Dave Porter - Skipper B-17 Mast Die Report Back in late 2012, for the 2013 season the C class purchased a new die for extruding masts. Three runs of masts have been produced with a total of 97 masts. Each group of masts was measured for deflection and serial numbers applied. Several of these were rejected for various reasons so a total of about 90 masts were available out of this group. Figure 1 below is a histogram of the results of the tests. It shows that the first group was more flexible than the second and the second was more flexible than the third. These measurements were done before anodizing, this allows for acid etching after measurement.
Figure 1
Based on the increasing stiffness of the masts I am recommending that the class invest in a new die, this should cost about $3,000. Melges is on board with this suggestion. For those who do not know, the die is owned by the class and Melges pays a royalty on each mast they sell to the class. Recent Mast Bending and Breaking As many of you know, there has been a recent increase in mast problems. We have put together a list and identified 17 masts that have either bent or broken in the last two years. I believe that this is a result of inadequate stiffness/strength in the jackstays, jackstays too loose and sailing with over 475lb of crew. I am recommending that starting in 2016, all new jack stays be 5/32" jack stays. Then in 2017, all existing C masts used in competition will be required to use 5/32" jack stays. This rule gives boats a year to comply by changing their jackstays to the stiffer 5/32" cable. The reason to require all masts to be upgraded is to not end up with some 1/8" jack stay masts that are considered "fast" when not every sailor has that option. Two ways are available to upgrade existing boats. The first is to take the mast to a rigger like Melges. They can remove the old stays and put in larger stays. The second is to do it yourself. This would involve slotting the end of the spreader and drilling a small hole about 1/2" inside of the slot. The new stay is then put into the slot, and a copper or mild steel wire is used to hold the stay in the spreader. If this rule change is approved, we will put together a set of instructions for changing the stays yourself. There will be discussions at the nationals at Minnetonka, at the ILYA C invite at Beulah, and at the ILYA championship at Geneva. Additionally, you can contact any member of the National C board or the ILYA C fleet committee to express your opinion on these issues. |