Utilizing free wheeling prop spin

[robmclennan]

If you don't want to disassemble the drive shaft I recommend using a hub chain sprocket. Bored to the exact diameter of your drive shaft. Drill and tap two hole, one one on each side of the bore in the hub. Cut the sprocket in half. Re-assemble. Best bet is to have a machine shop do it precisely.

[CaptTom]

Originally Posted by Make_My_Day

I am always looking for additional alternative ways to add to the charging system to help keep the batteries topped up. When sailing at night, this seems like a good way to use energy that would otherwise be wasted.

Am I missing something?

Yes. The energy you'd be harvesting is not being wasted. It's being used to propel you through the water.

Originally Posted by Mango51

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.

Let's do a little math then. 14-17A at 12VDC is 168-204 Watts. Being an optimist, I'll say 200W. Put another way, in 10 hours of sailing at 7 kts you've generated 140-170 AH. For some folks, that's enough to power their normal house loads for 12-24 hours. However, shorter travel days, slower speeds and conversion and storage losses will impact this estimate quite a bit.

It's a trade-off. On the one hand, there are cheaper and more reliable ways to make 200W. On the other hand, it's just a fraction of a HP that you're diverting from your propulsion to make electricity, so if you have the time, money and inclination to add complexity to your drive train, it WILL work.

Originally Posted by Cherod

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 .

I guess it all comes down to how much you value those extra 200 Watts, and what you're willing to give up to harvest them.

[Cherod]

Originally Posted by CaptTom

Yes. The energy you'd be harvesting is not being wasted. It's being used to propel you through the water.



Let's do a little math then. 14-17A at 12VDC is 168-204 Watts. Being an optimist, I'll say 200W. Put another way, in 10 hours of sailing at 7 kts you've generated 140-170 AH. For some folks, that's enough to power their normal house loads for 12-24 hours. However, shorter travel days, slower speeds and conversion and storage losses will impact this estimate quite a bit.

It's a trade-off. On the one hand, there are cheaper and more reliable ways to make 200W. On the other hand, it's just a fraction of a HP that you're diverting from your propulsion to make electricity, so if you have the time, money and inclination to add complexity to your drive train, it WILL work.



I guess it all comes down to how much you value those extra 200 Watts, and what you're willing to give up to harvest them.

A quarter ( or less ) of a knot to power your AP , fridge , radar whatever seems worth it , maybe it's just me but a cog and a belt off the shaft certainly is not " complexity " in any form , and easy / cheap enough to make , ( how much is a decent alternator? Not much )

[NahanniV]

A prop-shaft alternator or towed gen is certainly worthwhile for people making long passages.

When you are sailing there are times that all your solar will be shaded by rigging and sails, could be the same every day on a long passage.

[robmclennan]

Thank You Capt. Tom! It is nice to see that a few a people actually understand what I am saying. The free wheeling Prop on boats with fixed propeller's is a method of generating useable power that would normally be non existent. It is meant to work in conjunction with your solar panels to keep the house batteries fully charged when sailing. It doesn't need the clutch if your transmission warrantee states it's OKAY to let the prop be free spinning. The free spinning prop 250% less drag then a fixed prop. I think we have beaten this to death!

[robmclennan]

More good news is there are numerous companies who have gotten Patents that are developing "Solar Sails" Yep the whole Main Sail will be a flexible solar sail. The best part it will generate power on both sides. So you are covered both ways, coming or going!

[Astrid]

Originally Posted by robmclennan

More good news is there are numerous companies who have gotten Patents that are developing "Solar Sails" Yep the whole Main Sail will be a flexible solar sail. The best part it will generate power on both sides. So you are covered both ways, coming or going!

I wonder durability and cost would be?

[robmclennan]

Well they spent the money for the patent and it was granted. So they have a working prototype. It is through Research and Development (trial & Error) to find the correct materials for strength, flexibility, and performance. It will be expensive when it first comes out, all new technologies are. If they go to China to have them made cheaply they will be knocked off, after the first year. Have you ever wondered why hybrid and electric vehicles don't incorporate a solar cell on the Roof and Hood? Because a 10 year old student got a patent! No one wants to buy the patent, or lease the technology!

[Matt Johnson]

Not true. Toyota Prius was (is?) available with a solar panel on the roof. Just a marketing gimmick as a panel that size does nothing for the battery charge.

Matt

[robmclennan]

funjohnson Mark you answered my post with your answer. The tiny solar panel on Toyota and Fords is not designed to recharge the battery pack, but to run a small circulating fan on the interior of said vehicles.

[David M]

I have not read through all 85 posts so far I admit (Is anyone here that diligent?), but has anyone suggested looking at a hydrogenerator?

It is not going to make much noise, and it is not going to put wear and tear on your boats drivetrain. A boats drivetrain is also going to be less efficient with all of its sources of drag.

Hydrogenerators - tested - Sailing Today

[robmclennan]

Yes David we have, but they are semi expensive. So my thread is for boats that have fixed props (NON Folding). Should we free wheel or lock them? Testing has shown that a fixed (Locked) Prop generates 250% more drag then a rotating one. As long as you are letting the prop rotate in neutral why not tap into the potential energy? By running an axillary generator off the free spinning prop shaft. Solar panels don't work at night. Long night cruises the generator would supply an adequate amount say 200 watts to recharge the house batteries.

[leftbrainstuff]

Then it wont be free apinning and produce drag.

Water generation is more efficient than wind generation, all things being equal.

[David M]

The power to turn the water impeller comes from the wind.

[Cadence]

Originally Posted by robmclennan

Well they spent the money for the patent and it was granted. So they have a working prototype. It is through Research and Development (trial & Error) to find the correct materials for strength, flexibility, and performance. It will be expensive when it first comes out, all new technologies are. If they go to China to have them made cheaply they will be knocked off, after the first year. Have you ever wondered why hybrid and electric vehicles don't incorporate a solar cell on the Roof and Hood? Because a 10 year old student got a patent! No one wants to buy the patent, or lease the technology!

I've worked in R&D so got a kick out of the trial and error. Truer works were never spoken.