ESPcat Curvaceous Narrow Bottom

Just look at that lovely, curvaceous bottom. It reminds me of a Kylie Minogue music video! Those water molecules have no trouble sliding along that lovely hull causing almost no wave action at 8 knots.

I finished the arduous task of cleaning and sanding the bottom and applying two coats of antifouling paint. I used War Paint by Wet & Forget. It seems to be as good as any and is relatively cheap, much like myself.

I replaced the two old 100 watt flexible (and useless) solar panels with a single, solid 200 watt panel.

The solid panels are much heavier (12 kg) than the flexible type (3 kg) but those flexible solar panels did not even last 2 years while the solid ones are much less expensive ($1 NZ per watt) and guaranteed to still put out 90% of rated power after 10 years and 80% for 25 years. Holy shit; in 25 years I’ll be 100! I bought the panel from Superstart Batteries in Auckland. The measured the output yesterday at 13:00 was 165 watts (from a 200 watt panel). I am not certain that the sky was completely clear or if the sun was shining directly at the panel but it was close. I was totally pleased with the performance and the fridge and microwave are loving the new panel.

One panel down and 19 more to go. Yes with 20 of these panels I will have a total of 4,000 watts which is 2,000 watts per electric outboard. Each outboard is rated at 15,000 watts but I plan to cruise at around 6,000 watts. The idea of 6,000 watts is that is about 8 hp which is what the gasoline outboards I am now using put out. The gasoline outboards give me 8 knots of boat speed and the electric outboards should do the same at 6 kW. I would like to have a pair of 24 kWh, 24 V batteries. I should get more than 4 hours cruising and recharge from dead in 2 or 3 days.

There is a great number of questionable claims published that compares the performance of electric outboards to gasoline outboards. One manufacturer of electric outboards claims that their 2,000 watt electric outboard has the same “propulsive power” as a 5 hp gasoline outboard. Note that 5 hp is an output of 3,730 watts (1 hp = 746 W). That is why it is called a 5 hp outboard motor.

How can you get more than 3,730 watts of “propulsive power from an electric motor with an input of 2,000 watts? I don’t think you can. I can’t wait to try it all out for myself.

And speaking of outrageous claims, I claim that Borderline goes 8 knots with her tiny, twin 8 hp outboards. The beam of Borderline is 0.654 m and the waterline length is 8.5 meters (27.9 feet). Hull speed in knots is 1.34 times the square root of the waterline length in feet or 7.08 knots. How can Borderline go 8 knots?

Well, Borderline’s ratio of waterline length to beam is 13. There is no such thing as hull speed with this narrow hull type. That is why Borderline can go an amazing 8 knots with a pair of tiny 8 hp outboard motors. Once the hull gets so narrow that the ratio of waterline to beam is greater than 7, there is almost no bow wave so there is no hull speed limitation. Boat speed is all down to friction with a very narrow catamaran hull. Honest!

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