Page 47 - NAVAL FORCES 03/2017

Expeditionary Warfare

that extend and contract, lower and lift, or by
articulated cranes that also rotate about their Creative Technology Applications (CTA) continues development
mountings. of its Soft Rail system that employs a net drogue akin to a fishing trawl to
put sufficient tension on two polyethylene cables that then serve as rails.
A basic choice with cranes and davits is Features
whether they lift the boat/unmanned surface
vessel (USV) at one point or two. Single point
lifting is popular because it is simple, versatile
and reliable. However, it requires a painter line
to run from bow of the boat to a point forward
on the ship deck to stabilise it in yaw, with
further yaw control exercised by deck person-
nel using tag lines connected to the boat’s bow
and stern.
Some single point lift devices can limit the
daughter craft’s yawing with a rigid lift con-
nection, reducing the need for tag line han-
dlers, but they are more complicated and rely
on tailored connections to the loads. Single Stern Recommendations While often designed for a specific vehicle,
point systems are adequate up to 6kts, but the they can usually handle others. They are an im-
USCG’s National Security Cutter, for example, Well-docks are proven in larger ships, and portant focus of development in automation,
was converted to dual point davits for L&R at stern ramps are increasingly common in small- although automated capture devices usually
higher speeds. er vessels, while the offshore industry and the work only with specific vehicle geometries.
Dual lift requires a more sophisticated lift- scientific community regularly use A-frames. Of the two types of evolution, recoveries are
ing appliance that brings with it the risk of un- Most well-docks were designed with amphib- the more demanding and tend to be the lim-
intentional release of one of the connections. ious vehicles in mind, but also work well with iting factor, said the SMST. Sea state five is
Side-mounted systems are often in alcoves, boats and submersibles. Both well-docks and usually the limit, and recoveries are usually
which provide shelter for crews but can restrict stern ramps have a heavy influence on ship carried out into head seas at 3-6 knots.
space and visibility from the bridge, while size and design. While stern ramps are affected by many of
over-the-stern options can be quicker and eas- Stern ramps provide quick L&R of, typical- the same factors as lateral L&R systems, they
ier to supervise. ly, RHIBs and USV designs based on RHIBs. also have their own issues, one of which is the

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