T-Pain Is On A Boat: RE: [Electric Boats] Electric planing dinghy

Thursday, May 5, 2011

RE: [Electric Boats] Electric planing dinghy

Myles,
The only reason I'm involved is because of my amazement how little it needed and how fast it got on plane, that and the ballast (about half future battery weight)
The belt for extra gearing will be considered.
We still have to do some measurements and trials with smaller outboards, before hard choices are made.
Imho if it doesn't get on the plane in 30 sec. it will not get on the plane at all.
At present with the 15Hp it's more like 1 or 2 seconds to get up. It felt like it got up, while still turning the throttle.
Rob on Linda

--- On Thu, 5/5/11, Myles Twete <matwete@comcast.net> wrote:

From: Myles Twete <matwete@comcast.net>
Subject: RE: [Electric Boats] Electric planing dinghy
To: electricboats@yahoogroups.com
Date: Thursday, May 5, 2011, 7:18 PM

Well, at 48v the ETEK's no load speed is about 3600RPM. Assuming a nominal 2:1 ratio in the lower unit, you'd be looking at about 1800RPM at the prop.
The 2-stroke motor is probably rated to over 5000RPM…you could add more "gearing" by belt-driving the drive shaft and be able to reach over 5000RPM without overreving the PM motor…assuming a power reduction after getting up on plane and that you could get up on plane within 30-seconds, even the 15HP short term rating on the ETEK is a bit conservative. I've seen a car with 8 ETEK's deliver over 50HP each going down the drag strip---they were being driven with a contactor controller from a 96v pack!

-Myles

From: electricboats@yahoogroups.com [mailto:electricboats@yahoogroups.com] On Behalf Of rob_linda_2000
Sent: Thursday, May 05, 2011 6:40 AM
To: electricboats@yahoogroups.com
Subject: [Electric Boats] Electric planing dinghy

Since liveaboards and cruisers anchored here in the lagoon have gotten used to seeing me move around in all weather in my solar powered sailing dinghy "Big Oil", without ever having to buy gas, I do a lot of explaining (preaching),answering questions etc.
So I got an invitation to assist in the design and electrifying of a planing dinghy. Since I was impressed with the performance/weight of said dinghy, I accepted the invitation and would like ideas/comments/etc from this group.
Dinghy:
16 Feet, made from some high tech foam, so light, that the guy has to BALLAST it. Presently it has a 15 HP in the back and if you open the throttle halfway, it jumps straight on the plane and remains planing throttled back to about half that.
Range:
It will only serves as ship to shore tender, 2 15min trips and back at most per day (between charges), so design is for 1 hour usage at minimum planing speed
Motor;
DIY outboard conversion using 48V ETEK or simular
Batteries:
Lithium 130Ah (for now)
Charging from solar panels/generator on mother ship
Question:
We're trying to establish lowest RPM for planing with the 15HP and needed RPM for planing threshold, but still looking for right handheld tachometer.Any ideas out there, how RPM's of typical 2cyl outboard compares to ETEK/MARS at 48V
Other question:
We will be looking for 48V solar controller for lithium. Any suggestions?
Any feedback is welcome
Thank you

Rob on Linda