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Old 02-02-2021, 12:04 PM   #21
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It appears to have a lot of wetted area and very hard chines, so I can't imagine it being real efficient until it comes on plane. How about the larger eProp? If it were my experiment, I'd borrow a couple of different size gas engines and see what the characteristics were. Keeping in mind the claims of electric vendors must be discounted - 1 hp is about 800W regardless of what the may advertise.

Yeah I would really like to do some experimenting before I haul off and spend $2000 on that epropulsion outboard. The battery on the Spirt plus is almost 1300 watts, so is it really only about 1.5 HP? If that’s all it is wide open it doesn’t sound like enough. I run this 3.5 hp gas engine at 1/3 to 1/2 throttle usually.
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Old 02-03-2021, 09:01 AM   #22
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I've been thinking about a) an electric dinghy, and b) treating ourselves to a steering wheel.

Our main usage would be anchored/moored boat to dock, or boat to sandbar for the dog. (We're currently dog-less, actually.) Any additional usage -- longer distance sightseeing, etc. -- could be easily tailored around whatever the propulsion system might support.

The AB Alumina or the Highfield Classic center console RIBs -- or similar -- look to be what I'm thinking of, but also way fancier than we would care about. And they seem to want an arm and a leg for those, too. OTOH, they do sort of illustrate what's in my mind. Light weight (comparatively) would be a goal.

The Elco electric outboards look like a decent propulsion option. Either the 24V EP-5 or the 48V EP-9.9 would seem viable. A couple Group 31 AGM batteries in a 24V system would seem to be most economical, even though that path would weigh more than a L-Ion power supply. Four Group 31 AGMs in a 48V system sounds like beginning to get weight-prohibitive. The two L-Ion power supplies weigh much less; in fact both 24V and 48V weigh the same 55-lbs. The 24V L-Ion power supply cost doesn't put me off... but the 48V version is getting on toward serious bucks$$$.

The RIBs I mentioned recommend 20-30 horsepower. I don't so much care about going fast, don't necessarily care about planing... but I wonder if the 5-hp/24V version on a ~300-lb RIB (plus motor, pax, and "stuff") might be a bit tooooo tiny. In fact, maybe even the 9.9-hp/48V system might be too puny, too.

Hmmm....

-Chris
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Old 02-03-2021, 10:29 AM   #23
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Our cooking propane seems to last a long time.

But I think some heating appliances are less efficient w propane fuel. One of the reasons I chose the Wabasto for heating. Not sure though.
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Old 02-03-2021, 12:30 PM   #24
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Yeah I would really like to do some experimenting before I haul off and spend $2000 on that epropulsion outboard. The battery on the Spirt plus is almost 1300 watts, so is it really only about 1.5 HP? If that’s all it is wide open it doesn’t sound like enough. I run this 3.5 hp gas engine at 1/3 to 1/2 throttle usually.
I think the Spirit Plus has the same motor as the Spirit (the battery is slightly higher capacity) The motor is 1000W so if 100% efficient 1.34 hp by definition. The prop is slower turning and larger than the gas, practically I'd expect it to be about the same as the gas at 1/3 or 1/2. Keep in mind that at displacement speeds, the resistance rises exponentially, so doubling the power may only get you a small increase in speed. For example I think with my Spirit and Bullfrog dinghy, 500 watts power gives about 3.6 knots and 1000 watts about 4.1 or so. The extra power is useful for punching through a chop or against wind. I got 4.6 knots wide open on a supposedly 5 hp gas outboard.
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Old 02-03-2021, 12:33 PM   #25
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With the larger, slower turning props the electrics are generally better optimized for low speed thrust. That's why they claim a 1.5hp electric has the "same thrust" as a 3hp gas outboard. At low speeds, it likely does. But assuming a dinghy that will plane, the higher powered gas outboard will move it faster.
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Old 02-03-2021, 12:46 PM   #26
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I think the Spirit Plus has the same motor as the Spirit (the battery is slightly higher capacity) The motor is 1000W so if 100% efficient 1.34 hp by definition. The prop is slower turning and larger than the gas, practically I'd expect it to be about the same as the gas at 1/3 or 1/2. Keep in mind that at displacement speeds, the resistance rises exponentially, so doubling the power may only get you a small increase in speed. For example I think with my Spirit and Bullfrog dinghy, 500 watts power gives about 3.6 knots and 1000 watts about 4.1 or so. The extra power is useful for punching through a chop or against wind. I got 4.6 knots wide open on a supposedly 5 hp gas outboard.

Hey thanks. I appreciate those real-world numbers. This barge weighs about 500lbs; not sure how that compares to the Bullfrog.
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