Hydrogenerators

[Koeketiene]

Hydrogenerators make sense on long passages (boat moving all the time) on fast boats. Looking at the output curves, you need a good 6kts log speed to reach a mere 100W! A racing trimaran or IMOCA 60 is where these things show their teeth. The 40' AWB cruising from bay to bay would only see meaningful output if you manage to anchor one in the Corryvreckan...

My bet is on solar, if you need more power, then more solar or a genset...

A bit unfair to just quote the performance at low speed for the small high speed prop.

 

[Dave100456]

Hydrogenerators make sense on long passages (boat moving all the time) on fast boats. Looking at the output curves, you need a good 6kts log speed to reach a mere 100W! A racing trimaran or IMOCA 60 is where these things show their teeth. The 40' AWB cruising from bay to bay would only see meaningful output if you manage to anchor one in the Corryvreckan...

My bet is on solar, if you need more power, then more solar or a genset...

100W is nearly 8 amps on a '12'v system.

Many boat owners would be happy with a 'constant' 100W input.

With the larger dia prop you will get more watts. See post 29 for empirical results.

 

[GTom]

A bit unfair to just quote the performance at low speed for the small high speed prop.

Reality rarely matches the ideal curve presented on the manufacturer's website, hence the pessimism. You decided the speed when you bought the boat. If you can sustain an average 5+kts, then with the largest prop, you'll get your 8Amps. Btw, no wind = no water speed either.

100W is nearly 8 amps on a '12'v system.
Many boat owners would be happy with a 'constant' 100W input.
With the larger dia prop you will get more watts. See post 29 for empirical results.

I don't see numbers here...
You'll get nil in an anchorage, while your genset is still available.

If I understand right, the boat is in question is a 36' mono. This translates to a hull speed of 8kts, defining your max output. Haven't read all the posts, no idea if perpetual crossings or the rare crossing and lengthy cruising is the plan.

 

[laika]

You'll get nil in an anchorage, while your genset is still available.

Your genset will be available to disturb everyone around you. I have a generator fitted to my boat. The times I want to use it have been long periods at anchor in quiet secluded anchorages where I couldn't use it as it would disturb others. Hence it's on the list of thing to de-install and sell when I get round to it, replace it with solar, and just be a bit more frugal on power.

 

[geem]

Your genset will be available to disturb everyone around you. I have a generator fitted to my boat. The times I want to use it have been long periods at anchor in quiet secluded anchorages where I couldn't use it as it would disturb others. Hence it's on the list of thing to de-install and sell when I get round to it, replace it with solar, and just be a bit more frugal on power.

Do you mean portable petrol generator or inbuilt diesel genset. Quite a difference in annoyance factor

 

[GTom]

Your genset will be available to disturb everyone around you. I have a generator fitted to my boat. The times I want to use it have been long periods at anchor in quiet secluded anchorages where I couldn't use it as it would disturb others. Hence it's on the list of thing to de-install and sell when I get round to it, replace it with solar, and just be a bit more frugal on power.

Hydrogenerator wont be of much help in that quiet anchorage... I spoke up for solar earlier in the thread.

 

[laika]

Do you mean portable petrol generator or inbuilt diesel genset. Quite a difference in annoyance factor

4kw built in diesel. It's in a sound insulated case and not "bad" but I'm hyper-sensitive to disturbing others in a place of natural beauty: Same reason I need to swap the 2 stroke dinghy outboard for electric.

And sure a hydrogenerator won't work at anchor but it should mostly cover off the additional power requirements of instruments and autopilot when under way and if I don't want to use a genset at anchor, there's not much point to having one.

 

[Koeketiene]

You'll get nil in an anchorage, while your genset is still available.

I agree, your hydrogenerator wouldn't work when at anchor.
Equally:
- your solar panels won't work at night or when it's overcast.
- your genset won't work when you run out of fuel.

 

[GTom]

I agree, your hydrogenerator wouldn't work when at anchor.
Equally:
- your solar panels won't work at night or when it's overcast.
- your genset won't work when you run out of fuel.

Add: your hydrogenerator wouldn't work when there is little wind and your speed is low .

Depending on your solar setup and how dark the overcast day is, you can still squeeze a few Watts:

 

[Dave100456]

Reality rarely matches the ideal curve presented on the manufacturer's website, hence the pessimism. You decided the speed when you bought the boat. If you can sustain an average 5+kts, then with the largest prop, you'll get your 8Amps. Btw, no wind = no water speed either.


I don't see numbers here...
You'll get nil in an anchorage, while your genset is still available.

If I understand right, the boat is in question is a 36' mono. This translates to a hull speed of 8kts, defining your max output. Haven't read all the posts, no idea if perpetual crossings or the rare crossing and lengthy cruising is the plan.

My mistake; not post 29 but post 20.

 

[geem]

I agree, your hydrogenerator wouldn't work when at anchor.
Equally:
- your solar panels won't work at night or when it's overcast.
- your genset won't work when you run out of fuel.

Well you could do what we do and have 720w of solar on domestic bank, 40w on engine battery, 10w on diesel generator battery. We have a 5kva genset, wind and water charging, two shore power chargers that run off the genset. We also have a Windpilot that uses no power under sail when we want to. Have a missed anything? ? oh, and we have 450l diesel fuel tank so it should last a while when running the generator to make water?

 

[MarkCX]

Might need a helluva bigger boat for all that ?

 

[Koeketiene]

Well you could do what we do and have 720w of solar on domestic bank, 40w on engine battery, 10w on diesel generator battery. We have a 5kva genset, wind and water charging, two shore power chargers that run off the genset. We also have a Windpilot that uses no power under sail when we want to. Have a missed anything? ? oh, and we have 450l diesel fuel tank so it should last a while when running the generator to make water?

Are we still talking about a boat that sails or something like this: a caravan that floats?



Even if I wanted to, I have no room for all that kit.

 

[GTom]

My mistake; not post 29 but post 20.

2Amps/kts means you get 12Amps or 150ish Watts @6kts? That sounds good, you're close to the manufacturer's curve .

OTOH, sailing at 6kts with a 36'er implies a decent windspeed and a decent windgen can serve you just as well. At anchor/mooring too.
Again, highly efficient racing machines on downwind races = go with hydro.

 

[Neeves]

Quite a few lvm/aerogen units still around. A decent charge controler for one is virtually impossible to get though.
How many amps at what speed can you get when towing?
Heard a few story's about sharks taking a liking to the propellors ?

Rappey,

Sorry I did not forget...

Our impeller is a really solid shaft with fibre glass blades at the end, big ones for when travelling more slowly and smaller ones for when at speed. We have tended to use the small blades and one blade did get damaged (whether a shark or it hit something more sold - I don't know (but no bite marks). I made some stainless blades to replace the small fibreglass blades - and they have been fine, so far (we've had the unit for 20 years now). A friend with a smaller Aerogen smashed a wind blade when someone let go the main halyard and the shackle hit the blade.

The biggest problem is that at speed the impeller skips and leaps out of the water. We can average 10 knots - which means we might peak at 14 knots. We typically will produce 8amps and I'd say at around 8 knots we produce an amp a knot (more when you go faster and less (than an amp a knot) when you go slower.

Our averages seem high but we choose our weather windows and don't try to sail to windward, so we might enjoy being pinned into an anchorage and spend more time anchored than might a gung ho monohull sailor.

I find it very sad that LVM was bought up, the production transferred to China - and then (my understanding) the whole thing closed down. Why did ITT buy a going concern and then let it flounder.

But moving on

I too am waiting for the budget version of the WattnSea to enter the market (I've been want a long time now ) or hoping someone will produce a sensible competitive product. The technology is hardy new.

Jonathan

 

[geem]

Are we still talking about a boat that sails or something like this: a caravan that floats?

View attachment 91933

Even if I wanted to, I have no room for all that kit.

No! I hate monkey bars! All that weight and windage high up! We mount solar on the guardwires. No davits as our nesting hard dinghy goes on deck when on passage. Flush deck boat helps as we have loads of deck space?
We dont even have fenders hanging over the stern as we use Avon hyperlon fenders that you pump up with a dinghy pump. They stow flat in a locker.

 

[Slowboat35]

Are you sure its 3ltr/hr? My 4.4litre Perkins uses 2.2 ltr/hr at 5kts. 6kts costs me 3.3ltr/hr

I think you're talking gallons per hour, not litres!
An 84Bhp engine's consumption cannot be much less than 4gph (20lph near full power and I'd have thought would be over 2.2l (1/2gph) even at idle, which is about what a 20Bhp Yanmar or Volvo uses at cruising speed.

Rule of thumb for most traditional piston engines; 1 gallon or 4,5l per 20Hp per hr

 

[kalanka]

I also rate the Aquair and found it very reliable and effective at charging the battery bank on a short handed Atlantic circuit in a 34 foot sloop. However, I found that in trade wind conditions - speed 6-8 kt, poled out foresails, preventer on the main - retrieving the rotor was difficult, simply because of the problems in conveniently reducing the speed to the necessary 3 kt or less. I tried sending a shield down the rope to diminish the pull from the rotor but never found this to be effective.

Of course if the rotor is still turning it is very easy to get ensnared in the twisting warp as you hand over hand it in and this happened to me one night watch. I was quite unable to escape and tiring rapidly. Fortunately I was able to call my son from below and he released me. As a result I did not attempt retrieval when single handing except under fully favourable conditions, and always had a very sharp knife to hand.

Another consequence is that the rotor makes it difficult to stream a fishing line and, more importantly, makes it unrealistic to stream warps in storm conditions - unless you have retrieved the rotor earlier. I don't know if the alternative bits of engineering avoid these problems.

 

[Koeketiene]

No! I hate monkey bars! All that weight and windage high up! We mount solar on the guardwires. No davits as our nesting hard dinghy goes on deck when on passage. Flush deck boat helps as we have loads of deck space?
We dont even have fenders hanging over the stern as we use Avon hyperlon fenders that you pump up with a dinghy pump. They stow flat in a locker.

Have a flush deck too - the RIB dinghy will go there when underway.
I plan to mount my solars on the guardwires too, but due too boat size it will not be a massive amount of solars. And only when at anchor.
I am reluctant to mount solars on deck as I think they will spent a significant amount of time in the shade of the sails when sailing.

 

[geem]

I think you're talking gallons per hour, not litres!
An 84Bhp engine's consumption cannot be much less than 4gph (20lph near full power and I'd have thought would be over 2.2l (1/2gph) even at idle, which is about what a 20Bhp Yanmar or Volvo uses at cruising speed.

Rule of thumb for most traditional piston engines; 1 gallon or 4,5l per 20Hp per hr

You need to change your rule of thumb. Its totally useless.
We fill the tank to the top. Log hours and revs. Refill and work it out. If you dont believe my figures I attached the Perkins Sabre curve for my engine that happens to be pretty accurate against my own findings