Please Help Me Build An Electric Boat Drive!

You might pick up some info here...

http://www.propulsionmarine.com/electric

Something like this?

http://www.andamanboatyard.com/picnic-21/

Thank you! Yes! Like that... Those are some very nice systems...let me add that money is an option.... or limited.. which is why I'm trying to design one and build it myself.(or with you guys help) I can buy the AC system listed above for about $1800.00. Will it work? I dunno...how easily can I build one of those systems listed on the website?

Thanks Solar!

Have you considered the losses incurred by the system you describe?

Why not just drive the prop with a more conventional mechanical transmission?

Well I imagine it's fuel costs...I would run this like a Chevy Volt, using electricity primarily with the diesel generator as a backup....It would be a lot cheaper to charge these batteries dockside or at home, then using diesel fuel all the time....my take

Well,

I'm all for it if it's the way to go. I'm not sure 7.5 HP will push it very fast.

800 pounds is not light.

OP: How far out is "offshore"?

Thanks for the replies. I plan on going about 30 miles offshore in this boat and I want to use electric motors for torque. They produce more torque at a lower RPM.

Will you have batteries or run the drive motors directly from the generator to save weight?

I think your generator is too small in either case.

I was planning on running AC straight to the AC motor. I am open to suggestions for DC motors and exactly how much horsepower will I need to push an 800lb non-planing boat 20mph. I recently saw a DC output generator which could possibly power a DC motor or charge a battery bank. Thanks

Well to start off with it will no longer be a 800 pound boat once the propulsion system is in it. Most likely its going to be a 1400+ pound boat.

From there going 20 MPH on water is probably going to take 50+ HP!

If it was me and I was going for most the most efficient drive system with the least about of weight and volume I would be looking at hydrostatic drive using a variable displacement piston pump and motor combination.

It would have an overall mechanical efficiency in the mid to upper 90% range plus the widest range of speed control and power transfer with the least overall mass and volume of components. Plus there is no high voltage high current electrical gear to deal with in a wet environment.

But thats just me.

Well you lost me there, using a generator to drive an electric motor makes no sense...AC or DC....A diesel to drive the boat, or a diesel generator to charge a battery pack which in turn powers an electric motor, would make sense to save fuel, but would be very costly....So if you're on a limited budget, get an outboard....800lb boat is only what 14 ft? 20hp...

I want to use electric motors for torque. They produce more torque at a lower RPM. I want to start out running by generator then slowly build up a battery bank/inverter system.

Torque is what the propeller presents to the motive unit, not the other way round!

Be aware that a propeller that is cavitating produces no more torque than a propeller that is operating just below the cavitation point. Once it is cavitating, the power must be reduced to avoid damage to the impeller and wastage of fuel.

Depends on the pitch of the prop.

Probably worth a looksee - http://www.agnimotors.com

Used by http://www.electricboatsthailand.com/

Inventor interviewed at

http://www.dailymotion.com/video/x7oq1p_cedric-lynch-and-agni-motors-the-le_tech

Heard a great quote the other day - 'a couple of months in the lab can save you a couple of hours in the library'

Sounds like you want to 'remake the field'.

Don't hold your breath, but good luck. I recommend going with a proven solution, unless time & money are no problem.

Let's start from the beginning so we can all get on the same page....What is the length and hull design of the boat you want to build? What is the thickness gauge of the aluminum? What is the approximate dimensions of the cabin? How many people and total weight of gear estimate?

Maybe something like this...only a little shorter

http://tadroberts.ca/services/small-boats/displacement/pocketcruiser16

Very similar Solar! 1/8 inch aluminum construction. 10' x 14' trimaran off sorts. Cabin above waterline and loaded out I want to be at 2000#. Boat 800, propulsion 500, 2 adults +gear 500, and 200# fuel. Again not your average boat.

So far from you guys posts I have found my 7.5hp electric motor powered by a super silent generator isn't nearly enough to get me to 20mph no matter how much low RPM torque electric motors have. I guess its back to the drawing board.

Either that or the local yacht chandlers to purchase a 7.5hp outboard motor weighing, oh, say 35kg tops.

http://classified.nauticexpo.com/small-ads-used-boat-classifieds/alloy-tri-hull-water-taxi-117536.html
Another electric tri hull....note the top speed on these is 5 mph....http://evworld.com/article.cfm?storyid=156

This is interesting....land sea snow, 21 knots on the water...what's not to love?

"The new Archimedes™ Heli-RIB introduced at the February 2010 Miami Boat show by SkämtaMarin, of Göteborg, Sweden, revolutionizes the yacht tender. Unlike conventional rigid or inflatable tenders whose use is limited to operation on the water, the Archimedes operates with equal ease in water, across beaches, adjacent grassy areas and through muddy or swampy areas. For those planning a Northwest Passage attempt, it can even cross ice or snow.

The inboard engine supplies power to DriveBlades turning on a pair of bouyant cylinders called drive tubes that rotate in opposite directions. Baffle-type fenders protect the passengers from contact with the DriveBlades and spray.

The Archimedes Heli-RIB (helical drive rigid inflatable boat) can navigate areas previously prohibited to all except air cushion vehicles, but without suffering their load limitations, high noise levels and poor fuel efficiency. Not only does the Archimedes carry a greater load than comparable inflatable yacht tenders, it can carry this load to shore, and straight up the beach!

Amazingly, when fully loaded, Archimedes draws just four inches and exhibits a top speed of 21 knots. Take away the water and it still operates at speeds up to eight knots across marsh, sand, grass, and other relatively soft surfaces. Having no propeller and powered by a diesel motor, Archimedes is both safe and reliable in environments where other boats fear to tread.Viewed from almost any angle, the Heli-RIB looks like a conventional twin tube RIB. The Hel-RIB sports a lightweight carbon fiber hull with twin side baffles. The key to its ability to operate over virtually any surface lies in the design of the twin cylindrical flotation/propulsion tubes that are partially enclosed within side baffles or fenders that keep spray from passengers and the passengers from contacting the drive screw. I discovered that each of its almost full-length cylinders is made of a durable Kevlar reinforced membrane with a molded-in helical channel that spirals around the length of the tube. This channel provides the attachment point for the unique DriveBlade™ that gives the Archimedes its extraordinary capabilities. (Right and left tubes carry opposing helical channels). Each drive tube is attached at its forward and aft ends to an articulated suspension arm and bearing. The internal surface of each baffle has multiple low-friction Delrin rollers, each supported on liquid-filled shock absorbing dampers. The drive tubes are rotated in opposite directions by the air-cooled, silenced, diesel motor at the aft end of the center passenger/cargo compartment.I was impressed by the creation of a computer-controlled dual continuously-variable transmission to rotate the drive tubes in opposite directions (the port tube rotates clockwise, while the starboard tube rotates counterclockwise). All control is via a joystick, which directs the computer to rotate the drive tubes at different speeds for turning, and at slow speeds can even reverse one tube to allow the craft to spin in its own length, or crab directly sidewards.Heli-RIB marks the first time that a Helmholtz resonator active noise canceling system has been used in a marine propulsion application. By phase-controlling air flows, almost all intake and cooling air noise from the engine is cancelled in a manner similar to that used in high-quality headphones. Mechanical noise is also damped because the engine is in a double shell casing filled with inert fire-retardant oil, which is mounted on liquid dampers similar to those used inside the baffles.The entire drive system package weighs just 73 kgs, and may be fully detached from the Archimedes without tools in less than 10 minutes. This permits a spare engine to be carried aboard the mothership. An optional rechargeable electric drive system may be used in place of the diesel system to provide silent, limited duration operation for fishing or military use where silence is particularly valuable.According to company founder, Pavl Skämt, the concept for the Heli-RIB originated during his time working for Saab, the now-defunct Swedish auto company ditched in late 2009 by General Motors."I was working on a new design for an electric auto having both a continuously-variable transmission and a computer-controlled stability system," Paul told me. "We knew that being able to individually drive the wheels according to load and desired direction would allow better control, but being in Sweden, driving on ice is always an important consideration. That is when we stumbled upon the history of the helical drive system from the 1920s in the United States. One look at it, and we knew that it was a boater's dream, and so I started my company immediately. Working with Volvo Penta for the engine design, and with Anco Corporation in the US for the DriveBlade, we finished our prototype in just eight months. We are very happy to offer it to the world now."The Archimedes Heli-RIB is available for special order in lengths from 4 meters up to 7.7 meters, with load capacities up to 2,200 kg. Log on to SkamtMarin.com for more information or to order."

add on kit...

If tou really want to get crazy:Fordson Snow Machine - 1929 Concept - YouTube

found some more, these things are cool...

http://www.youtube.com/watch?NR=1&feature=endscreen&v=H5NsmZcLAdM

http://www.youtube.com/watch?v=kC1fsTg9BrE&feature=related

Now there's a concept... If I can't top hull speed in my displacement boat...I may as well stick with the 7.5hp motor etc