Halcyon Class Minesweepers

Halcyon Class Ships
Trials 1936

Trials 1936
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1937 Specs



Source: ADM1/9085 

(The following are extracts from the report on trials held by the 1st MSF in Alexandria.)


OTHER USES OF MINESWEEPERS - Capt V Crutchley 12th April 1936

Circumstances may frequently occur when the fleet is at sea when minesweepers are practically the only armed vessel available to the Base commander and, therefore, they will sometimes be required to act as night patrols in the vicinity of the base. At present they are not suitable for this for two reasons: 

(1) Complement of Officers.

The complement allowed is a commanding officer and two executive officers and, under war conditions, it is almost certain that they will be employed from dawn to dark sweeping and that, in consequence, any night patrol is not likely to be fully efficient. The complement should be increased to a Commanding Officer and three executive officers.

(2) Ammunition allowed for practice purposes

The ammunition allowed for practice purposes in Halcyon Class ... is in my opinion inadequate and ... it is all allocated for day firings. I consider that the sub-calibre allowance should be trebled and that the full calibre allowance doubled, the extra full calibre ammunition being allocated to night firings. 


Comments on report:

A minesweeping flotilla composed entirely of HALCYON class is eminently suitable for despatch at very short notice to any point where it is likely to be required. The Flotilla is practically self contained, but it will require the assistance of a repair ship or repair base.

The minesweeping trials carried out in September 1936 proved that our minesweeping methods are sound in principle, and that by comparatively simple modification of material, i.e. arming sweeps, we should be capable of dealing with any anti-minesweeping devices known to us.

Considerably more experience is required in the tactical employment of a sloop minesweeping flotilla and arrangements are being made with the C in C Home Fleet for the 1st MSF to work in conjunction with the Home Fleet in 1937.

It is hard to see how gunnery efficiency can attain a very high standard with the present allowances of ammunition. I consider that a flotilla armed with two four inch guns and provided with director training would be able to make some combined use of their armament by day, and they should be individually efficient by night. They may be expected to make long passages where they may be liable to be attacked by enemy light aircraft, and they have not the speed to avoid action.


Source: ADM1/9362 Halcyon Class Sloop Minesweepers Remarks


23 November 1934

Letter from SO 1st MSF, HMS HALCYON to Captain FP & M Portland

It is understood that one feature of Halcyon Class lies in the possibility of mass production in case of necessity. Six month's experience having now been gained in HM Ships HALCYON and SKIPJACK in service in the 1st MSF, the opportunity has been taken of placing on record points where it would appear improvement could be made.

These remarks are forwarded not in the spirit of carping criticism, but with a view to the evolution of the perfect sloop-minesweeper, if such a combination is, in fact, a feasible proposition. General impressions are contained in the body of this letter. More detailed remarks are contained in the appendices (not shown here).

It is emphasised that experience has been gained almost exclusively in the role of minesweeper. It is therefore, with some diffidence that remarks on sloop performance are included. Should wider experience of sloop work and capabilities be desired an opportunity will present itself early in the coming year ahead when it is suggested HARRIER and HUSSAR should proceed on an extended cruise.

Speed: The maximum speed which will apparently be attainable on service will be but little over 13 knots. Is this sufficient?

Armament: The 4" HA gun is not supplied with any form of HA control and its AA capabilities are, therefore, limited. The height of the trunnions of this gun is such that loading is difficult and slow, the rate of LA fire being less than the after 4" gun and well under the capabilities of the control. 

Depth Charge Arrangements: No anti-submarine exercise have been carried out, but it is anticipated that greater depth charge efficiency would be obtainable with the depth charge release apparatus situated on the navigating bridge instead of, as at present, on the flag deck below the bridge.

Minesweeping Work: This matter has been investigated in a series of trials, the report on which is contained in my letter dated 11th November 1934. The conclusion reached is that the ships have a poorer performance than Twin Screw Minesweepers ... they lack one knot of speed. Whether this lack of speed is due to lack of power or to inefficient propellers, is not clear to me, but it is hoped that sufficient information is available in my letter of 11th November for the reason to be established.

Leeway: It is suggested that proportion of windage area to underwater area is greater than in any other class of ship except Aircraft Carriers - certainly than in TSMS. The 'sloop characteristics' are presumably governing factors in the above water form, while the shallow draught is required solely in virtue of minesweeping duties. This disproportion makes the handling of the class difficult when taking up a berth alongside or between buoys at a trot in a cross wind in narrow waters, the leeway made being very great. Ability to berth and to proceed to sea quickly in congested harbours is considered an important factor for a minesweeping flotilla.

A more serious matter of leeway is the loss of efficiency when sweeping, not only in respect of the lateral drift, but also in respect of the practical difficulty of selecting the sweeping course and of 'making' a danbuoy accurately, with the consequential risk of leaving unswept ground. The alternative of increasing the overlap of the danlayers while minimising the risk referred to in the preceding sentence, will decrease the area swept in a given time, and thereby reduce the sweeping value of individual ships. The difficulties regarding weighing of danbuoys are fundamentally due to the high Forecastle.

These considerations prompt the thought that the desiderata for sloops and for minesweepers are such that a combination in one ship of both types is not likely to meet with complete success.   

H G E Ackland




The HALCYON and SKIPJACK are the first of their class; improvements have been made in the machinery of later ships of this class and in these there should be less difficulty in maintaining the requisite power and speed. Be that as it may, there is no question that the class as a whole has no reserve of power over what is required for war minesweeping: the main reason for this is that the class was designed with severe draft restrictions and with a view to rapid reproduction in the event of war; in consequence, the reciprocating engine as opposed to the turbine was chosen. Broadly speaking, for any substantial increase in power it would be necessary to fit turbines which, apart from limiting production, are not so thoroughly understood by the personnel who are likely to man such craft, namely the Royal Naval Reserve.  

The high forecastle which causes increased leeway is there on account of the duties of the class as a sloop, and also as an aid in making passages across the oceans. If there were no limitations as to draught, then this leeway could be reduced; hence in design there is a conflict and the problem of leeway must therefore be solved as far as possible by seamanship. However in the two minesweepers about to be ordered, the forecastle height will be cut down, the freeboard at the stem head being reduced by 2 to 3 feet and at the forecastle break by 6 inches.   

It is clear that, in the view of the captain of the HALCYON, in a sea of 5 her speed would be reduced to 7 knots, mainly on account of the propellers racing, and so she would not be able to sweep in this state of sea in any case.

There are a few remarks as to strength, but on the whole the construction is similar to that of an ordinary sloop and much stronger than in destroyers. In a few instances there is evidence of defective work.

The chief criticism is on speed and it is stated that the maximum speed on service will be a little over 13 knots. The speed approved in the design of these vessels (HALCYON and SKIPJACK) 16 - 16 1/2 knots. As a result of the trials the HARRIER and HUSSAR were fitted with another type of propeller.

The staff requirements for speed of minesweepers and sloops was 18 knots, and at a conference held by Controller on 5/5/32, this was passed by DCNS if it could be provided without difficulty or extra cost. 4th Sea Lord (Admiral Preston) was of the opinion a maximum speed of 16 knots was ample , and it was agreed a maximum speed of 16 knots was acceptable.

Note: The convoy sloops are of 18 knots speed and the estimated costs of a convoy sloop, ordinary sloop and minesweeper sloop are as follows:

    Convoy Sloop              170,000

    Ordinary Sloop            150,000

    Sloop-Minesweeper     110,000

I propose to increase the design speed by 3/4 knot by increasing the power 25 percent.

Another serious criticism is in the leeway made when sweeping. Compared to the Town Class of Minesweepers, there is a greater area of profile. This results from the fitting of a forecastle, Town Class having a bulwark only round fore deck.

As the design was intended for service as a Sloop a forecastle was considered necessary, more especially as alternative quarters for the crew during minesweeping was an important feature. 

Further than this, at the Conference on 8/5/32 the 4th Sea Lord stated the Town Class had proved themselves to be very good sea boats, but it was generally agreed they would be greatly improved by having a raised forecastle and this would be embodied in the new design.

The inadequacy of the arrangements for carrying, laying and recovering danbuoys and the difficulty in handling the war sweeping equipment are serious limitations on the operation of the vessels.

It is submitted that the statements contained in this report, if they are confirmed, indicate that the strategical, tactical and operational performance of the Halcyon Class falls short of requirements to a serious degree, and that action is required to obtain improvement in these ships and those now under construction. 

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