[Amel] Re: Maramu prop shaft alternator


Dave_Benjamin
 

David,

In my flying career I spent close to 5000 hours in large turbo-prop aircraft so gyroscopic effects are well known to me. (Not all twin engine aircraft have counter-rotating props). In any case, perhaps you can explain how "P-factor" would impair a wind generator that is free to swivel. The force vector is going to simply cause it to rotate one way or the other, isn't it? Given the movement of the boat, there's not going to be a steady force in any one direction.

--- In amelyachtowners@..., David Mackintosh <sv.highland.fling@...> wrote:

I think you will find a wind generator is not really usable when sailing in
decent winds and seas as gyroscopic effects and precession all start to have
a serious effect.

You are correct of course water being denser than air it is much easier to
extract power from a water driven propeller. BUT i think you miss the point
- lets say a PSA producing 10/15 Amp takes 1.5 HP to drive That HP has to
come from somewhere - the sails :-) To get your say what 22 metric ton
Amel up to hull speed is going to take say 80 HP so the losses assuming
they can be measured in a real live real time situation are going to be
insignificant really

Plus if you have 150/200 HP from your sails you have an excess of power and
since your Amel cant get up and plane - you have oodles of spare free HP to
drive your PSA. Any time you have more power from your sails than that
needed to drive the boat at hull speed..there will be no actual loss of
performance when using the PSA.

Actual real time real life reports on the PAS performance say the losses are
insignificant - not really measurable.

Now lets look at the trasmission designed to drive this 22MT boat with say
70 SHP..............do you really think you can damage that transmission in
any way by powering a 1.5 HP PSA with it? I think NOT!!!

IF anyone wants to dump their PSA then please contact me i would love to
have it :-)

regards

David

On 20 July 2011 00:13, Dave_Benjamin <dave_benjamin@...> wrote:

**


I'm a bit confused about the comparison in losses between the PSA and a
wind generator. Water is far denser than air. The prop becomes a speed brake
of sort. I'm not a physicist but I'd wager that amp for amp the performance
loss with a wind generator is negligible compared to a PSA.



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