Hi,
One way you might get the speeds you want with low power is to make it a hydro foil catamaran. We are starting to see lots of sail power vessels foiling. The technology is starting to mature and is becoming more common place.
An electric power vessel would certainly have a more reliable motive force than wind and should foil easier. With foils any added weight and drag from the batteries, hulls, etc would be negated so a short waterline is possible with higher speed. Do a search for kite foiling boards. They are 5' long and do 20+knts with wind power alone.
I am not a boat designer so I don't know how much power and speed you would need for the initial lift but after the hulls lift clear of the water the power demands would drop drastically. I am sure there is a compromise between foil size and shape for lift versus speed and drag from size, but it would be interesting to experiment and find the right combo for an electric catamaran in the size you are talking about.
This would be an interesting problem as a senior thesis for any up and coming navel architects.
Mike Roll Lurking
At May 14, 2015, 6:25:40 PM, 'cal' h20dragon@centurytel.net [electricboats]electricboats@yahoogroups.com'> wrote: Yep, a lot of power to drive any round bottomed or pontoon type hull. Poor power usage with all that drag, so a lot of power to get 12 ft anything over 4 mph foe very long, unless it is empty, no people or batteries. With that weight added, I doubt any would do what you want. look at the hull maximum capacity on one in that size in pounds first. Then look at the maximum HP on the plate for safe operation. Even if you build it, a related figure applies. bear in mind that if you build it, you are responsible for lives on board, if your creation causes loss of life or property – you are at risk, and an insurance company can back out of payments really easy. Not CG certified for use, "sorry sir, we must have a coast guard number or our coverage is not valid", you take that risk unless you get it in writing from the company – not your agent. My 11 ft inflatable will do, 4 mph max, with a minn kota 50, efficiently. More than that drains batteries waaay fast. So, probably no you cannot get that small a 11' pontoon boat to 10 mph, not even close with batteries and people. Maybe 4 to 5 is closer, I have plans on a better hull that I might build someday, but so far not a Hobie cat, or Pringle cat set of hulls would work, and the round tube hulls suck power fast. One answer is longer hulls for higher speeds, wider hulls to carry more weight, tough to do. Sent: Thursday, May 14, 2015 1:29 AM Subject: Re: [Electric Boats] Daydreaming about the next project: An electric day cruiser... Thats displacement speeds.
Doable, but expensive.
About 35k in battery (12-20 k), 5 k engine and VFD or servo.
(30-50 kWh lion battery, 20 kW motor, 2 hr range).
On 14/05/2015 05:03, oak oak_box@yahoo.com [electricboats] wrote:
>
> If I built something like a 6' by 12 or 13' pontoon boat, any idea how
> many HP it would take to get it cruising at 10mph?
>
> Thoughts?
>
> John
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-hanermo (cnc designs)
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