My situation and needs are very different from everyone else's. Because of my higher minimum cruise speeds (10-12mph), and max speed (15mph) all my equations and power requirements are very different. In my situation the propeller itself is critical to all my equations. An analogy of a propeller in operation is a nut spinning on a threaded rod. At a fixed thread pitch at a certain rpm the nut will travel down that rod a certain distance and speed (not accounting for slip and prop loss). There are tons of prop pitch vs boat speed calculators available on line. It makes no difference what your horsepower is, or how many motors you have in the water, or the size and weight of your boat, that pitch number is constant.
All my calculations are completely upside down from normal calculations because of my tri-power system. A normal hp/prop calculation would be multiply the max rpm x pitch x some boat length drag and loss numbers = horsepower requirement to propel the boat at X proposed speed. With my boat that number is likely around 15-20hp for my max designed speed (15mph in this example). You can actually test this number by dropping a free wheeling prop in the water and measure the rpm at a given speed (in my case 15mph). I have to adjust the prop pitch to insure I don't exceed the max rpm of the motor (if the max rpm is exceeded the motor explodes (I have exploded a couple already accidentally). Now I calculate backwards my horsepower requirements. With my current setup my hybrid gas motors are outputting exactly 1 hp each, if my hp requirement to propel the boat at 15 mph on plane (I have a planing type hull), if the hp requirement is 15hp, and the motors are providing 2hp, then the sail and pedal system has to provide the remaining 13 hp.
In my case the battery/solar power consumption number will be a fixed number, just a wild guess at this time is 500 watts per motor (I'm just guessing here if at max power the motors are consuming is 1000 watts ea, I will want half that number). Now I only need to provide enough storage energy to provide 500 watts per motor (1000 watts total) power times 25 hrs of continuous operation. Some of that energy will be supplemented by solar cells (during daylight), and some will be provided by my fuel cell (aux storage energy), the rest needs to be from stored battery energy, how many batteries that comes out to is totally unknown at this time.
Here is one of my spreadsheets attempting to calculate my power requirements, this one only covers points of sail from zero to 20 degrees off the wind (direct upwind), there are six more spreadsheets needed to cover all the other points of sail, and wind conditions. What I do is is go out and test in different conditions, then record my speeds and fuel usage. Once I know my fuel usage in given conditions I can hopefully convert that to electrical energy storage requirements.
These calculations were done a couple years ago, and only account for my current system which has a cruise speed of 8-10 mph. As I have stated my desired final cruise speed is 10-12mph, which the current configuration is not capable of providing, I have to convert to a full wing mainsail to achieve the 10-12 mph cruise figures, which is designed but not built yet. Once I get all the rest of the calculations and testing out of the way I will likely build the new mainsail (I'm years away realistically).
Going in nobody know what the actual sailing conditions will be thru the race, this is why I need to have available up to 260 sq ft of sail area to be able to adjust sails to suit whatever conditions I come across. Working with a fixed energy consumption limit makes the task daunting.
With my hybrid gas system, it's easy to just increase throttle slightly to make up for the sails and pedals not providing quite enough energy (or pedal harder). Because the energy density of gas is 100x higher then electric, it's easy to just carry along an extra gallon or two of fuel to make up the difference and variables. You can't do that with batteries and solar cells (if your batteries go dead halfway thru the race, with no means to recharge them, you are done).
As battery and solar tech improves, I get closer and closer to actually being able to pull this off. The information you guys are providing as this stuff advances is extremely valuable to me. The newer batteries from Torqeedo, and the ability of their system to be able adapt to and utilize input power from solar, and fuel cell aux power sources is monumental toward my goal.
From the information you guys are providing me, I may just be able to pull this off with 4 rotating banks of battery sets (4 battery sets for the left motor, and 4 battery sets for the right motor). With the fuel cell charging one bank (though I may now need two fuel cells), the solar charging another in a round robin fashion. This is 5 yrs ahead of schedule.
My ideal situation would be in normal sunlight (after all it's Florida) to not use any battery power at all during daylight, but still be able to charge the batteries on top of driving the propulsion during daylight hrs would be a really big plus.
I'm sure all this sounds insane to everyone (sorry for the long explanations).
FE