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BigBeakie · 12-02-2015, 21:53

Yeah, two up without diving gear. And probably not with the 30Kg Spaniard we'd be bringing back to the boat after trolling the reef edge.

Actually, I wouldn't keep one that big anyway.

And probably won't plane unless it is a really nice planing hull, so not a RIB. Maybe a Takacat or similar.

But it would be slower, no question. Just be nice not to have too many jerrycans up on deck. Hate that.

I was told Stabil, the petrol preservative, doesn't work very well if the fuel gets too hot, so another thing to check on, when I remember it again.

As they say, one bad thing about getting older is that your short term memory starts to go, and another bad thing is that your short term memory starts to go

alctel · 12-02-2015, 22:25

I was seriously looking at an electric engine, but I decided if I could get 30 nautical miles at 5 knots easily then I'd switch, else I wouldn't.

I couldn't - though if battery tech and solar tech continues to improve I'll probably switch in a few years.

BigBeakie · 12-02-2015, 22:33

Quote:

Originally Posted by alctel

I was seriously looking at an electric engine, but I decided if I could get 30 nautical miles at 5 knots easily then I'd switch, else I wouldn't.

I couldn't - though if battery tech and solar tech continues to improve I'll probably switch in a few years.

Alctel;

You mean with your existing batteries on board, and just swapping out the diesel? What size, in kW, electric motor were you considering? Or another way to ask the question is how many kW does it take to move your boat at 5 knots?

downunder · 12-02-2015, 23:06

Another electric thread.

Starside's Electric Conversion - Cruisers & Sailing Forums

nimblemotors · 12-02-2015, 23:25

If you can go 5 knots with 5 hp. 6 hours to go 30 miles,
that is battery size of 22kwh.
The battery pack in a Nissan Leaf is 24kwh, 600lbs. A good used pack is less than $10k. How much dead weight lead ballast does a monohull boat have?
What does a diesel weigh? 2gm20 16hp yanmar is 250lbs, cat has two? == 500lbs.
A TeslaS has 85kwh, a smashed one can be bought for $35k.
No problem if you have the funds.
Solar or generator just add to it, can charge up at the marina.
You just go 30-100 miles and anchor until recharged, with 5kw solar, that would be 1-2 days if the sun is shining. Go slower than 5 knots.
If you sail to a schedule, this isn't convenient, it might take additional effort for planning and routing.

I'm in no hurry, but if I was for any reason, I have a small lightweight 50hp gas motor that will power the boat and charge the batteries.
Can run the engine, then get some peace and quiet continuing with the EP.

Size of nissan leaf pack:

Quote:

Originally Posted by alctel

I was seriously looking at an electric engine, but I decided if I could get 30 nautical miles at 5 knots easily then I'd switch, else I wouldn't.

I couldn't - though if battery tech and solar tech continues to improve I'll probably switch in a few years.

BigBeakie · 12-02-2015, 23:30

OK, now it's my turn to FUD you guys re diesel.

I have made the point several times in the past that one of my points of interest in EP was that I've heard there will be a drying up of supply of diesel in South Pacific cruising grounds as Pacific island nations try to get off generating power with diesel generators. Response (predictably) in a couple of cases was polite scorn at the idea. But I heard it from a guy who works at the World Bank, and upon checking, seemed to validate his comments on it. It is a plan with not very long timeframes, as in it is happening NOW.

And earlier in this thread cwjohm said "All of the issues you state in regard to diesel (all of which are imaginary by the way) in the Pacific will still be there." So the idea that diesel supply will dwindle is imaginary?

For those of you who can read the writing on the wall read this;

More Solar For Pacific Island Nations - Energy Matters

There's an even better piece on this issue but I can't find it again. The number of nations would surprise you.

This is indicative of what's called a TREND One driven by undeniable economics, and supported by the UN, the World Bank, Chinese solar manufacturers, and various and sundry other organisations, a couple mentioned in the energymatters article.

So all you diesel powered cruisers should be contemplating big, big tanks to lug around as much liquified prehistoric swamp detritus as you can if you want to cruise the South Pacific.

Of course that will trash your multihulls sailing performance in light airs (if it had any in the first place), and make your boat LESS safe with all the added weight, but tough luck.

So maybe you should stay away from the Pacific, and leave it to us tree hugging green zealot close-minded & dogmatic ideologues with our electric propulsion that can't work.

Ahhh, FUD is FUN

Seaslug Caravan · 13-02-2015, 01:53

Quote:

Originally Posted by BigBeakie

Thanks Seaslug, I needed a chuckle

Why, is a solar top tender such a blasphemous concept????

Not blasphemous, but there is a few practicalities that need ironing out.

You may find it difficult to board and exit said dinghy with said lid in place.

A quick entry/ exit on a choppy surf beach is probably going to end with someone getting a wet bottom.

Is this lid going to have standing headroom (Egyptian funeral barge look) or the more sporty sitting headroom, requiring a commando crawl/dive entry/exit

How far inboard from the gunnel line will the lid start so as not to belt the bejesus out of your topsides when rafted alongside.

Putting a hard top on a tender puts weight and windage right where you dont want it.

A light easily handled tender can be a joy in areas of big tides.

Anyway lots to think about before dusting off the slide rule to determine power requirements.

valhalla360 · 13-02-2015, 07:26

Quote:

Originally Posted by BigBeakie

OK, now it's my turn to FUD you guys re diesel.

I have made the point several times in the past that one of my points of interest in EP was that I've heard there will be a drying up of supply of diesel in South Pacific cruising grounds as Pacific island nations try to get off generating power with diesel generators. Response (predictably) in a couple of cases was polite scorn at the idea. But I heard it from a guy who works at the World Bank, and upon checking, seemed to validate his comments on it. It is a plan with not very long timeframes, as in it is happening NOW.

And earlier in this thread cwjohm said "All of the issues you state in regard to diesel (all of which are imaginary by the way) in the Pacific will still be there." So the idea that diesel supply will dwindle is imaginary?

For those of you who can read the writing on the wall read this;

More Solar For Pacific Island Nations - Energy Matters

There's an even better piece on this issue but I can't find it again. The number of nations would surprise you.

This is indicative of what's called a TREND One driven by undeniable economics, and supported by the UN, the World Bank, Chinese solar manufacturers, and various and sundry other organisations, a couple mentioned in the energymatters article.

So all you diesel powered cruisers should be contemplating big, big tanks to lug around as much liquified prehistoric swamp detritus as you can if you want to cruise the South Pacific.

Of course that will trash your multihulls sailing performance in light airs (if it had any in the first place), and make your boat LESS safe with all the added weight, but tough luck.

So maybe you should stay away from the Pacific, and leave it to us tree hugging green zealot close-minded & dogmatic ideologues with our electric propulsion that can't work.

Ahhh, FUD is FUN

99% of cruisers never make it to the south pacific and those that do 99% cover the vast majority of miles under sail. For these people just a few gallons can supply thier propulsion needs for months (just a little to get in and out of tight harbors).

Really this is only an issue on very small out of the way islands. Of course, getting fuel on these islands has always been a hassle.

If you are running the diesel generator to top up an electric powered boat will experience the same problems.

Any of the larger islands will still have diesel for the trucks, so it can also be obtained for your boat.

Someday, this may be a problem but not for many years.

BigBeakie · 13-02-2015, 13:10

Quote:

Originally Posted by valhalla360

99% of cruisers never make it to the south pacific and those that do 99% cover the vast majority of miles under sail. For these people just a few gallons can supply thier propulsion needs for months (just a little to get in and out of tight harbors).

Really this is only an issue on very small out of the way islands. Of course, getting fuel on these islands has always been a hassle.

If you are running the diesel generator to top up an electric powered boat will experience the same problems.

Any of the larger islands will still have diesel for the trucks, so it can also be obtained for your boat.

Someday, this may be a problem but not for many years.

Sure, those are all valid points. My post was more lighthearted than it may have read. Where there is local trucking, there will be diesel, but if that is the only diesel they have, the price may rise significantly.

It is always the case that for a boat that has good sailing performance, in both light air and when it's much more "breezy", the engine hours should be relatively minimal unless you use your engines/alternators as power source all the time.

GoingWalkabout · 13-02-2015, 14:20

Quote:

Originally Posted by cwjohm

No you are not. You refuse to acknowledge the reality of people who live in the real world and cruise every day.

By the time your 46" cat is loaded up with all of this stuff it will be about the same weight as any other similar boat of the same size.

My boat for safe cruising in any number of circumstances requires 30Kw PER MOTOR at the prop. Yes, lighter and faster boats may get away with down to 20Kw, but 6Kw is simply fanciful.

Kw at the prop is the same for electric and diesel as Greg notes. This is a matter of simple physics.

On a 46" cat when you are motoring into a 40kn blow on the nose and a 3m swell you are going to need both motors for at least 60Kw to have a margin of safety.

So I put this proposition to you. Go out on a cat of this length, and confine the revs on a single motor to 6Kw as per the torque curve and see how you go. That is if you can find someone who will do this as it would be unsafe in the extreme.

CW Thanks. You have settled the argument for me. I'm going to keep with diesel and get the best Solar and battery combination money can buy. I do love my creature comforts.

thanks.

Stumble · 13-02-2015, 15:16

I didn't realize we were talking about a boat this big. Sadly the bigger the boat the worse it is for electric conversion. But look at some numbers to see why.

Assuming a Lagoon 450 as a similar vessel we can get a pretty good idea of the HP a required to achieve a given speed. Based on the Volvo D2-55 here is what we get with both engines turning.

Rpm ...... Measured speed ...... HP (Shaft) ......... Kw (shaft) .....Boat output
1800 ..... 4.5kn (WAG) ........... 12 ..................... 8................. 16kw
2000 ..... 6.7kn (flexofold)....... 14 ..................... 12 ............... 24kw
2600 ..... 8kn (flexofold) ......... 35 ..................... 37 ............... 44 kw
3000...... 8kn (fixed 3 blade).... 50 ..................... 39 ............... 78 kw

I wish I could get posted numbers at lower rpm, but I couldn't find anything. So as I understand it we are getting 6kw sustained output from the generator, so that's the ideal power we can use for propulsion over time. So I am guessing a reasonable speed projection of 2.25kn in dead calm conditions, probably a realistic 1.5-1.75kn in clam conditions.

I guess if you are happy with that it could work. I am not, and most people I know wouldn't be.

44'cruisingcat · 13-02-2015, 22:28

Quote:

Originally Posted by BigBeakie

Yeah, two up without diving gear. And probably not with the 30Kg Spaniard we'd be bringing back to the boat after trolling the reef edge.

Actually, I wouldn't keep one that big anyway.

And probably won't plane unless it is a really nice planing hull, so not a RIB. Maybe a Takacat or similar.

But it would be slower, no question. Just be nice not to have too many jerrycans up on deck. Hate that.

If we want to, we can carry 120 litres of fuel for the dinghy, all in lockers. (Self draining aft lockers, where we keep the smelly stuff, like fuel and garbage.) In fact we could fit more, but that's all the jerry cans we have just now. Plenty of storage on a cat.

alctel · 16-02-2015, 12:24

Quote:

Originally Posted by BigBeakie

Alctel;

You mean with your existing batteries on board, and just swapping out the diesel? What size, in kW, electric motor were you considering? Or another way to ask the question is how many kW does it take to move your boat at 5 knots?

No, I was going to replace the batteries as well.

As it turned out, I'd need around a 800AH 48volt lithium battery bank to be able to do that (assuming no charging) and that is really expensive and out of my current price range :<

44'cruisingcat · 16-02-2015, 16:07

Quote:

Originally Posted by BigBeakie

Thanks 44CC,

BTW, what do you think of using the Cruise 4 for the tender? The reason I raise it was I spoke to a guy cruising the GBR and parts north, and he said they went through so much more petrol for their 9,9 Yammie than they thought they would, in fact they ran out and had to head somewhere to re-fill the jerrycans. They were doing alot of diving and fishing everyday, so used the tender alot.

Was thinking the tender sunshade roof could be all semi rigid solar panels to keep the electric outboard battery topped up? You wouldn't go as fast as with a petrol outboard, but you'd keep going.

Just watch out for jellyfish!