5.11 Mast Step (Section IV)

The mast step shall be located on the centerline of the boat and shall consist of an aluminum casting (as supplied by Cape Cod Ship Building) that is fastened to a fixed plate parallel to the deck by four machine screws through the central portion of the casting. After the effective date of this Specification, the mast step shall not be moved except under the supervision of a fleet measurer, who shall record the boat's Bury, Y and X dimensions after the step has been moved so as to be in a position to certify that the step location appears to be in conformity with this Specification. To compete in the National Championship Regatta a boat shall not move its mast step within 30 days of the commencement of the Regatta.

(a) The maximum permissible forward position of the mast step shall be determined as follows for:

  1. Measure the maximum permissible aft position of the after edge of the mast partners (135.75 inches aft of the mooring line groove in the bow chock, see Specification 2.2). Mark this position (PMax) on the deck at centerline.
  2. Measure the distance (Y) from the aft edge of the cockpit (on centerline at the surface of the deck behind the coaming, Point AC) to PMax.
  3. Measure the Bury, the distance from the surface of the deck at the aft most position of the partners to the surface of the mast step flange upon which the mast sits.
  4. Using dimensions of Bury and Y find the dimension X in Table X. X is measured from Point AC to the intersection of the aft edge of the mast where it rests on the step.
Table X : Shields Mast Step Location Guide
Two (2) Degrees of Positive Rake
All dimensions in Inches
For a measured Y and Bury rounded off there is a unique X
Bury\Y134.250134.500134.750135.000135.250135.500135.750136.000136.250136.500136.750137.000
33.000139.360139.603139.846140.089140.332140.575140.818141.061141.304141.547141.791142.034
33.500139.496139.739139.982140.225140.467140.710140.953141.196141.439141.682141.925142.167
33.750139.565139.808140.050140.293140.536140.778141.021141.264141.507141.749141.992142.235
34.000139.634139.877140.119140.362140.604140.847141.089141.332141.575141.817142.060142.303
34.250139.703139.946140.188140.431140.673140.916141.158141.401141.643141.886142.129142.371
34.500139.773140.016140.258140.500140.743140.985141.228141.470141.712141.955142.197142.440
34.750139.844140.086140.328140.570140.813141.055141.297141.540141.782142.024142.267142.509
35.000139.914140.156140.399140.641140.883141.125141.367141.609141.852142.094142.336142.579
35.250139.985140.227140.469140.711140.954141.196141.438141.680141.922142.164142.406142.649
35.500140.057140.299140.541140.783141.025141.267141.509141.751141.993142.235142.477142.719
35.750140.129140.371140.612140.854141.096141.338141.580141.822142.064142.306142.548142.790
36.000140.201140.443140.685140.926141.168141.410141.652141.893142.135142.377142.619142.861
36.250140.274140.516140.757140.999141.240141.482141.724141.965142.207142.449142.691142.933
36.500140.347140.589140.830141.072141.313141.555141.796142.038142.279142.521142.763143.004
36.750140.421140.662140.903141.145141.386141.628141.869142.111142.352142.594142.835143.077
37.000140.495140.736140.977141.218141.460141.701141.942142.184142.425142.667142.908143.150

Shields Measurement Form
PDF of Mast Step Form