Electric Motor to drive fishing boat

Depends on how far you are planning to travel on plane. Let see an electric fork lift drive motor should get you up. A lower unit rated about 1 1/2 times the HP of the fork lift motor. While you scrapping out the fork lift you mite as well take the direction controls. The drive motors for fork lift are design for torque not speed. Rated about 2600 rpm so you need gears and chain to increase the speed to the lower unit. Now the battery on that though hang it up. Would ether be a short trip to the bottom because you over loaded the boat or short trip out and you row back boat batteries don't have that much juice.

Sea water and electricity are not good bedfellows in most marine applications........... why make matters worse................to my mind, not a particularly good idea.

You could figure on using roughly the same system as in a Tesla car, but with a little less HP. A 100 hp motor (75kW) would be adequate, and probably 50 kWh of batteries. In lithium ion, the batteries would be around $60,000. Once on plane, a 5000lb boat (w/ 1000 lb batteries) would have a resistance of about 750lb, so to do 30, you'd be using about 60 hp (44kw), You'd have roughly one hour's range (30 miles). A displacement trawler hull operated at a lower speed (10 mph) would give you much better range. Lead acid batteries would be far cheaper, but probably too heavy at around 3000 for 50kWh.

http://www.thameselectric.com/inboards.html

yes I know this is the lower end of the power spectrum, but I've always liked the idea. The water carries the weight of the batteries so it's more do-able than an electric car.

I would have to ask how electric do you want to be? 100% or 50%. Think about a Train, they have incredible power due to electric motors. And here is the but... they have on board diesel generators. You would have to do the math on fuel weight generator weight and the electric drive motor weight. Sounds like to me 10 gallons of crap in a 5 gallon bucket. The electric motor is however much more efficient, an internal combustion engine is about 70% heat, 30% to the work load.electric is around 95%(friction and such) and a bit more with the brushless DC. I say it can be done with the correct engineering.

Thank you logix101, I also believe that it can be done and I was also tinkering with that same idea about generating power what do you think about using hydrogen for the gas motor to run the gen. set to power the elec. drive? I have seen this work as a stand alone unit not hooked to anything but will it work hooked to a gen. set?

Outstanding idea. Think about this, and hold on it's gonna be bumpy ride. Lets use solar power to separate the sea water( heavy salt ) so it will be very conductive, use stainless probes in a tank to separate the Hydrogen and oxygen then salvage that gas to power the generator. No need for a big fuel tank!!

Here's a different spin boys and girls. I understand that hull design will dictate max speed and planing capability. You may want to investigate planing hulls vs displacement hulls. One is designed to climb on top of the water while the other one is just a plow.

This is true. A good displacement hull, operating at a speed close to hull speed (about 7 knots for a 24' boat) has on the order of 8-9% resistance (and even less at very low speeds). A planing hull has about 15% once it is on a plane, and more than that at the hump in the resistance curve just before coming up onto a plane. A displacement hull, if forced to plane (if there is enough power available) will have a drag of 20% or more -- it's the worst of both worlds, in a way.

The ideal solution(for efficiency), which I've thought about doing if I ever have the time, might be hydrofoils that could be retracted at low speed. This would yield the low drag of a displacement hull at low speed, and the very low drag of a hydrofoil at high speeds (as low as about 10%). There's a hump at the transition, as there is with a planing hull, but the low drag at speed pays off. Lots of complexity, however.

A catamaran hull is yet another alternative. If slender, (as in a sporty sailing cat) these have no planing resistance hump in the drag curve, and at moderate speeds, (around 15-20 knots in a 24' boat) have less drag than a planing hull at the same speed. The limiting drag in a displacement hull comes about from wave making drag, and if you push harder, you just make a bigger wave. It's not precisely true, but is said that no matter how much horsepower you have available, you cannot get a displacement hull to exceed its hull speed. The slender hulls of a catamaran, however, do not make significant bow waves, so they can go right past their theoretical hull speed easily. Once at high speed, however, they still suffer from skin friction drag -- because they are in the water rather on top of it.

If resistance were constant (it's not), HP would go up directly with speed: twice the speed, twice the HP. So a catamaran doing about 12 knots can be quite efficient (at a speed where a planing boat would still be on its resistance hump). At that speed, the HP consumed would be on the order of 1/4 that of a planing hull (because the planing hull is not yet truly planing, and therefore has high drag.) In a true displacement hull, resistance goes up with the cube of speed as the boat nears hull speed, and HP (which is also speed dependent) goes up even faster (roughly with the fourth power.)

Also in an electric boat, weight will be very high, even with high tech batteries (The Tesla has 900# pounds of batteries in what was as 2000# car in its Lotus incarnation). So for range, you are better off going relatively slowly, and knifing through the water rather than trying to lift above it.

Very good thought Mr. beard. as water weighs .0361 lbs pee cubic inch and 62.427 lbs per cubic ft. perhaps a modified V hull would be in order. a deep V in front and a flat "boat tail" shape for the rear. I would like even a surface drive but that is more for speed . There is a group in Florida that modifies hulls, they put surface drive under the boat in chambers and introduce air in the chamber, which allows the props to cavitate quicker, faster RPMs and the boat planes out quicker with out all the junk be hind the boat.

While the electric components can probably be waterproofed sufficiently for safety under normal operating conditions, and whereas the hull shape is the primary factor for speed in water (it's referred to as the hull speed for a reason...), I think it unlikely to be economical. Unless that solar dissociation of seawater works - of course, cloudy weather will make you wish for a nice tank of diesel. What's wrong with wind power if you want cheaper operations?

OK lets go wind. I will use a wind generator to power the HOO gas converter. Sails do look much better though.

Yeah, nothing like a schooner under full sail for grace. Don't leave off all of the solar cells though, a calm day will render the wind generator into a pretty good boat anchor...

If only we had the time and funding/recourses to build one of our contraptions that has been designed (on the fly). You do really have to wonder what it would look like. I think that is what happened to Atlantis, they packed a ton of stuff on it to make it better and it sank. Hooray for technology!

all you guy's are insane all I wanted was ideas for the best boat for fishing for crabs and reg. fishing but, don't let me stop you there hell while we are at it why don't we just throw jets on the damn thing and call it a day?

Woo-hoo-hoo! Now THAT'S what I'M talkin' about! Them crabs won't stand a chance.

I suspect that with this bit of clarification, a more appropriate set of responses will be forthcoming. Still, the comments about safety and waterproofing are always going to be germane, so don't disregard all of it as insane. Which might be too harsh a term - after all, it may be overkill, but what's wrong with a little overkill? It's usually better than underkill... Give an engineer a chance, he'll over-engineer things every time just because he can!

Yes I suppose you are right that all though insanity as well as laziness has it's definite advantages, my bad CR4er's keep up the good work. I happen to be one of the crazy people that I infact have been talking to and some people believe me to be either dumb or crazy for my ideals and how I carry on in my life. So please excuse me for my outburst.

Old school is your best answer. Use sails like the ancient mariners. Current sail technolgy is far superior and they are cheaper than batteries and will last longer. Keep you motor for a backup on still days. In the long run, you'll be dollars ahead.

As a long time sailor, I'd have to agree.

Maybe you should try crabbing in the Bearing Sea.................Not that I have.

I have only experienced some pretty foul weather in the Tasman Sea, the Great Australian Bight and the Southern Ocean...........also typhoons in the South China Sea and if you forgive me saying...............to hell with the ancient mariners, I would sooner have quite a bit of the old reliable horse power/kW under my feet thank you very much................and not electrical powered shafts either.

Hiya Mate

I second that! I have also been in some rather nasty weather and sea conditions in small fishing boats off the coast here (South Africa) and, without reliable power to the prop, might have run into some serious trouble. A diesel engine will keep on running with a flooded engine room as long as the air intake is clear.... However, unless the electric motor is suitably "packaged" and sealed, it will short out and die when it gets wet.

There certainly does seem to be a trend towards azimuth electric propulsion pods for large ships, but that is not what we are on about here.

What if all those sails in #11 were solar panels charging capacitors and or Li batteries?

I imagine the boat would easily capsize with all that weight aloft. You'd also want to orient them so they face upward at noon.

But with the solar cells down lower, you have this sort of thing.

It is hard to get enough power from solar cells to propel a boat continuously, but the link above describes several attempts that have worked to a greater or lesser extent. Where solar power makes a lot of sense in a sailboat is for auxiliary power. While it is difficult to harness enough power to go fast, it is possible to gather enough energy over time to charge batteries to enable you to maneuver for an hour or two under ample power for navigating harbors, etc.

For a while, I owned a sailboat that had been modified for single-handed ocean racing, and it had fairly large solar cells on deck. I did some overnight races, and some cruising, and it was nice to have ample electrical power all the time, without any need to use a battery charger. For the way I used the boat, I could have powered a 2 hp electric motor for getting away from the dock and back.

It would be fun to make very light catamaran (out of two racing shells, for example) with an overhead panel (ala a party boat). A 30 x 60 panel produces about 160 watts, so a 60 x 120 panel over a boat 5' wide would produce 640 watts, or nearly 1hp. That would be plenty to power such a boat, given that it could be rowed by one 1/6 hp person. The panel weight is about 35# each, so four would be 140 lb -- about the weight of an extra person on board.

Below is a boat I built to be wind-powered, but I used a tolling motor of about 1/3 hp to get around when the wind died. I could do about 4 mph under trolling motor power -- and this was a relatively large boat (compared to the cat I just described): 20' wide, 16' long and 20 feet tall. Of course under wind power, it was much faster - 32 knots at one point, but capable of substantially more.

I posted today a new thread which is close to this one http://cr4.globalspec.com/thread/17506/What-kind-of-pump-motor-and-valves-etc (don't bother to go there unless you are a hydraulic specialist). The main idea I'm thinking of is having a windturbine giving the energy for propulsion (among other things). There's more about the subject in http://www.boatdesign.net/forums/showthread.php?t=14182&highlight=windturbine

Sorry for going off track so much, so Michael you like the crabin'. Now I will try to remain focused on the task at hand. Sails are the best, but I am wondering, is there any fishing you do in the shallows. I am curious about the keel depth, if it is needed. Stay with the basics , sail, paddle, and motor's, electric or IC. As with electric cars , many factors are to weighed,literally weight will play the major factor on water,yes, yes hull design. But this is a regular boat. I would say best bet to mock up a small hybrid system, one man skiff. 8k to 10k generator and a geared 10hp motor. You are not in it for speed so use a reducing gear set up and increase the prop pitch. I do like the scale models. If that works then we can go on to the magnetic propulsion. Please remember the vale between genius and insanity is thin and some what fractured.