Re: [Amel] Re: Maramu prop shaft alternator


woods deborah <woodsdeborah_56@...>
 

I do feel we are missing the point here,  Its virtually free power with almost ZERO carbon foot print. Yes I am factoring in the costs of belts, manufacture of gearbox and pulley. I will continue to use my PSA rather than buy diesel.

Regards Deb



________________________________
From: David Wallace <svairops@hotmail.com>
To: amelyachtowners@yahoogroups.com
Sent: Tuesday, 19 July 2011, 6:36
Subject: RE: [Amel] Re: Maramu prop shaft alternator


A couple of things to think about:
• If a PSA is generating 20 amps @ 13 volts, that's 260 watts which is about 1/3 HP.  So you need a motive force equal to that level of drag to overcome it.  Hard to imagine that that level of drag would cost the boat 1/2 kt. 
• Also, it would seem to be no different if you were "using" 1/3 HP of motive force to generate the power with either a PSA or a wind generator, and I've never heard anyone say they were losing 1/2 kt because of a wind gen. 
• In any case, if your boat has a fixed prop, the prop/shaft/gearbox is already generating drag so the PSA would just be incremental on top of that.
• But we really need a marine architect to figure out the actual drag/HP required and tradeoffs.
Daves/v Air OpsMaramu #104

To: amelyachtowners@yahoogroups.com
From: dave_benjamin@yahoo.com
Date: Tue, 19 Jul 2011 03:15:47 +0000
Subject: [Amel] Re: Maramu prop shaft alternator






















 


   
     
     
      Capt Amel also used hank on sails for many years. In fact the original design of the Maramu was for hank on sails, not furling. So using this logic we could justify hank on sails.



Capt Amel made decisions based on the technology available at the time. What was a great thought in the 1980's is not necessarily the best choice today. While I would not necessarily scrap a PSA if I had one, I wouldn't be inclined to install it given the alternatives that produce reasonable amounts of power without slowing the boat by half a knot.



--- In amelyachtowners@yahoogroups.com, Chris Smither <yachtakwaaba@...> wrote:

David - I agree. Capt Amel always thought through his equipment, and if he fitted a PSA you can bet your life he would have thought through the need for:
1. A lubrication system that works whether the prop is driven - either way, or idling
2. A hurth gearbox that can rotate freely in neutral when not under engine load.
On my santorin there was a notice - in french which said - when sailing NEVER select forward gear!
To stop the prop (fixed pitch) you select reverse and with a resounding "KLONK" the shaft stops rotating.
In 20 years and 58,000 sea miles I've done it twice........to clear lines around the prop
Mike & Chris
Akwaaba
SN027
________________________________
From: David Mackintosh <sv.highland.fling@...>
To: amelyachtowners@yahoogroups.com
Sent: Saturday, July 16, 2011 3:07 AM
Subject: Re: [Amel] Re: Maramu prop shaft alternator
Come on get real - we have a gearbox/transmission designed for what (to
transmit 50 or so HP in Forward and Reverse) and you think you can damage it
by driving a small alternator  Please folks that suggestion is just so far
off the mark it makes me want to write some rather nasty comments.
For those with telepathic or cryptic powers WPAYO!!!
regards
David
On 15 July 2011 15:46, Joel Potter <jfpottercys@...> wrote:
**
When things are turning there is wear. The driveline is designed to,
primarily, transmit power in the other direction. My experiences using the
PSA on the Super Maramu caused a half Knot loss in speed compared to a
stopped and feathered Max or Autoprop.
Joel F. Potter
Cruising Yacht Specialist.
Amel's Sole Associate For America.
Sent from my iPhone.
Office: 954 462 5869
Cell: 954 812 2485
On Jul 15, 2011, at 10:19 AM, Pat <sailw32@...> wrote:
Joel, There has been postings suggesting wear to the drive train
associated with the prop freewheeling while the PSA is engaged. Can you
answer a couple questions?
First, are the gears being lubricated while freewheeling and do you
believe there is an amount of wear occurring to be concerned about? Second,
while sailing and the prop spinning, can the transmission be damaged putting
it reverse? I really like the PSA, I went sailing last night for about 5
hrs. in 15 knts. and came in with higher voltage than when I left my
mooring. One last comment, people mention losing half a knt. while the PSA
is engaged. I have never seen that kind of speed loss, while you have to
lose some speed, it has to be a fraction of a knt., for I cannot see it
reflected on the SOG., any thoughts on speed loss?
Thanks,
Pat SM 123
PS. Thanks, for your help in regards to my re-rig this past spring, took
your suggestion painted entire mast, lots of work but looks new.
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