[Public-List] Prop Size

Wed Feb 24 13:26:12 PST 2021

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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