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Spinnaker Rule ChangeGraham Williamson briefs us on the 'big' (sorry, 'new rule') kite - Summer 2002 |
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The observant will have noticed that a rule change proposal affecting the Merlin Rocket
spinnaker is on the table for adoption at this year's AGM. This note is to explain the
background to the proposal and to try and answer concerns that some members are known
to have. Background The Merlin Rocket spinnaker rule has been in place for a number of years - since the decision was taken to increase the size of the sail from the old pocket handkerchief. In many ways the current rule is an anomaly; in practice, very few sails are actually built to all the current dimensions, because of the impractical shape it would produce, and philosophically, the rest of the sail plan revolves around an area rule, which allows owners to experiment and choose the balance of main & jib sizes within a formula that best suits them, whereas the spinnaker has prescribed dimensions which effectively prevent development of the most effective shape for the size of the sail. There has long been a groundswell of opinion that an update of the rule making it an Area Rule should be brought forward. The Proposal The proposal IS NOT AN ATTEMPT TO INCREASE THE PERMITTED SIZE OF THE SPINNAKER, either overtly or covertly. The rule proposes a formula which trades length against width and which will encourage experimentation with the longer narrower sails that those with knowledge of the subject say will make the sail easier to handle. This may in turn lead to slightly shorter poles being used, which, again, would make the sail easier to handle. The formula is calculated to measure the sail as a series of squares and triangles, and has been developed from the maxima prescribed in the existing rule. This means that all existing measured spinnakers will measure under the new rule. Since the change is intended to encourage development in sail design, the rule does not limit the Foot Median (the dimension from the head point to the middle of the foot). This is to allow experimentation with the shape of the sail low down where area becomes much more 'drive' than 'heeling moment'. Experience in other classes such as the International 14 and the 505 showed that 'excessive droopy foot' syndrome was self limiting, since in light weather the weight of the cloth, particularly if wet, dragged the middle of the sail down far too readily. The optimum foot shape for us will emerge very quickly by trial and error. The proposed rule change is as follows. All the definitions of the measurement points involved have been omitted here for clarity, but will be incorporated into the full rule wording. Measurement rule 13 (c) be deleted and replaced by:
The sail laid out on a flat surface, shall be measured dry, and with sufficient tension
applied to remove wrinkles across the line of measurement taken.
The Area (A) of the spinnaker, as defined, shall not exceed 10 square metres. Area = 0.25 x Leech x ((0.5 x Foot)+ Quarter width + Half width + Three Quarter width) A hollow in the edge of the sail at a measurement point shall be bridged by a straight line and measurements shall be taken through the measurement point at the bridge line. Implementation All the active sailmakers in the class have been consulted about the change and have agreed that there is scope for development, although all equally agree that the development is not likely to be radical - more a process of refinement. A trial sail has been commissioned and will be available for all interested to try out. However it is the nature of development that the trial sail will not be the finished article. The committee have agreed that the sail can be used in Silver Tiller races to try to ensure proper evaluation of the proposal before voting its adoption at the AGM. Conclusion The committee were directed by the AGM two years ago to investigate this rule change and after a long period of debate this rule change has developed. It is carefully designed to maintain the Restricted Development ethos of the Merlin Rocket Class, by a continuous process of refining areas of identified weakness, leading to a product that stays current and modem, while retaining its essential unique characteristics. If you have any thoughts or comments on the proposal, please let us know. We commend the proposal to the house. |