Very good summary, thanks.
At this moment I like to add a few cents of my own disbelieve that regen in the discussed way is a good direction of search for the jackpot.
There are two important issues;
A- the prop
B- the generator.
A-
The prop is optimised for pushing a sailboat. ie efficient airfoilsection, large diameter and slow turning and preferably high aspectratioblades wich can hide behind a keel and, if you have the money, is feathering.
A sailboatprop when pushing has a highwaterpressure on his backside en a low pressure on the front. That is what makes the boat going.
In regenmode the high and low pressuresides are reversed,.thus the airfoilshape is very detrimental for efficient regen.
Airplanes do fly many times upside down but lookig how they hang tail down it shows that the wing is not very effective in producing lift upside down. There are symmetrical airfoilshapes but they are a compromise for aerobatics at the cost of lift. Symmetrical airfoilshapes are more practical at high speeds but high revs is not what we want for electro saildrive.
What might be a way is a feathering prop who can "overfeather" and so present its hollow side to the inflowing water.
B-
Also the generator needs to high rev to produce current at an economical scale. See the dynamo/generator on your bike or car. They are very geared up. An electric motor at 1000 rpm is producing current but verry inefficient.
The best way is to use a real alternator wich is geared up a lot and not using the motor.
Noting that most sailors go a long way to minimize the drag from a prop and noting the inefficiency of the drivetrain "in reverse" I will believe for a long time to come this is NOT the way tro produce electricity on a sailboat.
The most practical to me is a windturbine on your ship at the same spot where in the sixties and seventies the vane of the selfsteering mechanism was. These things are bought from the shelf. They only produce drag when you sail to the wind. If the wind is at 90 degrees there is hardly any drag (only drift) and when the wind is aft the drag is even pushing you.
You eleminate the whole chain of inefficiencies from sail, hull, drift, prop, bearings, chain or belt. generator.
If you do not need the power from the windturbie you take of the propellors and drag iz (nearly) zero.
When you are in the doldrums I would trust on enough solarpanels for the fridge and to search for wind.
Carel
----- Original Message -----From: aweekdaysailorSent: Monday, March 08, 2010 4:11 AMSubject: Re: [Electric Boats] propellersHere's my summary of the discussion over the last few years.
http://sites.google.com/ which includes a link to a thread here on this group which i think best explains the problem and gives some idea of the theoretical maximums available.site/electricboa ting/Home/ range-optimizati on/regeneration
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