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

Monday, May 16, 2011

Re: [Electric Boats] Electric planing dinghy

We're still trying to make up our mind about the rpm issue, one encounters, if replacing the ICE power head on the outboard with an electric motor for planing speed.
Miles suggested belt gearing, which means extra bearing at high end of drive shaft.
There also may be props pitched high enough, if we can find them.
There is the Agni motor, which is pricey and probably overpowered.
We're focussing at the moment on using an AC induction motor like this: http://www.electricmotorsport.com/store/ems_ev_parts_motors_ac9.php
At 6000 rpm this seems like a candidate.
Looking at the power/rev curve : http://www.electricmotorsport.com/store/pdf-downloads/AC_Drives/AC9.pdf , it has this "bump" at 2000 rpm and looks like the power curve for a planing dinghy, where the "bump" happens while "getting on the plane", or am I guilty of naive and wishful thinking.
Any opinions on this ?
Anybody has experience with AC induction motors?
Thank you

Rob on Linda

--- On Fri, 5/6/11, chris Baker <chris@currentsunshine.com> wrote:

From: chris Baker <chris@currentsunshine.com>
Subject: Re: [Electric Boats] Electric planing dinghy
To: electricboats@yahoogroups.com
Date: Friday, May 6, 2011, 11:01 AM

Hi Rob,

The Cruise 4 motors are meant to be 4kw, but they quite often will work at higher levels. Im not sure whats going on here, and I haven't got a handle on whether they all allow greater than the 4kw, or just some of them. The 22.5 km we got was at 4400 watts and I'm guessing most Cruise 4s would be good for that.

As for mixed voltage charging, Solar Converters Inc http://www.solarconverters.com/ specialise in charge controllers that adjust the charging voltage up or down as required to do the very things you talk about. Check out their products. These device not only adjust the voltage but manage the charging profile to the required voltages.

I'll be using their controllers for charging a 24 v pack from 12v solar panels.

cheers

chris

On 06/05/2011, at 7:12 AM, rob linda wrote:

Hi Chris,
Very interesting and useful info, thanx
I will suggest the dinghy owner to have a good look at the Torqeedo Cruise 4 and save himself the hassle and uncertainties of an outboard conversion. I wasn't aware, the Torqeedo could handle 5500Watt. I doubt however, he will be happy with your 12 knot top speed, the way I see him usually shooting over this lagoon. I keep telling him: "Speed isn't as cool as it used to be"", but to no avail.
As far as DC to DC converters are concerned, I have a question about their behavior
On Big Oil I'm limited to 1 solar panel, so I decided, I was stuck with a 12V motor, while eyeballing 24V scooter motors for the conversion. I decided, that charging a 24V pack however with 1 12V panel, a DC to DC converter wouldn't do the trick, since I expected the thing to regulate the 18V open panel voltage to a regulated 24V, rather than 36V needed for recharging a 24V pack or do they indeed just double the voltage?
The same problem we have with the planing dinghy, where we have to charge the 48V pack from the 24V board system of the mother ship.
Is there a DC to DC intelligent charging solution or do we have to go via inverter and battery charger, which seems expensive/vulnerable/extra losses/etc.??

Rob on Linda

--- On Thu, 5/5/11, chris Baker <chris@currentsunshine.com> wrote:

From: chris Baker <chris@currentsunshine.com>
Subject: Re: [Electric Boats] Electric planing dinghy
To: electricboats@yahoogroups.com
Date: Thursday, May 5, 2011, 10:11 PM

Hi Rob,

Coincidently I did a planing dinghy test just a few days ago using my Torqeedo Cruise 4, taken out of trimaran for the test. I wanted to see how it went on a 9ft6inch tri hull dinghy that is available from nearby where I keep my boat. (In Pittwater, Sydney). I sell Torqeedoes so am interested to find a suitable dinghy that would work well together with it.

This dinghy is reported to do 20 knots with a 6hp outboard.

We tried it with two props, a high speed prop and a weedless prop from Torqeedo. I used the weedless prop first because I'd heard that someone in Germany had got good results with that. We got to 19 km/hr, it was on the plane but not as fast as I had hoped.

Then we tried the speed prop and we got to 21 km/hr on the first run. With a bit of tinkering with trim angles we saw 22.5 km/hr as best speed. There was about 10 knots of wind around and we were on the lee shore and so there was some chop from the wave action—we were going across the wind to minimize the wind effect. The waves were knocking the dinghy around a surprising amount and so we decided to go across to the other side to be in the lee of the hills there and have flatter water. The water was nicer but we still topped out at 22.5 km/hr and shortly after the batteries were flat. So I expect we could have been limited by sagging voltage on the those tests.

The dinghy was a Lamoore design and it had dirty bottom which we cleaned off with a scraper before the test, but I expect it would have been better with a new or least cleaner hull. We were using Optima 55 ah batteries being a weight of about 76kg. And I'm about 65 kg wringing wet.

I suspect we can get a few more k out of it by tinkering some more, and using a lithium pack for lighter weight and less voltage sag. I've seen 5500 watts on my motor at times, when being powered by lithiums, and the most we saw was 4400 watts in these tests. I think there's two possible reasons for the lower peak power. One is that we hit maximum revs, these motors are electronically rev limited, and that was maximum power available because of voltage sag in the AGM batteries. If it is that we are limited by revs, which I doubt, it could mean a higher pitched prop would help. If limited by voltage, it will mean that a lithium pack will help.

I know this doesn't answer any of the questions, but could be of interest.

But I can offer some info to the question about the solar regulator. I like the Xantrex series such as C40 because the voltage set points can easily be adjusted with a screw driver. I'm also getting a solar boat built just now (I'll do a post about that soon) and am using some regulators from Solar Converters in Canada. I have 12v panels and will be charging at 24v and they make good converters for matching differing voltages between panels and batteries.

Cheers

Chris

On 05/05/2011, at 11:40 PM, rob_linda_2000 wrote:

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