Installing electric propulsion on a 14.6m motor cruiser: realistic and feasible?

[marshmat]

Good points from all here.... and I think there's some validity to all cases.

I think it comes down to how you use the boat, how often, and at what speeds. I will qualify that, and all that follows, by pointing out that all of this is only meaningful once you have a solid design brief, use profile, resistance calculations, etc. and have done the mathematical comparisons between various forms of various systems.

For a liveaboard, or for auxiliary power on a sailing cruiser, I think there is significant appeal to going electric. The key point here is that house loads are of the same magnitude as propulsion loads, on average. As house loads increase, the engine's role becomes more and more to drive alternators than to spin the prop- eventually, you may as well just design the whole thing for optimum efficiency when charging the batteries, and drive your prop off an electric motor. This also applies to boats that frequently operate in no-wake or no-IC-engine zones (of which there are plenty in my area) and would thus benefit from being able to power without running an engine.

As your use profile moves towards more time under power and thus a lower house load fraction, the arguments raised by Fred, Alan and Masalai seem to become dominant. With most of the power going straight to the prop, it makes sense to simply size the engine for ideal cruise speed (with a bit extra for beating into the wind, of course) and drive the prop directly. The potential gains from a hybrid system become so small that the expense of the electrics is no longer worthwhile.

My analysis (and that of the large cruise ship builders) suggests that there are cases where diesel-electric or battery-electric systems are worthwhile, but it's not a universal solution. It is absolutely essential to do the proper analysis for the specific boat and usage profile under scrutiny.

As for Watervole's original question- Calculate your house loads (all your electronics, lights, gear, fridge, etc. basically everything except props, rudders and stabilizers), and calculate your hull resistance and powering curves (or at least estimate them). Figure out how far you'll go at what speeds in a typical week of cruising and compare the total energy used in that week- how many kWh for house loads, and how many kWh through the prop. If the numbers are comparable or the house load is larger than the propulsion load, maybe you should consider hybrid. If your propulsion energy needs significantly outstrip what you'll use on board, as is the case for most motor cruisers, Fred's suggestion of a couple of cheap diesels will likely be your most economical option.

[Rvanvoris]

I thought I would post this picture of me at the shop in the early stages of strip planking my Jay Benford designed 32'Friday Island Ferry. As you can see it is a long way to Tipperary as well as some time before I install the power plant.
I am strip planking with 7/8 x7/8 Atlantic White Cedar epoxied and pegged.
Over this I will put 2 layers of Biaxial cloth set in Epoxy.
This is primarly a houseboat which means it is a destination rather than a means of transport. My plan is to keep her on a mooring during the summer and drop down to a slip in a boatyard during the winter.
I figure the project will take from 5- 7 years to complete, given that I already have a full time job and other obligations. In 10 years I hope to retire and cruise her on the Great Loop route.

[alan white]

Just a question, Van. Your pegs------ how big around relative to strip thickness, how long, what adhesive, and what material?
Another question, how much does altantic cedar cost, and is it knot free (or nearly so?
Sorry about so many questions. I like the idea of pegging, also guessing staggering is absolutely critical.


Alan

[Rvanvoris]

OK the pegs first, I use a technique that I learned from an old swamp yankee wood worker which sounds far feched at first, namely a square peg in a round hole.
I cut 7/32"(a 32nd less than 1/4") square strips from Douglas Fir scrap, I use doug fir because it is slighter harder than the cedar and I have some scrap in the shop. Cross cut the strips to 2 1/2 inches long. I then taper the end for the first 1/4" or so by sticking the end into a pencil sharpener. Thats my square peg I brush on epoxy on the edge of the cedar and hold it in place on my forms with spring clamps I then drill a 1/4 "hole in the edge of my strip making sure of the alingment of the abutting strips and inject with Gorilla Glue I put in a West System syringe. I then pound the peg in with a deadblow rubber mallet. I know it sounds weird but try it before you pass judgement. The Gorilla glue expands and is easier to clean up after it has cured than epoxy. This technique allows me to use edge tools without fear of nicking blades also I don't have to pay for metal fasteners and when I run out I just make more pegs. Also the square edges of the peg force the surrounding fibers back and puts pressure on the peg much like a nail does when driven into wood
As for the Cedar it is very good and clear I forget what I payed except that I bought $6000 worth I will check my records when I get back to the shop.

[alan white]

Thanks for the reply. It sounded like a unique method and I see what you mean about the gap-filling properties of Gorilla type glues.


A.

[SReuther]

see other post

[SReuther]

Check out www.electricmarinepropulsion.org. They are doing some good stuff and have a larger engine that might work in your boat.

Originally Posted by FAST FRED

Cheapest would be to be willing to go slow , and install used diesels of about 50 hp each.

There is no "electric " way to go that wont run over $100K $200K US and be a bear to design , install and operate.
Actual performance and resale value will be really iffy.

There is little IF in an off the used shelf diesel.

How about repairing the existing engines?

What are they? Some old engines are a snap to rebuild .

FF

have to agree with this
we have a new 45 footer ready to buuild and th e best oprion is a single John Deere 107 shp at 2400, we will run it at canal sp of 4.5 using .68 gph, driving through ZF 45A 2.4 :1 But also I am thinking a sail to raise between locks and on rivers with the head of a yankee type on the stem and a pole(mast) on each side deck, the pole would hinge down and the sail would reach and run

[StianM]

If a diesel is bether depends.
If you want to operate at various speed's a diesel electric system is the way to go since you can have 2,3,4 or 10 smal diesels instead of one big and only run the amount of diesels required for your current operation condition.

I know that in 2010 we are going to deliver a ATHS with main engines coupled directly to the propellers and PTI with electric motors witch are engaged in BOOST mode where the aux engines are feeding additional power to propulsion.

Going slower will save fuel and a 70hp engine will be more efficiant then a 100hp at a output of only 50hp.

There are several ways to set up a system and only the cash and the fantasy sets the limit.

The disadvantage of a system where a diesel and a electric motor run in parallel is that it require CP propellers just like a standalon diesel, but it could be solved by clutching out the diesel during manuvering and let the frequensy drive do the job.

you are right Stian, but its IS about cost, , and engine hours if you put 100000 electric system in and run 20000 hours in 20 years, which the average power boater will never do, it will be 5 and hour per capital investment, simply put? if you run a diesel that cost 20k, then it will be one dollar and so on,