- Description of contents
wy @) a e| | Oa ites TM MAP HOBBY MAGAZINE TWO SHILLINGS AND AUGUST 1967 SIXPENCE ee ae U.S.A. & CANADA MODEL BOATS BOATING FOR BEGINNERS Completion details for the popular Starlet yacht, radio or free sailing FrOR a free-sailing model horses are required for the jib and main sheets. These are simply wires set across the hull top on which the sheet hooks slide from side to side. Brazing rod, is in., is a hard brass wire obtainable from welders’ workshops, and is suitable for these horses; it is probably the easiest form of thickish brass wire to obtain. It is suggested that the jib horse is fitted over the front of the cabin as sketched at A, by screwing two screweyes through into the front member (S1) each side, locking them in with epoxy, and soldering the legs of the horse into the eyes. It should project above the cabin top by about } in.; and before fitting should have a washer soldered at each end of the cross part (as al D) to prevent the hook from sliding over the corner. The main horse can be similar (eyes into S2, as at B) but it is more efficient 10 have the sheet as near the tip of the boom as possible and making as near a right angle to the boom as possible. Thus it is a slight improvement to mount the horse near the aft end of the well, (C), in which case a small block should be firmly glued inside the well sides, to deck and sides, to receive the eyes. Anyone who has built the yacht flush-decked (no cabin) will need to silver-solder the horses to deck plates (E) or turn the ends to make flat eyes (F) and screw or bolt the horses in place, reaching inside the hatch to place reinforcement blocks under the deck. For free-sailing, the rudder must be completely free, so before permanently fitting the pintle (see plan) ensure freedom of movement by polishing the rudder stock etc. Without a free rudder you will never get the boat sailing satisfactorily, so it is worth a few minutes at this stage; don’t accept it until the rudder’s own weight will move it when the model is rocked gently on its stand. Since the model is intended for sport sailing, a fully self-tacking and infinitely adjustable steering gear is not necessary. Adequate control for most people can be achieved with the simple gear-wheel vane introduced by Geoff Draper some three years ago. This simply constitutes a gear G fitted to the rudder stock and another, H, with approximately half the number of teeth, meshed with it and pivoting on its own spindle I immediately abaft the first. The greater the number of teeth the finer the adjustment. A vane feather J of 3/32 in. balsa is fixed to the smaller gear and this gear can be lifted out of mesh, rotated to any position, and dropped back into mesh. A 10-tooth gear gives an udjustment of 36° per tooth, a 40-tooth 9°. With the latter something near 80 teeth would be needed on the rudder gear; this is probably a practical limit and certainly adequate for average pleasure sailing. Fairly substantial forces can be desirable. involved, so reasonably stout gears are Spindle I involves drilling the deck and epoxying in a brass tube, but it has the advantage that the spindle can be used to solder (or silver solder) the vane arm in place. The alternative, K, mounts the spindle on a deck plate but the bearing plate and vane arm have to be fastened to the top, no problem with a brass gear but more difficult with plastic. Plate L can be fitted to the small gear to prevent it being lifted right off. The vane arm simply has an eye to which feather J is bolted, with a couple of large thin washers, and at its front end requires a counterbalance M so that when the yacht heels the vane weight and the rudder buoyancy have no material effect. The gear fitted to the rudder needs a very light centring pull provided by means of a single strand of very thin elastic tied through a hole drilled in the gear and carried forward to an eye on the deck some inches in front. This centering line should overcome any slight stickiness so that the rudder returns to central unless it is being influenced by the vane. The basic principle of vane steering is simple. If the boat is pointed in the direction it is required to travel and the vane feather rotated to line up with the wind direction, all the time the yacht is held pointing in that direction the wind will simply pass the feather. If, however, the boat is turned slightly to one side or the other, one side of the feather is presented to the wind which will naturally try to blow it back straight. This puts force on the rudder, 326 AUGUST 1967 turning it in the direction needed to turn the boat to its original heading, when the feather is once more need not be stopped when reaching the bank, but is turned with a pole on to the opposite tack. It is therefore necessary to have a gear which will control the boat on either tack, which is what is meant by a self tacking gear. Anyone anxious to go further into this should refer to the “Notes for the Novice Yachtsman” series which ran through the whole of 1965 in this journal, and also the extremely useful notes on vane handling in the Priest and Lewis book “Model Racing Yachts”. The simple gear described for Starlet does no more than allow the owner to lay a course with reasonable accuracy, and as such it adds to the interest of sailing the model. For the radio model, a 4 channel set is required. It is possible to sail a yacht with some degree of control with single channel equipment operating an escapement driving the rudder only, but in many cases the rudder would be fighting the sails and the yacht would not be sailing efficiently. We have, however, seen yachts steer quite complicated courses of buoys on rudder only, so that anyone with single channel equipment spare could have some amusing sailing by installing a clockwork or electric escanement in the conventional way, operating the rudder through a push rod as described later. A yacht relies normally on its sails to make good a course, and can, in fact, be sailed without a rudder at all, so that it might be thought that single channel used to operate the sheeting would be preferable. The yacht would certainly sail more efficiently, but it would take much longer to make an alteration of course and would not really be a practical proposition, esnecially when one takes into account the mechanics of operating a sheeting system with only one channel. An alternative single channel system would be to employ the radio on the rudder and to use an automatic sheeting system worked from a _ vane are even greater with yachts than with other types of model. Since the boats derive their speed from the wind and the wind can vary considerably, timing one model round a course and comparing the time with that of another model sailed earlier or later does not give a true comparison of ‘performance. It is really necessary to sail both models together and superheit equipment allows this to be done. Any conventional rudder servo can be employed, and this should be mounted above deck level, or with its output shaft above deck level, so that a simple push rod can be connected to a tiller on the rudder. The servo could even be mounted in a box in the well aft of the cabin, though there is ample room for it to be installed inside the cabin. The main receiver and battery box fits down inside the hull so that the servo should be mounted to leave adequate clearance for insertion of the box. A yacht may sail for an hour or two without being brought into the bank, and all model vachts seem to collect a certain amount of water inside, so that the tadio box needs to be as water-tight as possible. A plastic sandwich box is an ideal container, sealed by means of plastic tape and fitted with g-ommets or Bostik blobs where wires emerge. Inside the box should be stowed the receiver and its power supply (Deacs or dry battery) and the servo batteries. Alternatively two smaller boxes could be used. stowing the servo batteries separately. The receiver aerial may be bound to the mast, with its lower end soldered to a tag bolted to a convenient point inside the hull: the receiver itself has a short aerial lead which can be bolted to the same tag. The servos should be plugged into sockets on top, or |= edge on to the wind. A slight complication is that when the boat is released, its motion itself produces a draught in the direction of travel equivalent to the boat’s speed. This has to be allowed for in setting the vane gear. For example, if the wind is 5 m.p.h. from the west and the boat is sailing north at, for illustration purposes, 5 m.p.h., the apparent wind will be at 45° to its course and the feather will have to be set at this angle. Obviously the boat’s speed would not at any time match the wind speed, but this gives a fairly clear idea of what is meant by the “apparent wind”. A little practice on the pond will soon show how much allowance has to be made on various courses at various wind strengths. A racing skipper must know his vane settings to a single degree which is why a “real” vane gear is much more complex. In racing, too, if the trim of the boat is right when beating into wind. the boat feather as described in our booklet “Radio Control Yachts” (reference MM.727 price 3/9d. including post), and for electronic enthusiasts this could be an interesting method. Most people, however, will use 4 channel gear using a self-neutralising rudder with one channel to give left and one right, plus a progressive winch control using one channel for sheeting in and one for sheeting out. Any lightweight 4 channel equipment is suitable. but of course the advantages of a superhet radio 327 i” MODEL BOATS near the top of the side, of the receiver box, so that by unplugging the servos and unbolting the aerial lead, the receiver unit can easily be removed. Bearers of, say, 4 in. square spruce, or cut from 7s in. ply to form a frame, should be fitted low in the hull, when the radio can be secured in place by crossed rubber bands fitted with wire hooks. After flotation ROTOR HUB LIMIT ADJ. SCREWS Yo” sa. SPRUCE SEE-SAW HINGE AXIS OF ROTATION FOR DIFFERENT TACKS tests which could well involve shifting the radio fore or aft to trim the model, permanent position stops ROTOR AXIS can be glued across the bearers. _ The sail servo was briefly mentioned earlier, and is simply a Marx-Luder Mini-Richard fitted with a sheet drum. The motor/gearbox unit is screwed or bolted to a block glued into the hull (to B3, for example) and its shaft is extended to take a winch drum or spool. The extension can be effected by soldering with care or epoxying a brass tube to the existing shaft, or by removing the eccentrically drilled brass rod from a break-off connector (sold for electrical connections in blocks and broken off as needed) and using it with its two brass screws to couple the motor shaft to a length cut from the end of a cycle spoke. The spool can then be held on the thread of the spoke; if brass tube is used, the spoke can be soldered into it. Those with access to a lathe can turn a suitable connector, with grub screws. The spool is of course best turned on a lathe, but CONING ANGLE 5° END VIEW ROTOR er slight eccentricity of its core would not be a serious disadvantage, so that if two 7s in. ply discs are marked and cut out and a wood core fitted between them. provided the bottom ply disc runs fairly true no real problem should arise. The discs can be trued after assembly by revolving in a power or hand dril. and applying glasspaper. When in place on the cabin top a balsa ring must be fitted close up to the lower ply disc, leaving a gap less than the thickness of the sheet. so that there is no possibility of a slack sheet tangling. A Novel Starlet One of the first Starlets finished was that of John Bridge (Blackburn) who sent in photos, including this month’s heading picture, in April. At the time, the model was on single-channel rudder only and ROTOR BLADE //16″ SPRUCE. ROOT CHORD (HUB) 1v2″ TIP CHORD | Yo” sq. HUB | | +—PLANE OF ROTOR BLADE/ HUB JOINT BOUND WITH FIBRE GLASS ROTATION 3° NEG. PITCH-7” | performed well in calm to middling breezes, though tending to round up into a strong wind. The builder was therefore incorporating a Braine-type automatic steering unit, with the radio actuator driving the same unit through a differential device. This prevents the necessity of pulsing the rudder to maintain a heading. We have since seen the model sailing in a stiff breeze and it certainly now sails dead straight. Being gadget-minded and experimenting with a Bensen type gyroplane, John thought it would be interesting to rig the hull experimentally with a rotor. The photographs show the result—the yacht sails at about the same speed as it does with conventional sails, but it is much noisier, the rotor sounding like a full-size helicopter! At present the rotor axis thas to be pre-set for the jappropriate tack, but it could _be set by servo. ; The next step is to drive water-screw from the rotor, which brings up the age-old question of would it sail traight into wind? Any ‘reader comments? Rotor propulsion has one drawback–with snearly 4ft. of rotor spinning fast, one needs to keep clear of it. Performance ‘is interesting – note bow wave in heeled : picture, though water indicates that wind is light. 328 AUGUST 1967 GUPSY MOWE WY “MODEL BOATS” BUILDS AND COMMENTS ON THE LATEST KIT FROM HOBBIES LTD. THE latest addition to the Hobbies range of boat construction kits is a model of Sir Francis ; Chichester’s Gipsy Moth IV. The model is attractively packaged in a cardboard box with a large picture of Sir Francis and Gipsy Moth on the cover. The description on the cover proclaims the contents to be complete with detailed drawings of the vane steering gear (which we never managed to find) and an extraction of log details as told to the Sunday Times. This consisted of a double page newspaper size information sheet which will be of great interest to keen followers of Sir Francis’ adventures. First impressions on opening the box are those of disappointment, the contents appearing to be rather “in a rough state’. Construction calls for a fair amount of cleaning up the pre-formed vacuum formed pieces etc. and therefore is not, as we had rather expected, a simple put together job, although to be fair the finished yacht can be made to look rather attractive, providing patience in construction is used. The drawings and instructions are on the whole rather poor and show haste in preparation, the worst by far being the quality of the drawing. Full size templates are shown on which to bend the 14 s.w.g. wire to form the cockpit and main boom runner. The latter proved to be } in. too long, and subsequently the runner fitted perfectly over the cockpit, rather than inside it! However, the kit is complete—-apart from paint and glue we had only to find a couple of inches of wire and a spot of ballast for the bow. Even the keel ballast is included. 22 stanchions are provided (2 spares). Unfortunately, these are only plastic, some #z in. thick, and great care has to be taken to avoid catching these when retrieving the craft from the water. A wellwisher, turning our model round on the far side of the pond, managed to snap off four of them by accident! The rigging is rather limited in adjustment, and would need some fairly drastic re-designing to To sum up. Perhaps a bit on the expensive side at 97/6, but builds up to be rather an attractive yacht. The yacht sails pretty well and, with a slight breeze behind it, produces a fair turn of speed. Ours drew quite an amount of attention on the channel radio control, without any drastic alterations. with the younger sailing fans. enable the craft to be completely versatile. The model can be adapted for use with single CABLE ENTERPRISE (Continued from page 322) A further refinement is a small brass hand-wheel mounted outside the glass case, for operating the cable gear. By turning this one way or the other the cable gear will pick up or pay out “cable” over the bow baulks, the cable passing around all the sheaves and wheels as in full-size practice. The cable passes through a hole in the base-board below the bow baulks, round a pulley to the small battery operated winch under the base-board, through a Gipsy Moth to the free sailing yacht it is primarily intended to be. The ballast weight will have to be adjusted accordingly to compensate for the additional weight of batteries, etc. Instructions are given for installation of such gear on the instruction sheet. The finished model is 27 in. long, 31 in. high (from the base of the keel to the top of the foremast) and weighs 4 Ibs. This includes the extra 8 oz. ballast for the bow (not included in the kit). pond. We wouldn’t however, consider it to be an enthusiast’s model, but should be a big attraction Lake again, which is perfect for sailing models and only half an hour’s drive from my house. A glass case is, in my opinion, essential for protecting scale models from dust and flapping dresses in the house. My only other scale model was unprotected, and suffered broken masts several times (Magga Dan, Model Maker Plans Service). Further details of model:Length: 40 in. Breadth 63 in. Weight 18 lbs. tensioner device and up the aft support column into the model. It is then led through several pulleys and emerges at the bridge front door and into the cable handling gear. The model will be living in its glass case until the warmer weather, when I will be sailing at Coniston IV pictured above on her maiden yoyage across the local pond. Further details of ship:- Shaft H.P. 3,300 at 144 r.p.m. Bow propeller side thrust: 3 tons. Ship was chosen by Shipbuilding Conference in 1965 as one of the world’s best ships. 347
