Hi James,
I have found that 1kW of drive per ton of displacement will push a sailboat hull (fairly low drag) to about 90% of theoretical hull speed. This is sufficient for most electric boats and promotes "right sizing" the drive, enough power to be safe, but not too expensive.
So your choice to power with bigger drives should pay off, you might still be able to hit hull speed at somewhere near full power.
I just wanted to help set your expectations.
Fair winds and smooth seas,
Eric
Marina del Rey, CA
--- In electricboats@yahoogroups.com, James Sizemore <james@...> wrote:
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> The design parameters, are to travel at hull speed, for short bursts and travel extended distance at around 4 knots. And to do so without needing ongoing money outlays, in either repairs or fuel.
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> As far as expected performance, I don't really have any expectations, I have an ideal of what would be nice. As their are only a few other boats around the same weight and type as mine that have been converted to electric/solar it would be naive to think I have good enough historical data to base expectations on. The only commercial boats similar to mine I know of is the Greenline Hydrid 40. But the Chris Craft hulls are heavy, even compared to other cabin cruisers.
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> Either way there are some general rules that I hope will hold true for my class of boat.
> Such as 1000 watts per ton of displacement, to reach hull speed. So given my 13 tons displacement I would need a 13kw motor. Knowing my boat is heavier then is typical I decided on a 34kw motor. Roughly twice what the rule called for. So I do expect to at least be able to reach hull speed. But I don't expect to reach 8-9 knots at 13kw, but it would be nice.
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> I honestly have no ideal what my range will be at 4 knots. 1000ah of lithium and the unknown variable of my hull efficiency at displacement speeds, add together with the unknown solar arrays output, just make it to hard to even guess at. There are a number of similar weight solar canal boats that can basically travel indefinitely during the day with similar sized arrays. But they typical travel smoother waterways then I am planning.
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> Only time will tell. I should have some basic number before years end. So at the very least my project will help the next guy have some expectations.
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