Doubts about three shafts stern of Bismarck

ontheslipway · Post by **ontheslipway** » Tue Feb 14, 2006 11:59 pm

Nice link. 130 tons, wow, that's extremely heavy. Lips (my former employer) used to be a heavy record holder as well with 100 tons.

THe controllable pitch propellers are restrained in power due to stresses and actuating pressures in the hub. The actuating mechanism can only take so much. The QE2 had variable pitch propellers (blades cannot pass each other) with the highest power (can't rememebr the total amount).

Ulrich Rudofsky · Post by **Ulrich Rudofsky** » Wed Feb 15, 2006 1:21 am

The QM2 has a very complex hybrid propulsion system of 2 fixed and 2 variable pitch props, apparently the ship puts out 157000 shp. Does that mean that the fixed props push harder than the adjustable pitch and how would you use them. Perhaps that is to complicated a question. But it looks like one of the engines has already failed.

Name : Queen Mary 2
Alias : QM2
Gross Registered Tonnage: Approximately 150,000 tons
Length: 345 meters / 1132 feet
Beam: 40 meters / 135 feet
Beam at Bridge Wings: 45 meters / 147.5 feet
Draft: 10 meters / 32 feet ten inches
Height (Keel to Funnel): 72 meters / 237 feet
Passengers: 2660
Crew: 1254
Top Speed: Approximately 30 knots (34.5 mph)
Power: 157,000 horsepower, Environmentally friendly plant.
Propulsion: Four pods of 20 MW each. 2 fixed and 2 variable pitch.
Strength: Extra thick steel hull for strength and stability.
Stabilizers: Two sets of Denny Brown.

ontheslipway · Post by **ontheslipway** » Wed Feb 15, 2006 1:08 pm

The QM2 has two fixed pods and two azimuthing pods (rudder action) which means the entire pod can rotate. The propellers are all fixed pitch.

I was refering to the QE2 btw, she has variable pitch props after her major overhaul.

Javier L. · Post by **Javier L.** » Wed Feb 15, 2006 3:03 pm

Ulrich Rudofsky wrote: Name : Queen Mary 2
Gross Registered Tonnage: Approximately 150,000 tons
Top Speed: Approximately 30 knots (34.5 mph)
Power: 157,000 horsepower, Environmentally friendly plant.

a bit off topic but can anybody explain to me how QM2 and Bismarck with about the same power (150,000 hp) get about the same speed 30 knots, when the QM2 weights 3 times as much (150,000 vs. 50,000 tons)?

marcelo_malara · Post by **marcelo_malara** » Wed Feb 15, 2006 3:36 pm

The longer hull diminishes the wave making resistance.

ontheslipway · Post by **ontheslipway** » Wed Feb 15, 2006 4:04 pm

QM2 operates in a different regime than B so it probably is, combined with the fact that her hull is state of the art. Her lines may be classic, her hull is not. Friction on QM is significantly higher. Still, hull form drag is most certainly much lower and the efficiency of the propulsive components is much higher. Battleships operate at very infavourable regimes at top speed, QM does not. (well, define infavourable, probably still very expensive to run at 30 kts).

Hartmann10 · Post by **Hartmann10** » Wed Feb 15, 2006 6:41 pm

Hello to all, and a lot of thanks for your help in this matter.

I don't know where you got the 60000 shp from.

.
Well, I saw something like this in the now out of action page warship projects forum (not the current one) about the study carried by the company ¿Zoelly? in switzerland, about the engine limits in the 30-40, but I don´t if it´s true, so I decided ask for it if someone knew about this supposed theoretic limit. It could be an explanation for the 4 shaft arrangement in the Graff Zeppelin, with almost 200.000 shp.
best regards to all

Bgile · Post by **Bgile** » Sat Feb 25, 2006 1:14 am

The Iowa class had 212,000 shp and 4 shafts. They had to experiment with different screws to solve vibration problems, ending I think with two 5 and two 4 bladed screws.

Ulrich Rudofsky · Post by **Ulrich Rudofsky** » Sun Feb 26, 2006 1:23 am

The IOWA had two 4-blade screws outboard (5.5 m) and two 5-blade screws inboard (5.3 m). She was able to develop 44 000 shp in reverse! What do you suppose the BISMARCK did in reverse?

ontheslipway · Post by **ontheslipway** » Mon Feb 27, 2006 1:52 pm

What do you suppose the BISMARCK did in reverse?

I think she sailed backward.

Ulrich Rudofsky · Post by **Ulrich Rudofsky** » Mon Feb 27, 2006 2:48 pm

Karl Heidenreich · Post by **Karl Heidenreich** » Fri Mar 17, 2006 8:42 pm

About this topic of Bismarck´s three shafts there are two things to point: the first one concerns to the efficiency of the design in terms of power transmited from the turbines to the shaft. In this case Bismarck design is more efficient than the four shaft-four propeller arrange in the KGV Class because each of Bismarck´s shafts is transmitting 50,056 (nominal) hp while the KGV´s shafts are transmiting 28,250 hp each. But, on the other hand it came to my attention than even a "pointed" arrange as the three shafts of Bismarck (having one over the longitudinal axis) would always produce a torque to one side. Why? Because two screws would rotate clockwise and one anticlockwise (or viceversa). This means that the Bismarck must always been considering this and constantly making corrections.
Thus, I always regarded redudancy as a bonus. The British, the Japanese and the Americans choose for their main battle units four shaft-four propeller arragements. No three out of four are dead wrong.

ontheslipway · Post by **ontheslipway** » Fri Mar 17, 2006 11:26 pm

In this case Bismarck design is more efficient than the four shaft-four propeller arrange in the KGV Class because each of Bismarck´s shafts is transmitting 50,056 (nominal) hp while the KGV´s shafts are transmiting 28,250 hp each.

Nope, transmitted power has NOTHING to do with efficiency.

Why? Because two screws would rotate clockwise and one anticlockwise (or viceversa).

Not necessarily, this depends heavily on the afterbody shape and propeller infow. Still, you don't need "constant corrections" if you have your rudders calibrated for sailing straight ahead... normally you're not really troubled by the "wheel effect" which is only effective at very low speed. There's a million single screw ships sailing without any difficulties.

ontheslipway · Post by **ontheslipway** » Fri Mar 17, 2006 11:27 pm

No three out of four are dead wrong.

This is a BS argument (even ignoring the fact that the RN used triple shafted aircraft carriers)

Karl Heidenreich · Post by **Karl Heidenreich** » Fri Mar 17, 2006 11:42 pm

Maybe you are right and maybe I´m dead wrong: that´s why we post on the forum, to discuss. However that´s not the way to answer a friendly post, I´m not doing any offense.