PDQ 32 vs Gemini 105MC

[Canibul]

I was remembering a solar parabolic cooker I made as a science project, which would definitely fry a burger...
but the gyro and heading stabilized servo setup to keep it pointed at the sun might be problematic.

hey, we could attach it to the top of a KVH antenna....

[deckofficer]

Byron,

This is the reason I think house and propulsion batteries should be the same 48 volt bank. The above mentioned heating element for the BBQ would at 1500 watts draw 125 amps at 12 volts from the inverter. Add an instant on-demand tankless hot water heater at 3000 watts that might kick on during BBQing and you have 4500 watts, short term, but that is still a draw of 375 amps on the 12 volt side. This means a larger Puerkett effect on battery storage, heavy cabling to the inverter, and all connections needing to be torqued properly and maintained because of that high amperage draw. Now using a 48 VDC inverter will reduce for the same load of 4500 watts, 375 amps at 12 volts down to 94 amps at 48 volts. This is about the same amperage as 1000 watt powered windlass.

[Canibul]

Hmm...If we can use it to generate steam....

I always wanted a steam powered sailboat...:

Green Steam Engine Home Page

[deckofficer]

Now this is what I would like to see power a generator, can run on diesel or most any fuel, weighs 13 lbs, doesn't need a pressure lube or cooling system, so no thru hulls, and efficient.
BladonJets Multi-fuel Micro Gas Turbine Engines

[thinwater]

Originally Posted by Canibul

And for you guys who think you don't need your rudders with twin motors....try this little experiment:

Next time you're docking, turn one of the motors off and go ahead and dock the boat without touching the rudders.

Obviously the boat will turn until you get to about 3 knots. I never said you never use rudders, I said you don't use them backing into a dock. Now, if one engine is out it is still practical to dock head-in. I've done so a few times. Hell, I've docked without engines.

Docking is also difficult on the Gemini with an engine out.

[deckofficer]

Originally Posted by Canibul

Hmm...If we can use it to generate steam....

I always wanted a steam powered sailboat...:

Green Steam Engine Home Page

Pretty cool little engines. I was in the lucky class at CMA as we changed out our training ship that was a steam turbine old style to a medium speed diesel for my senior cruise, so got training on both.

[thinwater]

Originally Posted by Canibul

I didn't hear any of the non-motor sailing purist crowd claiming they didn't NEED rudders to dock.

Gotcha back. ha.

The first time I docked with no engine I had my 13-year old handle the helm.

[Mr B]

I wouldnt even try docking my Gemini with my single motor not going,

[Canibul]

Originally Posted by thinwater

The first time I docked with no engine I had my 13-year old handle the helm.

You should take a dog along to blame these things on. They can't argue or threaten to tell the truth. Teenagers will turn on ya.


bob, did you notice they are condensing the steam and reusing it? Closed system.

I was looking at that as a watermaker, too, but the brine would be an issue.

[smj]

Originally Posted by deckofficer

Byron,

This is the reason I think house and propulsion batteries should be the same 48 volt bank. The above mentioned heating element for the BBQ would at 1500 watts draw 125 amps at 12 volts from the inverter. Add an instant on-demand tankless hot water heater at 3000 watts that might kick on during BBQing and you have 4500 watts, short term, but that is still a draw of 375 amps on the 12 volt side. This means a larger Puerkett effect on battery storage, heavy cabling to the inverter, and all connections needing to be torqued properly and maintained because of that high amperage draw. Now using a 48 VDC inverter will reduce for the same load of 4500 watts, 375 amps at 12 volts down to 94 amps at 48 volts. This is about the same amperage as 1000 watt powered windlass.

What would the weight, cost and life span of the batteries be in this setup?

[Canibul]

This is a heck of a battery, by the way. Waterproof, easily handled.
New Torqeedo lithium battery

[deckofficer]

Originally Posted by smj

What would the weight, cost and life span of the batteries be in this setup?

The pre-assembled packs are too expensive, I would purchase single cells of 180 a/hr each for (2) 48 volt banks. Total 32 cells.

Total weight = 393 lbs
Cost = $ 7,488
Life span = 3,000 cycles (longer than MY remaining life span)
18.4 Kw/hr
Now that solar panels are down to $1.03 per watt (Thank you China), no reason not to have 1,000 watts or more of panels except for available, good sun exposure space on the boat.

[Canibul]

i thought the pre-assembled packs were $ 2500 ea, making two of them $ 5K. Did I misread the price somewhere? The german ones have all those nifty electronics to protect them if they get splashed, hooked up backwards, or shorted, overcharged etc. They're watertight, to one meter depth for half an hour. Can you build all that, including your labor, and end up with something as good?

I have the time and place and tools to build battery packs, but doubt I could match the production unit quality at the same price. What would a home made battery pack do to the Torqueedo warranty? Are they okay with that?


If the batts weigh 393 lbs, and the diesel gen you like is 320 lbs, it would seem you could distribute that fairly evenly in the two hulls. There must be 60 lbs of controllers, switches, and cabling you could put on the side with the gen to even things out. Or play some games with tankage.

[deckofficer]

Byron, (BTW, enjoying your blog)

You are correct about the price of the Torqeedo battery pack, but they are capacity of 2,685 Wh from just 44 lbs of battery weight (61 Wh/lbs). 2.685 Kw/hr is a lot less capacity than the 18.4 Kw/hr bank I would assemble.

If a warranty issue came up and they knew you had your own battery, it would probably void the warranty, that is why I'm leaning towards this aquawatt green power electric outboard motors
even though more than 3X the power needed at 13 Kw, it is only 15 mm wider than a 9.9, uses a 3 phase AC PM motor, and controller is inside the motor cover. Even though not needed, it is nice to have the flexibility for fast motoring (maybe as fast as 15 kt) if your choosing to out run weather. That is the main reason for a diesel gen set that is a battery charging only unit, light weight AND 20 Kw charging output. If you have the fuel, you can run fast for a long haul.

[Canibul]

I see what you mean, but I am going to suggest maybe this setup needs more flotation, i.e. a bigger boat. Or something with some real fat hulls.

We're talking about 320 lbs. gen. plus 390 lbs batts, plus 80 lbs torqueedos, for a total of 790 lets call it 800lbs. You are still going to have, what, two hundred pounds in inverters, lots of heavy cables, battery hold down straps, hardware, connectors, etc. That's a thousand pounds, fixed. Before you add diesel fuel, filters, etc.

the stock outboards weigh 88 lbs each. That's what the boat was designed to sail well with.

I still like it. I just think it probably needs to be installed on a 40 ft. boat, with the current state of technology....('current state' yuk yuk..)


added: I just looked at the aquawatt. did you realize that those weigh 126 lbs each, come in 20" transom height only ( I think the Yammies are longer?) and cost (at today's exchange rate) $ 8,575. each? I'm just saying...