[Public-List] Propeller Question

Tue Mar 12 08:46:01 PDT 2024

Thank you Mike
I will get to our boat next weekend and try and find the pitch, shaft dia.  etc. and further  information from our 3 blade prop.
It did get in touch with Thomas Stevens re the Indigo Prop as per other good advice.  He has been very helpful. He educated  me that most diesels, including the Westerbeke 25hp, are geared down to 2:1 (not direct drive 1:1 as per the Atomic4) so suggested the Indigo prop will not the best for my situation.
If we find nothing really conclusive after measuring my current prop, I may try another year with it and send him better information on the speed vrs rpm's in different conditions, to see if I really do need more torque.  I should have recorded rpm/speed etc better in the log  last year.   Got a little nervous getting through some spots in the wind last year- did not seem I was  getting enough speed against the wind.

Thanks all for further advice
Sue (and Steph)

________________________________
From: Public-List <public-list-bounces at lists.alberg30.org> on behalf of Mike Lehman via Public-List <public-list at lists.alberg30.org>
Sent: March 12, 2024 10:25 AM
To: Alberg 30 Public List -- open to all <public-list at lists.alberg30.org>
Cc: Mike Lehman <mlehman at gmail.com>
Subject: Re: [Public-List] Propeller Question

Sue, finally  got down to the boat...my prop is:
12" diameter x 10 pitch, 3 blade on 7/8" shaft. Righ hand.

Hope this help

On Thu, Feb 29, 2024, 2:33 PM Mike Lehman <mlehman at gmail.com> wrote:

> Next time I'm at my boat, I'll check the diameter and pitch. I have a
> Universal M430 (30 HP) and have no speed issues. I changed the original
> prop when I repowered. I'll send you a picture of the prop.
>
> On Thu, Feb 29, 2024, 2:27 PM Sue Pilling via Public-List <
> public-list at lists.alberg30.org> wrote:
>
>> Even though I have a 25hp Westerbeke diesel, I found my Alberg would
>> sometimes hardly make way against wind/waves.
>> It is a three blade prop, not sure of diameter and pitch as not near boat.
>> Wondered who to ask re this
>> Thanks Sue. (A30 #63)
>>
>> > On Feb 19, 2024, at 5:18 PM, Markus Hutzler via Public-List <
>> public-list at lists.alberg30.org> wrote:
>> >
>> > I made the conversation last year and I’m getting lower speeds. I have
>> a 1:2 gear (belt) and i’m using some random prop the boat came with. This
>> said, I’m not concerned about range. I just need to get in an out of the
>> mooring and have some backup in emergencies.
>> >
>> > 10A (550W): 2.2 kn
>> > 20A (1.1kW): 2.8 kn
>> > 40A (2.2kW): 3.3 kn
>> >
>> > I will record some more numbers once the ice melts.
>> >
>> > Cheers, Markus
>> >
>> >> On Feb 4, 2024, at 16:28, Hugh McCormack via Public-List <
>> public-list at lists.alberg30.org> wrote:
>> >>
>> >> Good day all,
>> >>
>> >> I know that there are some Albergs that have been converted to
>> electric motor propulsion and I am contemplating this myself since the
>> original inboard Graymarine has issues that are not worth fixing.
>> >>
>> >> In searching through the list archives I have found some useful
>> information but one bit of helpful data seems to be hard to find.  This
>> applies not just to Alberg conversions but to those on other manufacturers'
>> boats as well.  What I am looking for is a table or graph showing the
>> relationship between motor wattage draw and boat speed through the water
>> and/or shaft rpm (which, with details about the prop, can be converted to
>> boat speed).  Has anyone here who has converted to electric propulsion
>> recorded this data for their boat under various conditions?
>> >>
>> >> One motor supplier gave me the following (which helps to a point but
>> was derived in calm water from a "similar" boat):
>> >> 3.5 knots - ~1000 watts (~20 amps)
>> >> 4.5 knots - ~2000 watts (~40 amps)
>> >> 5.5 knots - ~5000-6000 watts (~100-125 amps)
>> >> 6 knots (hull speed) - ~12,000-15,0000 watts (~250-312 amps)
>> >> Most can only provide motor data from a test bench which has no
>> connection to real operating conditions with influences such as prop
>> pitch/diameter/# of blades, and boat hydrodynamics when motoring into a
>> headwind or in choppy seas.
>> >>
>> >> Having this data will help me determine optimum battery bank capacity
>> which then determines bank size and associated costs.
>> >>
>> >> Thanks in advance if you can help.
>> >>
>> >> Cheers,
>> >>
>> >> Hugh
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