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.

Goldspar/flexible rig

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

Tuning

‘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

Hull

The hull must be clean, fair and have exceedingly good slot strips to minimise turbulence.

Mast Rake

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)

Rig Tension

Straight rig: (low shrouds 4750/4950mm) 250/300 lbs

Prebend rig: (high shrouds 5050mmor higher) 200/250 lbs

Measured on jib luff.

Prebend

Straight rig: 50mm

Prebend rig: 75mm

Spreaders

Length: – low shrouds 420mm

– high shrouds 430mm

Deflection: straight rig 145-165mm

prebend rig: 150-170mm

Rig Types

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.