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
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
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
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:
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
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
H G E Ackland
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
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 2½ 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
16 - 16 1/2 knots. As a result of the trials the HARRIER
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:
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
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
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.