Castle 550 Technical Stuff...

The content for the following topics has largely been drawn from the answers to questions we have received over the last two years. Please feel free to contact us with your take on these or any other 550 related issue.

The Rig:

To date, the Association has not been successful in procuring an 'official' set of Yachtworks rig drawings. What we can offer are an accurate set of measurments taken from a Yachtworks produced fibre-tipped mast supplied with boat #17. These drawings were used by Spunspar to produce a legally dimensioned replacement.

Please note that the staying base, as drawn, is for the later boats which have the chainplates set further aft. This change appears to have been brought in around boat #10. This boat has evidence of having been originally built with the forward set chainplates but changed (by Yachtworks) to the more rearward position.

Click here for a PDF file of the mast drawings.

Click here for a PDF file of the spreader details.

The 550 rules allow the altering of rig tension whilst underway. We have used the following arrangement as it not only allows on the water tuning but also makes rigging the boat so much easier. The main loop is of 3mm wire as the rules stipulate wire standing rigging. Tail is 3mm spectra running back to a cam cleat on the side deck.

The forestay is 3mm wire terninated in a rolled swage. The shackle between the block and the forestay is replaced at the end of every season.

Correct lower shroud tension is crucial in getting the most out of a 550. We use German made NIRO units as they allow rapid adjustment in increments of around 2 mm. Spectra lanyards between two 6mm shackles would be a suitable (if not slower to adjust) alternative.

   The clip on the outer adjuster holds the spinnaker sheet when not in use.

Running Rigging:

This boat was launched with 4mm diameter spectra halyards for all three sails. It was soon evident that the 'creep' inherent in loaded spectra made this arrangement unworkable. Within 20 minutes of being hoisted, the mainsail would drop 100mm as the spectra 'relaxed'. Replacing the main and jib halyards with 5mm Vectran resolved this problem. 4mm spectra was fine for the spinnaker halyard.

All halyards and control lines coming from the mast base were cut 3m overlength. This allowed the mast to be placed in its transport position without having to remove them from their organisers/blocks/deadeyes/cleats etc. As the ends of the halyards fray at their exit sheaves they can simply be trimmed back using some of that extra length...much more economical in the long run than replacing whole halyards.

The Boom:

The standard factory 80mm boom provides a good basis for a little customisation.

Here the outhaul (red 3mm) can be seen exiting the boom via a Ronstan micro block. The outhaul tackle comprises 2 triple blocks fully contained in the boom to provide a 7:1 advantage. The spinnaker pole is held by a custom fitting fabricated from 11mm rod to which plastic ball ends have been epoxied.

This fitting allows the pole to be rapidly stowed by simply spearing the parrot beak into the gap between the balls.

The aft end of the pole rests in a pair of holders rescued from a long gone dinghy. The mainsheet is attached to by a snug fitting webbing loop which is free to align itself on the boom. The strop between the clip and the block is made of spectra core.

Spinnaker Pole:

The bridles have D rings lashed to their midpoints using thin spectra line, they have never shown any sign of slippage. The bindings are covered with velcro as is the centre of the pole. This arrangement keeps the bridles tucked neatly out of the way.

We sail with the topping lift clipped to the bridle to save time on a set. This also prevents the pole from going for a swim if dropped!

The bridles are looped around the pole ends and are held in place by low profile custom saddles. The height of standard saddles prevent the pole laying against the boom as well as snagging on the holders.


The vang is also a wire free zone, spectra is perfect for the job. The final ratio here is 14:1 which allows the vang to be tuned by one hand in most circumstances.

The upper block is a high load item attached to the boom by a spliced loop of 8mm spectra. A quick release captive-pin shackle between the block and the strap allows the vang to be dropped out of the way easily when raising the board. The upper part of the cascade is 5mm spectra and the tail back to the cockpit is 4mm.