The boat (Hammer P) is a 1966 -35 ft. OWENS flagship. She is double plank mahogany on oak frames, Teak decks and fiberglass cabin shell and fly bridge.

Equipment when we got her included mismatched and somewhat tired For V8 engines, Borg-Warner Velvet Drive transmissions all fresh water-cooled. Also outfitted with a 6.5 KW Kohler Gen- Set.

 

 

By mid 2006, I had decided that re-powering was essential. Having toyed with the electric idea for a year or so, I finally decided- "Just Do it" and began the search for a supplier for all the components.  After considerable browsing catalogs and online information, this is what I chose for our application: (This is basic electric stuff)

2- Advanced DC Motors-L91-4003-13hp-72Volt

2 -Curtis-PMC Motor Controllers- 72Volt-400amp

2 -Merritt Inline Joystick control

2 -Albright Main Contactors

2 -Albright Reversing Contactors

3 -400 amp Ferraz/S'mut Safety Fuses

1-Link 10 E Meter

1-Onboard Charger 48-108 volt

2-Deltec Amp meter shunts

2-Westberg Ammeters

180 Lin. feet 2/0 Welding cable

90 Cable Lugs

24 -L16H Trojan Batteries 

That is pretty much the electrics of the system, plus misc. hook up wire, etc.

 

      The Mechanics portion needs some thought: Motor to shaft reduction, belt tensioner and battery placement.  As you will see by the photos, I had to lengthen the propeller shaft to accommodate the larger pulley for a reduction ratio.  I chose a 4:1 reduction because the motors need to turn fast enough to run cool and I need 1000rpm at the shaft to match our previous cruising speed. The rest of the mounting hardware is like a big erector set. All bolted parts were pre-drilled except for bolting to the original engine bunks. These were bolted in place after shaft augment.  Motor mounts are adjustable for belt tension and tracking.

There are two flange bearings each side, and opposed for thrust bearings. This all makes a fairly compact package and we can now decide on battery placement. In our case, we are designing a 72 Volt system. Battery placement is somewhat a balancing act. Original components, (fuel) was stored behind the drive train and of course, motors amid ship. Fuel weight (160 gallons) was about 1300 lbs. Motors and transmissions about 1500 lbs.  New battery pack weight: about 3000 lbs. To best balance the boat, I put 8 batteries forward and four behind each motor. With motors, batteries and electrical equipment we have an approximate weight gain of 1000 lbs. 

      Now, looking at performance. First we need to consider the boat Shape and Hull design. As the professionals see it, this is the second poorest hull design for electric power. Only a barge with square ends is worse.  The ideal craft would have a sharp entry, a long waterline length and the transom out of the water.  Boat design is always subject to compromise and the ideal form is not always practical.  In our case, we will work with what is at hand and improvise, compromise and succeed.

Operation of the boat has not really changed. Still have twin props, still a hull speed just short of 6 knots (6.9 mph). What has changed is the planning and navigation. Without regenerative power we have to plan with power consumption.  With batteries one should not run them totally dead. Always plan for about a 20% 'no touch' area to protect the battery life.   In our case, we have about 670 usable amps that are available. Our "E' meter tells us exactly what power we have used and how long it will last based upon the rate of discharge over the last 10-12 minutes.  It’s nice to have that information available at the touch of a button.

For our longer distance cruises, we have adapted a temporary generator that run our battery charger at about 10 amps at best. Hi tech. chargers and modified sine wave generators are not very compatible for high output. Even the 10 amps will help some to increase longer distances.  Over a 6-hour cruise, those 10 amps will return 60amps.  If we are traveling at 60 amps this has gained an extra hour of travel time. Of course now that we have made the trip, if it was one way, we need to allow adequate time to recharge.  If we have used 550 amps and the charger output is 20 amps, potentially it could take 30-36 hours to recharge.  Discharge rate and your speed are directly related and the need for speed shortens the trip. Here are some discharge rates that will help:

    40-amp draw will run about 12.5 hrs.

    60-amp draw will run about 8.5 hrs.

    80-amp draw will run about 6.25 hrs.

Needless to say, the faster you attempt to travel, the shorter your travel time will be. This is where hull speed, weight and power storage need to be considered.

If you would like to discuss this information further, please give us a call at:

253-884-3691- or email the Hammer P @ hammerp@centurytel.net