[Public-List] propeller choice

Mon Feb 2 13:36:00 PST 2015

Jay:
     There is a note on propellers on the A30 site under maintenance and 
drive train. (There is also a note on the bottom of that page from one Jay 
Davenport.) If you want to play with the various numbers to determine a 
prop, get a copy of Propcalc ( open software) and have fun.  Contact me off 
list if the URL is not here.
http://www.surfbaud.co.uk/wave/
  You do need to know the specifics for your motor and transmission, but 
your will get the prop specs. Remember that one inch diameter = 2.5 inches 
of pitch, and two inches extra pitch will cut engine rpm by 450.  These 
figures then need to be related to the horsepower and torque curves of your 
specific engine  to get the performance out of your engine you think you 
deserve for the price you have paid!  So if your engine produces maximum 
torque at 75% of maximum RPMs and that does not get to enough Horsepower to 
give the work to push an Alberg to Hull Speed, only then do you need to go 
bigger.
    I use a 13:8 two blade and that fits an A4 just fine for me. I don't 
really care  about slip at low RPMs and want less slip at high RPMs, so have 
gone higher than recommend for pitch.
Don

-----Original Message----- 
From: Jay Davenport via Public-List
Sent: Monday, February 02, 2015 2:54 PM
To: Gordon Laco ; Bill Woodford ; Alberg 30 Public List -- open to all ; 
Alberg 30 Public List -- open to all
Subject: Re: [Public-List] propeller choice

Farron, at Beta Marine, has recommended a 12 x 9 three-blade prop. He is 
basing this specifically on his experience with Betas in A30s. Based on 
this, and  all the good advice received from all of you, I intend to order 
the 12 x 9 (Michigan Wheel, "M" series, Sailor).
regards, JayRevolution, A30 #526
      From: Gordon Laco via Public-List <public-list at lists.alberg30.org>
To: Bill Woodford <williamwoodford at charleswoodford.com>; Alberg 30 Public 
List -- open to all <public-list at lists.alberg30.org>
Sent: Monday, February 2, 2015 2:44 PM
Subject: Re: [Public-List] propeller choice

I guess the reduction gearing in the Yanmar is preventing the prop from
hitting high enough RPM in the water....  I think you can have up to 2" more
pitch added to your existing prop.  It's not expensive but may resolve your
issue.

As someone else wrote, there's software available, there's also the chapter
on props in Skene's Elements of Yacht Design.  There's a graph in that book
that's very informative and practical.

Gord #426 Surprise

On 02/02/15 2:29 PM, "Bill Woodford via Public-List"
<public-list at lists.alberg30.org> wrote:

> I recently re-powered my GrayMarine with a Yanmar 2GM20f.  I installed a
> three blade 12x14 "Chesapeake 3" prop.  I am NOT satisfied with this prop.
> The boat does not seem to move well at all unless I am really pushing the
> RPM's.
>
> On my old Graymarine, I had a three blade 12x10 that moved the boat nicely
> with little effort from the engine.
>
> No problems with cavitation from either prop.
>
>
> Best of luck,
>
> Woody
> US11
>
>
>
> On Mon, Feb 2, 2015 at 2:02 PM, Dwayne Back via Public-List <
> public-list at lists.alberg30.org> wrote:
>
>> Jay,  I can move at hull speed at around 3/4 open throttle if I remember
>> correctly.  Most of the propeller shops have software they can input
>> specifics into and you can get some pretty good info, Stanley at Beta is
>> very knowledgeable as well..  I do not deal with large wave or currents 
>> on
>> Lake St. Clair so the engine and propeller seem sufficient.  With either
>> heavy currents or waves you may actually want the 20hp Beta, not sure 
>> what
>> others have experienced.
>> Dwayne
>>
>>      On Monday, February 2, 2015 1:53 PM, Bill Wallace <
>> wayfarer3134 at yahoo.com> wrote:
>>
>>
>>  The 13 MIGHT fit - I would check your actual clearance, as the larger
>> props perform better, although they do slow down sailing a bit more.  I'm
>> currently running a variprop 13x12 on a Yanmar 2gm20f at 2.2 ratio, and
>> plan on adjusting it down to 13x11 for this coming summer.  I notice the
>> feathering when sailing on light air days.  The variprop is REALLY tight
>> length wise, but otherwise fits quite nicely (I had to trim part of the
>> rudder to make a bigger opening so it wouldn't hit when feathered - but 
>> no
>> loss of turning performance, actually I think the boat handles a bit 
>> better
>> after the change).
>> Bill.
>>
>>      On Monday, February 2, 2015 1:42 PM, Dwayne Back via Public-List <
>> public-list at lists.alberg30.org> wrote:
>>
>>
>>  I have a Beta 16 with a 12 x 9 three blade propeller.  Ideally 
>> (according
>> to beta) you would use a 13 x 8 propeller but the Albergs do not have 
>> room
>> for the 13 blade.  I have no real complaints.  Purchased mine from 
>> Michigan
>> Wheel.
>> DwayneOrion #94
>>
>>    On Monday, February 2, 2015 1:20 PM, Jay Davenport via Public-List <
>> public-list at lists.alberg30.org> wrote:
>>
>>
>>  I am installing a Beta 16 diesel in my Alberg 30. It will run at 3600
>> rpm, with a 2:1 reduction ratio.
>> The old Atomic 4 engine spun a 10 x 6 three-bladed prop. I made hull 
>> speed
>> at about 2200 rpm direct.
>> I would appreciate any advice (preferably from experience) on what 
>> 3-blade
>> prop size would work best with the Beta. I am considering a 11 x 9. Part 
>> of
>> my concern is getting the most effective push from the prop, while 
>> avoiding
>> cavitation from excessive prop diameter.
>> Jay DavenportRevolution, A30 #526
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