DESIGN
The Plan B design is the culmination of more than three years of development, sailing with the very competitive Paradise Radio Yacht Club at Emerald Lakes, Queensland , Australia. Paradise Radio Yacht Club ( pryc.com.au ) is the largest radio yacht club in Australia and Queensland ( qrya.com.au ) is the largest radio yachting State in Australia. We are fortunate with our climate, in being able to sail throughout the year in varied conditions and in a full range of wind strengths. We Australians enjoy IOM competition at an elite International standard. It's a demanding field and our yachts must meet the challenge.
This Plan B hull design is the third version of the concept, each development requiring a complete set of hull moulds. Twelve yachts were built and evaluated before Plan B was first offered for sale. Refinement continues, with Plan B yachts now competing in local, regional, national and international regattas. I receive and act upon input from those at the forefront of competition.
This photograph shows one prototype, # 128, racing at the Eddie Cowell Regatta, Kawana.
Plan B is a yacht designed to win both single races and protracted events. It is simple, strong, reliable and easily maintained. Not withstanding, it’s a racing machine.
Behind the clean appearance is a sophistication of thought, design and construction not readily apparent. I race my boat and know. There are features like an adjustable, ball-ended shaft to centralise the rudder with the Tx trim at 0; wire topping lifts; white foils remain cooler in the sun; neat and accessible wiring; adjustable silicone seal in the rudder bearing; adjustable mainsheet post within the central spine, all lines readily accessible, moulded bow buffer, heat-shrink over all wire terminations, UV resistant silicone O rings, Nyloc limit nuts on the turnbuckles and more.
The easily driven, chined hull has a long, fine entry to elliptical sections in front of the keel and a shallow vee aft into a straight run at the rudder: clean and balanced. The hull shape and foil profile promote responsive steering. This is most apparent when the yacht tacks quickly and easily at low speed and in very strong winds and waves.
It floats bow-high at rest and uses the dynamic lift of the forward sections together with Daniel Bernoulli Effect from the aft sections to maintain this attitude downwind at speed. The topsides aft curve mirrors the keel spring to track true and keep the bow high when heeled. A fine entry minimises ‘tripping’ and burying the bow. When heeled, the hull presents a straight run with narrow cross sections. A low stem and the sheer line radius minimise windage. The concave, raised fore-deck closely follows the jib-boom and positions the mast ram for effective mast control.
There is a large central hatch, recessed to be flush with the deck, for ventilation and access to the rudder servo, receiver, battery, switch, wiring and corrector weight. This hatch gives adequate ventilation, without the need to remove the rear deck patch. The layout is convenient and practical.
If needed, the flush, deck mounted RMG switch can be circumvented by simply exchanging the installed XT-60 plugs. The waterproof Hitec HS-646 WP, precisely self-centering rudder servo and the RMG 290 EF winch can be removed and changed through the main hatch, without removing the rear deck patch.
The rudder shaft, aluminium tiller and also the winch are readily accessed through the large rear deck opening, covered by the rear deck patch: one flat, easily applied deck patch only, that seldom needs removal. This picture also shows the ‘Rambler’ style rudder with tubercles. This rudder allows an increased angle of incidence before stalling. Its lesser area gives a milder steering reaction.
The winch, rudder servo, battery and corrector weight are placed alongside and behind the keel to suit the hull displacement and minimise the overall moment of inertia of the yacht.
Above-deck RMG 32 mm. self-tensioning winch drum and lines give quick and easy access without sheet openings that allow water ingress to the hull. Sheets, winch drum and lines can be adjusted and changed from outside the hull. The winch drum is shielded with a smooth, rounded cover. This drum and the Hales deck mounted, ball-raced deck blocks can be readily flushed after racing. The mainsheet runs freely through a wire loop post, to facilitate flick-jibes with the ‘extra-fast’ winch.
The keel foil is an example of form following function and experience. During 2019 the ‘Plan B Group’ has extensively trialled several keels in varied conditions at four venues. I have made new moulds and this tapered keel foil will be supplied from mid-2020. All previous Plan B yachts can mount this upgrade.
The 90mm chord, NACA 0009 section near the hull tapers in width and thickness to the ballast. The forward flare at the hull has theoretical merit in the more transverse upper flow and a practical advantage of moving possible strands of weed away from adhering to the hull. A new blade rudder is supplied as standard. The ‘Rambler’ rudder with tubercles will continue as an option. Both rudders are positioned a distance from the transom to minimise cavitation from the wake.
The ballast is a low drag laminar-flow profile with circular section. The ballast centre of gravity is at a distance forward of the foil null point, giving the foil slight wash-out under heeled load.
Plan B was drawn using engineering CAD, giving accuracy to lines and calculation.
Parameters were calculated and extensively checked before construction.
CAD enabled, for instance, the displacement distribution, wetted surface area and prismatic coefficient to be ascertained and optimised at incremental angles of heel. The result is a well balanced yacht that can be readily trimmed to 'hands-off' sailing.
Plan B is an attractive yacht, both on and off the water. Good, standard practice; what looks good, is good.