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Old 15-08-2017, 13:26   #31
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Re: Utilizing free wheeling prop spin

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Pete7 The people I know all have Cats and travel often. They use the auto pilot at night when in open sea's. Why not utilize the free spinning prop to keep the battery bank at 99% charge? All have 5 or 6 solar panels that are great on a sunny day. What I am proposing is a secondary charging system.
How many of those cats have shaft drives that could use your system?

I'd guestimate that the majority of cats today have sail drives and more and more new monos have them as well.
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Old 15-08-2017, 13:27   #32
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Re: Utilizing free wheeling prop spin

Mango51 Thank you as it is feasible! The only difference is I proposed adding a electromechanical clutch so the prop could Free spin while under sail. Because the clutch is mounted after the transmission there is no wear on the Transmission in free spin. I was just throwing an idea out here!
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Old 15-08-2017, 14:14   #33
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Re: Utilizing free wheeling prop spin

From experience, here are some negative observations.

How will the shaft thrust be absorbed.
If you have something big and clunky and complicated on the shaft , how will you get a replacement drive belt on and off.
You may gain a few amps, but you will have a propeller that won't fold.

I have one, but it is saved for mostly o'night passages, when the solar is not working.
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Old 15-08-2017, 14:53   #34
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Re: Utilizing free wheeling prop spin

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My fathers 1982 Amel mango #31 came with a propeller shaft alternator and so did mine(1983 mango #33).from factory. It use the same key as the main engine to ignite. It made 14-17 amps at 7 knots. Mine is missing the alternator but have all wiring,gauge and pulley.

If the vaunted Amel line has the feature then it is surely achievable in a high performance manner. Follow closely in the patterns of their yard and you are on a proven path.

Amel's are so well designed that even knowledgeable sailors learn a lot from asking why they did this or that.
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Old 15-08-2017, 15:04   #35
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Re: Utilizing free wheeling prop spin

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If the vaunted Amel line has the feature then it is surely achievable in a high performance manner. Follow closely in the patterns of their yard and you are on a proven path.

Amel's are so well designed that even knowledgeable sailors learn a lot from asking why they did this or that.
Then ask "why does Amel no longer have these fitted to their boats?" Technology has changed and there are better ways. A tow gen is one of those better ways.... as is solar of course. Things have improved from the 70s and 80s.

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Old 15-08-2017, 15:04   #36
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Re: Utilizing free wheeling prop spin

This is a thing which I have considered on my cat ( direct drive , non folding props ) tho not the electro clutch system , my thots were simple cog / belt pulley drive on a release cam driving a bracketed alternator , it would require attaching and releasing for use but would not be much of a problem . Also needed would be some protective metal sheeting to protect the hull in case of chain ( / not so much belt ) breakage / slap . Still have no definitive answere re the engage / disengage trans when sailing . I would bet the two different possible answers are available from two different " experts "
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Old 15-08-2017, 15:51   #37
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Re: Utilizing free wheeling prop spin

Fair point Matt. So would you say it is doable but there are better methods now?
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Old 15-08-2017, 16:17   #38
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Re: Utilizing free wheeling prop spin

for the OP:

Rob, you keep saying "free power" from your proposed system. You are not listening to those who tell you that it is not "free". Such systems DO slow the boat down, and this is anathema to many sailors,even cruisers... like Dockhead and myself and lots of other CF participants. Do realize that many of us spend some few thousands of dollars on folding or feathering propellers just to eliminate the drag of an UNLOADED spinning prop.

Some folks, again myself included, have purchased or DIYed towed propellers for power generation. Not expensive, and when not needed, simply removed from the water. A more practical and more efficient methodology IMO, one that allows the use of a folding prop for better sailing.

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Old 15-08-2017, 17:12   #39
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Re: Utilizing free wheeling prop spin

It may not be totally " free " but , not sure which logorithim to use , there will be some surplus ( " free " ) power where the power gained will outweigh the speed loss .
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Old 15-08-2017, 17:22   #40
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Re: Utilizing free wheeling prop spin

Jim Cate this post was aimed at all those that were asking about prop spin verses locking it up. Technology is always changing and many are dropping the diesels for electric regenerative sail drives. Like the battery banks that store the power all have evolved. My main fault here is the basic idea is a good one, but with so many different configurations all conversions would be custom. Next idea a super slick antifouling coating that never needs scraping! Collapsible props are Great until they are fouled and refuse to open, and you have a collision. But thank you for all the input.
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Old 15-08-2017, 17:40   #41
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Re: Utilizing free wheeling prop spin

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Still have no definitive answere re the engage / disengage trans when sailing . I would bet the two different possible answers are available from two different " experts "
I would bet the two different possible answers are available from two different manufacturers of engines and transmissions.

The appropriate mode depends on the specific combination of engine and transmission (gearbox and bearing lubrication and clutch type being important factors)
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Old 15-08-2017, 18:08   #42
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Re: Utilizing free wheeling prop spin

This is a goofy idea. This is like a mag clutch for AC. The goofy part is your prop would depend on 12v to power your boat, otherwise, the thing would quit. Don't even think about corroson..
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Old 15-08-2017, 18:15   #43
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Re: Utilizing free wheeling prop spin

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Originally Posted by robmclennan View Post
Jim Cate this post was aimed at all those that were asking about prop spin verses locking it up. Technology is always changing and many are dropping the diesels for electric regenerative sail drives. Like the battery banks that store the power all have evolved. My main fault here is the basic idea is a good one, but with so many different configurations all conversions would be custom. Next idea a super slick antifouling coating that never needs scraping! Collapsible props are Great until they are fouled and refuse to open, and you have a collision. But thank you for all the input.
Rob, I'm not seeing where "many" are switching from diesel to electric power so far. A few, yes, but the energy storage problem is far from solved, and for most applications, range/power limitations are as yet insuperable for a pure electric auxiliary. And regeneration is never free... if you extract energy to generate electricity, there will always be a reduction in sailing speed. May be less apparent in conditions were the boat is at hull speed, but it's still there. Some sailors are not willing to have that loss.

And somehow I've managed to use folding props for over forty years and well over 125,000 miles without the dire events you forecast. I think your warning is a bit silly.

We all await your "never needs scraping" coating with much anticipation. What a great idea... I wonder why no one has thought of that? Good luck with the development.

Innovation is wonderful, but practicality and achievability must be part of the development process, as well as being sure that there is a true need for the proposed item.

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Old 15-08-2017, 18:26   #44
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Re: Utilizing free wheeling prop spin

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Originally Posted by robmclennan View Post
Jim Cate this post was aimed at all those that were asking about prop spin verses locking it up. Technology is always changing and many are dropping the diesels for electric regenerative sail drives. Like the battery banks that store the power all have evolved. My main fault here is the basic idea is a good one, but with so many different configurations all conversions would be custom. Next idea a super slick antifouling coating that never needs scraping! Collapsible props are Great until they are fouled and refuse to open, and you have a collision. But thank you for all the input.
There is almost no usable power that can extracted from a "free spinning" prop. As soon as you stated to harvest any power from the "free spinning" prop, it no longer is "free spinning"; it actually starts to slow down and the rate of rotational decreases proportionally to the amount of energy harvested from the now slower spinning prop. This continues until the pro stops spinning (i.e. stalled) at which time, no power is available.

What happens in essence is that the wind power that drives the boat has been converted to electrical power and your boat speed is decreased. Whether or not you are OK with the efficiency (or otherwise) of this energy transfer (from wind to electricity via the sails / boat / prop / generator) is your call.
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Old 15-08-2017, 19:27   #45
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Re: Utilizing free wheeling prop spin

Jim Cate here's one of many video's, enjoy. Notice it is a Sail Drive, but there are other youtube video's as well.
CRUNCH!!!
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