UNREP
UNREP stands for underway replenishment. This permits us to stay at sea for an essentially unlimited time. We have both specialty ships, which provide one basic service, such as ammunition or fuel, and multipurpose ships that provide combinations of food and oil.
The whole operation is strictly choreographed and requires adherence to the rules to complete successfully
Imagine two large trucks on the highway exchanging cargo and fuel while the drivers have to relay instructions to one person doing the steering and another controlling the gas. These two trucks must stay next to each other for hours at a time and never touch while people pass cargo between them.
Sometimes food, ammunition, and spare parts are delivered slung from a cable beneath a helicopter, but most of the time they come by what is called HighLine. Although US Navy ships can go a long time between refueling it is the general practice that they be refueled every four of five days to insure they are ready to respond to any contingency without delay. Since Fuel can only be transferred in the quantities needed from one ship to another it makes sense that other supplies be transferred at the same time.
The deck division, which maintains the condition of all deck equipment, has started to prepare for the operation long before the ship is called to UNREP stations. They are checking all of the equipment that will be used to be sure that everything that might be needed in various unusual and usual situations is in place and ready for use. This includes rigging a Kingpost at the mid-ship station.
For this UNREP we will be using 3 stations. The forward and aft stations will be for fuel and the mid-ships station for transfer of mail, movies, repair parts, and fresh foodstuffs. All of this has been arranged several days in advance. Our mail, spare parts, fresh fruits and vegetables, as ordered by our supply officer, have been loaded onto the refueling ship (called an OILER) before it left port. A point that is convenient to our itinerary is chosen as a rendezvous point and a time set.
The Plan of the Day, a daily handout listing the expected operations of the upcoming day, has prepared the crew for the call to underway replenishment stations. This evolution requires a combination of very skilled people to be at certain places on the ship and a lot of plane old muscle power to accomplish safely and efficiently. Much of the crew will be involved in one way or another.
Up on the bridge they have plotted the course to the rendezvous and adjusted the ship’s speed to be in the right place at the right time. As we approach the oiler is identified on the radar and her course and speed are calculated. And an intercept course is calculated and initiated. As we close in the oiler signals the Romeo Corpen (replenishment course) and the speed she intends to conduct the operation at. We will be to starboard, on the oilers right side. This course is chosen based upon the wind and seas primarily and secondarily upon our destination. If we can replenish while proceeding towards our destination great, but if the sea conditions dictate a different direction would be safer we will take it. We are going to have a lot of men exposed to the elements for the duration of the operation.
The chosen course is 120 and the speed will be 12 knots and the oiler comes to that course and speed. This puts us on a course that is about 60 degrees from hers and we are traveling at 20 knots. In order to pull into position behind her and then move into position alongside her the Officer of the deck gives orders to the helm to keep our bow pointed at the stern of the oiler. We slow to 15 knots and continue our approach as the crew is called to UNREP stations one, two, and three. By keeping our bow pointed at her stern we make a nice gradual turn until we are on the same course as she is on. If things work out well and the bridge gets the word that all stations are manned in time we can just continue to our position alongside and commence the refueling. If we get behind the oiler and the stations are not all ready we can drop to 12 knots and follow the tanker until we are ready.
On The bridge the men assigned to their respective position have relieved the Helmsman and lea helmsman and other watch standers. The Captain and Executive Officer are on the bridge. I have relieved the Officer of the Deck and assumed the Con and continue our approach.
Each replenishment station has an officer in charge who is responsible for the safety of all the people at that station and for the safe operation of the equipment located there. There is also a Boson who will lead the team making the connection between the ships. The refueling stations, one and three, also have an engineer who is in charge of insuring the fuel is properly delivered. Station two will have the ship’s postal clerk to receive the incoming mail and see to it that the outgoing mail goes to the oiler. It will also have people from the Supply department who will guide the incoming supplies to the proper storage areas. There will also be some one to exchange movies with the other ship.
Additionally there will be a group of at least twenty, preferably more, men assigned to handle lines. They will due the manual labor of moving the big (almost12" diameter) hoses from the oiler to us and pulling supplies across at the mid ships station. There will be additional men amidships to handle striking (carrying below) the boxes of food we receive.
On the bridge we receive word that all stations are manned and ready. We signal the oiler that we are ready to come along side and proceed along side. This is where the conning officer really earns his keep. The goal is to pull up smartly, cut your speed at just the right time to get your relative motion to zero and be close enough to make it easy to get lines between the ships. The real danger is that if you get too close to the other ship the shape of the hulls will create the Bernoulli effect. The Bernoulli effect is created when a fluid is accelerated between the curved shapes of the ships; this causes a low pressure between the ships, which actually sucks them together.
You want to be as close as possible to make the work in pulling lines back and forth as simple as possible but not so close you get sucked into the other ship. With this ship I will try for a distance of between 85 feet and 100 feet for the initial line handling. Once we have good connection at all three stations I will open out a bit for comfort. Then when it is time to disconnect I will work a little closer to facilitate the clean breakaway. I keep this in mind while moving into position. If ideally executed I will appear to be pulling forward until the stations are lined up with their opposites on the oiler and just stop. Of course by stopping I mean match the speed of the oiler exactly.
We have a relative movement of about three knots so the droop in speed will be rather quick once the engines are at that speed, but my 12 knots most likely will not match her 12 knots exactly. I will have to make adjustments of one or two rpm and directions left and right by just fractions of a degree throughout the entire operation.
I .am on the port (left) bridge wing and can see the men at station one below and just ahead of me. As I look aft I can see some of the people from station two and a few from station three. Station one will be the one I use to make my adjustments. One of the lines that they will pass between the ships will include a sound powered telephone and markers at ten foot intervals to confirm my judgement about the distance between the ships.
I give the order to come to twelve knots in time to see us slide into and just a bit beyond the ideal placement of my station one and the appropriate station on the oiler. Only off by a few feet, but I give the order to decrease speed by 3rpm. As we slow I can see the Boson on the forward station winding up and throwing his bolo. (This is a small weighted bag attached to a heavy string, which provides the first connection between ships) This is a good sign that I am close enough, If I were out a bit further the boson would have used a rifle with a plastic bottle attached to the string to send the first line across. Meanwhile strings are being slung across to the oiler at stations two and three. Now the real physical work begins as the people on the oiler attach the strings we sent over to slightly larger line (rope). Our crewmen now pull the string and the first line back to our ship. The first line is attached to a heavier line and this in turn is connected to a steel cable and other connections that go with that station. The boson and his men connect the cable to a fitting on our ship. And a signal is given to the oiler that we are ready to take tension on the cable. Through a complex system of weights and engines on the providing ship the slack is taken out of the cable and a constant tensio0n is maintained. We now have the phone line which permits our Captain to speak by sound powered phone to the Captain of the oiler and the measurement line that tells me exactly how far it is from my forward station to his. I am continually ordering add one rpm or drop two-rpm to adjust speed to keep me in position with our stations lined up. Once we have made the cable connection at all three stations I can start easing away from the oiler by 10 to 20 feet.
The manual work for the crew is not over yet either. At the fueling stations they must pull the fuel hose across the cable where the engineers can connect the hose to our fuel intakes. The connections are very similar in appearance to those used by aircraft in mid air refueling on a much larger scale. Once the end of the hose with its probe is seated in our receiver and locked in place the fuel starts to flow and it is up to the engineers to distribute it to the correct tanks. As we are pulling all of this line aboard the ship it is being very carefully flaked down (laid out on the deck in a big flat "S" shaped pattern on the deck). This accomplishes two goals, safety (no one should get tangled in it) and efficiency (it can easily be sent back without us having to deal with kinks or knots).
The work at the mid-ships station is a lot more active. Once the cable between it and the providing ship is tensioned the work begins in earnest. Since this station is being used for supplies a hook is attached to a wheel which is pulled back and forth between the ships. Suspended from this hook can be a variety of things depending on the load being transferred. Mail and movies might be sent over in a bag, a pallet of boxes in a cargo net, or even a man in a boatswain’s chair. The men must manually pull each of these loads across the cable on the ship and then paying out the line at a controlled rate returns the hook. Generally the first load will be the mail and movies. The mail is received by the ship’s postal clerk who quickly takes it to the ship’s post office for sorting. The Movies are a highly treasured property and have been negotiated very carefully are received by an IC man (Interior Communications specialist) who controls the movie inventory on board.
Each evening a movie is played on 16mm projectors on the mess deck for the crew and in the wardroom for the officers. The crew has first choice if there is any dispute as to which film is shown where.
During this UNREP we will receive three pallets of fresh fruits, vegetables, milk and eggs. This is where coordination is really needed. There is a limited area of the deck for receiving the pallets. There are all the line handlers who pull the load back and forth, and now we have to clear a pallet of boxes of perishable food between the time it is delivered to the deck and cleared of the rigging and the delivery of the next pallet. A chain of men is formed to pass the boxes. It’s like an old fashion bucket brigade, but the boxes are bulky and must be moved up and down ladders (stairways) to get them out of the way quickly. An evolution like this, involving all three stations can well involve everyone on the ship in one way or another.
As the evolution is terminating I have eased the ship back a bit closer to the oiler. Once the fueling is completed a large lever is tripped that in one-motion stops the flow of fuel, seals the end of the pipe and disconnects the probe from the receiver. The oiler starts retrieving the hose and the line attached to it is feed out as needed. Once the hose has returned to the ship the cable tension is relieved, the safety officer insures everyone is clear and the boson releases the connection between the ship and the cable. The line handlers now feed line out at a rate that keeps the end of the cable from hitting the water.
The operation at the mid-ships station is rather similar, instead of the hose being sent back under control, the hook and the empty pallets are sent back. When it is safely back on the oiler that connection is released and the cable returned rapidly and under control. Ideally, the only thing that drags in the water at all is the last bit of line and that is quickly pulled aboard the oiler. As soon as I receive word that all lines are clear, I make a quick visual check to see that they are, in fact clear, and give the order to bring the engines to full speed at 20kts and we move swiftly away from the oiler.
The Navigator has charted the new course to our destination and as soon as we are safely away from the other ship I come to that heading. Word is passed over the ship’s loud speaker system to stand down from UNREP stations and my relief is soon on the bridge.
Essentially the ship goes back to routine with the exception of the deck force who take care of cleaning up and storing gear at the three stations and the supply department is busy moving the supplies to their final destination.
