DSK wrote:


In the case of the Titanic at the time frame between sighting and
collision..... IF they had started to reduce steam to the turbine prior
to reversing the recips, this measured reduction while the other engines
were going full, would/should have created a "disturbance" aft of that
center prop which would/should have reduced the effectiveness of that
single, center rudder.

Yes, but I'm not sure they would have done that. The reciprocating
engines could be reversed with the throw of a lever... the valve gear
control. However there is no definite knowledge of what bells were rung,
when, and how long it took the engineers to answer them. Nor is there
definite knowledge of how long a warning time between sighting the 'berg
and hitting it... the oft-quoted 37 seconds is a figure calculated by
the American Inquiry board from som fairly vague data.

This becomes an engineering question and I'm not an engineer. However,
considering the mass involved, I'd assume that the process for reversing
engines running at full sea speeds (even recips) would involve a good
deal more than just "throwing a lever" G



If the steam to the turbine was cut off and the central prop left to
freewheel, then the rudder would have lost some effectiveness... but if
the prop was engaged in reverse (which the Titanic's couldn't be anyway)
then it would be far worse.

Would require another turbine, but agreed.


Now, since I can see another route to your question. If the ship was
steaming along (different scenario) at full speed with no steam to the
turbine (it's just "freewheeling") would this reduce effectiveness of
the rudder? I would have to say yes, as it becomes a rotating drag which
, in my opinion, has to create disturbed water aft of the prop, which
has to disturb the "smooth" flow of water across the rudder.

Agreed. But I'm saying it would be less than if the prop were engaged in
reverse, or stopped & locked.

True

Without specific test which address the many various conditions and
actions that where or would occur, you have to assume that the above is
speculation on my part based on my own sense of what has happened when
handling one or two ships. G I.E., I don't guarantee I'm
right....these are my observations.

Well, if you're interested there is a lot of data to look at
http://www.titanicinquiry.org/
has both American and British inquiries and all the testimony.

G I've been through much of this in the past, so I've forgotten many
of the specifics, but remember there being many unanswered questions
since their knowledge base was relatively new at the time.
One thing that sticks in my mind was that the turbine received it's
steam from the main recip's which is why I thought they would need to
secure this engine prior to maneuvering the others .....could very well
be wrong here.
At any rate, I'm a firm believer that the Titanic could have benefited
from today's technology on rudders, not only in size but in shape and
location (Hate a twin screw with single rudder).

otn