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Old 15-01-2015, 11:36   #1
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Anyone convert their freewheeling drive shaft to a hydro turbine?

The old inboard from my boat has been removed, but the drive shaft with the fixed blade prop is still there.
I noticed that it spins quite fast while underway. I had an idea where I could get some pulleys and an alternator of some sort to generate power that charges the batteries.

After searching google, I couldn't find a whole lot of info on it. I found some discussion, but not many people who had experience, let alone feedback on how well it works.

It seems like it would be a lot cheaper than solar and I doubt it would have to produce much power for weekend sailing since most of the time you would be underway, producing power constantly. At the very least it would significantly slow the speed at which they discharge...

I found this: Amazon.com : 300 Watt Bicycle Generator 3/8" Belt Drive Pedal Power Pulley Dynamo : Wind Generator : Patio, Lawn & Garden

Does anyone have any experience or input?
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Old 15-01-2015, 11:56   #2
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Re: Anyone convert their freewheeling drive shaft to a hydro turbine?

Quote:
Originally Posted by VinnyVincent View Post
The old inboard from my boat has been removed, but the drive shaft with the fixed blade prop is still there.
I noticed that it spins quite fast while underway. I had an idea where I could get some pulleys and an alternator of some sort to generate power that charges the batteries.

After searching google, I couldn't find a whole lot of info on it. I found some discussion, but not many people who had experience, let alone feedback on how well it works.

It seems like it would be a lot cheaper than solar and I doubt it would have to produce much power for weekend sailing since most of the time you would be underway, producing power constantly. At the very least it would significantly slow the speed at which they discharge...

I found this: Amazon.com : 300 Watt Bicycle Generator 3/8" Belt Drive Pedal Power Pulley Dynamo : Wind Generator : Patio, Lawn & Garden

Does anyone have any experience or input?
It used to be quite a common setup, I know of a few around our club on the older boats that have done serious miles and the owners swear by them. But, if you no longer need the inboard, I would think the performance benefit of removing the prop altogether would be too tempting for me to pass up.

A small solar setup would also probably be much cheaper in terms of $ per watt-hour produced, since the generator is only going to work when you are under way, solar will be going all week. (Unless you anchor in some pretty serious currents.) And the solar will mean you come to a boat that is fully charged before you set out, better for the battery life.

Matt


P.S. Then there is also the whole vexed debate about whether a freewheeling prop or a locked prop produces more drag. I can't tell the difference when I apply the prop brake on our boat, but I sure don't miss the noise.
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Old 15-01-2015, 12:34   #3
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Re: Anyone convert their freewheeling drive shaft to a hydro turbine?

Pull the prop, sell it and buy a solar panel
Your absolutely correct though you can actually get quite a lot of power from that spinning prop, but that power comes from your sails, better to charge batteries anytime the sun is shining as opposed to anytime your sailing.
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Old 15-01-2015, 13:46   #4
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Re: Anyone convert their freewheeling drive shaft to a hydro turbine?

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Pull the prop, sell it and buy a solar panel
.
Even if the prop can't be sold as a useable item, I just came back from the scrap metal dealer last week with AU$212, mainly old bits of boat that I have removed. As a64pilot points out, that'll buy some solar.

Matt
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Old 15-01-2015, 14:46   #5
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Re: Anyone convert their freewheeling drive shaft to a hydro turbine?

Vinny,
There have been some discussions about "prop shaft generators" and "towed water generators", etc. and many of those had quite detailed info about what you're looking at...

They do work, but not nearly as cost effective as they were decades ago, when solar was as pricey as gold!

Have a look here...
Water Generator Concept Thread

Permanent Magnet Generator on Propshaft

Waterpower?

Cruising hydrogenerator 300 or 600

Towing Generators / Update, Anyone?


There are other threads, as well as the Dashew's books describing these, do a search here, on the SSCA boards, and on-line....and you'll find more...


In a nutshell....it is doable, but not always every practical....especially since obviously you only generate electricity when you're sailing (and usually need to be actually sailing well, at least 4 kts..), with the cost of solar panels coming down so much in recent years, water generators of any type are not nearly as cost effective as many believe...
(FYI, I own and use a Ferris Power WP-200, towed water gen....and while it is great on long passages, I would never recommend it over a good solar array...)


I hope this helps..

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Old 15-01-2015, 15:02   #6
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Re: Anyone convert their freewheeling drive shaft to a hydro turbine?

The all work - at the expense of speed. There's no such thing as a free lunch.
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Old 16-01-2015, 09:55   #7
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Re: Anyone convert their freewheeling drive shaft to a hydro turbine?

It would seem to me you would be robbing Peter to pay Paul. The more load you place on the free wheeling prop the more drag you place on your hull. I'll bet efficiency is poor. Remove the prop.
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Old 16-01-2015, 12:37   #8
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Re: Anyone convert their freewheeling drive shaft to a hydro turbine?

The thing is the boat stays plugged into the marina most of the time and when I'm out, I'm always underway on either motor or sail power. Unless I'm anchored for the night(which solar wouldn't be helping anyways).

It also seems that with my schedule I am going out at night or dusk half the time and I would be generating power with the prop setup where with solar it would be little to none.

In other words it seems like on paper I would be getting more watts per dollar with solar...but in reality the small current generated by the prop. could add up to a lot more than I would be getting from a solar panel, since it is producing a a pretty constant rate.

The bicycle generator is about 130 dollars shipped and I would need a voltage regulator for it...so I'm thinking cost would be about the same as a 100-200 watt solar kit.

I dunno it seems like they would produce close to the same amount of power and the solar would definitely be more productive in the summer when I am doing more sailing during the daylight hours...Maybe I will take the advice about selling the prop and just using that cash to buy the solar kit. Seems like a lot less headache since there are no moving parts.


The question is; do I sell the prop and fill the hole with epoxy, or save the prop and leave the shaft in so if I go to sell the boat it's worth more?(possibly won't make a difference since it's a cheap boat, I doubt anyone would be interested in putting a new inboard in)
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Old 16-01-2015, 12:55   #9
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Re: Anyone convert their freewheeling drive shaft to a hydro turbine?

You're posts are a bit confusing. At first you indicate that there is no inboard motor but then you mention being under power. I will assume you have an outboard motor - but still have the shaft in place from the old inboard. Curious.

If you are doing serious long distance cruising it would make sense from a redundancy point of view. But if you plugged in after a day sail I would say it's not worth it.
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Old 16-01-2015, 13:13   #10
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Re: Anyone convert their freewheeling drive shaft to a hydro turbine?

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You're posts are a bit confusing. At first you indicate that there is no inboard motor but then you mention being under power. I will assume you have an outboard motor - but still have the shaft in place from the old inboard. Curious.

If you are doing serious long distance cruising it would make sense from a redundancy point of view. But if you plugged in after a day sail I would say it's not worth it.
Sorry for the conflicting info, let me clarify...

The previous owner had removed the inboard engine for repair. He had planned on fixing it and re-installing it.
I came along and bought the boat before this happened and He flaked out on giving me the engine to finish repairs, so I just put an outboard on. Now the shaft is still there with the piece that bolts onto the gearbox(gearbox is gone) with the prop. still on the other end.

It's sounding like it is not worth the hassle and that solar would be comparable in cost and a lot more simple to set up and maintain.

I just can't decide if I just wan't to remove the prop. and leave the shaft, or have to hole sealed permanently...
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Old 16-01-2015, 14:13   #11
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Re: Anyone convert their freewheeling drive shaft to a hydro turbine?

They work, I have one. Underway expect around 1A per knot boat speed so at 6kn you are looking a 125ah/day. Underway it keeps the batteries fully charged That would require around 4-500w of solar panels. Output will drop very rapidly below 5kn. I built my from standard auto parts for under $200. The other issue is whether you might consider reinstalling an inboard at a later date. I will put details on here later (don't have time now)
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Old 16-01-2015, 14:24   #12
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Re: Anyone convert their freewheeling drive shaft to a hydro turbine?

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They work, I have one. Underway expect around 1A per knot boat speed so at 6kn you are looking a 125ah/day. Underway it keeps the batteries fully charged That would require around 4-500w of solar panels. Output will drop very rapidly below 5kn. I built my from standard auto parts for under $200. The other issue is whether you might consider reinstalling an inboard at a later date. I will put details on here later (don't have time now)
Please post details when you get a chance. If I could get that kind of power for less than 200 dollars it seems like an option.

If I remove the shaft and seal it, I'd have to pay to have it sealed on top of the solar panel cost, so at the 200 dollar price tag for the hydro turbine, it seems like a more cost effective option.
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Old 16-01-2015, 14:53   #13
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Re: Anyone convert their freewheeling drive shaft to a hydro turbine?

If you make removal of the engine, etc, permanent you may want to consider closing off the prop aperture altogether. Some folks have done so and claim better steering with the opening gone.

I have seen some of the installations where a car alternator is used. They mention having some way of removing diodes from the unit when the engine is driving the shaft since it can cause problems if the alternator is charging from a motor driven prop shaft.
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Old 16-01-2015, 14:58   #14
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Re: Anyone convert their freewheeling drive shaft to a hydro turbine?

A couple of comments:

The power output of such systems does not go up linearly with speed but perhaps more like the square of the speed. In our old towed system, it produced ~1 amp at 4 kn, ~4 amps at 5 kn, ~10 amps at 6 kn, and at higher speeds the bloddy thing jumped out of the water so often that it wasn't possible to measure the peak current very well! That system used a 6 hp outboard prop and a permanent magnet DC motor. With your much larger prop, greater output could possibly be extracted.

If you choose to remove the prop and shaft, simply replacing the shaft with a short section of scrap shafting, just long enough to fill the shaft log and extend inward for some sort of positive keeper will keep the water out and the dollars in your pocket.

But really, if your usage is as described, perhaps the most cost effective approach would be adding another battery and using the shore power charger to replenish the system.

Cheers,

Jim
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Old 16-01-2015, 15:00   #15
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Re: Anyone convert their freewheeling drive shaft to a hydro turbine?

It's permanent for me because I just bought a new outboard for it.
My concern would be resale if an owner insisted on putting an inboard in...although it's unlikely with a cheap boat like mine.

The beauty of this alternator idea is that I can leave the shaft on and have it be functional. I get some use out of it and it doesn't hurt resale value...it's also likely cheaper than paying to have it sealed off.

I'm thinking about using a bicycle generator instead of a car alternator though...not much of a price difference and the bicycle gen. uses permanent magnets instead of electromagnets like a car alternator, which use up a decent amount of power.
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