UK-Cherub Class

Get Your Heart Racing

The Flat Stanley Story

By Derek Snow (1980 World Champion) as told to Peter Kay, North Sails UK.

The design of Flat Stanley was conceived specifica11y for an attempt on the 1980 World Championships held in British waters, off Felpham, Sussex. 2705-20060821a.jpg

It was decided at the outset that it would be difficult to predict the conditions that would be found at Felpham but, on the other hand, it was generally felt that the weather which would prevail during the New Zealand National Championships and selection trials off Takapuna would be light to moderate breezes combined with choppy water. Previous experience with a deck stepped mast (without post), and conventional sails cut from heavily resinated cloth, had shown that there was room for improvement especially in the performance of the boat to windward. It was for this reason that Flat Stanley was built to carry high rig loads in order to set a stiff rig which would allow the use of flatter sails with a relatively tight leech to aid pointing ability.

The hull itself was based on a 1976 lan Murray design which was modified by using U' d sections in the bow which had the effect of straightening the waterlines forward. The hull was built from a Kevlar and foam sandwich with wooden decks which kept the weight to a minimum. A 21/8in Super Spar mast was used which had a stiffening tube running from the heel for a distance of 9 feet. This spar was at a slight disadvantage in terms of weight but had the lowest available centre of gravity and a good record in previous World Championships. Since the sails had to be designed to suit this particular rig, it was felt that there was insufficient time to resort to a trial and error method of development and so it was decided to go to a sailmaker who had the technology to design a fast suit of sails straight off. North Sails were known to have a series of powerful computer sail design programs and so it was their Auckland loft which got the job of designing sails for Flat Stanley.

By using very high rig tension it was hoped to reduce the amount of luff stay sag and also to keep the mast as straight as possible and under accurate control. The mast was stepped on deck with the rig load supported by the stress frame construction of the hull. Fore and aft mast bend was controlled by the use of a strut running from the goose neck to the deck. This was adjustable, between races, by- running the end of the strut along a slide on the deck. Relatively long spreaders were used to hold the mast upright both in the athwartships plane and fore and aft. Lower shrouds running from the gooseneck to the gunwhale (directly athwartships), prevented undue mast bend caused by the thrust of the yang especially when off the wind. The shrouds, forestay and trapeze lines were all attached to the mast at the same point in order to prevent any bending moments being set up. Since forestay sag was controlled by rig tension 'vang sheeting' could be used so that leech tension and boom position could he controlled separately. A 24 to 1 vang lever was used for the leech, and a twin-ended mainsheet running from the transom to a take-off point in the centre of the boat was used for boom control. In order to reduce weight rig tension was set up by rigging the boat on its side and using an 8 to 1 tackle to pull the cringle on the head of the jib towards the mast. When the required tension was achieved a strop was shackled in place of the tackle and the tackle removed. The jib sheeting angle was adjustable and incorporated a Barber Hauler which ran the lead forward and out to the rail.

Once the mast bad been rigged, an estimate of the range of mast bend was taken to be used in the design of the sails. North Sails have a series of programs which can be used, firstly to evaluate the efficiency of a particular sail shape, and secondly to generate a sail design in terms of pane 1-shaping and luff curve. The computer model of P' Stanley' s rig was set up and after altering the sail shape to achieve an efficient configuration the program was then used to arrive at the broadseams and luff shaping necessary to achieve the same efficient sail shape on the water. High quality 3.8 oz. yarn tempered Dacron was used for both the main and jib. A loose-footed main was designed which used five battens rather than six in order to reduce weight. A moderate roach was cut into the jib leech supported by three battens, and in general the sails appeared to be flatter than normal. However, the North design technique is intended to produce sails whose shape can be adjusted to suit the prevailing conditions and therefore the camber could be increased in order to achieve good downwind speed.

One of the first races in which the new boat competed took place in ideal conditions to test the new concept, unfortunately the new boat was soundly beaten! However, this initial setback was put down to lack of experience with the new style of rig and after more practice it became evident that the boat was potentially very fast indeed. The main difficulty was the way in which the new stiff rig would not react automatically to changes in wind strength especially sudden gusts. In order to maintain speed in these conditions it was necessary to continually trim the main- sheet to keep the boat on its feet and footing. In trapezing conditions this job was given to the crew who was better able to cope with the strenuous task. Many more hours were spent on the water practising before the National Championships in the Summer of '79/80' and by the time the series began the boat was consistently pointing high and going fast! Flat Stanley recorded finishes of 1, 1, 2, 2 in the New Zealand Championships thus winning its first major regatta and booking a place at the 1980 World Championships. The rest is history. Flat Stanley went on to win the World Championship held under a wide range of conditions and pushed development in the Cherub class yet another step forward..

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history/flat_stanley_story.txt · Last modified: 2013/06/25 15:55 (external edit)