Thanks for your advice. I picked up 4 X T105's today. Initially I plan to use my trolling motor because I have it. I modified it to create a remote head. I'll need to create a tiller horn so I can steer. I'll use the 4 batteries as a 12v pack and do some testing. There is a small boat event close by next month called the howl at the moon cruise. Its on Priest Lake in the Idaho Panhandle. It will be a good place to test as I'll have a willing tow boat if needed.
If anyone is interested the boat is a converted sailboat. A one of a kind prototype from a famous small boat designer. For me, I already have a smaller version of a design by this person (Matt Layden, of Paradox fame) and there were things I did not like about the design as a sailboat. One day while I was dreaming about boat designs I came on a Phil Bolger design called the Delaware Trawler and realized my e460 looked a small version of the boat. Knowing I'd always chose my Paradox over the 460, I decided the boat would better serve me as a trawler when the weather was not ideal for sailing. The builders website is still up if anyone wants to take a look.
I'll post later next month after I spend a long weekend testing the motor and its endurance.
Chris Curtis
---In electricboats@yahoogroups.com, <cpcanoesailor@...> wrote :
Hull speed for your boat is about 5.3 knots, so 4 knots is about 75% of that. I don't think a 50lb trolling motor will give the performance you want. If you change the prop, you could make it more efficient and get closer to your desired speed. A 100lb thrust motor would probably be appropriate.
One rule of thumb is 1A for each pound of thrust at 12V. I'd suggest going with a higher voltage system, like 24V or even 48V, since that will divide the current draw by 2 or 4, so you don't need to use really thick wires and the associated connections. Also, your Peukert losses will be divided as well, so less wasted energy.
It sounds like you want to use your batteries as ballast, which works in your favour. So you can use reasonably priced heavy batteries i.e. lead-acid.
Power required vs. speed is quite exponential, meaning it takes very little energy to make the boat start moving, but each increase in speed (say 1/2 knot) takes more and more energy than the last increase. So if you want to go 4 knots, and you're operating at 75% of hull speed, the last knot to get there will require a fair bit of power. I've seen graphs of power vs displacement speed on this forum.
Let us know how you progress with your plans.
One rule of thumb is 1A for each pound of thrust at 12V. I'd suggest going with a higher voltage system, like 24V or even 48V, since that will divide the current draw by 2 or 4, so you don't need to use really thick wires and the associated connections. Also, your Peukert losses will be divided as well, so less wasted energy.
It sounds like you want to use your batteries as ballast, which works in your favour. So you can use reasonably priced heavy batteries i.e. lead-acid.
Power required vs. speed is quite exponential, meaning it takes very little energy to make the boat start moving, but each increase in speed (say 1/2 knot) takes more and more energy than the last increase. So if you want to go 4 knots, and you're operating at 75% of hull speed, the last knot to get there will require a fair bit of power. I've seen graphs of power vs displacement speed on this forum.
Let us know how you progress with your plans.
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Posted by: yahoomail@curtisteam.org
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