Hydroelectric Generator

[KISS]

Yikes, just looked at a couple feathering props: big $$$ and they seem to mostly come in sizes much too large for this application. On the other hand, the commercial units don't use feathering props, and people report minimal speed loss.

Originally Posted by Kenomac

Then why not just get a few solar panels?

Primary would be solar for me, this would be a backup/supplement.

[hellosailor]

Hybrids: Yes, even more expensive and more exotic. They're not "just" MPPT controllers. And again, if there are no solar panels, having the ability to match charger output to optimum solar panel output could seem wasteful. Kinda like the 100-160mph part of the speedometer in my car, on city streets.(G)

[Jim Cate]

In a boat with an engine and prop already installed, coupling a generator to the prop shaft makes some sense, for all the expensive and difficult to install bits are already in place. In your putative engineless boat, it makes no sense at all. Some form of towed or stern bracket mounted generator will be much less expensive, easier to install, can readily be "fine tuned" as to prop size etc and easily removable to reduce drag when not needed.

An earlier poster suggested using a second hand wind gen alternator coupled to a towed outboard prop. Damn good advice IMO! On our previous boat we used a towed generator employing a repurposed tape drive motor and a 6 hp Johnson outboard prop. Worked well for years, generating around 10 amps at 6 knots.

Your screen name is "KISS"... why don't you follow that principle?

Jim

[Bleemus]

Originally Posted by Kenomac

Then why not just get a few solar panels?

Because the alternator running off the shaft worked at night too.

[Bleemus]

Let me interject to those who are speculating as I have sailed a few thousand miles with an alternator run off a prop shaft. It worked, it wasn't impressive but it pumped about 3-5 amps into the batteries day and night sailing from San Diego to the Marquesas and beyond. This was a 67 foot steel Jongert that averages much higher speeds than the typical cruiser here on this forum. Dont expect miracles from these setups. Watt and Sea seems to be the best contender for hydrogen but for the average cruiser it is big bucks that are better spent on solar and wind sources that can be used at anchor. IMHO these are best left to the long distance shorthanded race guys and gals who want to limit fuel weights for performance. As we witnessed in the last Vendee Globe the Watt and Sea units did an amazing job but those boats are sailing over 12 knots most of the time. Put one on a Westsail 32 and you will be sorely disappointed.

Buy some solar panels first then a wind genny and if you arent broke start playing with alternators on shafts. As I said that is my humble opinion.

[KISS]

Originally Posted by Jim Cate

towed or stern bracket mounted generator

How would you weatherproof it?

[Jim Cate]

Originally Posted by KISS

How would you weatherproof it?

Well, if it was weather proof as a wind generator, it would be weatherproof as a towing generator. In the case of our old home brew tower, there was no weather proofing... and it worked for over 80,000 miles of cruising (not deployed all the time, but out there in the weather). Don't over complicate things when you are trying to KISS.

Jim

[KISS]

Originally Posted by Jim Cate

Well, if it was weather proof as a wind generator, it would be weatherproof as a towing generator. In the case of our old home brew tower, there was no weather proofing... and it worked for over 80,000 miles of cruising (not deployed all the time, but out there in the weather). Don't over complicate things when you are trying to KISS.

Jim

Well, apart from weatherproofing issues, here's why I'm inclined to an inboard type generator: (1) Always running, doesn't have to be deployed/retrieved, (2) Can be used in any weather, (3) Tow impellers can get caught on things/eaten, (4) Outboard type generators take up valuable space at the stern. The disadvantages are drag and having a BWL thruhull. As for cost/complexity of installation, I don't see the big problem: alternator ($200), shaft ($200), stuffing box ($100), prop ($100). Direct drive. What am I missing?

[KISS]

Originally Posted by Bleemus

Let me interject to those who are speculating as I have sailed a few thousand miles with an alternator run off a prop shaft. It worked, it wasn't impressive but it pumped about 3-5 amps into the batteries day and night sailing from San Diego to the Marquesas and beyond. This was a 67 foot steel Jongert that averages much higher speeds than the typical cruiser here on this forum.

My daily budget underway is <50AH, so 1A would be great, 2A fantastic.

I wouldn't know what to do with more (install rotating disco ball?).

[hellosailor]

Missing?
$100 seems like a cheap small prop. And you might need a cutlass bearing and strut further down that shaft to get the prop in clear water. Direct drive? Really geared up, no belts, no clutch, no way to adjust tension on the connection?
As for drag and speed loss, that's a personal choice. I've seen "the same" boat with a fixed three bladed prop, and a folding 2-blade, and if the difference is only 2/10th's of a knot...for some people that matters. Either for evening races, or multiplied out times 1000 nautical miles at six and a half knots.
Could be 154 hours one way, 159 hours the other. No biggie, just five hours, a half day on a 6-1/2 day trip. (And that's with JUST a paltry 2/10th's of a knot, expect something more.)
Or, biggie, when that half day brings you into port clearance during weekend overtime hours, and the last mooring at the YC got taken three or four hours earlier. (This is how cruisers either get an appreciation for racing, or decide racers are insane.(G)

Jim-
"Weatherproofing" something against fresh water (rain) is all well and good. Fresh water will also work through an alternator/generator without doing much harm, and the rotational forces will tend to expel the moisture, the same way that disc brakes keep themselves dry, as compared to drum brakes on cars.
But now place the assembly in SALT water, where it cannot dry out, and you'll have corrosion and galvanic action and the sheer pressure from immersion, which tends to force water into the electronics, i.e. actually under the "cans" sealing transistors and the the like...You don't want to be the guy who has to warranty that part.(G)

[hellosailor]

"1A would be great"
So 24 Ah per day would be great...Then one 50-watt 12-volt solar panel very roughly two feet square, with even a cheap PWM controller, would be great.
$100-150 on Amazon or for $50 more, you go up to 100 watts and you're well beyond "great". Mo moving parts, and way cheaper.
Sure, there are overcast days, but with the time and money you'd save, you could easily add four more days worth of battery.

Just saying.

[KISS]

Originally Posted by hellosailor

$100 seems like a cheap small prop.

That's good for a prop the size of what the Watt and Sea uses.

And you might need a cutlass bearing and strut further down that shaft to get the prop in clear water.

True

Direct drive? Really geared up, no belts, no clutch, no way to adjust tension on the connection?

Could you explain that?

Can't the propshaft just be connected to the alternator shaft?

I don't understand why I'd need anything else, other than maybe a brake.

Originally Posted by hellosailor

"1A would be great"
So 24 Ah per day would be great...Then one 50-watt 12-volt solar panel very roughly two feet square, with even a cheap PWM controller, would be great.
$100-150 on Amazon or for $50 more, you go up to 100 watts and you're well beyond "great". Mo moving parts, and way cheaper.
Sure, there are overcast days, but with the time and money you'd save, you could easily add four more days worth of battery.

Just saying.

Already planning 250W of solar, which should be enough in almost all circumstances. But if I can get a backup that guarantees power when underway for $1000? I think that's worthwhile. People spend 10x that building a cabinet.

[hellosailor]

"Can't the propshaft just be connected to the alternator shaft?"
Sure, if you're prop is turning at 2500rpm.
Alternators all have output curves. Most prefer to run roughly between 2500 rpm and 10,000 rpm and don't even wake up until 1000 rpm. Which is why they use pulleys and belts to multiply engine speed and get the alternator going faster. If your alternator speed isn't matched up to your "engine" speed? You can be cheating yourself out of 50-90% of the potential output.

For a thousand dollars (wait, didn't I say $200?) you can easily add a redundant stored/deployable solar panel and controller. Or buy a decent genrerator and fuel cans.

Instead you're looking at a thousand dollar project with so many variables still unconsidered...that it pays to ask yourself "Is everyone missing something or is there a reason this stuff has failed on the mass market?" Usually it is the latter.

One Group31 battery ($150) charged in port and put away as a spare, would give you two days of spare emergency power. A thousand dollars? Would give you more than a week of emergency power that way. Just need a set of jumper cables.(G)

[Bleemus]

What he said. Ours had a belt and reduction gears to increase the rotation speed. Unless you are at sea doing over 7 knots on a regular basis buy a solar panel or wind generator. I have 560 watts of solar and a Superwind 350. Never even considered a water genny.

[KISS]

Originally Posted by hellosailor

"Can't the propshaft just be connected to the alternator shaft?"

Sure, if you're prop is turning at 2500rpm.
Alternators all have output curves. Most prefer to run roughly between 2500 rpm and 10,000 rpm and don't even wake up until 1000 rpm. Which is why they use pulleys and belts to multiply engine speed and get the alternator going faster. If your alternator speed isn't matched up to your "engine" speed? You can be cheating yourself out of 50-90% of the potential output.

The low RPM alternator I've mentioned (one designed for wind turbines) produces 12v at 130 rpm.

For a thousand dollars (wait, didn't I say $200?) you can easily add a redundant stored/deployable solar panel and controller. Or buy a decent genrerator and fuel cans.

I understand that solar is the better solution in many cases (hence I'm going to rely mainly on solar), but I think there's value in having a separate system that would run at night, in bad weather, if the rather vulnerable topside solar panels get damaged, etc. I don't like gasoline generators for various reasons. It's ultimately a matter of personal preference, as with just about everything else.

Instead you're looking at a thousand dollar project with so many variables still unconsidered...that it pays to ask yourself "Is everyone missing something or is there a reason this stuff has failed on the mass market?" Usually it is the latter.

My guess is that this system is too boat-specific to be readily mass produced, and most boat owners aren't interested in doing the customization required (the vast majority of boat owners aren't liveaboards and don't do long voyages). There's also the fact that most boat owners use gargantuan amounts of power, and already have a large diesel engine, and so their logical backup is an alternator run off the engine.

One Group31 battery ($150) charged in port and put away as a spare, would give you two days of spare emergency power. A thousand dollars? Would give you more than a week of emergency power that way. Just need a set of jumper cables.(G)

But that battery has to be charged. And that requires either luck (esp. good solar conditions), a larger solar array (more money, space, and weight), or reduced consumption (on an already minimalist budget). Again, there are always trade-offs.