Anonymous wrote:
Attached find are a couple of screenshots of the computer-generated performance prediction they made for my setup. It was calculated on the assumption that I will be using a 13 x 11 x 3 prop. I.e., !3" diameter with an 11" pitch and a three-blade propeller. We have in place now, a two-blade 13" x 10' pitch which has been tweaked to a higher pitch. Engine: Yanmar YSB12 (10 Hp) I'll see how that works first before trying the other. The vendor says I will have better maneuvering ability with a three-blade. For answers to questions that the website and this printout don't offer, I suggest getting in touch with these people directly by email or phone. If you're already wise to salesman's tricks, you'll know what questions to ask and recognize dodges and deceptions.
It is my intention to purchase a Honda EU2200i portable generator to serve as a genset for the propulsion. But it will have other uses aboard. Someone cautioned me not to expect too much in the way of regen in a motor this size
Sorry if the screenshots are a little fussy. The original file is 2.5 MB
Hi Jim, if you use your portable generator for anything other than an emergency "get home" you may hate it as much or more than a diesel. You will also need an 120ac to 48 volt converter/charger. The size is base on your generator. I have 15 amp converters which only give me 3 knots. More speed = bigger generator/bigger converter. A 2000 watt generator can do 30 amp? You will need 30 amp (ebay?) charger/converter.
For just propulsion I would keep the diesel. If you require a gen set to charge your batteries often while traveling it should be a dedicated watercooled housed and quiet diesel like all the big electric boats.
My batteries are a holding bank where you put energy in just as efficiently as you draw out. I have never regretted large hi voltage solar panels (higher than 52 volts will charge bank without combining panels together). Solar panels are my main power source. I had to make room for them on NA29 but your boat should be easier. I have 2 big ac shore power 12 volt chargers for the battery bank. I have never needed to use them even once. I am on a mooring with no shore power. Where there is absolutely no sun for days on end probably would be a problem. But, motor sailing with a junk rig with just the input from the panels (when everyone else is motoring) is a great joy if you can do it.
The thrust bearing is important as the torque of an electric motor is impressive. The motor shaft to prop rotation seems to be debatable. Some have no reduction and some like myself opt for a large transmission as a thrust bearing with ratio. It really depends on the mystery of the prop you will using. I have been told that a bigger slower moving prop is the most efficient. Na29 having a small aperture, I put in the largest 4 blade to fit. (Largest individual expense in the whole system!). If you have a large battery bank you can turn the prop constantly to diminish the prop drag. On my boat I can go for days like this due to the efficiency of the system. The motor can easily take it and the relatively inexpensive transmission was designed for industrial use (factory conveyor belt?) and is lightly loaded.
An advantage of an electric system is that it is modular. you can swap out pieces for better or bigger as life progresses. I can install a larger motor or differently geared transmission in about 30 minutes. The average cost of an air cooled pmac motor was around $600. $1500, maybe for a watercooled hi power model.The no maintenance trans was around $300. A large Sevcon controller with display was around $500 or so. I haven't looked at prices for a while but the individual parts seem to be actually going down in price.
I think that the greatest appeal for an assembled system is that the system is "turn key" and you are relying on their expertise. The disadvantage is if you need to actually change something in the "box" they give you and it won't fit. Most every thing but the "box" itself is right off the shelf and can be sourced easily. Nothing wrong with kit type installations if you understand what you are getting and you realize you are paying for expertise. An advantage is they seem to have" sales" on the assembled units and different distributors have competitive prices with nice discounts on the same unit.
For me, who grew up with complicated ic engines, electrical propulsion is so much easier to understand and to work on. For small sailboats, the real dilemma (and expense) is the ability to efficiently produce and store electrical energy on the boat itself. 4 x big 8d batteries /electric motor = 1 gal of diesel /(13 hp).If that does not deter you, you will probably be happy with an electric drive.