otnmbrd wrote in message nk.net...
Some comments interspersed

DSK wrote:
DSK the marine propulsion expert wrote:

In any case, the ship was going full speed, the loss of the prop
stream across the rudder would not reduce the rudder's effectiveness
very much.

This is probably most notable, in my experience, with variable pitch
props, but you can and will experience it with fixed pitch. You slow the
rpm of the prop and it tends to mess a bit with the smooth flow of
water past the rudder, reducing effectiveness until hull speed reduces
to rpm speed. (personal observation).

I agree.

Nav and Doug missed I think a key part of the story I heard.

That a full astern bell was rung on the port engine to speed the turn.











Nav wrote:

http://www.dellamente.com/titanic/engines5.htm


Interesting web site. Thanks for the link.

It does contain a number of inaccuracies, though.


"Regardless, most scenarios agree steam to the turbine would have been
cut off. While this had little effect on the ship's forward motion,


???

The central turbine was about 35% ~ 40% of the ships forward power. How
is it going to have "little effect on the ship's forward motion?"

Or do they mean that shutting off steam to the turbine would not have
produced significant stopping impulse? That would be much more correct.

They might be thinking that the mass of the ship will keep things moving
with a gradual reduction in speed, not readily apparent in the time
frame of this collision.

They also don't appear to know how the reciprocating engines were reversed.


... it deprived the rudder of the steady, forceful stream of water
necessary to turn a ship of that size.


???

A steady stream of water goin 22 + knots is not "forceful"?

It's forceful, but definitely not as forceful


... Several sources claim the rudder on the Titanic and her sister
ships was too small. If that was indeed the case, shutting down the
center turbine would be the last thing you would want to do in an
emergency."


The "rudder too small" claim is total malarkey. The Olympic was the same
design and had a long service career, with a reputation of being a good
handling ship.

Disagree. Rudder technology has come a long way. Although I don't doubt
that the ships may have been considered good handling by many of the
day, there are many possibilities which could have improved the
"overall" rudder effectiveness, though whether this could have saved the
day, is pure conjecture.


Hmm, seems to agree with me?


Sure. It's incorrect and based on assumptions when accurate data is
readily available.

Speaking of which, have you worked out the prop slip for the Olympic
class ships yet? Data readily available, all you need is the prop pitch,
top speed, and top speed rpm.

Slip is a variable ..... changes from day to day, based on a number of
factors.

... My yacht steers well without propwash because it's rudder, in
comparison, is huge... My point is that, most power vessels can have
much smaller rudders because they use the propwash to significantly
increase rudder effectiveness. It's standard naval architecture.


At low speed, sure. At full speed, the prop stream does increase rudder
effectiveness but I'd say that it's not "significant." Judgement call, I
guess... certainly your vast experience in handling large steam ships
and your claimed naval architect training give you a big advantage here.

DSK


Would disagree. Prop wash is a very important contributor to rudder
effectiveness at all speeds .... put a ship's engine on "stop" ....
trust me, your effectiveness decreases rapidly.

otn