Hi Jim,
What is the heading on your photos? I have a slow connection and it takes forever to browse through them.
I've been thinking along similar lines for quite some time and have settled on an existing hull for my prototype "camper". I found an old, engineless Albin 25 that I'm converting. I believe this is an almost ideal hull for the purpose as it was designed as a low-power displacement-hull live-aboard cruiser from the start, and it is trailerable (8 ft. beam). It is also a solid and seaworthy boat, not to mention I didn't have to go through all the work of building it!
It swings a 17 inch prop, which is also good for low-power efficiency.
Preliminary tests with a 48V Mars motor are encouraging.
Max 6.2 kt at 110A
5 kt at 40A
4 kt at 20A
3 kt at 10A
These are rough figures taken in calm conditions.
With a full length hardtop installed over the pilot house and cockpit, I have room for four 225W solar panels. I should be able to get over 3 kts on solar alone with this setup.
I'm not a fan of big wind-gennys on boats, I think all that windage and top-hamper would be trouble when the breeze kicks up and you're caught out in the open. Not to mention storms. Might be better off with a small sail rig to supplement your motive power, and maybe a smallish, deployable wind-gen.
I encourage you to press ahead with your ideas, your speed expectations sound reasonable if not conservative. As for motors, the e-tec is no longer on the market, but at 7HP that's probably a good size range. I'm not real familiar with Lynch. There are a few others in the 5-10HP range that would probably work fine. You could check out my brother's site (www.electricyacht.com) for some ideas. One of his smallest units would probably be about right. You shouldn't have much trouble picking a motor size, especially with all the help available on this group. Some of the guys here have the math pretty well dialed-in. Basically you want as big a prop as you can fit, and size the motor a little bigger than the math says you'll need. Then set up your reduction ratio so full power amp draw doesn't fry your batteries.
Battery selection and energy harvesting capability will determine your range of course, and that's probably the trickiest part to anticipate. There is some good solar and wind info on-line at WWW.NREL.GOV.
Please keep us posted!
Jim McMillan
--- In electricboats@yahoogroups.com, "Eric" <ewdysar@...> wrote:
>
> Jim,
>
> Interesting model. There are a few things that will make out estimates more accurate. What is your intended displacment with people, gear, panels, drive, batteries, etc.? What is your intended range?
>
> 4 knots shouldn't be too bad in calm condition, but with the windage that you're proposing, dealing with 12-15 knot winds will really raise your power requirements. If you can find a similarly sized boat, you can get an idea of the performance from regular IC engines and that can be translated into electric drive requirements. Of course with a completely custom design, collecting comparable data can be difficult. Most of the small trailerable 20-25' cruisers that I looked up are aiming for higher performance (cruise around 14kts) but they typically have 40-50hp outboards.
>
> If you get the basic structure built, you might want to temporarily mount a 10hp outboard to determine whether the boat will need more or less power, allowing you to size the electric drive correctly. On your test runs you would need to add ballast where you expect weight, like on the roof to simulate the solar panels, around the cabin to simulate gear and guests and in the bilge to simulate the batteries. You'll be able to learn a lot without investing thousands of dollars in the solar, drive and batteries. I would definitely verify the stability with the panels mounted high, I find that they weigh more than people think that they do and have a bigger effect on stability than expected.
>
> Fair winds,
> Eric
>
> --- In electricboats@yahoogroups.com, "jdketchell" <jdketchell@> wrote:
> >
> > Hello to all out there, my name is Jim and I have been working on a electric boat concept for a few weeks now. a 20' water camper,wood/epoxy construction, that will use both solar and wind for battery recharge. a vawt or vertical axis wind turbine would be mounted to roof and would power a axial flux generator. the hull design is based on John Bell's (blondie) sail boat and has been stretched from 9 feet to 20' with an 8 foot beam. a boxed keel will be slotted for each bulkhead (also slotted) which should speed up assembly and provide water tight chambers under floor for 2 banks of batteries, water tanks ,etc. with this being a displacement hull for sheltered to slight chop waters, I am unsure of the power requirements needed to push this hull on a sedate cruise speed at around 2 to 4 knots. a single lynch or e-tec motor via belt reduction is being considered, but alternatives would be helpful. please have a look in the photos section for drawings and a model hull for insight on this matter. any input or suggestions will be helpful. thank you in advance. Jim
> >
>
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