New Solidnav Video

This video is a rough cut from motoring around Santa Cruz on a client's 27' Ericson sailboat.

Posted By: Jason

january 23, 2009 08:26pm

The Waterline, the Wallet and the Submarine

During training sessions with shipyards, and in conversations with customers, we encounter many of the same questions. Most want to know if electric propulsion meets their needs, what they will cost compared to diesel engines and how the long the technology has been proven.

When we suggest length and displacement maximums for our motors, we are making recommendations based that we know will push hulls to a speed similar to a well matched internal combustion motor. The performance of the Explorer is very similar to the Universal atomic 4, Yanmar 2gm20 and similar diesel engines. These engines are often installed in vessels much larger than they are capable of pushing to hull speed. At one time, the Atomic 4 was installed in about 80% of sailing vessels under 40 ft. and we have many people inquire as to which motor will replace this need. We have found that a vessel, whether Ranger 37, Columbia 36, Westsail 32', or any other vessel powered by the Atomic will perform at least to the level it does with a similar sized gas or diesel engine with an Explorer. The answer is that any size vessel powered, by a 24hp or smaller diesel or gas engine is a candidate for installation.

(This is snapshot a customer sent of an Explorer in a hull very similar to Westsail '32,This boat left San Diego a few weeks ago and is cruising Mexico. Last seen around Mazatlan, this boat weighs in at 24,000lbs. and makes between 3-4 knts at around a reported 40 -45 amps underway. The primary use for this motor is maneuvering.)

The range requirement for most sailors is easily met by replacing the wet weight of an engine, fuel, tankage, wet-exhaust, cooling system, and etc. with batteries. Energy stored on board is less than when packing around dead dinosaurs, but how many trips a year does your fuel tank go from completely full to absolutely empty? How often are you actually utilizing all your stored energy? The net weight for most boats is a wash. Some sailors who move shorter distances have opted for minimal installations that have weighed in at over 200lbs lighter than their preexisting engines. In real world tests, weighing engines as they sit, we come in between 540 and 605lbs (includes 23 gallon fuel tank, wet weight of exhaust/engine, and other systems that are removed from a motor as weighed on a hanging scale). This equates to 6 8volt AGM's, all the charging and peripheral systems required, as well as spares and maintenance tools. Let's take a look at a more common installation, the Ericson '27.

As you may notice, the overall range is greatly reduced as you push the hull closer to speeds that create a large bow wake. The range curve is inverse to a force curve. It takes a lot of force to push every pound of an Ericson '27 at 4 knts compared to a longer waterline but much heavier Cal '40. The Ericson moves at 20 amps or 960 watts (about 1/3 less than a home space heater) and the Cal motors are motoring at 50 amps or 2400 watts. The Cal uses 6.6watts/pound and the Ericson uses 7.8 watts/pound. The Cal is actually more efficient moving weight at that speed. Waterline and hull shape create major differences in performance that make displacement less important than most assume. When examining your choice in motor, consider what motor you have onboard currently, your boats overall performance, and your how often you motor over 40 miles or so without any wind what-so-ever.

Electric vehicles made their appearance before the introduction of internal combustion engines. As a child I made a journey to Dwight D. Eisenhower's childhood home and looked at his electric car. It was somewhere between a carriage, a car and a well a lacquered canopy bed. Years later, I discovered similar cars online being restored and to my utter astonishment, some of these turn of the century canopy beds are still on the road!!! If you invest much time researching electric boats, you will quickly find General Dynamics Electric boat out of Groton, Connecticut, which consumes monsters amounts of capital in insuring that the US Navy has little concern when trusting the world's most dangerous weapons to Nuclear Generators and electric motors. In the field of recreational craft, there is some real spin-off technologies and technological hurdles that have emerged. The military began working with electric propulsion shortly after the civil war and continue to utilize it to this day. In the past, control electronics were dependent upon thin strips of mild steel to alter acceleration and change direction. To demonstrate how this functions take a straightened paper-clip (which is many times thicker and stronger) dip it in seawater and leave it outside on your dock for a week. Now dip that paperclip in rubber cement thoroughly and attempt the same test. SolidNav addressed these concerns with true sealed electronics that are potted in an anaerobic environment; both waterproof and impervious to corrosion, our switches have no contacting surfaces and can survive this same test with zero damage. The advent of a motor that has no brushes to corrode and performs very well at low RPM was an advancement that allowed scaling of cost and size. This allows a complete installation that would cost $30,000 to $60,000 to now cost less than a complete diesel. You can install a complete system for $6,995 (one of our dealers was selling a complete package for this price on special).

The net cost of a DIY atomic four conversion to a beta marine diesel in an article by DIY boater was over $12,000. A complete Explorer system including charger and monitor runs $6,995. The labor cost at shipyards that we work with for an Atomic-4 conversion run between $14,000 and $20,000 thousand depending on location of existing engine and the labor required for removal. Our systems run between $8,900 and $12,000 installed. Imagine for a second if the auto industry followed that model...a Prius for half of the price of a standard car?

Coming Next Week:

Your wife, the Propellor and Sleeping Indoors

Posted By: zach