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The Development and Running of the Brave Class Fast Patrol Boat By PETER DU CANE, M.R.I.N.A., M.I.Mech.E., A.F.R.Ae.S.

All the photographs supplied throughout these pages are with the kind permission of Mr C du Cane, from the archives of Commander P du Cane.

P1011 is Brave Borderer, the rest as well as the interior shots are of the Vospers built Brave Class for the Danish Navy.

FOREWORD

Here is a description of the design and development of a Fast Patrol Boat including a discussion of a number of the technical problems considered.

The speed reached is in excess of 50 knots, which is achieved making use of gas turbine propelling machinery possessing novel features.

This is the first warship to have no piston engines aboard at all as the Rover generators are also gas turbine driven.

Very special measures were taken to ensure a satisfactory propulsive coefficient by making careful study of propeller characteristics and appendages associated therewith.

Structural considerations are discussed as are reasons underlying selection of hull form.
A brief account is given of experience gained on trials and performances achieved.

Following preliminary discussions with representatives of Admiralty departments a contract was placed with the writer’s firm, Vosper Ltd., on 3rd June, 1954, for the preparation of a series of design studies of a fast patrol boat incorporating a number of alternative machinery arrangements. The craft resulting from this study were named the ‘‘Brave’’ class.

This contract also covered the preparation of a sketch design from the number of design studies above mentioned as selected by the Admiralty. This sketch design would then be submitted to the Board of Admiralty for approval.

Subsequent to Board approval ‘‘a detail design of the hull, machinery and electrical arrangements complete in all respects, including building drawings, specifications arid full particulars of calculation of weights, strength, stability, machinery per¬formance,” was to be prepared.

All this work to be undertaken in consultation with the Director of Naval Construction, the Engineer in Chief of the Navy and Director of Electrical Engineering as appropriate.
It was agreed that as a matter of administrative convenience and to avoid any possibility of overlapping, all written com¬munication relating to this design work should be carried out between a named officer representing the Admiralty and the writer representing Vosper Ltd., the shipbuilders and naval architects.

STAFF REQUIREMENTS
The following outline requirements were given to Vosper Ltd., who were instructed to design a craft to meet these requirements as far as they considered this to be possible. In the event that any particular requirement could not be met, the extent to which it appeared likely that there would be a shortcoming was to be reported at the time the studies were submitted.

(1) Form and Dimensions

The boat to be of hard chine type and as small as possible commensurate with seakeeping and speed requirements,
(2) Speed and Seakeeping

The top speed to be the maximum obtainable and not less than 44 knots in the gunboat version with half fuel consumed. This speed to be maintained for a quarter of an hour in waves 3 feet high, the ultimate aim being to produce a boat capable of so knots under these conditions.

The boat to be capable of continuous operation in 3-foot waves at the continuous rating of the machinery. This speed I shall be not more than 6 knots less than the maximum.

Slow speed to be not more than 12 knots (8 knots is pre¬ferable) and should be maintained for 4 hours. Harbour manoeuvring at 4-6 knots is required.
Range. 400 miles at maximum continuous speed in fair weather.
Armament. To be as specified for three different roles:
1. Gunboat
2. Gunboat / Torpedo boat
3. Torpedo boat
4. Minelayer
5. Raiding craft

Special Features
(a) Arrangements are to be made to permit the removal and replacement of any machinery component (including main engines) within 6 working hours.
(b) Main engine life is expected to be not less than 1,000 hours between overhauls.
(c) Thrust and torque meters are to be fitted on all shafts for at least the prototype, capable of making a continuous record.
(d) Noise is to be too low for detection by an enemy boat
stopped in any weather and sea conditions at the following
ranges: -
(i) At 500 yards (by ear) or 2,000 yards (by hydrophone) at slow speeds.
(ii) At too yards (by ear) when stopped.
(e) Mast to be capable of being lowered within is minutes and re-erected within 15 minutes.
(f) The craft will normally operate in temperate climate but should be capable of quick conversion for operation in sub—arctic or tropical climates.
(g) In order to produce the best possible seakeeping at all speeds and to reduce slamming to a minimum considera¬tion to be given to the use of transom flaps (adjustable),
(h) Turning circle at full speed to be not less than S lengths. Complement. Expected to be 3 officers and 19 men including
3 P.O.s.
TYPES OF MACHINERY CONSIDERED
At the first design study meeting instructions were received to investigate various combinations of machinery, including:
(a) Two 5,000 b.h.p. gas turbines.
(b) Simple high speed diesels (s).
(c) Compounded high speed diesels (2).
(d) The Bristol Aeroplane Co.’s turbines as suggested by Vosper Ltd. (3). (See Figs. 1 (a)-(d).)

The following suggestions were put forward for discussion regarding possible methods of meeting the requirement for harbour manoeuvring and silent running at slow speed:
(a) Small diesel engines cum reverse gear mechanically coupled to main shafting (wings).
(b) Electric motors supplied from the ship’s generators and driving main shafts.
(c) Small auxiliary propellers housed in tunnels which dry out at high speed. The auxiliary propellers can be driven by diesels, electric motors or small gas turbines.
(d) Independent drive on a separate shaft.
(e) Reverse reduction gear coupled to Proteus turbine. (See (Fig. 2.)

 
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