Bismarck's port rudder

Anything concerning the wreck. Expeditions, submersibles, photos, etc.
Walter

Re: Bismarck's port rudder

Postby Walter » Wed Apr 02, 2014 9:45 pm

This may sound naive, but I have always thought that I would have tried lowering charges to the starboard area in an attempt to clear debris and attempt to steer with the propelers.

Steve Crandell
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Re: Bismarck's port rudder

Postby Steve Crandell » Fri Apr 04, 2014 3:43 am

Walter wrote:This may sound naive, but I have always thought that I would have tried lowering charges to the starboard area in an attempt to clear debris and attempt to steer with the propelers.


That was considered and rejected because they thought they would do more harm than good. I believe the seas made it impossible to work over the side, and water was surging in and out of the rudder room making it very difficult to get in there and work. They were trying to disengage the rudder as designed to do so. People became exhausted pretty quickly though, and I think they finally just gave up trying. The thing is, in trials I believe they were unable to steer the ship with the screws with the rudders amidships, so when one became jammed it was pretty hopeless.

I don't have the info with me right now and I'm sure if I'm way off base someone will say so.

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tommy303
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Re: Bismarck's port rudder

Postby tommy303 » Fri Apr 04, 2014 5:52 pm

It is possible that blowing the rudders free, even if it caused no further damage to the ship, would probably have made things worse rather than better, as was found to be the case with USS intrepid after her rudder was damaged by a torpedo hit in 1944:

http://www.researcheratlarge.com/Ships/ ... ering.html

At the time the torpedo hit the INTREPID was in a left turn using 15° left rudder and at 25 knots. The detonation ruptured the bottom of the steering engine ram room and motor room, immediately flooded these two compartments and jammed the rudder. Propellers and engines sustained no damage. The crosshead and the rams of the steering gear were completely wrecked. The rudder was severely distorted and the fin which fills in over the counterbalance of the rudder was blown off, (See enclosures). The detonation opened a hole in the starboard side which extended from near the keel to above the fourth deck. The fourth deck in way of the explosion was completely missing. The third deck in the Chief Petty Officers' country was pushed up to the overhead of the second deck, and missiles penetrated the hangar deck. Complete details of the damage are contained in the Action Report. The net result of this damage insofar as ship control was concerned was to create the permanent effect of approximately 6½° left rudder. The INTREPID had the advantage of having made the standardization trials for the CV-9 class. One of the tests conducted was to lock an outboard shaft on one side, go ahead full power on the two shafts on the other side and determine the rudder angle necessary to maintain a steady course. This rudder angle during the trial proved to be approximately 6½°. After the torpedo hit it was found that the combination needed to maintain a steady course approximated the condition found during trials.

Steering control was lost immediately and the gyros tumbled. Until the gyros were brought back to the meridian the course was determined by using the bridge alidade as a dummy pelorus by observation of the North Star, which was visible. At the time of the explosion the vessel was on a south heading and continued in a left turn. As soon as it became obvious that steering control could not be regained, because of the rudder damage, the starboard engines were stopped and the effect noted. It was apparent that the ship could be controlled by the engines, so a slow turn was continued to the left through north, west and south and the ship steadied on course east. The yaw was reduced to about 30° on either side of east and in general a good course was made good. Shortly after steadying on course east, instructions were received to proceed to Eniwetok and course was changed to 065. The wind was almost dead ahead and, as experience was gained in steering with the engines, the yaw was reduced to about 15° to either side of the course. The average combination for steering on a course into the wind was approximately full power on the two port engines and stop to one-third on the starboard engines. This combination gave a speed of between 20 and 22 knots. Control could not be maintained below this speed because it was necessary to go full power on the left engines to prevent the ship from swinging left. On the following day, orders were received to proceed via Majuro. This necessitated taking the wind on the port bow and steering control of the vessel was lost. The CV-9 class has a tendency, with way on the ship, to weathercock into the wind. This is due to the fact that the center of pressure of the hull is near the forward edge of the island structure. The island acts as the mainsail of a schooner. The trim immediately after the detonation of the torpedo was 10 feet down by the stern. This was reduced by damage control to a drag aft of about 5 feet and maintained at that trim in order to improve steering and reduce yaw. It was obvious that the ship needed some headsail and the problem was how to rig a jib or to reduce the effect of the jammed left rudder. The first step taken was to lock No. 1 (outboard starboard) shaft. The effect of this was beneficial but was still insufficient to keep the ship from swinging left. The next step taken was to move all the airplanes on the flight deck forward of the island to act as a foresail. This worked satisfactorily for about 24 hours when control was again lost. The possibility of rigging canvas on the forward radio masts was investigated but it was decided that the structure was of insufficient strength and rigging in any case extremely difficult. A jury sail was then rigged between the forecastle deck and the underside of the flight deck. A Sail of approximately 3000 square feet was improvised using cargo nets and such canvas as could be found around the ship, (See enclosures). The wind continued throughout the passage to Pearl at velocities from 20 to 30 knots. The tendency of the wind to weathercock the ship was found to be a maximum when the wind was about 45° on either bow. With No. 1 shaft locked, the planes forward and the sail rigged, it was found that the ship could be adequately controlled with the engines. At low wind, velocities a speed as low as 18 knots could be made good.

Upon arrival at Pearl the vessel was immediately docked and the damage already described was disclosed. (see enclosures). The decision was made by technical personnel at Pearl to remove the damaged rudder and send the vessel to a West Coast yard for permanent repairs. The vessel sortied from Pearl in this condition and was found to be completely unmanageable. Vessels of the CV-9 class have an unusually small tactical diameter. To accomplish this the hull was designed with practically no dead wood. The designed rudder acts as a fin to provide directional stability for the hull. With the rudder completely removed it was found the hull had no directional stability, whatsoever. It could be compared to an arrow without a feather or an airplane without a vertical stabilizer. The heading of the ship had no direct relation to the direction of motion of the hull. It was found that it was impossible to steady the ship on my course. At times the ship would swing uncontrollably through 360°. . .

Upon returning to the dry dock at Pearl a jury fin was installed to restore a fin area equal to that of the original rudder. One hundred square feet of this fin was hinged. This hinged portion represented about one-fifth of the area of the original rudder. (See enclosures). It had a maximum angle of 20° right or left and was controlled by wire cables brought up outboard to the fan tail. The ends of the rudder cables were secured to three-fold wire jiggers, the running ends of which were taken to the after capstan. The large hole in the skin of the ship on the starboard side was filled in to reduce the drag on that side although the patch was not watertight.

It was the intention of the designers of the jury rig that the movable part of the fin would be used to overcome the effect of the wind and that steering would be done primarily with the engines. Upon sortie from Pearl, however, it was found that steering by engines was extremely difficult and the yaw to each side could not be reduced below an average of about 40°. The jury rig to the capstan worked so smoothly that the final combination, which proved very satisfactory, was to adjust engine revolutions to overcome the effect of the wind and use the jury rudder to steer. The effect of the jury rudder when hard over, appeared to bo equivalent to about 4° to 5° of the designed rudder. The yaw, using the jury rudder to steer, averaged from 10° to 15° on either side. Winds of 15 to 25 knots were encountered. The passage from Pearl was made at speeds of 14 to 16 knots without any further difficulty. The starting panel of the capstan is not designed for continuous service, such as that required for steering, but frequent cleaning of the contacters prevented shorting due to arcing. Special arrangements were necessary to provide lubrication for the capstan shaft, because the pump did not provide sufficient lubrication during the short starts and stops necessary.

It was the intention of the designers of the jury rig that the movable part of the fin would be used to overcome the effect of the wind and that steering would be done primarily with the engines. Upon sortie from Pearl, however, it was found that steering by engines was extremely difficult and the yaw to each side could not be reduced below an average of about 40°. The jury rig to the capstan worked so smoothly that the final combination, which proved very satisfactory, was to adjust engine revolutions to overcome the effect of the wind and use the jury rudder to steer. The effect of the jury rudder when hard over, appeared to bo equivalent to about 4° to 5° of the designed rudder. The yaw, using the jury rudder to steer, averaged from 10° to 15° on either side. Winds of 15 to 25 knots were encountered. The passage from Pearl was made at speeds of 14 to 16 knots without any further difficulty. The starting panel of the capstan is not designed for continuous service, such as that required for steering, but frequent cleaning of the contacters prevented shorting due to arcing. Special arrangements were necessary to provide lubrication for the capstan shaft, because the pump did not provide sufficient lubrication during the short starts and stops necessary.

Upon arrival at the Parallon Islands the vessel was met by four tugs and a line was taken from a single tug. The vessel was towed to the entrance of the dredged channel over the bar at a speed of about 10.5 knots, the INTREPID making turns for about 7 knots and the tug making turns for about 14 knots. 150 fathoms of wire and 30 fathoms of the port chain were used. The weather was perfect - no sea and very light wind. At the entrance to the dredged channel the ship slowed down and four additional tugs were taken alongside, two on each side. At slow speeds the ship was very difficult to control because of insufficient rudder effect. It was planned to arrive at the Golden Gate at high slack before ebb. Due to local conditions the ebb actually commenced about half an hour earlier than shown in the current tables. The result was that the ship was caught in some very erratic tidal currents and at times was almost completely out of control.

Upon arrival at the Parallon Islands the vessel was met by four tugs and a line was taken from a single tug. The vessel was towed to the entrance of the dredged channel over the bar at a speed of about 10.5 knots, the INTREPID making turns for about 7 knots and the tug making turns for about 14 knots. 150 fathoms of wire and 30 fathoms of the port chain were used. The weather was perfect - no sea and very light wind. At the entrance to the dredged channel the ship slowed down and four additional tugs were taken alongside, two on each side. At slow speeds the ship was very difficult to control because of insufficient rudder effect. It was planned to arrive at the Golden Gate at high slack before ebb. Due to local conditions the ebb actually commenced about half an hour earlier than shown in the current tables. The result was that the ship was caught in some very erratic tidal currents and at times was almost completely out of control. It was frequently necessary to use the engines at high powers to correct a sheer to the right or left. After passing under the Golden Gate Bridge the scope of the towing tug ahead was shortened to 100 fathoms. A towing speed of about 7 knots was used, which in certain places, gave a speed of advance of about one knot due to strong ebb current.

The steps taken to maintain steering control of the ship as described in the proceeding narrative, were as follows:

(a) Trim the ship by the stern.
(b) Slow down, stop or lock shafts on one side.
(c) Move aircraft on the flight deck forward to act as a headsail
(d) Rig a sail between flight dock and forecastle, Additional canvas could have been rigged, with some difficulty, on the radio masts forward, from a stay leading forward from the island structure, or on palisades arranged fore and aft.

Further steps which could have been taken but which proved to be unnecessary during the INTREPID's voyage are as follows:

(a) Rig a paravane on one side. A paravane creates a very considerable pull on its towing cable and would materially assist in keeping the bow out of the wind, if rigged on the leeward bow.

(b) Tow a small vessel (an escort destroyer or, preferably, a tug) with a short scope astern. This scheme was successfully employed in the Pacific some years ago in the case of a large passenger vessel that was unlucky enough to have lost her rudder, The towed tug, in this case, stopped her engines and used her rudder to steer the heavy vessel which provided the motive power. Speeds as high as 18 knots were maintained.

Their shoulders held the sky suspended;
They stood and Earth's foundations stay;
What God abandoned these defended;
And saved the sum of things for pay.


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