Re: [electricboats] 15kW electric motors for Sailing Catamaran

Hi Matt,

I feel I'm in the easier boat :) in that we have straight shafts not sail drives.

So it's relatively easy to put in a pillow block to account for shaft side pull, and attach the electric motor in parallel mode onto the shaft. The reduction comes from the relative size of the wheels the serpentine belts run on and 48v seems to allow about 89-90% efficiency motors. Our gearbox also can also freewheel according to the manufacturer, meaning a clutch isn't needed to separate the diesel - we priced the Italian one and saved the money for the oxygen and drink needed for recovery!

I'm not sure the kW a serpentine belt can take/provide, but we'll probably limit to 8kW per motor anyway for the speed we expect from electric and I think the belt can take that based on the large alternators that use them. 

The other thing is that while the gearbox can freewheel, spinning it at 1600rpm (our expected electric speed) may not be best longterm! I don't have an answer for that problem though, so would love some help!

Everything else - battery bank size and type, solar sizing, genset size, all just then can be done based on usage needs: for 8hr travel days with a 15kW usable battery and 8kW solar, a 15kW genset need only be on for 2 out of the 8 hours at 6kn. 24hr days is much harder and the best (least use of genset/diesel) I can get at 6kn is 12 out of the 24hrs on genset. Above 7.5kn it's diesel-only time though - the benefits of a parallel hybrid!

Robert 

On 27 Apr 2020, at 9:47 pm, Matt Foley <matt@sunlightconversions.com> wrote:



Hi Steve/Rob,

Totally possible to use existing sail drives and add a motor on top. While doable its not trivial and at the end of the day, you may find its just better to go with something already on the market. The devil is in the details which may not be apparent at the onset. Another tricky aspect is getting the motor/reduction/prop just right for efficiency. Electric motors are most efficient near their upper rpm range, and props are most efficient when spinning slow. A typical motor may be anywhere from 4,000 to 10,000 RPM.  Once and awhile you will come across a motor designed to spin at low RPM's which are closer to prop RPM, they are generally big and heavy. 

As per the retractable drives, I'm betting you will keep them down most of the time. Regen on a cat can be significant due to the speed, if you don't need the regen and want to reduce drag, you can spin the props to match the speed of the boat and make the prop "invisible", that doesn't take much power at all.  And adding just a little more power will give you a nice little boost under sail. I find myself motor sailing most of the time, with an electric boat, there is almost no reason not to. Some may call it cheating. 

Matt Foley 

Sunlight Conversions

Perpetual Energy, LLC

201-914-0466

sunlightconversions.com

instagram.com/sunlightconversions/

youtube/sunlightconversions

On Sunday, April 26, 2020, 11:24:49 PM EDT, Steven Chmura <contact@care2gosailing.org> wrote:

First of all, wow, what an incredible daunting project.  Do you have a website or info on the progression of your project?

Not really able to offer advice, however, I am working on the planning aspect converting my 44' FP from ICE to electric. I'm now about 1 yr from conversion. But looking at around 10-12kw motors connecting to my existing sail drive. Based on conversations, considering 20-25kwh bank. I also am planning around a 3kw solar array. 

Anyways looking forward to following the progress and direction you go.

Steve

On Apr 19, 2020, at 5:23 PM, Rob Cave via groups.io <rob=careinvest.com.au@groups.io> wrote:

Greetings,

Reposting this topic the new group location with some photos. Hopefully some feedback or suggestions.,

Looking for advice on a 15kW 48V electric motors to fit to a Yanmar SD25 sail drive (new model of the SD20).

Application is an under construction 52' sailing catamaran.

Some broad boat parameters:

Ocean going world cruising catamaran – composite epoxy structure.

L 52', Draft 2' Weight approx. 8500kg / 19,000lb

Full electric propulsion, galley and other services including hot water.

Motors retractable: 2 x 15kw 48v + regen

Battery bank: circa 16kw 48v

House loads: 24V DC – Estimated peak approx. 3kw

Solar: circa 3kW.

16kW 48v DC gen set.

The plan is to fit motor to a Yanmar sail drive SD25 and complete unit be retractable. This involves a wet lower tube and a watertight inner tube with hull closure plate below the prop – motor and sail drive leg fitted to this at their join. We should be able to couple motor shaft to SD25 upper gear box shaft with a coupler and bolt units together without too many modifications. Be great to hear of others experience with this.

We are trying to limit motor voltage to 48V – makes batteries & solar easier plus ability to share bank via DCC converters & battery for house loads at 24V.

The boat will be light and shallow draft = easily driven. A similar 62' catamaran was fitted with 2 x OV SD15s and achieved over 9 knots in flat water so we believe 12 to 15kW motors will be adequate.

According to Vic Prop boat specs, twin 12kW (16hp) motors with RPM max of 2200 (2:1 gear reduction on SD25 so prop speed 1100 max.) & 3 blade 15" x 13" prop will yield a top speed of 8.92 kts which is fine.

We have looked at turn-key offerings from Bell marine, Oceanvolt & Electric yachts but none tick all our boxes so would like to have a crack at customizing our own solution.

Some motor options Ive stumbled across include:

1. Motenergy ME1302 or ME1616 Liquid cooled

2. Parker GVM210-100-DPW

3. Go cart or Elec motorcycle motors: Revolt, Zero, ???

Bearing in mind 48V supply and max RPM of around 2400, be grateful to get your thoughts on best motor and associated controller and any tips or constructive suggestions for our project.

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