Plan B

International One Metre Racing Yacht

SHOWCASING - PLAN B - A HIGH PERFORMANCE IOM RACING YACHT FOR COMPETITIVE RC SAILING

CONSTRUCTION

The following will give some detail of the extraordinary care taken in the build of Plan B.

 

The one-piece hull and full-deck  are moulded separately from layers of high-strength S 'glass fabric reinforced epoxy resin.  There are three full layers of fabric in the hull and two in the deck.

This smooth, uniform, one piece hull moulding, without  the interruption and stresses of additional joining and cross-members and with only the longitudinal spine and rudder attachments on the inner surface, will maintain it's flowing low-drag shape without distortion.  This has proven so over three years of racing.

Having a separate deck moulding enables the central spine mouldings of integral mast-trunk, keel-case, rudder servo-mount and sheet post-trunk to be bonded and braced with pultruded fibreglass reinforced struts.  These struts, together with the deck form, triangulate the jib and shroud mounts, mast trunk and keel case into an integrated structure.  Similarly, with ready access,  the stay  attachments and deck hardware mountings are reinforced from beneath the deck.

The central spine mouldings, stem and transom mouldings are flanged to give strength and to locate them within the hull and deck.  This spine firmly mounts the rudder servo, incorporates the mast trunk and main-sheet post and gives strength to the winch mounting.  The accuracy of CAD and CAM assures the integrity of the assembly to provide a wide, waterproof bond.  The separate stem and transom mouldings give added strength behind the bow bumper and at the back-stay mount.

The one-piece deck moulding is flanged to fasten securely within a moulded channel at the hull sheer line.  This forms a strong triple layer at the point of side impact.  The hull is moulded with an aligned flange at the keel opening.  This locates within the keel case of the central spine.  Deck openings are rounded and flanged around their perimeters.  The bespoke, moulded winch cover is neatly recessed in the deck.    

Final assembly is done within a fixture that gives accurate positioning and alignment of the mast, keel and rudder mountings.

The 316 stainless steel rudder shaft is held in a multi-part acetyl bearing incorporating an adjustable O-ring gland seal and an additional support bearing at deck level.

The hull is finished with two-pack epoxy primer, two-pack automotive acrylic colour coat and clear two-pack top coat.  The colour coat can be plain or metallic pearlescent.   The hard, UV resistant clear top coat is durable and allows minor scratches to be removed by polishing.

A  strong, polycarbonate hatch rim is glued in place to accept a substantial, UV resistant polyethylene lid.  This is recessed to be flush with the deck.

The bow buffer is a smooth, resilient silicone rubber moulding, either plain or fluted.

The keel and rudder have a pre-moulded, syntactic foam core.  At the core faces is a Kevlar/carbon fabric with the weave at 45 degrees to give torsional stiffness.  The core is strong in it's own right and is impervious to water ingress. 

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This moulded core is subsequently compression moulded within a S'glass and unidirectional carbon fibre reinforced epoxy composite shell.  Reinforcement is placed and graded to give strength and stiffness.  At the leading and trailing edges there is tightly woven S 'glass for impact strength.  The construction method assures that the outer shell is of a precise thickness to completely encapsulate the core, without the weakness of joins at the leading and trailing edges. 

The lead ballast is gravity die-cast in a three part steel mould and then compression moulded within a S 'glass and unidirectional carbon fibre reinforced epoxy composite shell.  This hard shell gives strength to maintain an accurate, laminar flow, low drag bulb.

The most important,  keel, rudder and ballast need six CNC machined metal moulds and various clamps and fixtures for the manufacturing processes.  The appendages are critical for the yacht's performance and attention is paid to their mechanical properties and strong mountings within the hull.  The keel is particularly stiff, at only 9 mm. total deflection.

 

The foils and bulb are finished in white two-pack paint.

The rudder with shaft weighs 35 gm.  The keel and bulb are at around 2490 gm, allowing for a later maintenance coat of paint.

 

All mouldings are oven, post cured to develop their optimum strength.

The yacht build emphasis is on simple, strong and durable using premium materials and fittings.  

The weight distribution has been calculated and optimised.  The completed yacht needs about 150 gm of correcter weight, placed alongside the keel.

A PERFORMANCE IOM DESIGNED AND BUILT IN AUSTRALIA BY PETER BURFORD
"Everyone needs a Plan B"