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U.S.S INTREPID (CV-11)

S24/00-redm 28 March 1944.

Ser: 051

C-O-N-F-I-D-E-N-T-I-A-L

From: The Commanding Officer
To  : Commander Air Force, Pacific Fleet.
 
Subject: U.S.S. INTREPID - handling of after Battle Damage.
 
Enclosures:    Ten (10) Photographs

     1.       At 0011, 17 February 1944, Zone plus 12 Time, the U.S.S. INTREPID was hit, by an aircraft torpedo, just forward of the rudder post. The night was clear but dark. The resultant damage presented various problems which may be of interest in handling similar damage in the future.

NARRATIVE

     2.       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.

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S24/00-redm U.S.S INTREPID (CV-11)
 
Ser:  051 28 March 1944.

C-O-N-F-I-D-E-N-T-I-A-L

Subject:       U.S.S. INTREPID - handling of after Battle Damage.

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     3.       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

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S24/00-redm U.S.S INTREPID (CV-11)
 
Ser:  051 28 March 1944.

C-O-N-F-I-D-E-N-T-I-A-L

Subject:       U.S.S. INTREPID - handling of after Battle Damage.

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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.

     4.       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. It is to be noted, however, that the track made good as shown by DRT was almost exactly into the wind. During the time spent in efforts to gain control, the track made good was in a southeast direction directly into the wind and away from the entrance to Pearl. Because it was obviously undesirable to stop and drift back towards Pearl, efforts were then made to turn the ship abound and proceed at low speed in a northwest direction. It was found by going ahead standard on one side and back two-thirds to full on the other, that the yaw could be reduced and a reasonably accurate course could be steered at a speed of advance of four to five knots. Due to a strong Kona wind blowing, conditions for entry were dangerous and the vessel was ordered to remain outside

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S24/00-redm U.S.S INTREPID (CV-11)
 
Ser:  051 28 March 1944.

C-O-N-F-I-D-E-N-T-I-A-L

Subject:       U.S.S. INTREPID - handling of after Battle Damage.

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until weather conditions improved. For 48 hours the vessel was controlled by going ahead standard on one side and backing two-thirds to full on the other, alternately. The continuous backing, coupled with the hull damage aft, however, created so much vibration that numerous steam and water leaks began to develop in the engine rooms. The rapid increase of make up feed required began to approach the capacity of the evaporators and some other means of controlling the vessel became a necessity. It was then decided to tow the vessel with the seagoing tugs which had been made available. A 2½" wire was taken from the towing engine of the tug USS MUNSEE, and secured to the port anchor chain. The chain was veered to place the 60 fathom shackle on the forecastle and about 240 fathoms of wire was put out by the tug. This rig worked very well towing into the wind, with a good catenary. The tug worked up to 14 knots and the INTREPID made 5 knots for a net speed made good of about 8 knots. An attempt was then made to reverse the course. It was found that the tug could not pull the ship out of the wind. The tug immediately got in stays and worked back to a position on the port quarter in spite of stopping the INTREPID's engines. A second tug then passed a line to the bow of the towing tug to assist in holding up the head of the towing tug. This tandem combination worked satisfactorily and the vessel was turned through 180 in about 1¼ hours. For the remaining three days of the wait outside Pearl, during the storm, the tandem towing arrangement worked very well, making good about 5 knots, the tug making turns for about 14 knots and the INTREPID's engines stopped. The tugs would find a position of about 45 on the lee bow. In this connection it is worthy of note that the tugs used in this operation have their towing engine too far aft and their rudder appears to be of insufficient area. Tugs designed for towing heavy ships should have the towing engine located near the pivot point of the tug.

     5.       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

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S24/00-redm U.S.S INTREPID (CV-11)
 
Ser:  051 28 March 1944.

C-O-N-F-I-D-E-N-T-I-A-L

Subject:       U.S.S. INTREPID - handling of after Battle Damage.

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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.

     6.       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.

     7.       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

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S24/00-redm U.S.S INTREPID (CV-11)
 
Ser:  051 28 March 1944.

C-O-N-F-I-D-E-N-T-I-A-L

Subject:       U.S.S. INTREPID - handling of after Battle Damage.

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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.

CONCLUSIONS

     8.       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.

     9.       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. A little consideration will indicate that the tug's rudder was put right when the heavy vessel desired

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S24/00-redm U.S.S INTREPID (CV-11)
 
Ser:  051 28 March 1944.

C-O-N-F-I-D-E-N-T-I-A-L

Subject:       U.S.S. INTREPID - handling of after Battle Damage.

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to turn left, and vice versa. This method of maintaining steering control offers the opportunity of saving a heavy vessel, uncontrollable by self-contained means.

    10.       The jury fin and rudder as installed by the Navy Yard, Pearl Harbor, proved to be entirely satisfactory. The rig worked smoothly and the only adjustment necessary during the passage to the West Coast was to readjust the running ends of the jiggers on the capstan to take up the stretch of the wire cables. This stretch was taken up during the first three days of the voyage and thereafter needed no further attention.

Signature

 

Copies to:
   Cominch
   Cincpac
   ComSerPac
   Comdt NY, Pearl
   BuShips (2)
   ComAirPac, additional
     15 copies for dis-
     tribution to CV-9
     class carriers as
     desired.

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Photo Dated 2-20-44, showing temporary sail made of wood (forward, to right) and canvas and cargo nets (aft, at left behind the sailors). Same date, from forward of the canvas portion of the sail. Note the wood "sail" at the extreme left of the photo.
 
Photo Dated 2-26-44, in Drydock, showing port side of damage rudder and missing Same day, starboard side, showing damage on the side that the torpedo hit.
 
Photo dated 3-16-44 showing one of the stern capstans, usually used for mooring, jury-rigged to move the temporary rudder under the ship. Photo same day, showing some of the gear used by the crew to know how many degrees the jury-rigged rudder was turning.
 
Photo dated 3-16-44 showing the pully that allowed a cable to run over the edge of the deck to the jury-rigged rudder below. There was one on each side of the ship. Photo same date showing cable running down to jury-rigged temporary rudder at Pearl Harbor Naval Shipyard.
 
Photo dated 3-16-44 showing faired-over hull; this section was not water tight and was only covered to reduce drag during steaming and tow. Photo same date showing further detail of jury-rigged rudder at Pearl Harbor Navy Yard.


For Further Reading:

  • CV-11 - Repair in Forward Area from Structural Repair in Forward Areas During World War II
  • SOURCE:
    National Archives & Records Administration, San Bruno
    Record Group 181, Pearl Harbor Naval Shipyard General Correspondence, 1941-45.
    Declassification Project NDD 868129

    Transcribed by RESEARCHER @ LARGE. Formatting & Comments Copyright R@L.

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    In memory of Wally Bigelow, who will always be "Mr. Intrepid" to me.