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Author Topic: another slight oops..  (Read 1225 times)

Quaysider

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another slight oops..
« on: November 04, 2008, 22:21:14 »

Just spotted - the propeller on the Agile Solution is on back to front. Let me explain.

To provide the answer to my trivia question I just started up free roam, selected Hamburg then chose the small harbour in the Dradenauhafen (close to the Petroleumhafen). I then selected the Agile Solution and started the game. Unfortunately on startup the AS stern was berthed 'in' the quay - so I run full ahead and the steern rose majestically up onto the quayside. Just for curiosity at the detail I zoomed in - then spotted when running ahead the propeller blades would actually provide thrust forward, ie taking the vessel astern! Try it yourselves.... it could be my pc playing silly...  ;D

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Agent|Austin

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Re: another slight oops..
« Reply #1 on: November 04, 2008, 22:44:38 »

What way is it rotating? Looks to me if it rotates clock-wise it will provide forward thrust taking the ship forward.

Thrust: Thrust is a reaction force described quantitatively by Newton's Second and Third Laws. When a system expels or accelerates mass in one direction the accelerated mass will cause a proportional but opposite force on that system.

So if it provides thrust forward that means water is moving to the stern providing the reaction of the vessel forward.
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Quaysider

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Re: another slight oops..
« Reply #2 on: November 04, 2008, 23:03:13 »

It rotates anti-clockwise...

try starting anywhere and running full ahead with both anchors down - eventually the bow dips and the stern rises enough to see the prop turning
« Last Edit: November 04, 2008, 23:07:57 by Quaysider »
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Agent|Austin

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Re: another slight oops..
« Reply #3 on: November 04, 2008, 23:05:57 »

ah Counter-Clockwise. In that case, then yes it would go backwards. :p
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mvsmith

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Re: another slight oops..
« Reply #4 on: November 04, 2008, 23:20:07 »

Hi A|A,
Good explanation. There was much confusion about “Thrust” in questions about Red Eagle and VSP in general. Many had in mind that the direction of thrust was the direction that the water was pushed.
This really does not apply at all to the VSP because the blades act like airplane wings and don’t “thrust” the water that much.

For understanding ship propulsion, the direction of thrust is always the direction the ship is pushed.

Regards,
Marty
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LucAtC

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Re: another slight oops..
« Reply #5 on: November 05, 2008, 01:42:53 »

Hello A|A,
Most fixed pitch propellers of single screw ships are indeed generally right-handed, turning clock-wise to go ahead, in fact for traditional reasons, and also practical for the pilots.
There are of course also left-handed propellers, generally the port fixed pitch propeller for ease of manoeuvring.
Likewise, there are right-handed and left-handed controllable pitch propellers, where the pitch is changed to go astern. To the contrary of fixed pitch propellers, the pitch is such that to go ahead, the starboard propeller turns counter-clockwise, left-handed, and the port one clockwise.
So, with the pitch astern, the side-thrust of the propeller helps increase the moment due to the eccentricity of the propeller, instead of neutralizing it. The net result is that it works astern like fixed pitch propellers, and anyway ahead you have the rudder, some 2 degrees being enough to counter the effect.

The Agile Solution should have a ahead counter-clockwise CPP, turning clockwise astern (ie right-handed astern). So, the direction of rotation is correct in the game, and the pitch, when coming above water or being looked at, returns to a right-handed pitch.
And of course, it is the thrust, the force that pushes and accelerates the ship, countering water and air resistances, the product of thrust by speed being the effective power. 
I hope I made it clear (not sure, though  :-[ )

Regards,
Luc
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Quaysider

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Re: another slight oops..
« Reply #6 on: November 05, 2008, 13:45:59 »

Ok - so AS prop turns the right way - it's just on back to front.  ;D
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