Spinning prop

[Guest]

While sailing my prop spins which I guess is normal, so I always engage reverse and leave it stopped. I intend a 6/12 month cruise and thought of buying a wind/water charger but was horrified by cost. Could I use the spinning prop to charge a battery? I dont know much about electronics so any suggestions please?


Thanks

TaoRichard

 

[jfkal]

There is supposed to be a shaft-generator. Can't remember the name of the company. But it appears to be equally expensive. -And you need a certain length of exposed shaft to fit the thing.

 

[yoda]

The electrical problem is very simple, the larger problem may be the effect on the stern shaft of taking a drive from it and the wear on the bearings that support the shaft. If you have a well supported shaft with room to fit a pully you could certainly drive an alternator and since that is all a commercial water driven generator is you should be in luck. What may be a bit difficult is ensuring the correct range of rotational speed and ratio of pully sizes on shaft and alternator. What is certainly ttrue however is that a small charging current 24 hours a day adds up to quite a bit. Used a water powered generator crossing the pond and was delighted with it's performance. Certainly worth looking into.

Yoda

 

[Guest]

Thanks fr your comments both of you. Yes there is enough shaft exposed - about a foot maybe more. I ll try a second hand car alternator and I can get a friend to make a pulley for me. I also intend fitting a pair of the excellent solar panels from Maplin Electronics which are only about 35pstg ea so with both systems working I should get a useful amount of current.

Thanks again.

Richard

 

[Guest]

I remember reading an article about just such a project in either PBO or YM last back end.
The guy reckoned the free wheeling prop rotated at somewhere between 1/2 and 1/3 of the speed when driven under 50% power. He suggested fitting appropriate pulleys to drive another alternator.
Seemed like a feasable notion.
I was wondering if I could concoct a "chuck it over the side" prop version for my little boat.
I'll try to find the back number if required.
Rod

 

[Guest]

You can buy an impeller for a line driven alternator from Ampair fairly cheaply I guess its then only a question of fitting an alternator in a "dry" location. Over the past couple of days this has actually seemed the simplest solution to the whole problem! The alternator could be mounted under the cockpit seating and a bearing with attachment for line in the transom. Anyway tks fr yr comments its getting more and more practical

 

[Guest]

Have seen a small alternator fitted to a little 2 cylinder 600cc diesel made by Kabuta(? spelling) This unit was supposed to power a small digger/dumper so the alternator just kept the battery topped up, no headlights etc.
The current rating was about 10 amps. Don't know what/if regulator system employed.
Might be worth having a chat with perveyors of light industrial equipment in your area.
As far as solar panels go, check if a protection diode is included. If not, use a Schottky type--- there is less forward drop voltage so you will get a bit more umph.
Wasn't able to liberate said alternator---Owner watching!!!

 

[HaraldS]

Wouldn't recommend that. Efficiency is very low as the prop isn't designed as a turbine, radial laod with a V-belt is not good for the bearings and seals. Also the spinning prop has more drag than the stopped one, that's what helicopters use to sink slower in an emergency.