SS06 Ships Lack Good Propwash Steering

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[zoomad]

The Russian Tug and Agile Solution SS06 ships now available as an addon to SS08 lost most of their SS06 prop wash steering effects when brought over to SS08.  Some of this might be due to efforts to make steering more realistic and hence slower to respond, but the ships are far less "fun".  In SS06 you could back and fill by using the initial prop wash effect over a turned rudder before the ship had built up much if any forward momentum.  In SS08 however these two ships don't turn much at all until they have achieved a lot of forward velocity (which takes a long time and considerable forward distance).  While I don't claim to know the real steering traits of these vessels, they lost a lot of what made them interesting when moved over to SS08.

[LucAtC]

Hello,
Do you have the Build Nr 1015? On my system, the Russian tug is twin propelled, and reacts like in the 2006 addon.
But indeed, the Agile Solution characteristics have been degraded, but groennegaard told us that a solution is coming:

I don't think it is back to the 2006 characteristics. I believe SS08 uses a different dynamics engine and I guess they started from scratch when setting the dynamics for the SS08 ships. I think it is far better now than it was in SS06.

I don't when the 'stand alone add-on'/update will be ready for release. I think VSTEP has learned the lesson from the v1.1: Not to mention even an estimated release date... 

Regards
groennegaard

Good news, then, it will be better even than in 2006 addon 
Regards,

[zoomad]

I am running Ver 1.2 Build 1015.   I just now compared the Russian Tug in SS06 and SS08.  In SS06 with full left rudder applied and then full throttle on the starboard engine, the tug starts to turn almost immediately and achieves what feels like about 20 degrees of turn before any significant forward motion begins.  In SS08 the same controls cause very little turning at all before the tug has moved quite aways forward and attained signifcant forward velocity.

[LucAtC]

You are quite right indeed, the "kick effect" disappeared completely, and even the maximum rate of turn of the tug is more or less divided by 2 or perhaps more.
The Russian tug in the 2006 addon almost reached 360°/min with one propeller full astern and the other one ahead so as to turn on the spot, while on the 2008 version she doesnt reach 150°/min in the same configuration, which seems to me also a rather low value, although it could be a realistic value. Also, the tug seems to have a low towrope pull, if any. We can think (hope?) the moderators already mentioned it to the development team, and that they will improve the kick effect, in fact for most of the ships.
A propos, did you try the historical yacht?
Regards,
Luc

[LucAtC]

Sorry, but may I ask a question of vocabulary?
When you quote "prop wash steering effects", does the term apply to the "kick effect" (coup de fouet in french), or to the "paddlewheel, corkscrew, propeller transverse thrust or side thrust effect" or both?
Regards,
Luc

[zoomad]

(1) Historical Yacht seems better.
(2) My use of the term "prop wash steering effects" refers to the initial deflection of the propeller driven moving water against a turned rudder generating an immediate sideways thrust that exerts a turning force on the boat well before the forward component of thrust is able to overcome the boats inertia and start moving it forward.  One of the nice things about this effect is that it pretty much does not apply when in reverse (since the water is no longer pushed against the rudder).  Therefore using "back and fill" you can almost turn a boat in its own length without ever touching the wheel -- just put the wheel hard over and go forward and back.  Everytime you shift into forward the boat turns some, then when you shift to reverse you cancel any forward momentum with very little turning force or effect.

This is very different from "prop walk" which is due to the "handedness" of the propeller.  Actually, as I understand it, the larger component of "prop walk" results from any vertical tilt angle in the prop shaft -- which causes an increased pitch for the blade on one side (going up say) and, simultaneously, a decreased pitch for the blade going down on the other side, thus resulting in an asymetric thrust laterally.  The other (and generally smaller) component of prop walk is the simple side slip effect of the propeller turning in one direction causing a slight paddle wheel effect to one side or the other.

[LucAtC]

Hello zoomad,
Prop wash steering effects is , translated by "coup de fouet" ie "whiplash", and named "kickstartforce" in SS2006 ...  That effect exists indeed as long as the available turning moment can stall the hull.
Also thanks to your answer (and after some Googling) I learned that propeller walk, propeller effect, asymmetric thrust and asymmetric blade effect, are still some more translations of the French "effet de pas d'hélice" or "prop pitch effect".
As for the explanation given in this Wiki (http://en.wikipedia.org/wiki/Propeller_walk), I am not quite sure, because the effect does not decrease with an horizontal shaft, whether ahead (zero rudder shifted 1 or 2° starboard) or astern.
Also, the ship needs to go ahead/astern for any wake to exist, and the side thrust (prop in reverse) is nevertheless strong enough to be the major turning force at low speeds (no wind!) or being stopped.
Anyway, it is due to an asymmetric thrust like you mention. For instance, I was told (teached?), many years ago, that it was due to the important loss of efficiency (unsteady flow) around the blades passing nearest to the surface with regard to the immersed ones. It is a pity one cannot find more precise answers on the internet about such a discernable effect, although largely known and used by many thousands of sailors.
Ill search further...
Regards,
Luc