,
>
> The boat came with the autoprop and unfortuneately it is about worn out so I'm not sure if I'll have it rebuilt or go back to the original 3 blade prop that came with the boat. The old owner did do some comparisons and the autoprop definitely increase the boat performance, by about 15%. I could go back to the old prop and just change the gear ratio of my sprocket to compensate. I'm thinking a couple of sprockets might be a lot cheaper than having the prop rebuilt but I'll look into it before I make a decision.
>
> Regen from the prop is not really an option because I don't have sails to drive it. I think the controller does have a regen feature but the drive train would have to be significantly modified to use it and with 5kW of solar I'm hoping I won't need it. I'm leaning toward eventually scrapping the ancient diesel and putting in a small diesel genset that puts out 48V for when the sun is not shining.
>
> My first mate is the blogger but I'll tell her about the eyefi card. I've never heard of it before.
>
> Carter
>
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