[Public-List] Prop Size

Wed Feb 24 13:49:17 PST 2021

I installed a Universal M430 diesel (4 cly 30 HP) in our A30 #505 20+
years ago and changed the prop to a 12"D x 10"P 3-blade and it has
performed well. Less prop wash against the hull...quieter and plenty of
thrust. RPMS up to 2200. People claim I can pull water skiers 😊

Mike Lehman
~~~_/)_/)~~_/)~~~

On Wed, Feb 24, 2021, 4:26 PM John Johnston via Public-List <
public-list at lists.alberg30.org> wrote:

> 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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