Hybrid Catamaran Power

[Girtbysea]

I'm keen to purchase a 10m sailing catamaran, likely a Seawind1000.

I understand the many benefits of their twin 9.9hp petrol outboard motors.
When it is time to replace the outboards, I would like to replace 1 with a petrol
motor, and 1 with an electric outboard.

The electric motor adds cost and complexity etc, however I see several benefits:
* Quiet
* Clean
* No fuel costs
* Less vibration
* Exhaust free
I understand from talking to Seawind owners, that much of the time when motoring they only use 1 motor (motor sailing, turning to windward to raise the mainsail, anchoring etc).
Range on the electric motor is relatively short.

The petrol motor benefits are:
* Cheaper
* Longer range
* Easily extend the range with jerry cans
* Easily repaired, anywhere

Is there anyone who has done this, who can share their experiences?
I'm keen to learn more of the pro's and con's of this type of hybrid system.

Cheers Girtbysea

[Simon.Sails]

Can't give you any first hand experience but look at the ePropulsion Navy Line, the first outboard to my knowledge to have hydro regeneration. A very cool feature for a fast catamaran like the Seawind. Two of these and sufficient solar should get you decent range, and a small backup generator just in case.

[tkeithlu]

Two lines of thinking here. One is conceptual, which is represented by your pros and cons. The other is a calculated energy framework. That's how much solar you can add, its efficiency, how much battery, its efficiency, how much genset as backup, and so forth. Figure for worst case need, not just routine need.

I should think it easier for to go all electric than to balance gasoline and electric motors. They have very different torque patterns, for example. Consider the possibility of two electric motors with all the solar/battery you can handle plus a genset able to power the motors without battery assist. To get full power from the motors, a theoretical 27 KW genset would be needed. Reality would be worse than that. That's pretty big for a 33 ft. boat.

[Girtbysea]

Originally Posted by tkeithlu

Two lines of thinking here. One is conceptual, which is represented by your pros and cons. The other is a calculated energy framework. That's how much solar you can add, its efficiency, how much battery, its efficiency, how much genset as backup, and so forth. Figure for worst case need, not just routine need.

I should think it easier for to go all electric than to balance gasoline and electric motors. They have very different torque patterns, for example. Consider the possibility of two electric motors with all the solar/battery you can handle plus a genset able to power the motors without battery assist. To get full power from the motors, a theoretical 27 KW genset would be needed. Reality would be worse than that. That's pretty big for a 33 ft. boat.

Thanks for your thoughts Tkeithlu.
You are right about possibly needing a big generator to power twin electric motors. Having 2 electric motors, while cleaner, no fuel costs etc, etc, makes the whole thing very expensive & problematic.
I can’t see myself running both motors simultaneously for long periods often, so the differences in torque should not be an issue.
Seawind have built in many redundancies (2 motors, 2 fuel tanks, 2 helms etc) & I think having 2 fuel types actually adds a further redundancy.
Should the motor batteries (?48v) get low, & I still want to motor, simply crank up the petrol (gas) one.
To me, I doesn’t make much sense having all electric motors, if one then has a large generator, fuel, fuel tanks etc).
I’m thinking more like a hybrid car (which doesn’t always need to be plugged into the mains).
A fully electric car ‘needs’ to be plugged into the mains.
I guess it all comes down to how often & for how long I wish to motor. 😁

[tkeithlu]

Good thinking, Girtbysea. If she runs well, and I'm thinking maneuvering into a marina with a crosswind, on one engine, then the alternator on the engine can even make a small contribution to your electrical budget.

One final thought. Remember that any claim of regeneration, using the propeller as an impeller to return energy to the batteries, comes at the expense of sailing performance. The drag induced is more than the propulsion gained. It's the painful reality of thermodynamics.

[valhalla360]

There most certainly is fuel costs. Depending how you use it, they may be substantially more.

The torque curves shouldn't be a big issue for handling. Props slip and with twin gas engines, you aren't going to be dialing in RPM exactly anyway.

So the real question is how are you planning to fuel the electric outboard and how are you planning to use the boat?
- If you will typically weekend out of a slip, where you can plug in let a modest battery bank recharge over the weekend before day sails...sure. In fact, just get 2 electric outboards.
- If you plan to coastal cruise anchoring out covering 30-50miles per day with back to back days on a fairly regular basis, a large battery bank and means of recharging becomes very problematic. If you install a big generator to recharge, you are defeating much of the other goals.

Not saying it can't be done but you really need to lay out more details than...just swap out the motor in order to get an idea of if it will work.

[Girtbysea]

G’day Valhalla360,
You make some good points.
We plan to live aboard.
We hope to minimise the use of marinas.
We will install as many PV panels as practicable & a wind generator.
Have never been keen on regeneration.
For the times when the motor battery bank is low, we either sail, stay at anchor or fire up the petrol motor.
We will be working in blocks of a few months a year, so we’ll not be pressed for time very often.
I haven’t yet calculated how many watts of solar I could reasonably fit on a 10m cat, & in full sun how long it may take to top up the batteries. Nor have I chosen battery type or size etc.
Maybe other’s can assist with real world examples of their own ��.
We are more inclined to design our travelling around the vessel, than set-up the vessel to do ‘anything’ (at great cost & complexity).
Cheers n tail winds ��

[valhalla360]

Originally Posted by Girtbysea

G’day Valhalla360,
You make some good points.
We plan to live aboard.
We hope to minimise the use of marinas.
We will install as many PV panels as practicable & a wind generator.
Have never been keen on regeneration.
For the times when the motor battery bank is low, we either sail, stay at anchor or fire up the petrol motor.
We will be working in blocks of a few months a year, so we’ll not be pressed for time very often.
I haven’t yet calculated how many watts of solar I could reasonably fit on a 10m cat, & in full sun how long it may take to top up the batteries. Nor have I chosen battery type or size etc.
Maybe other’s can assist with real world examples of their own ��.
We are more inclined to design our travelling around the vessel, than set-up the vessel to do ‘anything’ (at great cost & complexity).
Cheers n tail winds ��

Run the math on how many solar panels and how big of a battery bank you will need to generate say a modest 10kw at the prop for a short 4hr run.

There are plenty of threads just don't get caught up in magic electric HP. For a displacement boat running at steady speed, HP is HP. Unless you plan to not travel for several days in a row before a short run, it's just not practical to recharge with solar on a sailboat where the rig will kill solar output by shading the panels.