[Public-List] Public-List Digest, Vol 3380, Issue 1

Mon Nov 28 13:28:12 PST 2016

Hello Sergui - 

Is that the nylon one?  I'd love to, but the trouble is that I can't easily
or quickly do the trials.  I've got to get hauled out and that only happens
seasonally.

Thanks anyway.  

What did you think of it?

Gord
426 Surprise

On 2016-11-28, 4:07 PM, "SNCSoft via Public-List"
<public-list at lists.alberg30.org> wrote:

> Hello Gord,
> 
> Interested to try out three blades propeller from Indigo Electronics?
> 
> http://www.atomic4.com/propeller.html
> 
> I have spare one laying around. :-)
> 
> Serguei
> #602
> 
> 
> 
>> Message: 3
>> Date: Mon, 28 Nov 2016 10:30:13 -0500
>> From: Gordon Laco via Public-List <public-list at lists.alberg30.org>
>> To: <mpcbi at aol.com>,    <public-list at lists.alberg30.org>
>> Subject: Re: [Public-List] Propellers...
>> Message-ID: <D461B7B5.2E0A3%mainstay at csolve.net>
>> Content-Type: text/plain;       charset="UTF-8"
>> 
>> Good day friends,
>> 
>> Here's my report on the first season using the Campbell 'Sailor' propeller.
>> 
>> First, the 'Before' report.
>> 
>> Surprise is an apres hull #400 boat, with the usual two bladed prop, 13"
>> diameter, 7" pitch.  Our Atomic IV engine has the usual direct 1:1
>> transmission (so prop RPM = engine RPM)
>> 
>> What I liked about this set up was the following:
>> 
>> - superior 'grunt' when maneuvring... I liked the trememdous power the
>> engine delivered when making tight turns, stopping the boat with reverse
>> power (reversing in general)
>> - when idling at 600 rpm in gear, the boat moved at about 2knots which was
>> useful for maneauvring.
>> - maximum speed in flat water was about 6.7knots, which was excellent given
>> the hull characteristics of the Alberg 30
>> - headwinds made little difference in top speed
>> - towing our heavy Boston Whaler 'Squall' sailing dinghy knocked about
>> 1knot
>> off speed, but we figured that was acceptable.
>> - fuel economy seemed to be about the 1 gallon per hour published as normal
>> for the Atomic IV
>> 
>> What I didn't like:
>> 
>> - the boat's economical cruising speed was 5.2 knots, which we achieved at
>> about 1000 RPM... Which is too slow for the alternator to produce a useful
>> return
>> - flat out full throttle was about 1400 rpm, better for the alternator but
>> gulping fuel, and cooling was not optimimum.
>> 
>> What I wanted to achieve...
>> 
>> - I wanted the engine to spin up closer to it's rated 'normal' operating
>> RPM
>> to improve the output of the alternator and cooling systems
>> - I was intrigued by the promise of 'more horsepower in the water' given
>> that at 1000 rpm the Atomic IV is only delivering a small fraction of it's
>> rated 30 hp.
>> - I was also intrigued by the promise of a lower engine sound level (it was
>> already nice, particularly when compared to a diesel) better 'grunt' when
>> pushing against a head sea or wind, and towing, as promised with three
>> blades vs two.
>> 
>> What we observed this past summer.  The Campbell Sailor supplied was the
>> 11"
>> diameter 5" pitch they recommend for direct drive Atomic IV's for the
>> Alberg
>> 30.
>> 
>> First the good.
>> 
>> - the engine was so quiet even at full throttle, I disbelieved the knot
>> meter and double checked it with the GPS and a timed run.  The engine is
>> significantly quieter and smoother with the Campbell Sailor prop
>> - RPM rose as promised.  Flat out is about 1800rpm, we get 5.5 knots at
>> 1400.
>> - the engine ran cooler, more in the temp range recommended for the Atomic
>> IV engine.
>> 
>> And the not so good...
>> 
>> - there was a definite decrease in what I call 'grunt' when maneavring in
>> close quarters.  The Alberg 30 is particularly good with regard to using
>> the
>> engine to spin her in her length but where response was immediate with the
>> old prop, with this one I had to wait for the engine rpm to 'spool up'
>> before feeling the kick...and the kick was less.  Not good.
>> - power in reverse was about the same.
>> - top speed even at the higher RPM was about half or 3/4 of a knot lower
>> than with the old prop.  Not good.
>> - head wind and seas, and towing the dink had a dramatic effect on speed,
>> much worse than before. Not good.
>> - fuel ecomomy, even when not towing and in flat windless conditions, was
>> much worse.  I had hoped that despite the higher rpm, since the engine was
>> not labour as it seemed to be before, that fuel consumption might be the
>> same or better, but it was not.
>> 
>> And now some good news...
>> 
>> I made a detailed report to Kelsey at Campbell Props... He is well informed
>> with regard to the various factors affecting propeller performance.  We
>> discussed pitch adjustment, but settled on increasing the prop diameter and
>> leaving the pitch the same as a cure.   We agreed that it seemed my issue
>> was excess slip, and increasing the prop diameter by 1" (thereby increasing
>> blade area) would lower slip and hopefully offer me the cure I'm looking
>> for.
>> 
>> He was prompt and cheerful about offering me a new prop, even offering me
>> the new prop before sending the old one back to him.  Because I couldn't
>> comfortably change the prop till the boat was hauled for the winter, I
>> thanked him and suggested that if he sent me the new one after I'd sent him
>> back the old one that would be quite fine.
>> 
>> Surprise came out of the water last week, so I've pulled the prop and will
>> be sending the D11xP5 three blade Sailor back to him today.  I can't wait
>> to
>> try out the D12xP5.
>> 
>> If that doesn't work, I could always do what Bob Crinion in Nova Scotia
>> did... Remove 1" from the diameter of the stock 2 blade D13xP7 thereby
>> achieving the RPM increase he sought.  I didn't discuss noise with him when
>> I visited his boat last spring, but since the tip clearance is a little
>> better I expect his 12" diameter prop is a little quieter, although it'll
>> still have the thump that is inevitable with two blade props (this is
>> caused
>> by lack of water flow when the blades are lined up with the stern post.
>> Three or more bladed props don't develop this because two or more blades
>> are
>> always in clean water flow and pushing...)
>> 
>> Cheers -
>> 
>> Gord Surprise #426
>> 
>> I can't wait to try the new one out.
>> 
>> 
>> 
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