505 FAST NUMBERS GUIDE
Two distinct types are currently in use – the pre-bend and the stiff. Both have been used to good effect. Of the two the pre-bend type holds the advantage of extreme simplicity and with the bonus of low rig tension significantly prolonging competitive life of the hull.
The Goldspar section used for this tuning guide was the 60/2 which was rigged to the specifications below. With the spreaders fixed forward and approximately 50-60mm of poke, the mast is surprisingly stiff. fore and aft in the top two thirds, despite being very light (1.67mm wall thickness-60mm diameter). Low down bend is evident below the spreaders, mainly due to the inherent flexibility of the spar with no mast strut.
The shroud height is approximately at the balance point of the sideways forces on the mast and hence remains fairly straight sideways right through the wind range. This ensures good pointing ability in most conditions. The rig becomes self adjusting as the wind increases. The more the mast bends the more slack the rig becomes. This reduces the effect of the spreaders and allows the mast to « breath ». No adjustments are made to the mast from about 8 knots upward through the whole wind range. The only adjustments made to the boat are sheeting the jib wider as the wind freshens along with more vang and cunninger and adjusting centreboard up slightly.
Rig tension is 240 lb but the boat has fixed shrouds and an adjustable forestay. The forestay was never adjusted above about 8 knots, but we would consider loosening the rig on flatter water as the breeze freshens. Wooden chocks were used at deck level but these were never changed above 8 knots.
Back of mast at step of transom 3110mm
Spreader height above deck 3095mm
Spreader length-stay wire to side of mast 443mm
Back of mast at spreaders to straight
edge joining stays 175mm
Stay height above deck 5135mm
Trapeze height above deck 5185mm
Stay length below deck 196mm
Trapeze handle above deck 420mm
400mm Jib track on back of thwart
(inside distance from C) 455mm
Jib Halyard height above deck 4725mm
Spinnaker height above deck 5090mm
Topping lift height above deck 3840mm
Pole launcher pulley above deck 1150mm
Spinnaker sheeting block from transom 1015mm
‘O’ Type sails
Proctor Epsilon (squashed top)
Parker boat = all glass
Heights above deck band :-
Trapeze 16’6 (5038)
Shrouds 16’3 (4598)
Spreader 10’4 and 1/2″ (3158)
Spreader length 17″ (435)
rake 6’6″ (167)
Mast rake 24’2″ (7368)
Rig tension on shrouds 42
505 Tuning Guide
The hull must be clean, fair and have exceedingly good slot strips to minimise turbulence.
These measurements should be taken with full rig tension on. The main halyard should be locked in the normal position and then measured to the top of the transom.
Medium winds: 4’6″ (470mm)
Strong winds: 4’1″ (340mm)
Straight rig: (low shrouds 4750/4950mm) 250/300 lbs
Prebend rig: (high shrouds 5050mmor higher) 200/250 lbs
Measured on jib luff.
Straight rig: 50mm
Prebend rig: 75mm
Length: – low shrouds 420mm
– high shrouds 430mm
Deflection: straight rig 145-165mm
prebend rig: 150-170mm
Straight rigs: Proctor Epsilon and D+, Superspar M2.
Prebend rigs: Proctor D and Stratos, Superspar M3
NOTE: All measurements must be taken with full rig tension on.