THE "STAR" MODEL RACING YACHT.

Auckland Star, Volume LXIV, Issue 249, 21 October 1933, Page 3 (Supplement)

THE "STAR" MODEL RACING YACHT.

Part 11. Last week I gave you the plans and a number of details of tlie hull construction of the "Star" model lacing yacht. We had progressed as far as laying out the hull and finishing the shaping of the 'outside. Now we will proceed with the hollowing of the hull and fitting the keel. ]S T ow 'mark all around the deckline, pencilling in a mark from Jin to 3-Bin in from the outside shape, this, of course, being the line you will carve to later on. For a model of this size 3-Bin thickness of skin is the maximum desirable, and Jin the minimum. Fig. 8 shows how lioles. are bored in about lin deep, all over the space to be hollowed. The more holes you bore the better, but be careful not to bore the side ones too deep, or you will have holes where they arc not wanted—through the skin. Gouge out the surplus wood, and then bore another batch of holes. In this way tlie hull is gradually hollowed,

the final carving of the inside being done • entirely with a small slifirp gouge. Fig. 9 shows how the thickness can be tested by a home-made pair of callipers. These arc well worth making, and can be knocked up from a scrap picce of tlirecply, Make the callipers so that the pivot hole is ccntral, and then when you are trying out the thickness, as in Fig. 9, the .opening of the free ends will be the same as the thickness of the luill at that particular point. It is well to leave the very bottom of the hull, where the keel fits, thicker than the rest. Make it about Jin thick. Now you can spokesliavc away the, top or sheer line to the pricked marks as shown in Fig. 5 (Part 1). This gives you the longitudinal deck curve. The Keel: The keel is cut from a piece of close grained wood, 10 inches long by 9 J inches wide by j inch thick. Make a note of it that the grain of the wood runs the longest way of the wood, i.e., when the yacht is in its normal position the grain of the keel is running horizontally. The actual shape is given in Fig. 10, and also in the scale drawing (Part 1). Cut the rough shape out with a coping saw, bandsa\y, or even the veryrougli old keyhole saw, spokesliave to the correct shape, and finish with glasspaper.

Fig. 11 shows the streamline sectional view of the keel. Watch, however, that the point where the rudder butts up against the keel is not thinned down too finely. Looking again at Fig. 10 you will see that near the bottom of the keel is a line drawn two inches up from and parallel to the bottom. This is the lead weight. The idea is to finish the keel piece in wood, including the part which will afterwards be replaced with lead, then make the mould (Fig. 12) and push the wooden keel down into the plaster of paris to the liiie shown. With regard to the plaster of paris mould. Get about (id of plaster of paris from your chemist or dentist, they botli have it; knock up a rough cardboard box with inside measurement of about 12 x 1 x 3 inches deep. This will be big enough to take the casting of the lejid, but not too big so you will waste a lot of plaster of paris. Get your chemist to explain the amount of water to mix the plaster in, and, mixing it in a bowl, pour it into the mould-box and carefully insert the wooden keel until the line just shows. The plaster will set quickly, but it is well to have some support to hold the keel steady in the correct position mean- j while. Now remove the keel by gently j tapping it and the mould is complete. About eight pounds of Iqad are necessary to make this keel weight, and it may be melted in a metal pot. I would advise you to get a plumber friend to help you with this if you are not experienced. One important point must here be remembered. When voir have completed the mould, put it in a warm over for a couple of hours until every vestige of moisture is extracted from the plaster of paris. 1 whs once in too much of a hurry to iill up a mould like- this with molten lead, and the result was that the moisture in the plaster caused the molten lead to go oft' like a lot of gun shots, and very nasty, very hot pellets or lead were Hying round tlie room. I escaped damage j that time, but you mightn't be so lucky.

Xow cut oft' the wooden keel to the mark, and boring t lie lead weight, as shown in Fig. 13, screw in on to the keel with 3A in brass screws. Make the holes in the lead a clearance size for the screws, and"see that the heads tit flush. If you make a good job, the lead will lit the keel perfectly, but a little rasping may be necessary. Now conies the fitting: of the keel to the hull. The same method is used, the holes in the hull being just a shade biooer than the brass screws, and don t forn-et to bore down into the keel, so that the screws will not split it. The rudder (Fig. 1">) is made from a [piece of 20 s.w.g brass sheet, and cut to 'the shape shown. See also the scale drawing in Part 1. A piece of IS-lOin brass rod is used for the rudder stem, [and the rudder blade is turned'around it and carefuliv soldered into place. The 'stem is screwed for the first Jin with | 3-l(iiii Whitworth thread. I xext week I will give you some more I details of this attractive racing model vaelit.