T-Pain Is On A Boat: Re: [Electric Boats] New member, new boat, Dowsizing question

Thursday, April 30, 2015

Re: [Electric Boats] New member, new boat, Dowsizing question

Mike, The Venture 17 sailboat was built with 270# of ballast, about four T105s worth. All the sailing gear might be another 50# so 1000# of batteries is a lot more weight the designer intended.

Removing half the batteries but keeping the same 48v will let the boat go a little faster, float a little higher and be a little easier to launch and retrieve if you are trailering. All good things. Your range will be a little less than half than what it was with the 16 batteries. That may or may not be a bad thing depending on how you use the boat and availability to plug in to recharge.

There is absolutely no reason to replace the motor. Electric boats are really about batteries, not so much motors.

On Friday, April 24, 2015, dellariom@yahoo.com [electricboats] <electricboats@yahoogroups.com> wrote:

[Attachment(s) from dellariom@yahoo.com [electricboats] included below]
Hi all
I am new and just purchased a (one off) electric boat someone else built by converting a Venture 17 sailboat to an electric launch. He added a Torqueedo Cruise 4 with 16, 6v Trojan 105's (450AH) . The 1000lb battery weight is concentrated in the center of the boat to replace the ballast of the centerboard. He did some creative fiberglass work to move the Cutty Cabin to the aft end which houses a small day head and some resting bunks and converting the forward area into a lounge like the Duffy design. I love the concept of an all day electric boat that makes provision for both battery and bladder needs.

However, I wonder if it is overpowered and wonder if when it comes time to replace the batteries if I could replace the Cruise 4 (8hp-48v system) with a Cruise 2 (5hp-36v system) and reduce the batteries to 6(-620 lbs) or 12(-248 lbs). This would reduce the weight and hopefully increase efficiency? I am however concerned about power reduction and effect on ballast that may be needed to maintain stability. I am obviously not an engineer and hope someone can give me some insight on how to calculate this conversion.

Current Boat specifications are:
-Estimated weight 500lbs (without batteries and extra little things taken off boat). Original displacement 900lbs
-Length 17ft , Length at Water Line 15ft, Beam 6.5ft, Draft 18in,
-Max Engine size rating 10hp,
-Current speed is 6.5 mph max with an efficient cruise at 5mph with a Torqueedo calculated range of 80 to 100miles.

Any suggestion on how to calculate how much power is needed?
Thanks

Mike