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Old 06-01-2007, 01:20 PM   #1
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I was just reading the threat on sail boat propellors and was wondering if anybody has ever used their prop to generate electricity while under sail... seems like it would be easy enough... just install a gear on the shaft and connect it to some form of small turbine.... I would think this could be a pretty efficient way to charge batteries, etc. while under sail but I've never heard anyone comment on it.
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Old 06-01-2007, 03:39 PM   #2
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Yes, it is possible and it has been done.

http://www.haveblue.com/
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Old 06-01-2007, 04:46 PM   #3
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Better take a real good look at the installation "Costs and M&R" vs. "Usage" on these conversions. especially the M&R costs. Right now its still cheeper to install a small GenSet for recharge and hotel power and there are other more cost effective systems out there.

Do the research before you buy.....

RS
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Old 06-01-2007, 11:19 PM   #4
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Hi Atavist,

Hopefully we will get a response fromTrim50 on this topic as power generation is a subject about which he has exceptional knowledge. In the meantime, I guess the principle of generating power from your prop shaft is similar in concept to towing a 'waterpowered' generator. The towed generator was popular many years ago, but since the advent of solar cells and windgens, and of course the stories about H-U-G-E fish eating them, towed generators are now somewhat of an oddity.

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Old 06-02-2007, 12:07 PM   #5
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Hi,

Using a rotating prop-sahft to generate electricityis not a huge problem to overcome. What can be a problem is you gearbox. Some gearboxes don't tolerate a free turning shaft for very long. I assume it is a lubrication isue but wil cjeck up on it

Aye

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Old 06-03-2007, 09:47 AM   #6
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Quote:
Originally Posted by Nausikaa View Post
What can be a problem is you gearbox. Some gearboxes don't tolerate a free turning shaft for very long.
Hi,

Questions :- If an hydraulic gearbox can run continuously in either direction when under power - can it run continuously when the prop shaft is being turned by the forward motion of the boat (with the engine switched off and in neutral) ?

If the answer to the above is = yes, can a small generator be run off the turning prop shaft without a problem ?
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Old 06-03-2007, 06:59 PM   #7
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Here is what you want to use...

http://www.solomontechnologies.com/index2.html

http://www.solomontechnologies.com/m_recreational.htm
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Old 06-03-2007, 10:42 PM   #8
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In a retrofit situation - Where do you put the batteries in the average size cruising yacht ?
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Old 06-03-2007, 11:50 PM   #9
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In a retrofit situation - Where do you put the batteries in the average size cruising yacht ?
Pesky thing, the need to get them in and preferably low, huh? We're refitting our boat right now and because it needs a larger battery bank than it had, we're looking at storage space under our main saloon seating. That's midships just forward of our engine which resides under a small chart house. Our bilge is shallow and we don't see space to put battery boxes below the sole. The only other choice is building a "box" under our rather large main saloon table (this table is built around the main mast (its a schooner rigged boat). The weight would be in just the right place there--but we don't like the idea of giving up such premium and accessible space to a bank of batteries.

Heavy things, batteries, you can't just go stashing them just anywhere, that's for sure.

On this same thread--we are considering putting in a prop shaft generator since our Hurth/ZF transmission happens to be one that can freewheel without harm. It allows us to not feel bad for not replacing our fixed prop with a feathering prop, too, while we do this refit.
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Old 06-07-2007, 09:03 PM   #10
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About 20 year ago, I fitted out a ferro hull and installed an ordinary Lucas car alternator, via a layshaft and vee belts, to the prop shaft. The gearbox was a PRM and had, as I remember, an oil pump driven from both the input and output end, so it was OK to run it with the engine disengaged. It produced about 20 amps at 7 knots under sail and about the same at full engine rpm - the engine was a 97 hp Thorneycroft. I was told it would cause a lot of drag- 3 bladed fixed prop- but as it was fitted from the start and the yacht was rather heavy anyway (28 tons, 53 feet loa), I never noticed. The system was still working and had never given any sort of trouble when I sold the boat afer 10 years
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Old 06-11-2007, 03:23 AM   #11
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About 20 year ago, I fitted out a ferro hull and installed an ordinary Lucas car alternator, via a layshaft and vee belts, to the prop shaft. The gearbox was a PRM and had, as I remember, an oil pump driven from both the input and output end, so it was OK to run it with the engine disengaged. It produced about 20 amps at 7 knots under sail and about the same at full engine rpm - the engine was a 97 hp Thorneycroft. I was told it would cause a lot of drag- 3 bladed fixed prop- but as it was fitted from the start and the yacht was rather heavy anyway (28 tons, 53 feet loa), I never noticed. The system was still working and had never given any sort of trouble when I sold the boat afer 10 years
Oh, I'm thrilled to hear that you didn't notice too much in the way of performance detriment. We've been told to expect about 1 knot less in speed. Our boat's hull speed is just a tad under 10 knots. The boat is similiar in size and weight to the one you put the Lucas on. I'm happy to hear your experience also provided good charging, too. Most our friends aren't cruisers, they own boats that they race and wouldn't consider not having a feathering prop. The only worry we have w/o a feathering prop is that we won't be able to back down worth a darn with the fixed prop. It took me forever to get an answer out of ZF/Hurth about whether the particular transmission could "freewheel". I kept getting conflicting answers. I "polled" by calling several ZF service centers and got half saying yes and half saying no. Finally found a (non-zf) repair shop that has a copy of the manual for our mid-90's era Hurth and it clearly states we can freewheel w/o limitation.

Thanks again for the info!
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Old 04-09-2010, 05:29 PM   #12
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Lots of experience in this area. I've done if for years on my crusing sailboat. I have a Borg Warner reduction gear and although they say it shouldn't coast in their owner's manual, mine did it for 22 years and 40K ocean miles! No shaft brake. I had it rebuilt when I repowered at 20 years, and it was nearly perfect inside - no damge - put in clutches and seals anyway. Conclusion - they splash lube. I discussed this with their engineeres and they agree - not recommended but it works.

Other gears I cannot speak to - might recommend starting the engine twice or so per watch and put it in gear momentarily - perhaps during the charging of batteries since the gears I'm familiar with have their input shaft connected to the oil pump. That way everything gets lubed.

Ok - the charger - I made up a big pully that fastens to the shaft and a belt drive to a low start alternator I had made. I get 15 amps at 6 knots - enough to almost keep up with my autopilot, radar and frige when on a passage. I use an old fashioned Automac rheostate field charger so i can control the charge rate - if I go much faster than 6 kn it starts to put out a ton of electricity. That said, ou could just let the alternaor regulator do the job too.

I made a pivot joint so I can disconnect the shaft alternator belt when I'm powering although it does't hurt to leave it going, it spins way too fast when the shaft is powered. I hang two belts on the shaft before a long passage then secure one over the shaft log as a spare when I need it. Thus far I've never had to evoke the spare but to put a belt on I have to disconnect the coupling and shove the shaft backwards so I always keep two belts on.

Final thought - I'm now investigating a totally different charger - skipping the alternator and making a triple disk, 3 phase permanent magnet, axial alternator just like the home-made ones for wind generators. Lots of info on the internet. It would put out lots more juice and it would never need me running down below to engage the belt - no belts no worries. If it was disconnected it would just stop putting out electricity or one could regulate it with a dump load.

Mike Fitzpatrick Capt. USMM
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Old 04-10-2010, 03:37 AM   #13
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Hi Mike! Welcome to Cruiser Log and thanks for the info!

Since I posted my stuff, we've re-launched the boat and are using it with the prop spinning (no shaft brake) but haven't put an alternator on it--no room for a big sheave. Your idea about making the triple disk/3phase permanent magnet...that sounds very intriguing. I'll have to google it...

Regards, Brenda
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