TUGS & SALVAGE

Robert Allan and Voith introduce the RAVE – by Jack Gaston

16 years ago

Development in the towage sector continues to move on relentlessly. Just when it seems that every avenue in hull and propulsion design has been explored, yet another concept emerges.

The RAV 3700 design represents a new concept for escort towing and shiphandling in confined spaces.

The latest new concept, unveiled at ITS 2010, comes with impeccable credentials and is the result of a joint project from Robert Allan Ltd and Voith Turbo Marine. Introduced as RAVE (Robert Allan Voith Escort) tug, the concept brings together a well developed hull form and Voith cycloidal propellers and research in a new and unique configuration.

The RAVE tug is a new concept for a highly manoeuvrable, high performance escort and ship handling tug using two Voith Schneider Propulsion (VSP) units in longitudinal alignment in contrast to the more conventional transverse configuration. Both units are located on the centreline, one forward and one aft. An aft mounted skeg is retained but much reduced in size. The concept, which has been the subject of considerable CFD analyses and tank testing, offers very precise and improved force generation characteristics which are necessary not only for the demands of indirect escort towing, but also very important for working in narrow confined harbour and channel areas. The RAVE Tug uses the variable pitch characteristics and the X/Y logic of two Voith Schneider propellers for optimum power allocation and precise manoeuvring.

The advantages offered are:

a. High Indirect steering forces over a very wide speed range, especially at low speed.
b. A very maneuverable tug which needs low propulsion power by having a very low resistance.
c. Very quick response to directional commands.
d. Easy and logical control.
e. Excellent control capabilities and omni-directional thrust characteristics in confined ports, channels and locks.
f. Cost effective because of a very good ratio of ship assisting forces in relation to the building costs.

The performance and configuration optimisation of the RAVE tug is being actively documented through an extensive series of model tests and CFD analysis, sponsored jointly by the project partners. This technology can be applied to any size of VSP powered tug, depending upon the application and power requirements.

The new RAVE 3700 Class Escort tug measures 37m LOA with a beam of 14.5m, a depth of 5.6m, and an operating draft of 6.9m. It has a bollard pull of 80 tons and generates steering forces of 150 tons at 10 knots.