[Public-List] Prop Size Discussion
RICHARD HAZLEGROVE
hazlegrove at aol.com
Wed Mar 24 14:18:15 PDT 2021
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
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> 1. Re: Prop Size (scott at scottmaury.com)
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> 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
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> 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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