Catamaran run-about, outboard conversion

ecat

10 W
Joined
Apr 8, 2009
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This post is part one of a build log of my electric runabout project. This was a big project, it took about a year to complete. lots of pictures, and the max for a single post on ES is 30, so I will post a part two for the rest.
This boat was built for my sister, I figured she needed a fun runabout that would cost next to nothing to run, and would be environmentally friendly, and would have low maintenance requirements. I also wanted to demonstrate for others that there are other more responsible ways of getting around on a daily basis.

I am hoping that it will have the range and speed to make the 6 nautical mile trip from her water access only home to Deep Cove in North Vancouver in a reasonable amount of time, about 35-45 minutes. It takes about 15-20 minutes by regular speedboat, and costs about $10.00 in gas. Sparky should do it for about $0.15 worth of electricity.
The hulls are from a Hobie 16' sailing catamaran, the motor is a Mercury 9.8 two stroke outboard, with the power head removed, and a Mars 6 HP brush-less permanent magnet electric motor installed in its place.
Batteries are GB 48 volt, 100 amp hour lithium iron phosphate. They weigh about 100 lb. This build would not have been possible with lead acid batteries.View attachment 27
Basic CAD plan. The console may be moved back, not sure yet. As it sits now the throttle and gear shift cables are not long enough to reach the motor as drawn. An on the water trial will give some answers.
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I picked it up at Jericho Sailing Center for $840.00 ready to sail. I then sold the sailing gear , mast and sails for $525.00, so it was cheap. It needed a bit of work, mostly cosmetic. I beefed up the hull bottoms with Kevlar strips, and fared and painted the hulls. This cost more than the boat!
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Here the hulls have fresh epoxy paint, and a temporary deck has been built to do an on the water test for weight distribution and motor placement. The steering console was a great find at the local marine consignment store. It has the throttle and steering cables still attached.
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The Merc with engine removed and Lovejoy coupling installed. I cut the end off of the crankshaft, and it fits onto the splined shaft in the outboard leg.

The pic below shows the Lovejoy L090 coupling on the crankshaft stub, sitting on the outboard drive shaft. I had to have the crankshaft stub machined down slightly to .75", and also had the machinist add a key-way in the crankshaft stub to keep the coupling from spinning on the shaft.
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Batteries at front is slightly faster (0.2 knots) than at the back, at 5.6 knots. with the stock prop. Power draw is 1300 watts at 2500 RPM, which is max speed for this motor controller. The Sevcon controller will do 3500 RPM or more, and we will need a larger prop to get to 5000 watts
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The hulls seem low in the water, should be able to knock some weight off. The temporary lumber deck weighs in at about 130 lb, and the lead acid batteries at 180 lb. I figure the final version may come in 90 lb lighter. Turning radius is too large, I have to play with the steering, and maybe add a larger skeg to the motor
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The GBS 100 AH cells. These are an improvement over the Thundersky cells in that they were designed to take BMS boards and they have covers that protect the BMS and electrical terminals. The terminals have four small screws each instead of one large screw, which means that they can not rotate and come loose. I had to replace all of these button head screws with regular tall head screws in order to get enough torque on the connections. At first the connections were heating, and there was lots of voltage drop at high current. The motor can pull 100 amps.

More build pics on the way, stay tuned...

Installing the batteries. These are the 16 GB 100AH 3.3 V Lithium cells. Nominal voltage is 52.8 V for the pack, with a capacity of 5280 watt hours. So in theory I can draw 500 watts for 10 hours, or 5000 watts for an hour. They come in groups of four strapped together. Total weight is about 98 lb. If I used the lead acid car batteries that were used in initial testing there would be 12 batteries at a total of 550 lb to equal this energy storage. 6 of the 16 BMS circuit boards are mounted in this shot. They keep the cells in balance, and to warn of under or over voltage. I keep the yet to be mounted boards in a plastic bag so as to avoid a short circuit.
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The batteries are held in place by a groove in the oak frame, which is epoxied to the deck. The groove interfaces with the aluminum extrusion on the ends of the batteries. The oak piece across the top keeps the batteries pressed into the grove at the front and back, and holds the middle down. The cables going through the deck are steering, motor control, and shifter.
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I bought the batteries in an "application kit" which includes a video display that shows volts, amps, approximate capacity, and individual cell voltages. The kit also comes with the BMS boards. as well as the black box computer that monitors the system and generates the video for the display, and a 15 amp charger.
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For more build photos and final results, see part the part two post.
 
So at this point the motor is finished and running, and the batteries are in place on the new deck. Now for the console installation, wiring up lighting and charging, throttle, and shifter, then adapting a larger propeller and skeg.
BTW, getting the Sevcon Gen 4 controller running properly requires a programmer, and the knowledge to set up parameters for the motor. I bought the controller from Thunderstruck, and I really recommend getting a kit from them with the motor, controller and wiring harness. They make sure everything is working properly, and unless you are an expert, that will save you tons of grief.

I built an extension to the steering console that will take a passenger, an well as housing the batteries, charger, and storage for life jackets and tools.
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I got some super high density foam, and marine grade vinyl upholstery, and my sister sewed up some new seats.
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The first in water test showed that the original prop was not large enough. I needed to get the motor working to its maximum power with the 2:1 reduction gearing in the leg. Also the steering left a lot to be desired, with a large turning radius, and ineffective steering in reverse. The solution was to replace the original 8" prop with a Torqueedo 12" high efficiency plastic prop, and weld on a much larger skeg to protect the prop, and help with steering.
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The trip up the my sisters place went well, I think the speed surprised my brother in law, who was somewhat skeptical of the whole project, he is won over now. We did run into an issue with splashing around the motor, and I put in a deflector on the underside of the deck, as well as a cloth shield that covers most of the cut out where the outboard sits, this has solved the problem.
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Performance is as hoped. A surprise on the data below is the strong knee in the graph that corresponds with the hull speed. I figured that the catamaran would not have this effect. Having said that, it is very doable to exceed the hull speed. We usually cruise at 2400-2700 watts, about 7-8 knots.
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We built a floating dock that hinges down, and the boat can be winched up to sit out of the water. She sits there for about 4 months through the winter, it's just too cold and rainy to go out on an open boat.
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https://www.youtube.com/watch?v=l1fjDUzTOFQ

https://www.youtube.com/watch?v=kC345sPeCRk

https://www.youtube.com/watch?v=CAMCF331ayA

So the first lesson here is not to use a Hobie 16 as a power boat, it has asymmetrical hulls with a deep vee shape. It works fine, but a longer hull with a U shaped symmetrical hull would be more efficient. It would also have more buoyancy, allowing maybe 4 passengers or a cargo to be carried. I have actually bought an 18 foot cat, and the plan is to transfer the whole deck over to the new hulls this summer. We hope to get a knot or two of extra speed at the same power level...
 
Wow you should be teaching this stuff. Very high quality craftsmanship and a great demonstation of what electrics can do. The picture of cruising in the salt, quietly and respectfully, and enjoyably...awesome. 10 stars
 
Excellent, inspirational! You put in as much time posting, probably, as you did building! Wonderful attention to detail on both counts. Thank you!!!
 
Wow! Great write-up!
Thanks for letting us participate and learn from your findings!

Just a thought for your new project: Wouldn't it be more efficient to use a direct-drive,
placing the motor e.g. under the seat and with a long shaft directly into the water?
Like the longtail boats in asia

This would avoid the losses from the 90 degree power-redirection.
I have used a 1000W motor on my 2 person folding boat and it gets up to 12Km/h (with a non-matching prop from a 5HP outboard)
With your large deck construction it should be easy to mount and hold the shaft in 2 points.
Steering would be via the standard rudder of the catamaran, which should make it very agile.

Another idea that other, larger Cats use: Use 2 motors - one in each hull as direct drive.
But here the issue is of course how to get the shaft watertight where it goes through the hull.
Maybe someone already had a clever idea for that.

Just pondering some alternatives...
Anyway: nice seeing your project(s) progress!
Keep us in the loop with major news, we enjoy reading it!

Ulli
 
Thanks for the kind words. Out of the long tail and motor on each hull option, I think I would chose the two motors. Main reason in this case is maneuvering into the tight marina slip. The two motors would mean that you could spin the boat on a dime, that would be great. I started the project with a goal of keeping the budget low, hence the old outboard and used motor. Of course I totally underestimated the final cost. Two motors means two controllers so probably more expensive. I think that an off the shelf solution could be found for through hull shaft fittings, but the props would have to go under the hulls, not behind them, so there is a risk of prop damage. The outboard kicks up in the event of a grounding.
 
Very cool project,thanks for sharing it! :D

-JD
 
Torqeedo outboards are pricey, but effective. The first three or four finishers in the Wye Island Electric boat marathon (25 miles!) for the past two years have been with Torqeedos. Here's the opener; check the Dec edition PropTalk for standings.
http://www.proptalk.com/electric-boat-2015/
I was very impressed that a catamaran, relatively heavy from RI, came in 3 or 4 overall and first in class in 2015. 18 feet, powered by two Torqeedo Cruise 4.0's, piloted by Skip Barker. And I was impressed by the stability of the craft in the moderate chop. A lot of engineering has gone into the submerged brushless AC motor, the gear reduction, the prop, the electronics. Strong pricetags, and stronger motors.
 
Yup if I had the budget, two torqueedos would be the choice. (And a solar Bimini) :D
 
Hi ecat. Nice project! Long time cat sailor here... First w/an old 18-footer "Phoenix" class built in Ottawa, "graduated" to a 20-foot (what was at that time an Olympic class) Tornado. Couple of thoughts/items on your To Do List maybe?

First up... thinking "solar" here as (free) wind energy... and giving your sis a good spank... ermmm... that didn't come out right... one of these:
A4spankr.jpg


In other words, rigging some shorter mast with a small square "spanker" sail as an "assist" when winds do cooperative for some trips?

Other thought was to extend hull bows and transoms to add some bouyancy versus whole new hulls? (Where whole new hulls could admittedly be more "U"-shaped/hydrodynamic than the Hobie. Guessing Hobie was thinking of a hull better suited for beaching on shore.) Alternatively, going trimaran by adding a central sponson hull forward maybe...

Anyway... Just my sneaky way of bookmarking your thread. Vic BC-born Guy living in the armpit of Canada (on the not-so-great lakes in Ontario).

Cheers, and fair winds and following seas.
L
 
HI

Nice job

I have done something very similar with a 5 hp outboard and and astro 3220. I feel I need to fit a torqueedo prop as well. I think the one you chose would be good for me as well as my motor can put out around 4000watts. My question is how did you get the torqeedo propeller to fit on the outboard? My 5 hp has 9 splines on the shaft. Would I have to make an adapter?

Thanks

Peter
 
Nice job with the chart of speed, power, and run times. It clearly demonstrates rapidly increasing power requirements as you exceed hull speed of a displacement vessel. Yes a better form than a beach cat will help increase speed a bit along with efficiency below hull speed, but you really need to go far longer for a substantial benefit.

My dream is to build a 10-15 meter electric hybrid cat for charter fishing use. I absolutely need a minimum of 10m at the waterline, because it needs great efficiency at up to 7 knots, the max trolling speed used. The hybrid part will be dual wingsail rigs as helper power and/or backup that can also be used as shade when down. A small generator in each hull will see use for high power runs out and back in, so a relatively small battery pack can be used to keep weight down.

Once the system has the kinks worked out, the final stage of development would be detachable underwater wings for smooth high speed runs out and back in from the fishing grounds, which are 20-25 miles out from port.
 
heynow9991 said:
HI

Nice job

I have done something very similar with a 5 hp outboard and and astro 3220. I feel I need to fit a torqueedo prop as well. I think the one you chose would be good for me as well as my motor can put out around 4000watts. My question is how did you get the torqeedo propeller to fit on the outboard? My 5 hp has 9 splines on the shaft. Would I have to make an adapter?

Thanks

Peter

Hi Peter, as far as I can remember, I took the bottom shaft of the outboard and the prop to a machinist, and he reamed out the prop, and put a pin through the assembly to keep the prop from rotating on the shaft.
 
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