T-Pain Is On A Boat: Re: [Electric Boats] Re: motor overheating

Tuesday, June 23, 2009

Re: [Electric Boats] Re: motor overheating

Keith,

Slip does increase as the headwind (or any extra resistance increases) increases. Water is 'sorta' squishy ( not really compressible but flows 'sorts' easily) The 'sorta' is why amp draw goes up.

With increases resistance the amps go up AND the boat slows down. The slowing down is why the amps go up - because the slip increases. The work the motor does is based on accelerating a mass of water backwards. The faster the boat is going forward, the less the prop can accelerate it backwards - hence less work, less amps.

Next time you are out in your famous windy bay try WOT upwind and downwind and let us know the results. Up wind will be more.

Denny

----- Original Message -----
From: aweekdaysailor
To: electricboats@yahoogroups.com
Sent: Tuesday, June 23, 2009 12:26 AM
Subject: [Electric Boats] Re: motor overheating

Thanks Denny,

So tied to the dock, slip is 100%. Pushing into a headwind - doesn't slip increase as well? Based on experience and intuition the boat just slows down - amps stays constant at a given throttle. You have to up throttle (voltage) to compensate and try to maintain speed.

If we were talking golf carts again, I'd buy into the amps increasing. But water is squishy and will follow the path of least resistance - and given enough wind that would be sideways.

But I'll do some homework to make sure I'm not just talking through my hat.

-Keith

(and I'm wondering if I've got a problem in my motor or ammeter - I can pull 20amps at WOT no load, belt removed)

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