[Public-List] Prop Size Discussion
Michael
dickdurk at gmail.com
Thu Mar 25 10:08:01 PST 2021
It's nice to see an accurate description of what are really
uncomfortable seas.
Michael Grosh
@220
------ Original Message ------
From: "Mike Meinhold via Public-List" <public-list at lists.alberg30.org>
To: "Alberg 30 Public List -- open to all"
<public-list at lists.alberg30.org>
Cc: "Mike Meinhold" <meinhold272 at gmail.com>; "RICHARD HAZLEGROVE"
<hazlegrove at aol.com>
Sent: 3/24/2021 6:45:23 PM
Subject: Re: [Public-List] Prop Size Discussion
>Richard
> My beta 16 is installed with the TMC 40 gear at 2:1 ratio. I still have
>the 13x7 2-blade prop. The engine tops out at about 3600 rpm, spins the
>prop at 1800. This is where my Atomic 4 drove the same prop and gave me 6.5
>knots calm water, clean bottom. Based on the power -rpm curve for the A4
>this was just about 16 hp, so I was pretty confident I could use the same
>prop. It uses a lot less fuel than the Atomic 4. I have been in 20 knots
>head seas with 3 foot waves - nasty Chesapeake bay 30 foot long waves- and
>kept up 4.5 knots .
>
>I have neither heard or seen any evidence of cavitation .
>
>Regards
>Mike
>Rinn Duin 272
>On Wed, Mar 24, 2021 at 17:19 RICHARD HAZLEGROVE via Public-List <
>public-list at lists.alberg30.org> wrote:
>
>> In the prop discussion from February I noted a comment from Mike on Rinn
>> Duin 272 regarding his Beta 16 diesel conversion. I am considering the
>> same engine and would love to hear back from Mike with a few details such
>> as his transmission reduction ratio, prop size and performance in clear
>> water and in wind and chop. I have heard great things about these engines
>> and would like to learn of his experience in our Albergs.
>>
>> By the way, I currently have a little BMW 12 hp diesel that has been good
>> over the years but parts have gotten hard to come by. It has a lot of
>> torque and a 2.7 to 1 reduction gear spinning a 13”x14” three bladed prop.
>> It will approach 6 kts with a clean wheel and bottom but less than half
>> that in strong headwinds/chop. The 13” prop may be a little tight in the
>> aperture but I only hear/feel cavitation when running hard at full rpm’s
>> into strong headwinds.
>>
>> Richard Hazlegrove
>> Quest 433
>> Mobjack Bay, VA
>>
>> > On Mar 24, 2021, at 4:05 PM, public-list-request at lists.alberg30.org
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>> > Today's Topics:
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>> > 1. Re: Prop Size (scott at scottmaury.com)
>> >
>> >
>> > ----------------------------------------------------------------------
>> >
>> > Message: 1
>> > Date: Wed, 24 Mar 2021 14:40:52 -0500
>> > From: scott at scottmaury.com
>> > To: Alberg 30 Public List -- open to all
>> > <public-list at lists.alberg30.org>
>> > Subject: Re: [Public-List] Prop Size
>> > Message-ID:
>> > <20210324144053.Horde.DkBOojFrjFIqlYi_ChxyXk9 at gator2001.hostgator.com
>> >
>> > Content-Type: text/plain; charset=utf-8; format=flowed; DelSp=Yes
>> >
>> > hey just a follow up, Michigan wheel has recommended that I get a 12"
>> > / 11 three blade prop and that is what the engine guys have ordered
>> > for the Bill of Rights
>> >
>> > Thank you all for your response, I'll follow up with this further
>> > after some use this summer.
>> >
>> > Scott
>> >
>> >
>> > Quoting John Johnston via Public-List <public-list at lists.alberg30.org>:
>> >
>> >> Regarding prop size- My Alberg 30 ( # 69) spent many more months at
>> >> the slip this past year unattended than I had anticipated. Last
>> >> October I came down to the Bay from my home in Massachusetts
>> >> intending to spend a pleasant month sailing. It turned out that
>> >> while the diesel fired right up, I had no forward or reverse motion.
>> >> The shaft was turning, but no motion. I thought perhaps it was
>> >> barnacles on the prop, and I hired a diver to give it a scrape and a
>> >> scrub, but he resurfaced in a minute and informed me that I had no
>> >> prop, just a hub. Severe galvanic corrosion. The story goes on, but
>> >> the point is that I am looking to buy a new prop.
>> >> My diesel is a Westerbeke 20 2B. Not the original engine, but
>> >> when a previous owner installed it they kept the 2 blade prop that
>> >> was appropriate for the Atomic 4. I decided to upgrade to a three
>> >> blade Chesapeake prop at that time, (5 years ago) which was deemed
>> >> to be the proper, well, prop, for the new engine and transmission.
>> >> However, now it is time for a new prop. What I had bought was
>> >> a 13x12x3 from Miller Island. Lovely piece of work, but it is shot.
>> >> I have also been doing some research and reading, and came across an
>> >> article about prop size by Ted Brewer more than a decade ago, and he
>> >> maintains that the prop in an aperture should never have less than
>> >> two inches of clearance at the top of the blade, to avoid
>> >> cavitation. The aperture height on my Alberg is 14?. To achieve that
>> >> 2? would be a 10? prop, which seems awfully sleight. I am thinking
>> >> perhaps an 11? prop with whatever adjustment to pitch would be
>> >> appropriate. Or maybe 12? as a compromise.
>> >> I would very much welcome the wisdom of the elders, and
>> >> everyone else that has expertise or experience with this matter.
>> >> Thanks to anyone offering their experience or advice
>> >>
>> >>> On Feb 24, 2021, at 7:41 AM, Mike Meinhold via Public-List
>> >>> <public-list at lists.alberg30.org> wrote:
>> >>>
>> >>> ?Scott
>> >>> I am glad to hear Bill of Rights will be sailing again.
>> >>>
>> >>> If you have some specs on the Vetus 25 we can see how it compares with
>> the
>> >>> A4 -13x7 2-blade match that you most likely have
>> >>>
>> >>> I repowered with a beta 16 and kept the same prop as I found it was
>> about
>> >>> the same operating point
>> >>> We would need the engine torque and power vs rpm, and the gear ratio to
>> >>> check.
>> >>>
>> >>> For the sails I suggest you provide the sailmaker with the Chesapeake
>> >>> Alberg rules in the Association handbook. I highly recommend 2 reefs
>> and
>> >>> use both frequently.
>> >>>
>> >>> Mike
>> >>> Rinn Duin 272
>> >>>> On Tue, Feb 23, 2021 at 21:26 Bill of Rights #487 via Public-List <
>> >>>> public-list at lists.alberg30.org> wrote:
>> >>>>
>> >>>>
>> >>>> Hello everyone, I am a long time A30 owner and also had a Tartan 34-2
>> >>>> for 10 years, I just recently sold that boat.
>> >>>>
>> >>>> I'm putting all my efforts back into #487 "Bill of Rights" this year!
>> Yea!
>> >>>>
>> >>>> I am re-powering to a 25HP Vetus engine with a 2:1 hearth gear and
>> >>>> just wanted to hear what others have "sized" for a 2 blade sailor prop
>> >>>> on other diesel conversions?
>> >>>>
>> >>>> The At-4 engine was rebuilt and has less than 10 hrs. Any interested
>> >>>> parties should reach out to me
>> >>>>
>> >>>> I'm also getting a new suit of sails from Precision, #400 series! Does
>> >>>> anyone have any experience or suggestions would be helpful Main w/ 2
>> >>>> reefs, 135# headsail w luff ??????????
>> >>>>
>> >>>> New interior cushions!
>> >>>>
>> >>>> Boat still has some deck issues and I'll have to fix that as I go
>> >>>>
>> >>>> Hope to catch up with like-minded a-30 sailors this summer on the bay.
>> >>>> I am securing a slip on the Magothy River so I'll be closer to my home
>> >>>> and sail some new waters this summer!
>> >>>>
>> >>>> Thanks Scott
>> >>>>
>> >>>>
>> >>>>
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