Practical Junk Rig: Design Aerodynamics & Handling
Format: PDF / Kindle (mobi) / ePub
This encyclopedic volume synthesizes 25 years of research and development of this unique rig as adapted to Western craft. It is a work that has been welcomed by the growing number of yachtsmen and designers throughout the world who already enjoy the benefits of the junk rig or who wish to do so. Practical Junk Rig examines the design and aerodynamic theory behind junk rigs and discusses how best to sail them. It outlines the rig in detail, the principles that underlie it, considers possible alternative shapes and arrangements and analyzes performance, all assisted by a wealth of detailed line illustrations.
combined with anti-twist sheets (see Chapter 4). Conversely, there are many sails, both in China and the West, which have more balance at the tack than at the throat, a feature that may be difficult to avoid with a forward-raking mast, as inBatwing's foresail (Fig. 16.9). It is preferable to have the yard sling plate at or near the middle of the head of the sail, but it is often well forward of this point as in Redlapper (Fig. 16.2) and Galway Blazer II (Fig. 16.3), at the expense of greater
sharp edge. This point may then be transferred to your scale profile and marked as in Fig. 6.4. A common problem when trying to balance a trace of the underwater profile of a modern type of hull is that the piece of immersed hull in front of the rudder or skeg is Designing the Sail Plan (1) 93 too slender to support the after part of the trace, and too narrow to be pleated. This can be dealt with by using good-quality thin cardboard instead of tracing paper, and not using concertina pleats. The
P, and rise. FINDING THE CENTRE OF EFFORT. The CE is a fixed Fig. 6.20 Sail area and aspect ratio diagram (imperial) Fig. 6.21 Sail area and aspect ratio diagram (metric) 106 Practical Junk Rig Fig. 6.22 Calculating areas point on the sail's surface, and is the geometrical centre (centroid) of its area. It provides a convenient point of reference, but it would be wrong to assume that it is the same as the centre of pressure (CP), which is the point through which the total force
knocked down by a 'williwaw', i.e. a fierce whirlwind squall off the hills? Everything would depend on how suddenly it happened, or in scientific terms what accelerations were involved. A quick recovery to the upright position would also induce severe stresses in the mast. Again, when running before the wind in smooth water it would be too optimistic to expect the mast to be strong enough to make her pitchpole (somersault) when struck by a stupendous squall from astern. The best we can do is to
halyard. LIGHTS, INSTRUMENTS, AND LIGHTNING CONDUCTOR. Lights and instruments may be mounted on a horizontal plate attached to the masthead fitting. In Fig. 8.19 this is shown (P) welded to the three forward tangs. In Fig. 8.20 it is a separate plate (not shown) on the starboard side of the fitting, designed ad hoc and held to the fitting by machine screws entering the three tapped holes (R). Both fittings show cable exits (F) for lights or instruments and exits (L) for the lightning conductor.