Re: [electricboats] Re Power for SV/Retreat Time Catamaran

John,

Looking back and wondered how things went for you?

We have a 35,000lb, 12.5:1 L:B power cat, 50' x 17' which runs 23" x 18" props. 

At 750rpm (1500rpm using 2:1 reduction) we get about 7kn using both diesels, at something like 30hp each on a 2.8 prop curve.

We have some estimates for electric, where our acceptable sweet spot is more at 5-5.5kn.

We are looking at twin ME1616, preferably running at 8kW ea or 75%.

Thunderstruck 3:1 reduction seems a decent guesstimated match, though noone seems to "know", and finding prop people who know electric is nigh impossible locally. 

Rob

On Sun, 30 Jan 2022, 12:26 am john winterrowd via groups.io, <sailorboy55577=yahoo.com@groups.io> wrote:

Greetings my fellow Electrosailors, the day has come after nearly a year of waiting for chips, motors, pumps, fans and now the final details need to be identified, she is getting repowered with Thunderstruck 18 KW kits.



Facts and figures for SV/Retreat Time Catamaran
LOA 44 '
Water line 40'
Beam 20
Draft 3.5
Propeller 19 " Diameter 3 blade
Pitch 19 degree
Displacement 26,000 lbs.
Battery bank per hull consists of 12 group 31 AGM Duracell 100AH

Before I commit to keeping the 144-volt banks, I am asking the group to consider a few thoughts,

Sacrificing a few amps by dividing each battery bank in half operating at 72 volts, this way I may be able to parallel them together for higher total amp hours? Or have two separate banks for redundancy charging would be done on 110 volts instead of 220 volts.

Prop speed remains unknown to achieve at best half of hull speed, this is where I could use your help, without the variables of current and wind, I'm looking for a laboratory answer, this is to determine what gear reductions would best suit this vessels propulsion and efficiency. 

https://vicprop.com/displacement_size_new.php
Any help or advice will greatly be appreciated as Thunderstruck is planning to program and tune and ship next week. 
Thanks John

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