45' solar catamaran

We can clearly end, or start another thread, about the debate of electric equivalent HP.
Because, for this solar cat project, I will only rely on kW = HP/0.746 and I will only have a way to measure power and it will be battery power, so input power at motor.

Here is a rough shape of each one of the 80 kWh battery I plan to use.
How do I strongly fix this 1000 lbs and around 31'' x 26'' x 28'' to a wood hull?
I hope to integrated them low in the hull, so the center of gravity of those battery should be 6-8'' above waterline
Is I should bond supports? Is I'm better to drill multiples holes for screws in the wood frames?
The last picture is where the battery will fit. Before the engine and at the place of the diesel tank.

 

Securely.
Lots of fitted, glued and screwed, 3/4" plywood, 2x4's, 2x6's to distribute the load.
Up to you how much room you leave for thermal expansion.
They must be secured vertically too.
Think pitch-pole.

 

Too much weight. There is a very low likelihood the boat was designed for that loading, so you’d need to distribute the load across stringers, etc. To be sure, get an NA involved. Why would you want to be up 6-8”? Airflow?

By the way, the assessment is assumptive. 1000 pounds is 166 gallons of diesel less tank weight..

 

Not really. They are pretty poor on weight/power compared to gas or diesel.

 

Power = energy/time. There is no such thing as propulsive power. Outboard motors are rated at the shaft. That is output power.

 

Battery pack rearragment? More longitudinal setup will allow side mount and clean walk better weight distribution . Flat longitudal position of battery will be better too. Saftey concerns : its possible to fall over battery pack . And think is good to make evacuative hatch astern if there's no one.

 

Good point. Despite the battery is only 31'' long I can fix it over 6-8' to distribute the load in wood.

No. I will fix it as low as possible, but the center of gravity (cg) will be 6-8'' above waterline. Look at the picture.

Don't know why you think this.
I design and build battery pack since 15 years. I think this 80 kWh battery pack will weight around 1000 lbs. I plan alu 5052-H32 battery box at the moment, but can change if need. Inox 304 or 316 isn't exclude
The good think about designing a battery for a slow solar cat is I don't have to be sure that the pack will not fly in a 100 mph crash.

 

How many gallons are the diesel tanks that you are replacing?

 

Ok, it's maybe a french/english problem or the term propulsive who is in cause.
Please educate me and let me know how, in marine world, do you call the efficiency of a propeller.
Or more specifically, the power lost in the water (power who don't act to propel the boat) and the power who effectively propel the boat.
All this should have a name as most should know that for each kW at motor shaft there is kW minus propeller efficiency* put in the water to move the boat.
*efficiency, effectiveness, productivity, performance or any other good word.

 

Yes. I first thought I could build a long and low battery pack. Something like 20' long 15' wide and 5'' height. It had be use as floor, but it's not really possible with the current boat and battery modules.
The big square blue block in pictures is really the simplest design. The other possible and relatively easy design is two time longer and 1/2 the wide (rectangular block in picture). I can complexify the battery internal to have a better shape, but I highly prefer to have a simple and reliable battery internal and a not so good shape.
In both case, I plan this battery to be under a single place bed in the hull. There will probably have a wall just in front of the current engine (white on picture post #61) and the ''motor room'' will only be accessible be the exterior.

 

I'm not sure. I will have to remove them an take measures.
It's probably around 30-40 gallons each side.

 

No, it is not a french/english problem. The efficiency of a propeller has to first be defined according to the projected use. For example, a ski boat needs to have fast acceleration (hole shot) and moderate speed, but a tug needs to have high bollard pull at zero or almost zero speed. A race boat needs top speed and mid speed acceleration. Each one has a different definition of efficiency, but they all are calculated from shaft power. You need to clearly state what your parameters are, and not mix and match to win an argument. It is simple physics and math from measured and/or calculated values. Propellers have slip, which is needed to generate thrust. If there was no slip, like when you run aground, the engine stalls or something breaks.

 

If I understand correctly, you build your own batteries? If so it would be interesting to see how many kwh you could get into those tanks. Basically cut the top off the tank and use the tank as a battery box. Reinforce if needed....

 

Yes. It's what I do as job since many years and I design an build battery since 15 years.

Absolutely no!
I want those battery box to survive any situation. So I will entirely design it to survive a boat flip, full immerge hull and so on.

 

Sure. I'm waiting for your advices.
Project: 8-10 ton solar Cat cruising at 5-8 knot with two 1000 rpm motors directly connect to shaft drive. Actual propeller are 17 x 11 Variprofile.