Jet-14 plan and specification review: 2002/2003
June 3, 2003
At the 2002 annual meeting held at last years National Championship, the membership voted to have the class drawings and specifications reviewed along with a compilation of past and current rulings by Chief Measurers. The purpose was to bring together all relevant information pertaining to boat, sail and rig measurement issues and verify that they were accurate and up to date. In addition, where it was indicated, changes and/or clarifications would be offered.
A full report will be presented to the full membership at this years annual meeting at the National Championships. A preliminary report was given at the winter board of governor meeting. This progress report is meant to keep the general membership advised as to evolving issues, some of which are impacting existing boats. Owners of these boats deserve as much lead time as possible to respond.
The issue having the widest impact is the location limitations on the mast step, both keel stepped and deck stepped, and the maximum size and location of the deck opening or partners for the keel stepped masts. Over the years the classes position had become, formally and informally, that the locations for these items as shown on the plans were recommendations, not hard and fast limits. My current ruling is that these are limit dimensions and as such shall not be exceeded of varied. This ruling overturns earlier Chief Measurer rulings. This has the effect of causing boats that were previously measured and found to be within class tolerances to no longer measure in. This is a result that any One-Design class wants to avoid at almost all costs. Fortunately, in every case that I am aware of, the corrective measures are not overly difficult.
Different interpretations of the drawings as they are currently drawn are possible. Further more, because common practice saw boats setup outside these dimensions, it is easy to understand why some members assumed that this was the accepted interpretation of the rules.
The drawings themselves and this variable interpretation of the rules is the reason that I feel my current ruling is necessary. The call is for more consistently applied and easier to understand specifications. If previous approaches to the drawings and specifications were to hold, a new comer when studying the current drawings and specifications, would be hard pressed to know which dimensions were to be adhered to and which ones were in fact just recommendations. Hopefully the rulings and recommendations we are making will go far in removing such ambiguities.
Some members have voiced the opinion that this ruling leaves us with tolerances that are too tight in this area. I would propose that this is in reality a different issue. We as a class are open to such proposals. There is an approved process for making such a case and if a broad enough consensus can be formed, the class can decide to revise the specifications to remedy such a difficulty. The long-term benefit to the class must of course, be the prime consideration in such cases in my opinion.
A list of other approved specification changes and proposed rulings follow.
Approved Specification Changes:
* 31.H. Mainsail: Total area of windows not to exceed 350 sq. in.
* 31.I. Mainsail: Batten locations shall be as dimensioned on drawings +/- 2 in.
* 11.D. Hulls after #1142 may have a sloped thwart with an angle less than 90 deg to the centerboard trunk per the approved molds.
Approved Revisions to Drawing Notations:
* 1) Where no maximum/minimum dimensions or tolerance’s are shown, scantlings are minimums. Structural members may be divided and /or distributed if the result is of equal or superior strength and similar weight distribution.
* 2) Centerboard Tolerances: Maximum length: centerline of pivot bolt to bottom edge at the leading edge, 49 in. Maximum width: 17 in., perpendicular to leading edge. Maximum width at bottom: 8 in., perpendicular to leading edge at imaginary intersection of bottom and aft edge. All remaining dimensions as shown in plans +/- 1 in.
Approved Chief Measure Rulings:
* RH 1996: Digital electric compasses providing only current heading information are permitted. ( Built-in electric timing devises are excluded from restriction.)
* MZ 2003: Except at terminations of structural members such as the keel and hull core material, hulls shall be uniform in thickness. Fillers may be used to create a locally fair hull. Attempts to alter the overall hull shape from that of its approved mold are prohibited.
* MZ 2003: (1) one cubic ft. of floatation and 62.4 lbs. of buoyancy shall be considered equivalent for the purpose of satisfying individual boat floatation requirements.
Proposed Revisions to Drawing Notations:
* 1.) Angle’s shown on the plans shall have a tolerance of +/- 3 deg. unless otherwise noted.
Current Chief Measurers Rulings:
* Mast Step Location: Keel stepped mast shall be as shown on plans: 19 in. +/- ½ in. from the centerline of the mast to the centerline of the centerboard pivot bolt. Deck stepped mast shall be stepped such that the forward face is no closer than 53 in. to the stem and the aft face is forward of the 59 in. limiting band as shown on the plans. The deck opening for the keel stepped mast shall be a maximum of 6 in. long and shall remain between 53 in. and 59 in. aft of the stem as shown on the official drawings.
Pending the final resolution of the current Chief Measurer Ruling on Mast Step and Partner limitations, boats affected may make temporary corrections to bring the boat into compliance. In the case of a deck opening ahead of 53 in. to the stem, a black limiting band with the aft edge 53 in. min. from the stem will sufice if chocks are unworkable. The Chief Measurer will make a final judgment on a case by case basis
Jet-14 Class Association Chief Measurer