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Jackstay Transfer (Replenishment) at Sea

by John M. MacFarlane 2013

Jackstay Transfer

Canadian naval personnel being moved from ship to ship while underway. (Image from MacFarlane collection.)

The light jackstay is used for transferring personnel, provisions, and light stores with a maximum load of about 250kg. The hauling end of the jackstay is manned by up to 25 hands. The other end is secured by a grommet strop to slip in the receiving ship. A traveller block is hauled back and forth along the jackstay wire by an in–haul rope in the receiving ship and an out–haul rope in the delivering ship manned by up to six crew in each ship. Working distance limits are up to 24–61 meters with a normal working distance of about 34 meters.

Jackstay Transfer

Close–up of jackstay rigging on a Canadian Naval Frigate c1957. (Image from MacFarlane collection.)

This is a hazardous operation as the close approach of the two ships risks a collision caused by the rush of water between them. This can inadvertently cause the sterns of the ships to be pulled together and steering has to be constantly adjusted to counteract this effect.

Jackstay Transfer

Rear–Admiral Hugh Pullen RCN loved to be close to the action under his command. This often attracted favourable press coverage for the navy. (Image from MacFarlane collection.)

Replenishment at sea (or RAS for short) in NATO and Commonwealth navies is a method of transferring fuel, munitions, and stores from one ship to another while under way. Underway replenishment (UNREP) (US Navy) is the technique of underway replenishment perfected by the United States Navy in the 1920s and 1930s. These methods were used extensively as a logistics support technique in the Pacific theatre of World War II. Since it allowed extended range and striking capability to naval task forces the technique was classified so that enemy nations could not duplicate it. Presently, most underway replenishment for the United States Navy is handled by the Military Sealift Command. It is now used by most, if not all, blue–water navies.

Underway replenishment, or UNREP can be conducted by helicopter (vertical replenishment) or by attaching lines and hoses between two ships steaming alongside each other (connected replenishment). Normally this tricky maneuver is coordinated by radio, but in wartime conditions it would often be essential to refrain from transmissions that could reveal a battle group's position to the enemy. The U.S. Navy therefore makes regular use of the capability to conduct UNREPs in complete radio silence by using flag hoists. Four sets of signals are used for the enormously complex task of conducting underway replenishment at sea.

Jackstay Transfer

Jackstay transfer to HMCS Chaudiere. (Image from MacFarlane collection.)

When the control ship – normally the ship providing the replenishment – is steady on the prescribed course and speed, it hoists the ROMEO flag "at the dip" at the outboard halyard on the side it wants the receiving ship to come along. "At the dip" means that the flag is hoisted well below the top of the signal halyard. A flag hoisted at the dip normally signifies preparation for an evolution that is to be carried out when the flag is hoisted "close up".

The receiving ship responds by hoisting ROMEO at the dip when it is ready to come alongside. The control ship then two-blocks ROMEO close-up, signifying "I am ready for your approach," and the receiving ship does the same to say "I am commencing my approach." Once the messenger line used to connect the refueling hoses and re–supply lines is in hand, ROMEO is hauled down and (if fuel or explosives are being handled) BRAVO is hoisted in its place. If BRAVO is close–up, it means fuel or explosives are being transferred; if at the dip, that supply has been temporarily suspended. When the fueling or resupply is complete, BRAVO is hauled down. Meanwhile, 15 minutes before the two ships are to disengage, the control ship hoists the PREP pennant at the dip. When the transfer is complete, it is closed up, signifying that the last replenishment station is disengaging, then, when all lines are clear, it is hauled down and the evolution is complete.

Rorte St Jean Replenishment

U.N.T.D. Officer Cadets "learning the ropes" for the evolution of "replenishment at sea" in HMCS Port St. Louis on the Great Lakes 1967. The reserve vessels were only authorized to use fire hoses in case of a potential hose breakage (to prevent oil spills). But the principle was the same, and the training was successful. (Photo from MacFarlane collection.)

To quote from this article please cite:

MacFarlane, John M. (2013) Jackstay Transfer (Replenishment) at Sea. Nauticapedia.ca 2013. http://nauticapedia.ca/Articles/Jackstay_Transfer.php

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