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“ll MODEL WATE ~Radio Control Yacht Research Lt.-Col. C. E. Bowden discusses his experiments in the first of three articles Fig. 1.—This large 9-ft. long test radio-controlled model, 1/5th scale of an American wide beamed racer cruiser, has great stability, and good helm balance in spite of its so-called “unbalanced” shape. Note the wide after-sections acting as an anti-pitch support in the water to leeward aft. Since the Americas Cup Races, several groups have been taking action in research and development, notably the Red Duster Syndicate, the Australian Syndicate, and three other groups in this country interested in producing a future challenger. The Saunders Roe Tank Dept. has installed a revised dynamometer on American lines, and is looking into American methods. A prize has been offered to encourage match racing between helmsmen in various well known classes, in order to emphasise the special sailing technique necessary in this direction. Yacht research ACHT Research has received considerable impetus through Britain’s heavy defeat in the Americas Cup, which brought to notice the American superiority in hull, sails, and sailing technique, in these races. Research is of value to yachtsmen if significant findings are made public, and benefits through constructive criticism to check possible mistakes. Many yachtsmen in the past have been notoriously conservative. This attitude is now changing for the better. History has shown that almost every advance in yacht design has initially been strenuously condemned. For instance, we read that the use of lead ballast was regarded by the experts of the day when it was introduced, as so dangerous that a yacht so fitted was sure to either “tear itself to pieces or plunge under,” and of course the most horrible fate was predicted for the first yacht hull made from iron. The spoon bow, almost universally used today was denounced with its originator in no uncertain terms. Only a few years ago scorn was heaped upon my unmindful head by one or two “experts” of the time writing in this journal, when I advocated radio controlled model yacht racing after Mr. Honnest Redlich and I had sailed the first dual race, without The Yacht Research Council of a few years ago died for lack of contnued financial support after having done some excellent work which in my opinion ranked as a second milestone in research history, following the great work achieved by the much earlier American Warner Experiments on sail. The Warner findings had a very considerable influence on modern rigs, scientifically proving the close relationship between the fundamental action of the slow speed aircraft wing and the sail, and pinpointing the reasons for losses in the latter due to aerodynamic “twist” and “mast interference”. The importance of low pressure flow in lee of a curved sail, as in the case of the wing, was not properly understood before these experiments. radio interference, around a triangular course at Poole, thereby introducing the thrill and fun of tactical manoevre under full-scale yacht racing rules. This was aggravated when in addition I mentioned the value of more “upright” sailing providing increased performance, glass-fibre construction for model hulls, and appealed for a more moderate view on planing From this the “airfoil” action of the modern keel was later more clearly understood. Unfortunately the Yacht Research Council pursued a “confidential” policy except towards those like myself who, however modestly, financially supported their work. Thus the public’s attention was not fully conscious of the value of their work. model hulls and the rigid conception of the “symmetrically” balanced closely matched ended hull. My statement that the aerodynamics of the slow speed aeroplane had materially affected sail aspect ratio, reduction of rig drag, and the design of the modern “hydrofoil or airfoil” keel, embroiled me in some .vitriolic denunciation which today looks rather amusing. I draw attention to these points because they have since been, and still are, the subject of research in several different quarters, as we will see in these notes. My chief critics are now belatedly interesting themselves in glass fibre hulls for radio racing. It is certain that life never stands still, and much water has flowed beneath many different types of hull since those days. It will be surprising if these new notes do not generate some heat! Very briefly, and I fear inadequately, it can now be said that the Yacht Research Council’s instrumented full-scale trials, and tank tests, carried out on a 5.5 Metre and a Dragon keel yacht, for the first time scientifically confirmed the value of certain practices well known to most of the leading keel boat helmsmen, thus dispelling much controversy on the matter. Thus, in brief, the model tests were closely borne out in full-scale practice which was useful additional confirmation in respect of the value of models in research. It was proved that beyond an optimum angle of heel a keel yacht’s performance falls off sharply, and also on a conventional yacht the best advantage in speed to windward is to be obtained by achieving smaller angles of heel. “Freer” sailing in windward work did not produce such good speed and ground 278 JUNE, made course good sailed to windward by as “feathering” did a skilful closely to sinuous windgusts, thereby holding the hull more upright. This upright- ness creates lower hull resistance, and greater effici- ency for the “hydrofoil” keel action. Tank tests have also proved that a heeled hull offers greater resistance asthe heeling increases, and when heeled rail down or under, the resistance rises alarmingly. As a keel boat must heel to gain some of its stability, there must be some heeling, but the lower this can be achieved, by beam, a “stiff” hull design, sailing technique, and a moderate height rig, the better. How often one has seen model vane racing craft heeled ‘ with rail awash, thereby creating maximum resistance and reduced windward work from the keel. A new organization, the Yacht Advisory Committee, with a number of well known scientists and yachtsme n of experience sitting upon it, has recently been formed under the chairmanship of Mr. Handel Davies, the Deputy Director of the Royal Aircraft Establishment, Farnborough, with Professor Richards and the Southampton. University’s facilities in buildings, staff, windtunnels, and forthcoming towing tank, as a base. Information gained will be made available, through the University Yacht research library, to anyone interested. Financial support from the Public will be vital as time and work proceeds, for research work is expensive. Since I am a member of this Committee, it is only fair to emphasize that any opinions expressed in these notes, written in three parts, are not necessarily thos2 held by the Committee. My American friend and collaborator in yacht experiment, Dr. Austin Lamont, is assisting the Committee’s work in a number of ways, and is having various keels and leeboards tested in the Saunders Roe tank to assist in keel research. Modern leeboards designed by the well known Dutch expert Mr. Van Kuyck, take advantage of the aeroplane’s slow speed airfoil with undercamber, or concave undersurface, for windward sailing, thereby gaining the maximum of high pressure lift to windward below the board’s section, and low pressure “suction” above the board in the water. The windward board is of course retracted. It is interesting and of value that these keel and leeboard tests are to be done on a model hull which was initially tested in the well known Stevens Institute tank of America, which tested Columbia, the Americas Cup Winner. The model to be used was designed by that highly successful American designer Mr. Phil Rhodes. Furthermore, this model hull has already been built full-scale, and last season won its first races against the fastest of its kind in America. The craft is over 70 ft. L.O.A.. and a typical modern American big beamed shallow draft “wedge” shaped hull, which does most of the cruiser race winning nowadays. It is also intended that I shall build two identical models in glass-fibre of the model, to test keels etc. by radio controlled comparative sailing in open seawater. In this way we hope to obtain correlation of tank, radio test technique, and full-scale results, as the radio test technique, which I originated with the invaluable help of three friends, is something new in yacht test work. The three friends are well known in the radio model world, 1960 being Mr. J. C. Hogg, Mr. Bob Curwen, and our old friend Mr. George Honnest-Redlich who started me off on radio yacht racing interest. Radio tests on a large American model are illuminating During the past three years or so, I have sailed a 9 ft. long model on open seawater, designed by Mr. Phil Rhodes, which is a typical modern fast racing cruiser, like his famous Carina, the winner of so many events in our waters, and similar in concept to the 70 ft.+ hull he also designed and which is to be used for keel tests as mentioned above. The model is 1/5 th scale of full-size, and has a very big beam, shallow draft, long lean entry, with the modern American “wedge” shaped afterbody, in which the maximum beam is situated well aft of centre. The designer calls these hulls—‘big dinghies pulled out.” Practice has proved them to be generally faster than our more conventional craft of narrow beam and tucked in tails. Even the Americas Cup Twelve Metre Columbia and trial yachts, which were so much faster than our more “symmetrical” challenger, were modified versions of the wider stern theme, and it therefore behoves us to take note if we wish successfully to put up a challenger in the future. The interesting fact observed on the 9 ft. model on all points of sailing under radio control, is that this so-called “Unbalanced” hull is in fact very well balanced on the helm. We have been able to check this by observing a pointer, as the model is sailed past the observation launch, and recently helm alterations have been recorded on our models on a rotating chart mounted on a drum, designed by Mr. Hogg. These American hulls can be sailed more “upright” by virtue of their beam, and the wider anti-pitch stern aft adds to stiffness. Thus there is a lower hull resistance and greater sail carrying capacity. See Fig. 1, which shows the model sailing windward with the rudder quadrant showing only the trace of weatherhelm so helpful in windward sailing. Radio tests of the so-called unbalanced hull My American contacts, including a visit to this country by Mr. Rhodes, and the Arnericas Cup results, have taught me that there can be more in good hull balance than in the rigid British conception of the nineteen thirties and forties, of the very closely matched ended hull as netessarily being ‘the only answer to a well balanced model hull. In the full-scale world of British yachting, this conception is not so Fig. 2.—The author’s design for a light displacement cabin cruiser in model form 7ft. 6 in. long, }-scale of full-size. The model is made from glass fibre and is fitted with his fully rotating, and folding, low aspect ratio DELTA rig, the radio box being protected by a detachable moulded glass fibre cabin. Various conventional rigs are being tested in comparative sailing trials on two identical hulls from the same mould, sailed by dual radio 279 MM Fig. 3.—The Delta is seen sailing full-scale on the author’s test Flying Fifteen ull. Note that the rig rotates with the win d, and is balanced on all points of sailing. The model seen in previous photograph accurately forecast performance found on the full-scale craft the the Braine up for close hauled model sailing. That model sailed an exciting course very close to the wind, a matter of about two miles before being retrieved by our club boatman in his power launch. After this episode with an “unbalanced” hull generally condemned by the model experts, radio trials began, and since then a friend and I have sailed a number of convincing radio controlled trial “races” around various shaped courses, between _ the “symmetrical” very closely matched ended “A” Class hull shown in Fig. 4 of Part II of this article, and the modified Fifteen model. On average, in medium to strong scale winds, the Fifteen has proved faster and slightly closer to windward with far less pitching, with better manoeuverability and quicker acceleration after going about, than the “A” Class model. Light wind tests have so far not been made, when it is conceivable the heavy “A” hull might win. A low rig has been used on the Fifteen, with a genuine cutaway fin keel. These tests led me to make three glass-fibre Ten Rater type hulls from a modified and even wider transomed “Flying Ten” shape. We have learnt that even such an ultra model shape steers well if sailed reasonably upright, and has remarkable acceleration. rigid as in the model world, and in a number of quarters it is changing towards the American outlook. It fails in bad weather, being too wet for radio, with its very low freeboard, and a measure of unbalance I would refer readers to the discussion on the matter by “Argus” in the March issue of “Yachting Monthly”, if they are particularly interested in the problem, or have dreams of designing a model twelve creeps in. From the above two experiments I designed what I conceive to be a sound compromise for radio in two light displacement hulls 7 ft. 6in. long, being 4 scale of my thoughts on a 30 ft. light displacement full- metre for adoption full-scale. The American concept does, in actual fact, very successfully look after balance of hull buoyancy equality fore and aft as the hull heels, through skilful design, as I will endeavour to explain in Part II and III of these notes. It will be recalled that Mr. Waddington in 1950 surprised the model world by winning a ten rater Championship with a scaled down Flying Fifteen planing type hull with cutaway fin keel, and thereby creating some undeserved unfavourable comment for what was a very laudable departure from the conven- scale racing cruiser. See Fig. 2. tional. I knew from sailing our full-scale Flying Fifteen, and comparison with my full-scale fully displacement “X” One Design keel boat which I have raced for many years, that the light planing keel boat Fifteen hull, in spite of its so-called “unbalanced” hull form with wide planing transom, did in fact sail to windward very nearly as well as the weatherly “X” boat. The latter, like all fully displacement craft, model and full-scale, can only surge along waves in a strong breeze off the wind, whereas the Fifteen can hold a genuine plane, rising onto the top of the sea. I therefore decided to carry out some protracted research on models of the planing type, and see exactly how much there was in the “unbalanced” These hulls have proved excitingly fast and can take almost any sea, whilst keeping the radio dry because of greater buoyancy, shallow draft, big beam, high freeboard, and a detachable moulded glass-fibre cabin to cover the already waterproofed radio box. Two hulls were made from the same mould’in glass-fibre for comparative sailing trials of rigs and keels. The. hulls have instantly detachable cast bronze keels, whilst tangs fit into “centreboxes” in the hulls, and the top of the tang is retained by one pin only. The hulls fit into carriers fitted on the floor of a car trailer for transport in test work. In spite of their relatively large size, a single hull can be easily transported and operated by one man. Full-scale rigs developed through radio models A powered sea-sled was developed from a 5 ft. radio model, and four unusual sailing rigs produced in large model form later proved very similar in sailing characteristics when fitted full scale to a dinghy, a Flying we employ for Fifteen, and a six-ton cruiser which test experiments. up the large expanse of Poole harbour seawater. My latest fully rotating, folding one man delta rig, (patent applied for) was last season sailed on the fullscale Flying Fifteen with success, after all development work had been carried out on large radio-controlled models. This rig is being tried during the forthcoming season on our cruiser Tentative, to see whether larger size in such a rig is practical. This rig can be seen sailing in model form in Fig. 2. and in to the gusts, whilst the Braine gear sailed her off before luffing too much. I use Braine because Vane is The complete similarity will be noted. As a result of the model development no modification had to be model theory. I built several glass-fibre modified Fifteens of the same average length as an “A” Class hull. The first test sail with a low rigged Fifteen was an eye-opener. The model escaped by mistake close hauled under Braine gear, and pursued a lovely close winded course There was a stiff breeze, and the hull luffed nicely full-scale in Fig. 3. not practical with the long boom of a low rig. I link 280 made full-scale. | — ee MODEL MAKER) Part Three ¥ig1 Quorter beam buttock by = — John Lewis ee 4 EAS month we cons idered establishing a profi le and midship section and now it is time to look at the plan. Much time is spent look ing down on the deck of a model and it is well worthwhile making sure the deck plan There is no reas on for it to be distorted to Satisfy any gimmick in design and it should flow harmonio usly from bow to stern . So far, the only points fixin g this curve are the bow endings, the midship width and the length of counter, but the width at this Point is not decided. As a guide the width of a 10-Rater stern should be about 34in., and 44 in. for an A boat. There is nearly always a tendency for the beginner to draw the deck plan with the ends too fine and “spikey”, On the 10-Rater, a good shape can be achieved by crossing the quarter beam buttock line on section 10 aft and about Hin. aft of sectio n 0 at the bow. Similar Point s of check on guarter beam an A boat would buttock 44in. forward of section 0. aft on 10 be crossing and 34 in. Of, course, these points are arbitr ary and are only intended as a guide. Length of overhang and height of freeboard influence them a great deal, but you will find that they are in keepi ng with the other figures previously given. The actual curve through the point of maximum beam should be balanced; that is the width on section four should be the same as on section six. Aft of section six, the line will Straig hten out in comparison with the bow curve—but only slightly. Heeled : Typicol Yacht Design is attractive. Oeck fine ie woter lin ‘ ; Atel lke + c L.WL curve 10 and here again experien ce is the great help in designMuc ing. and h has been written about form Tesistan ce angles of entry and delivery but we will by- Pass all that and simp ly sweep in a an angle of 45° is reached at curve balanced the aft end of the L.W.L. and centre line. I must emphasise that the lines so far drawn determine the whole character of the hull so make quite sure that you are well satisfied. It is in these lines that the individuality of designers shows, as, so far, the design has been pure art. We now have to get down to a sessi on of mechanical drawing. From stations 1 to 9 we have 3 point s to determine the cross sectional shap e on each station, and with the Dixon Kemp curve s used in the same relative position as for the midship section it is possible to draw in a complete set of tentative sections. The shape of the overhang sec- tions can be quite accurately judged. It should be the aim to continue the gener al form of the midship section throughout the hull from end to end. If the quarter beam buttock curve is now drawn on the profile view, the under water parts of the cross section can be more accur ately faired up. The shape of this buttock about the L.W.L. will be somewhat tentative at this stage. As a further check on these sections draw in a coupl e of diagonals and set them fair. You will find that with the waterl ines your splines will be used with the thin end towar ds the ends of the boat, but the revers e is the case with the diagonals. I am not going to describe in detail the actual process of fairing up a set of lines, as it is too well ? ~_C in” wedge LWL LW. “Out” wedge Fig 2 Part body plan sum is multiplied by 2, the product multiplied by the showing distance between the sections (5.5in. if the L.W.L. is 55in.) and divided by 27.7; this divisio n is the in— Out wedges. Pod out here on forward section: number of cubic inches of fresh water in 1 Ib, but if the yacht is an A boat, it is conven ient to use 27.0, as this is the salt water figure. The result of this simple sum is the displac ement of the canoe body—remember we have to add the volume of the keel later. To find the position of the centre of buoyancy each section area is multiplied by its section number, and the sum of these products is multiplied by the section spacing. Into this figure divide the sum of the half areas and the result will Narrow Deck line | Fine down here ‘on oft sections L.W.L Fig 3 ~ be the distance from the forward L.W.L. ending of Correction of sections to reduce movement described in the books mentioned in the first article of this series. It is now advisable to check the displacement of the hull and also ensure that the centre of buoyancy does not move appreciably when the yacht heels. The calculations are quite simple, particu larly if they are set out in table form as shown. The area of each half section is measur ed and this aft of centre the C. of B. of buoyancy on heeling , This is the upright position, and we will now 292 JUNE, 1960 check° to see what movement takes place when the hull is heeled. Draw the heeled waterlines across the body plan 8 is added to the respective section 4 areas and the 28 gaz centre of buoyancy calculation is repeated. There $2 425 S32 S28 and measure the areas of the “in” and “out” wedges of the heeled sections. The difference in these areas 3 pe 2 53s Pee will be one difference, usually on section 10, where 3 se 3 32 <8 3 & oes 2 oo se) $3 49 i© eee Ve =§ 3 eae oO 3g 3. z Bg8 Ss3e 388 ABOS Eaz 9} 900 | x 0 Let it suffice to say that this is a mathematical necessity. 2| 3| #70 | x 2 9-40 | 4:70 | 2:50 | 690 | 13-80 820 | x 3 | 2460 | 640 | 4-00 | 10-60 | 31-80 moved aft, but if the movement does not exceed BAS You will probably find that the C. ~; 7 of B. has 5| 0.15 in. you are near enough. Should the movement be greater than 0.35in., it is probable that the deck plan and the L.W.L. plan require modification. It could be that the deckline aft is too full or too 7)| 0.35 in. can be corrected during the completion of Ul narrow forward. A movement between 0.15 in. and the hull lines. Modify the tentative sections by either filling out the L.W.L. in the after sections. 1 -70 ; >a Sule ela el PE A ; as ca 2 opposite treatment can be given underwater. When 126-40 are again fair, go straight on and complete the (Section ocks. i Oiler Wesst nes, pad, HUHOCKs Take great care in drawing pacing) Note Put g good quality paper divided Put in WOths. under area to be measured and count squores. Tedious but accurate. these lines and do 632000 63200 27:7 leas -200 buttock waterlines pleted. are com- of squared paper ; 0-00 3-10 3-10 ihe re ko cine : 6:60 4-40 | 10-40 | 72-80 Mathes ge aren ites win 316-30 , 5:5 8-10 ; 3-20 Fei atu! estas sd oe. aike thos3 : {hic elatint 5:90 | 14:30 | 71-50 1-00 iy Total 3-70 | 33-30 on 82:50 158150 5-5* 3082500 1581500 ——_- a0 416-50 208250 —— 82-5 = [2290-750 Sa As 27-76″ 27-52 (Position of C.B. Position of Heeled Aft of “O” Ss Fig. 4—_TABLE OF CALCULATIONS FOR 10-RATER CANOE BODY OF 55” L.W.L. buoyancy will be ofquite small. area is more thon half Mork : 1-00 25-09 Pounds Displacement Difference between Upright and Heeled 27 =76 27-52=0-24” (Movement Aft) Note.—This movement indicates some adjustment to sections is desirable. and centre ‘Count squares where Use the the repeat Now original calculations the and with luck the of movement Ignore Siborss half \ is less thanwhere area eg 5 I find it convenient to leave diagonals un- til : 2-40 = 55% 63-2 {1739-650 not be in a rush. Remember that an alteration to a waterline must be reflected in an alteration in the sections and buttocks. 1-70 1:50 | x 9 | 13-50 Total 63-20 – L.W.L., quarter beam buttock, and the diagonals 0:00 | 0:00 | 0:00 | 0-00 | 820 | x 7 | 57-40 pel Alternatively, the | 12:10 | x 5 | 60:50 9} in the bow above the L.W.L. or fining down above ‘ Py in the upright position the area is nil, and when heeled some area is 2 for the Ga “futhead This area, Z . immersed. purpose of calculations, is divided by 2 in the table. ‘ 5 e3 should not be allowed under any circumstances. With practice it will come down to about 0.01 in. which is just about as small as can be calculated. It is quite rare for the centre of buoyancy to move forward and this Do not lose sight of the fact that be beautiful. It helps greatly if the away for several days and brought a fresh look. It is quite surprising show up after a rest. the yacht must drawing is put out again for what blemishes TEST BENCH The Aerokits Patrol Torpedo Boat This largest of the Aerokits range has been available for some months, but although we handled the prototype and have seen examples of the model performing, we had never examined a kit until recently. The prospective purchaser would want to know what he gets for his £5 16s. 8d. and we can assure him that he certainly gets his money’s worth. The amount of work put into this kit represents at least two thirds of the building time of a boat of this size; all parts are in good quality ply or hardwood and every part required is supplied ready-made and shaped. There are even nicely moulded little plastic guns and turned torpedoes. The standard is what one expects from Aerokits—sound design, both structural and hydrodynamic, backed up by the quality and prefabrication mentioned. The 40 in. hull has an 11 in. beam and is quoted as suitable for 24 to 5 c.c. motors. Most of the examples we have seen have been powered by 34 c.c., which produces a very fast and lively boat. As a vehicle for radio control this model is excellent; the hull is divided into six separate compartments and a deck hatch lifts off to provide access to all bays. If you’re looking for a bigger boat you should certainly consider this, 293 ST \\ MODEL MAKER : class boat, i.e., length 110 ft., beam 17 ft. 0 in., which was of similar construction to that of the “A’’ class boat. The “D’’ class dimensions were length 115 ft., beam 21 ft. 3in., and the hull lines were different to that of the ‘‘A’’, “B’’ and “C’’ type boats. The first series of “D’’ class boats were built as M.G.B. after which the gunwales Ceiviiclinies | An elegant little wallet of chrome vanadium B A. spanners in the hard- to-get model sizes is presented to all ‘Readers Write” correspondents. C STORY DEAR Sir, I fear that on page 221 of the May issue there is a mistake — the Fairmile “little ship’’ is not a “D’’ but a “C’’. I notice that the error is repeated in the drawing on the previous page. The design you illustrate was, I believe, classed as a motor launch in its early days, so the M.L. 316 on either bow is probably correct. The boats (let’s not argue about ships and boats!) were armed as gun boats in order to counter the German E-boats; soon they were re-classified as gun-boats and numbered accordingly, so that in this case M.L. 316 would become S 316. Later they were re-armed and the one I commanded, were scolloped for two 21-inch torpedo tubes. After M.T.B. 724, all this class were fitted with four 18-inch torpedo tubes and fitted for mine laying equipment. During W.W. II they were the most heavily armoured M.G.B./M.T.B. in the world having four torpedo tubes and no less than 12 guns. Some of the “D’’ class hulls were converted for long distance Air/Sea rescue launches to operate in Eastern waters. If notes on the various armaments of the “D’’ boats are of interest, here they are. As M.G.B.s. 2 pdr. pom pom in power turret forward, two twin .5 MG.s in power turrets either side of bridge, one twin Oerlikon in power turret aft, two twin .303 M.G. on bridge, one Holman illuminant projector. Two depth charges. Subsequently two 21 inch torpedo tubes were fitted as additional armament. as M.T.B.s. Final armament ofthese craft was follows. One six pounder automatic power turret forward, two twin .5 M.G.s in power turret either side of bridge, one twin Oerlikon amidships, one six pounder automatic in power turret aft, two twin -303 M.G.s, on bridge. Four 18 in. torpedo tubes, two depth charges. As the original design displacement increased from 91 tons on trials to over 120 tons, so the speed decreased from 31 knots with no distinction, eventually carried two to 26 knots maximum. Later 2-1 gear boxes were fitted which increased the speed to 29 knots maximum. twin ‘5 Vickers guns and a third twin Oerlikon amidships. In addition, a pair of Vickers K -303 guns were mounted port and starboard immediately abaft the bridge. The bomb projector (shown in the model, amidships, but not on the drawing) was smartly returned to wherever drain-pipes are made, whence it should never have come in the first place! Eventually, too, the mast became a Chvistmas tree of R.D.F. (not Radar in those days!) aerials and the dinghy, in most cases, was put ashore and replaced by a raft. I mention these details because, unlike the types B and D, this type (and the ‘‘A’’ class M.L.) was not well known, was few in number and yet under the command of some of my brother officers took the strain in the Channel and southern North Sea for a long time, fighting stoutly without the glamour which shone round faster, or larger, but later boats. I suppose that for its size the C class gun boat was the most heavily armed of Coastal Forces vessels. Unfortunately, although re-armed, they were Wymering, Portsmouth. 2-pounder pom-poms in place of the two Rolls 2-pounder guns you show, twin Oerlikon guns in place of the power-operated never re-engined, so that as so often happens when one puts on weight in middle age they became slower and slower; I recollect a top speed of about 22 knots at the end of re-arming! There is one compelling reason for perpetuating this type of boat by modelling it — so far as I know it is the only one in which Coastal Forces gained two V.C.s in one action. That was at St. Nazaire when a C class gunboat led the attack (I don’t recall its number) commanded by Lieut. a Curtis, R.N.V.R. who received a : Oxford. $.331. D LIGHT DEar Sir, As one of my hobbies is that of collecting photographs of M.T.B.s and M.G.B.s, I was interested in the photographs of the Fairmile M.G.B. in the May, 1960, issue of MODEL Maker. However, I feel that a mistake has been made in classifying this as a Fairmile Type “D’’ boat. The hull lines, superstructure, and armament is that of the “C’’ A. HUNT. TYRING DEAR Sir, I have wondered for some time now why the models raced at Southport, Aintree, and similar model car race meetings are described as 3 scale models. In your review of electric car racing in December’s MopEL MAKER, there was a table of whéel and tyre overall diameters, from which I gathered that the tyre sizes made for a 3; scale Grand Prix car, say, were | in. or 26 mm. for rear wheels and + in. or 23 mm. for front wheels. If a model is to have scale appearance surely its wheels must be fairly true to scale. Modern racing tyres vary a great deal in overall diameter from race to race, according to circuit, drivers’ requirements and so on, but I would be surprised if they were often as much as 32 in. across. I believe S.M.E.C. wheels were first on the market and their series of kits included cars like pre-war Mercedes-Benz, which did fit huge tyres, and obviously so long as models from different areas of racing are competing with the same tyre sizes, some of them must be out of scale, but if we are going to claim a scale, I think we should make at least some concession to modern trends and take it as about 1/30th. I would also be interested to know if any of your readers think that 6-volt model car racing could prove interesting. Several members of our club recently made 6-volt cars costing less than 10s. each, and while obviously, not as fast as 12-volt models, they were very promising. As well as providing would-be enthusiasts with a cheap means of trying the hobby, it could develop into a proper ‘“formula’’ where skill would be needed to make up as much as possible for the lower power available. The Japanese motors which you have reviewed in MopDEL MAKER, are surprisingly powerful for their size and fit quite easily into models of production cars, enabling a complete model to be made for less than 9s. Clapham Common, London, S.W.4. I. M. CALVERT. 306 RAILLERY DEar Sir, 1/32 Scale and Southport Standards. I must take up the cudgels with my good friends of the Sale M.C.C. and I trust they, in particular, will take my comments in the spirit they are intended. First let me say that I am full of admiration and envy at the cars produced by the Sale members and I only wish I could emulate their skill and craftsmanship, but when they mention “Southport Standards’’ I blush for them because the guide rail on their track (mot the new one) is not to Southport Standards in the one essential dimension of height. Having thus pokeda fair-size hole in their front let us be serious and constructive. If we say that cars are to be 1/32nd scale precisely, then I doubt if there is a single car in existence, including the Sale cars, which would pass the scrutineers. We must, therefore, find some tolerance acceptable to the majority which gives a reasonable result. It is no use Mr. Barnes blaming the manufacturers for not making things right as he sees it. The very few people who make things for our sport, may they be preserved indefinitely, must operate on a paying basis and must, therefore, produce on a compromise basis if the resultant article is not to be priced out of reach. Not all of us have the skill or facilities to produce for ourselves and must rely on what is commercially available. This is also an important factor in attracting new blood to the sport which is vital to its virile continuance. I personally agree partially with Mr. Barnes that some tolerant control is necessary if rail and slot racing is not to go the way of diesel racing and the cars become mere projectiles on four wheels. A tolerance of +1/16in. has been mentioned as being a “generous’’ allowance. I think this is not only ungenerous but impracticable to apply considering the commercial parts available, and open to considerable argument if we try and measure from centre line to centre line. My own personal view after making a lot of tests with commercially available components us that a tolerance of plus or minus 1/8 in. would be a reasonable limit. I have had about 30 years’ experience of full scale motor sport and if I draw up any rules or regulations I always apply one acid test. Is it easy and practicable to apply and enforce? If it does not measure up to this I throw it out and start again. I would point out here that the original Southport folk in compiling their standards, and they have stood the test of time rather well, wisely omitted to insert any such rule and merely added an absolute maximum width. This doesnt mean that I agree with all they do or have done by any means. For instance, the use of the Walshaw tyre with the three ribs is so far out of scale as to represent a full scale tyre of 11 in. section. But I must add a word of warning to the purist — I know of a well-known 1500 c.c. car which has two spare axles both different in track from the standard, which in effect gives a choice of three tracks, whilst in the matter of bodywork a recent account of a race meeting in the technical press had pictures showing at least six variations on the Cooper body. Turning to tracks, it is really ratheTM naughty of Mr. Barnes to complain that his cars need maior modifications to run on the standard rail when his own rail is nonstandard. I sympathise with him to a certain extent re the return strip, but my own club track is placed in a cellar — it suffers badly from damp after really heavy rain and these conditions have had quite a considerable effect on the track ‘‘standards’’, Fortunately, however, the return is 3/16in. wide strip so that the variation has little or no effect and any car made to run on a wire return should and in fact does have no difficulty. I think that these are all matters for a national association and I have put down on paper some ideas and comments which the JUNE, 1960 Aintree M.R.C.C. RAIL TRIP? DEAR SIR, With reference to the letter “Let’s be sticklers’’ in Readers Write last month. I am a complete stranger to model car racing myself. Yet it seems strange to me that the Hon Secretary can be so fussy over + or — 1/16 in. and yet completely ignore a dirty big rail sticking up from the road. Does he think that if he was shown two models of a car, and was told that one was, say, } in. out of scale, he could say which it was? Could he also tell us whether competitors are disqualified on his track for exceeding the scale speed or using more than the real voltage? Perhaps he would care to design a tyre which will give the effect of having scale tyre pressure? No doubt he has reasons, but I’ve a feeling he’s going to be awfully lonely. WRIGHT. Farnham. B.Sc. NOT INSISTED UPON DEAR Sir, I am a keen modeller, and every month I read your correspondence page. And I hope one day I will be able to get a letter printed, to win a set of your spanners. I am 13 years old and hope that when I have a BSC (eng) I will be able to complete in your columb as I feel well liked book will carry on for ever. A friendly Modeller, MASTER NEvit HOLLIs. Sheldon, Birmingham. R/C YACHT SYSTEM DEAR SIR, I have read with interest your article “Radio Controlled Yacht Class’’ in the May issue. From the point of view of design I can offer no constructive criticism or help. I am only the “‘pilot’’. The paragraph entitled ‘‘Radio’’, however, is a different matter. With reference to dual operation of two yachts from one transmitter, Over six years ago I designed and successfully used a very simple inexpensive method. Colonel Bowden and I sailed our two “A’’ class yachts using this system at Poole and I believe that mention was made in the pages of the MODEL MAKER and other model periodicals at the time. As often in other spheres, we were before our time. Radio in connection with yachting was in some circles a “‘dirty’’ word then. However, times change. In brief, for system is thus : those now interested, the Requirements— (A) Two normal reed receivers with 4-reed units of differing frequencies (ours were plug in, so that others using the same system could operate by plugging in differing reed units). (B) One quite standard tone transmitter (not the expensive simultaneous type). C) Two control boxes for four channels. (D) A “splitter’’. This is the crux of the affair. Of two types I have used the following is the simpler. A rotary switch, electric motor operated, switches the transmitter modulation from one control box to the other at a speed of approximately six per second. Both control boxes can be operated at the same time but only the signal of one is sent out when the other is mute or vice versa. Reeds and their associated relay circuits have enough inherent delay to accept each interrupted signal as a continuous one, but even if they will not quite, as most yacht actuators are motorised, a slight relay chatter does no harm. The beauty and simplicity of this method advertising columns of the MODEL MAKER one of their transmitters, which should even in these days leave them with some beer money. Richmond. R/C YACHT G. HONNEST-REDLICH, CLASSES DEAR SiR, Giving some thought to the requirements of radio control and the design of suitable model yachts, I cannot read recent correspondence without being tempted to put forward my own views. It is inevitable with such a problem that many peculiar ideas will be ventilated but I hope the controlling authorities will se their authority with wisdom and not be panicked into hasty decisions. First and foremost I believe that the existing rules governing the racing classes of model yachts can stand unaltered for some years yet. I also believe that these rules can cover the requirements of radio control. Some months ago when drawing the lines for a full size 5.5 metre I examined the possibility of using this rule for radio control and came to the conclusion that although an attractive model could be produced it would have no practical advantage over the 10 rater rule. It would have the disadvantages of difficult measurement, inflexibility after building, the need for accurate construction and an above average appreciation of design. It is not reasonable for Mr. Andrews to dismiss these difficulties by saying that all one has to do is build exactly to the drawings and let the measurer do the rest. How many model yacht builders can or do in fact build exactly to the drawings? No, there must always be room for the builder to do a little “improving’’ and room for the inexperienced to make mistakes; without this elbow room newcomers to the sport would be few. I once turned up to a 6 metre National Championship with one of the few yachts correctly marked according to the rules. The 5.5 metre class demands similar markings so past experience does not promote confidence in club measurers and their ability to insist on adherence to rules. Before further comments are made let me mention that I was an Official measurer for some years and I know how even expert yachtsmen dislike complicated rules which make it difficult for them to carry out small modifications to their yachts. Let us regretfully put the 5.5 rule to one side and leave it to the full size boys to play with—and incidentally what a poor job they are making of it. The second consideration for radio control was the possibility of a One Design; on the basis that the interest will be primarily a matter of technical development and ability to manoeuvre, the idea is quite attractive. There would be sufficient variation in performance for no diminution in the competitive element. One should also consider whether the radio control yachtsman is going to be a yachtsman using radio as his tool or a radio enthusiast using a model. yacht as his vehicle. I think the latter is nearer the truth and the case for a One Design is further strengthened as he could purchase quite cheaply a mass produced glass fibre hull. 307 But picture if you can the comments of all the other ‘“‘experts,’’ should a designer have the temerity to produce the “ideal’’ design. He would be advised to remain anonymous and that would be most difficult in itself. The proposition for a 6 rater put forward by Vic Smeed deserves careful consideration but the underlying reason behind the idea is to prevent undue size in the model. Let us face this issue fair and square. A model yacht smaller than an ‘“M’’ class is too insignificant on the water and anything bigger becomes a transport problem unless you are a car owner. The difficulty is amplified as the radio controlled yacht will tend to be left at home rather than in the club boathouse. Furthermore a large number of radio control enthusiasts will not be members of clubs. The 6 rater idea is a good one but let it be unhampered by trying to admit existing ““M”’ class yachts into its ranks. Except for the transport element Marbleheads are poor craft and it would spoil the fun to use a wet, nosediving monstrosity when a seaworthy good looking 6 rater could be so easily built. Now look at the existing classes :— (a) M. Class: a 6 rater would be much better all round. (6) 6 Metre: these are what Messrs. Tucker and Andrews say are the only real model yachts but the rule complication will I am sure prevent a revival. How ~~ Barnston, Wirral. is that quite standard equipment can be used. The only extra is the “splitter’’ cost; one 44 y. electric motor, one reduction gear, one piece of paxolin, pieces of phosphor bronze, nuts and bolts. Of course, this system can be developed. An electronic ‘“‘splitter’’ can be used. Receivers reed/relay systems can be delayed to suit. Simultaneous on each half could be introduced, etc., etc., but why spoil the simplicity? Any two (or more) R/C yachtsmen using conventional reed equipment, and normally operating on the same lake, can within 24 hours adopt this method. The blades of one reed unit could be snipped shorter, or the other lowered in frequency by loading the tips with solder. The above-mentioned few components cost little, and the yachtsmen can sell via the many new 6 metres have been regis- (c ~ Editor might think worthy of publication in a future issue. If so, then perhaps we can finalise something round the table to please most of us most of the time. L. CRANSHAW, tered during the last 10 years? 10 Raters: It was most unfair for Mr. Andrews to dismiss this class in the way he did and I am in full agreement with Mr. Tucker on Mr. Andrews’ statements. I wonder if Mr. Andrews has seen a modern 10 rater? He would find that it contains in full measure all the attributes of his 5.5 metre design. The 10 rater radio control model should ideally be designed from the outset to include the weight of the controls. Some older designs, however, would be improved by the additional weight and would stand a reduction in sail area. For example, my old Halcyon design would be improved by it but my later No. 19 and Whirlwind would be spoilt. It is a matter to consult the designer about. The point is that a 10-rater should not be used for alternative sailing on free control and radio control but should be limited to either use. The only addition to the rules would be to have the yacht registered as radio or free control and a small “R’’ added after the registration number in the case of radio control. The same official register can be used for both types. Size in the 10 rater class somewhat limits mobility but keen people seem to get round well enough. It is likely that a specially designed 10 rater for radio control would not follow the present tendencies for free control and that a shorter waterline and heavier displacement would prove more satisfactory; say 48 L.W.L. and 38 Ibs. disp. On this shorter L.W.L. a good model need not exceed 63 in. overall. A’? Class Practically all I have said about the 10 raters applies to the A class but the inclusion of the extra weight should be compensated by a reduction in ballast, otherwise draught or freeboard limit may be exceeded. I do not think that L.W.L.s would necessarily be shortened by Radio Control. Once again the specially designed A class would be a better proposition and no international agreement need yet be made if the radio control variant is kept to its own use. Summing up, therefore, I would say that the choice between a “One Design’’ and a “6 rater’’ is a difficult one but I lean slightly in favour of the “One Design’’. There is no doubt in my mind, however, that the 10 rater and A class rules should be utilised in addition. With three available classes the radio enthusiast would have a good choice to suit his circumstances. Upton, Wirral. JOHN Lewis.
