Yes, absolutely. Getting a good match of the propeller to the motor/reduction/boat is paramount to getting good performance. And I think it is the least attended to part of these conversions. I was lucky and had a large three bladed feathering propeller that has an adjustable pitch that I could set to match the system. I think I am getting better performance than I initially predicted based on data from other similar conversions I had seen posted on line thanks to the better matched propeller. This season I made a change of the pitch to one setting higher on my prop and got a very significant increase in efficiency over my initial setting. Something on the order of 8 to 12% though I need to do some more testing to confirm that.
So yes, spend some time/effort/money on getting the prop match correct. Your starting point would be designing the reduction gear to match the prop RPM to what the original engine setup was if that was a good match. But, I have a large propeller and since I could change the pitch I decided it would be better to slow the prop down with a higher reduction gear (3 to 1 in my case) and increase the pitch. But I already had this relatively expensive and adjustable propeller to experiment with and the original diesel max RPM was about the same as the ME1616 at 2500 rpm.
Also, I think the big prop is better for potential regen. I have managed to get 400 watts of regen in conditions were I could sail at 6.5 to 7 knots. But I have not explored this in any detail. I think bigger boats are likely to be better at regen too. A 48' cat might be very good at it. But a 48' cat is also an ideal platform for lots of solar? So maybe the regen is not so important? But having a diverse set of energy inputs is a good thing?
Dan Pfeiffer
The item that rarely gets mentioned is the Propeller. How does the Propeller effect Range under Electric Propulsion in a monohull and/or catamaran while E-sailing ?On Saturday, October 21, 2023 at 09:58:02 AM EDT, Dan Pfeiffer <dan@pfeiffer.net> wrote:I know it's not directly comparable but I have the Thunderstruck 12kW kit in my 13,000 lb 33 ft mono hull. It is easily as powerful as the 23hp diesel it replaced (Volvo MD11) and can power the boat to hull speed at full power. It is an ME1616 running at 48V. This motor can be configured to run at up to 96V (24kW) so if you got the 12kW kit it would not be all that difficult to step up to 96V operation with a reconfigured battery setup and controller re-programming (or maybe a different controller?). Something to consider.
To run at higher speeds requires cooling. Up to about 5.5 knots or 75% of hull speed is OK for me without cooling.
Motor sailing is definitely a viable mode of operation. Here's some data from a recent trip I did where I motor sailed a bit.
Motor Sailing Data Point
TWA 93, TWS 5.2, BSP 5.38, Watts 1316
Motor Sailing Data Point
TWA 126, TWS 7.1, BSP 5.2, Watts 1024, RPM 1238 (prop RPM 412) About 60 miles range on full battery
Estimated range 70 miles at this rate and conditions from Victon meter.
When wind died I was making 4-4.5 at 1400 watts. About 36 miles range on full battery
So motor sailing in these conditions about doubled the range.
Details of my installation here:
http://dan.pfeiffer.net/10m/electric_drive.htm
Dan Pfeiffer
On 2023-10-19 11:19 am, Eric via groups.io wrote:
Hello all, complete newb here, so I'll start with a very basic newb question. First, the setup - we have a 1992 Privilege 482 catamaran with one dead diesel and the other still the original Volvo, but running well. Light displacement about 26,000 lbs., as loaded probably close to 30,000 lbs. With 2 old Volvo MD22's (50hp each) motoring speed was typically 7 knots at about 2000 rpm. With just the one motor we do about 5 - 5.5. We are full time long range cruisers so we're either at anchor or passage making - most hops are a full day, with many being multiple day passages. We also have a 6kw Northern Lights generator which performs well and currently only about 400 watts of useable solar (this will be upgraded soon to at least 1000, possibly up to about 1600). Our house bank is 900 amp hours of lithium, only 8 months old, but they're x3 12v 300 amp hour units, so not great for building a "master bank" for the motors from. This being the case, if we went electric, I would be inclined to set up the motor(s) with their own unique bank and charging system(s) and keep the house as it is, controlling what gets charged when manually.
With our port motor locked up AND 30 years old, I'm very seriously considering an electric motor conversion as opposed to a rebuild (as well as several pricey parts I know it will need). I really like what Thunderstruck Motors has to offer, but just with a very basic consultation, they're suggesting the 24kw motor kits (we would actually just do the one side at first, operating with one diesel and one electric, then once all (most? some?) wrinkles are ironed out, convert the other side as well). However, from my trip down the rabbit hole online (which actually doesn't seem all that deep) x2 of the 24kw motors seems like overkill. Plus, they run at 96v, which requires a monster battery setup, which is our biggest hurdle financially being in the Caribbean. Even the fancier setups I've seen seem to be closer to the 10-15kw range for a boat roughly our size. The 12kw motor kits from Thunderstruck run at 48v which is much more manageable and seem like they would do the trick, but again...newb.
We'd like decent potential range, but we sail 95% of the time already and when motoring, we don't have the "need for speed"...we sailed about 2000 miles already with just the one motor as mostly backup and have had no real issues getting where we needed to go. Running a conservative 1/2 power at something like 4-5 knots would be absolutely fine, while hopefully keeping up with solar, regen, and the genny. Heck, even motoring at 3-4 knots while waiting on wind or even just motor-sailing in the really light stuff would suit us just fine too. That said, when entering and leaving port and anchoring, or in the situations that always happen where being able to go pedal to the metal for a little bit can get you out of a jam, we don't want to find ourselves too wimpy on power.
Thoughts?
Thanks much.
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