Re: [Amel] shaft driven alternator


Eric Lindholm <etlindholm@...>
 

The transmission in my Maramu is a manual transmission, Hurth, which does not have a pump to lubricate the bearings. It is splash lubricated. You can free wheel it without concern. I think it is your hydraulic transmissions that have to be run every once in a while, as they do have a pump for pressure to the plates as well as the bearings. Same as a car. You can tow a manual trans car with no problems, not so with an automatic. Eric maramu 105




________________________________
From: Robin Cooter <robincooter@yahoo.co.uk>
To: amelyachtowners@yahoogroups.com
Sent: Monday, May 11, 2009 9:29:51 AM
Subject: RE: [Amel] shaft driven alternator





Good point.   The Santorin transmission is also designed for "free wheeling"
 
Robin Cooter
Santorin 004, Belouga

--- On Mon, 11/5/09, Richard Piller <richard03801@ yahoo.com> wrote:

From: Richard Piller <richard03801@ yahoo.com>
Subject: RE: [Amel] shaft driven alternator
To: amelyachtowners@ yahoogroups. com
Date: Monday, 11 May, 2009, 3:43 PM

Guys, the one point you are missing is that the Maramu transmission is designed to allow for free wheeling.  NOT all transmissions are.  Before anyone with a SM takes to sea with the prop turning undersail please take a look at the spec on YOUR transmission to be sure you can safely free wheel.  Regarding the speed of the boat; we did several trans-Atlantic crossings with the prop on our Maramu free wheeling and charging the batteries that worked better then the wind mill we have on our SM.  The fact is that in practice the free wheeling/charging solution is the better way to go..Best to all, Challenge in Annapolis SM 209Richard and Joan

--- On Tue, 5/5/09, G D <maramu@hotmail. com> wrote:

From: G D <maramu@hotmail. com>
Subject: RE: [Amel] shaft driven alternator
To: amelyachtowners@ yahoogroups. com
Date: Tuesday, May 5, 2009, 1:17 AM

Last but not the least. I wont bother you with rocket science or nuclear physic as I'm not an engineer. So I can tell you that when I engage the prop shaft driven alternator, I loose around half a knot when I'm between 5 and 9 knots

Again this has nothing to do with hydrodynamic theory or fluid mechanic, it is simply a true fact of sailing.

Best regards to all

Erick

To: amelyachtowners@ yahoogroups. com

From: maramu@hotmail. com

Date: Tue, 5 May 2009 07:09:59 +0200

Subject: RE: [Amel] shaft driven alternator

Dear All

I truly agree with David, a Max Prop can be manipulated so that it will drive a prop shaft alternator and in fact not many people know that. I use a Max prop with an alternator fited by amel. It works perfectly well, provided that you do the following

1 Start the engine and run it at idle,

2 While under sail, engage the reverse and accelerate slowly untill the gearbox is well engaged, you should hear a kind of "Klong"

3 While still runing the engine at idle with the reverse engaged under sail, turn on the alternator switch.

4 Bring back the Morse stick to neutral,(you will fell some kind of resistance)

5 Turn off the engine and ............ ......... ....your power plant is on runing with a max prop.

I have been using this method for the past 10 years and it works perfectly well, generating plentifull Amps. By eight knots, I manage to cover my heavy consumption.

In addition I have fited an Air wind turbine on the mizzaine mast which worls perfectly well.

Regards to all

Erick

To: amelyachtowners@ yahoogroups. com

From: dlm48@aol.com

Date: Mon, 4 May 2009 23:35:45 +0100

Subject: Re: [Amel] shaft driven alternator

Dave you are missing the point either deliberately or not.

IF you have an excess of HP from your sails and you are at hull speed and

pushing the envelope on the displacement drag curve with say 150/200 or more

HP coming off your sails on an Amel fully powered up - any drag from a prop

driving a shaft alternator is totally unimportant and incidental. As a

multiple disciplined engineer i can categorically prove mathematically that

a fixed bladed prop has less drag when held stationary than one that is

allowed to rotate 'freely' under the influence of the boats motion. HOWEVER

i have proven to myself that the actuality of this - the theory does not

work in practice - for 20 or more years i sailed with the prop stopped with

the engine in gear until i was doing a delivery trip with the owner on board

on a Privilege 37 Cat he had left the props free wheeling and when i stopped

them when i came on watch he came back on deck and explained that the boat

was faster with the props freewheeling. As i knew and could prove

empirically this was not the case i argued the point until he proved to me

that my expert opinion was rubbish. Why you would introduce folding or

feathering props into this topic - i truly dont understand - also fixed

props dont slow a boat down feathering or folding props are go-faster bits

of kit.

So to summarise

IF you have enough sail power to get hull speed then you wont notice any

drag from a prop shaft driven alternator.

IN every boat i have sailed and tested allowing the prop to rotate is less

draggy and is a faster way to sail than keeping it stopped.

A feathering or folding prop has less drag than a fixed bladed prop

A Max Prop can be manipulated so that it will drive a prop shaft alternator

(not many people know that)

regards

David

2009/5/4 Dave Benjamin <dave_benjamin@ yahoo.com>

Eric,
My professional background is in aviation and props in the water and props
in the air have some similarities. Air and water are both fluids albeit
water is a much denser medium. Also the laws of physics come into play.
Anotherwords the prop is not freewheeling since the generator places a load
on it. You cannot extract energy from the water in the form of a prop
generator without creating friction. People can believe what they want to
believe. The laws of physics and hydrodynamics will still apply. The only
way to really reduce the prop drag penalty is with a feathering or folding
prop which is precisely why the racing rules give credits for a fixed prop.
The handicappers know the fixed prop will slow a boat down and give a 3
second or 6 second per mile credit for it.
--- On Mon, 5/4/09, Eric Lindholm <etlindholm@ sbcgloba l.net<etlindholm% 40sbcglobal. net>>
wrote:
From: Eric Lindholm <etlindholm@ sbcgloba l.net <etlindholm% 40sbcglobal. net>
Subject: Re: [Amel] shaft driven alternator
To: amelyachtowners@ yahoogroups. com <amelyachtowners% 40yahoogroups. com>
Date: Monday, May 4, 2009, 2:12 PM
David, I actually read a study where the results showed that there was
less drag with the prop freewheeling, no alternator, like you said, rather
than locked. I also agree that this goes against everything I have ever
heard. Even after reading the article, I have a very difficult time
believing it. If I can find it I will post it for your info, or at least
amusement. It was a study comparing all of the props available for
sailboats, and there efficiency in forward, reverse, and under sail. It
compared 2 blade, 3 blade, maxi prop, etc. Eric maramu 105
--- On Mon, 5/4/09, David Mackintosh <dlm48@aol.com <dlm48%40aol. com>>
wrote:
From: David Mackintosh <dlm48@aol.com <dlm48%40aol. com>>
Subject: Re: [Amel] shaft driven alternator
To: amelyachtowners@ yahoogroups. com
Date: Monday, May 4, 2009, 3:41 AM
YES and NO there is theory and there is practice.... ...on my O461 the boat
IS faster by up to a knot (unless you are at hull speed with plenty of
wind)
if you let the prop free wheel and i know this is contrary to scientific
theory...i guess the prop is uneducated. I have discovered that this is the
case on quite a few boats i have sailed too - so this is not a one off
phenomenon.
Driving a shaft generator would i 'think' cause more drag - as you dont get
nothing for nothing - and the energy to drive that alternator has to come
from somewhere. However if you have an excess of sail power you 'might' not
see a decrease in boat speed which after all is all that matters. I am
ignoring wear and noise issues (for the pedantic).
regards
David
2009/5/3 Dave Benjamin <dave_benjamin@ yahoo.com>
Ettore and Silvana,
You are defying the laws of physics and hydrodynamics if you really think
the shaft alternator does not slow the boat down. In fact the turning
propeller acts almost like a disc. It generated more resistance than it
would if it was stationary. I would use one if it was already installed
but
I would not go out of my way to install a speed brake like that. There
are
some solutions in the form of a unit that is deployed from the transom.
One
of my neighbors used one to and from Hawaii and it generated electricity
quite well.
--- On Sun, 5/3/09, Arca di Noè <arcadinoesailing@ hotmail.com<
arcadinoesailing % 40hotmail. com>>
wrote:
From: Arca di Noè <arcadinoesailing@ hotmail.com< arcadinoesailing %
40hotmail. com>
Subject: Re: [Amel] shaft driven alternator
To: amelyachtowners@ yahoogroups. com <amelyachtowners% 40yahoogroups.
com>
Date: Sunday, May 3, 2009, 9:43 AM
Hi David and Hazel,
We use the shaft driven alternator in our Mango with much satisfaction.
No reduction the speed on sailing.
It will give 7/9 amp when running at 7/8 knots.
It don't works down 4 knots.
Very very important: if you have Hurth gearbox or similar, is imperative
to
run the motor half our every 12 ours, to lubricate the gearbox because r
shaft running isn't enaugh to lubricate the interior of the gearbox: if
the
motor is not on, is easy to break the interior disks of the gearbox.
Now our Mango is independent for the electriciy of Marina: 2 solar panel
and 1 wind generator is perfectly.
With 15/20 wind knots We have cooking the pizza in the electric four at
220v!!!
Ettore & Silvana of Arca di Noè
----- Original Message -----
From: "David and Hazel Worthington" <spritoaffine@ yahoo.co. uk>
To: <amelyachtowners@ yahoogroups. com>
Sent: Friday, May 01, 2009 1:43 PM
Subject: [Amel] shaft driven alternator
Hi All
Due to the charges being imposed by marina operators now for
electricity
in the Med I have been considering various options to allow free
battery
charging
Our rattly Max Prop needs rebuilding and I was wondering about
replacing
it with a standard fixed prop in order to use the propshaft alternator
but
am concerned about loss of speed and increase in noise when sailing,
does
anyone still use their prop driven alternator or has everyone turned to
solar and wind power instead. I understand we would need a 19 inch prop
but am not sure whether the 13 mentioned is inches or degrees of pitch.
Our aft cabin is too noisy to sleep in on passage due to
propshaft/cutless
bearing noise even after replacing the cutless bearing, is this normal?
Also would we go backwards straighter with the Max Prop or a fixed
prop?
we don't have a bow thruster
Your opinions would be appreciated
David and Hazel Sharki 148
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