45' solar catamaran

Yeah. Jury still out on what happened to them, but part of the reason to hire a NA is to establish how much weight you can put up how high. I only have a rudimentary understanding (if that), but basically all that solar and frame affects stability even in cat, and windage. Maybe for a wide cat the considerations are different, but pitching or hobby horsing, for example, would not be much fun. I had some in my boat and is now less after bow extensions.

 

You ought to at least check out what David Halliday had planned. I think they were going to run at about 4x48v on car batteries. Might be a couple youtubes. Customer ran out of cash.

 

I misunderstood the size of the motors. It was the battery size you were referring to.

Anyway, seems you are starting at a disadvantage with those hulls for what you have planned.

You won’t need big motors or a need for high voltage for high RPM because the hull speed will be limited by the addition of all the extra weight and windage from the solar array.

You could reduce a lot of the extra weight and complexity of your motor system by using a single motor mounted in the center with a sail drive leg or an old Silette Sonic leg and retain your current rudder setup for steerage.

This would allow you to reduce the size of your battery bank, perhaps even the solar array while reducing substantial weight aft.

 

I'm open to see that, but don't find anything after google search. Link?

 

Umm! serious doubt here. If the boat is ''lighweight'' at 18k lbs or heavy at 20k lbs I will certainly be happy to have ''big motor'' when facing some fast current or wind.

I absolutely don't see how 2 direct drive motor fix to a straight shaft can be more complex than a center mount saildrive.
But the single centered saildrive idea is not bad because it can allow the integration of a large prop and tilting mechanism. Down side is the lack of dual drive system in case one go wrong.

 

168vdc generator of course this is not all electric because they wanted range, but a fun video for you

the Tehini is a bit bigger and the project ran out of cash

 

Yes, thanks to share.
But to me there is a lot to dislike here: Netgain hyper9 motor, belt drive, unseal battery box, NCA chemistry cells, 168V.
I hope to do better than this.

 

Really?

For starters if you’re talking about redundancy as a benefit, then you’ll need to make the motor systems independent of one another.

That means 2X of everything -motors, gearboxes, props, shafts, bearings, controllers, wiring, batteries, etc.., maybe even splitting up the solar array and charge controllers.

Does that sound more or less complex than a single motor coupled to a sail drive?

Which one sounds heavier?

Which one would allow you to reduce the size of the solar array, reduce windage and weight aloft, and possibly reduce the amount of battery capacity needed?

I understand why you are attracted to dual motors. I’m not trying to be pessimistic, but it’s a slippery slope and the best electric boats and E boat conversions are ones that start with lightweight efficient hulls that have sufficient volume for reduced wetted surface area but also a streamlined shape above to reduce windage. Unfortunately, I don’t think your hull qualifies.

What you are proposing is a feed the beast kind of a build. Big motors to make up for big displacement, big batteries to power X2 big motors, lots of solar to keep the batteries charged, etc.. and in the end if you are not mindful about trying to trim as much fat as possible, you’ll likely end up with an inefficient slow speed cruiser that you’re trying to push through the water, which is fine if that is your goal.

As others have pointed out, weight will be your biggest enemy in this build.

 

No one of both choice will allow to reduce array size or battery size. This boat will need power to move and energy to move for long time.
The difference between a single motor or two motors will clearly not change much power requirement. In fact, with dual motor I could even idle one and use only the second on to move the boat.
My point is a 18k lbs cat with small battery, low solar and a single motor can need 15 kW to move at 6 knot and the 20k lbs cat with big battery lot of solar and dual motor can need 16 kW to move at 6 knot. It's not like if, at same speed, one solution need 5 kW and the other solution need 15 kW.

I don't consider I plan to use big motors with two time 15-20 kW. In fact, I bet many sailor will think it's way not enough and anything under 100 kW is too small.
What kind of motor power do you have in mind when you are talking about ''You won’t need big motors''?

 

I'm really interested in your plans, as I have been working for a year on a 40ft solar catamaran after the original builder spent 3.5 years building her but sadly died. His plan was for a power cat with two 60HP outboards controlled by a hydraulic steering system. I have bought two Aquamot Trend 15 electric outboards (15kW that are supposed to be equivalent to 38HP ICE). I will have a 6kw solar array and 90 kWh LiPO4 battery bank. The power will be divided across the two hulls for redundancy. I also have two 250lt petrol tanks, which will carry a minimum amount of fuel for two suitcase generators (2.5kW each).

 

Awesome! Where do you share details?

I'm always stunned by the prices of those unit when I shop for 200$ EV motor at scrap yard.
What is the propeller size on this unit?

 

That sales pitch is getting old. 15 KW is the same as 20 HP. 38HP is more than 20HP. There is no magical power in electricity that makes their horses more powerful than that of an ICE, steam engine, sail, or actual horses.

 

Sure, everyone should know how to convert kW to HP. But I think there are acceptable reasons for this kind of comparaison.

1 - Diesel/gaz engine are generally rated at peak power. Electric motor are generally rated at continuous power. And most should know that electric motor can ouput several time their rated power for short duration.
2 - The higher torque of electric motor allow, for the same output power, a bigger and more efficient prop. That can do a huge difference.

I've experiement the point 2 with our little 1.5kW dinghy electric motor who was able to push our 38' sailboat at 3.3 knot.
I've done a dinghy ride with friend who have a 4 hp outboard Honda engine and he was impress how more powerful was this low power motor compare with his gas engine.
To me the reason is simple: 10.7'' prop compare to inefficient 6'' high pitch prop.

 

Wouldn't trimaran configuration be better for this purpose? Big fat center hull for weight carrying capacity and floats for stability and to support frame for solar panel roof. Essentially monohull sailboat with keel removed and trimaran floats added. Endurance solar boat are not going to be fast so fat center hull with 8 knot hull speed limit would be perfectly fine.

 

Did you buy the unfinished Skoota from Martin Ellinson’s widow?

If so, we probably ought to speak privately, for your benefit, not mine.

Are the batteries King Kongs and do they weigh about 750kg? I’m more than a bit nervous if so.