3-12 



DESIGN DETAILS 



MAST STEP 



TRANSVERSE M 

 BELOW 



1 PLY OF MAT 

 UNDER STEF TO 

 PPEVENT WATER 

 SEEPAGE 



FULL LAM! NATE 

 WAY OF STEP TO 

 PROV I DE CRUSHI 

 STRENGTH 



"-CENTERL I NE 



-BULKHEAD OR 

 TRANSVERSE WEB 



8ERGLASS OR WOOD 

 STEP 



SANDWICH CONSTRUCTION 

 CABl N TOP Wl TH LOW 

 ENSI TY CORE 



MECHANI CAL FASTENERS TO 

 RESIST SIDE THRUST COVERED 

 WITH FIBERGLASS CONNECTING 

 ANGLES 



Fig. 3-34. Cabin Top Mast Step - Fiberglass or Wood 



but in fiberglass construction this heavy member is not necessary and a substantial step or 

 hull reinforcement must be added. Since definite advantages are gained in accommodation 

 arrangement, many fiberglass cruising sailboats have the mast stepped on the cabin top or 

 deck. The support under the cabin top must, however, be very carefully determined. The 

 most satisfactory solution is to locate the mast directly over a bulkhead. If this cannot be 

 done, then a heavy transverse beam with adequate end supports must be provided. Figs. 

 3-34 through 3-37 illustrate recommended details of mast steps. 



1 LAYER OF MAT UNDER 

 STEP TO PREVENT SEEPAGE 



COVER FASTENER HEADS 

 Wl TH F I BERGLASS CON- 

 NECT I NG ANGLES 



ALUMI NUM MAST 



CAST ALUMI NUM OR 

 FIBERGLASS MAST STEP 



SANDWI CH CONSTRUC- 

 ON CAB I N TOP 

 TH NORMAL CORE 



CABl N TOP RECESSED 

 TO FORM STEP 



FULL LAMINATE IN WAY 

 OF STEP TO PROVI DE 

 CRUSHI NG STRENGTH 



BULKHEAD OR 

 TRANSVERSE WEB 



FULL LAMI NATE I N 

 WAY OF STEP TO 

 PROVIDE CRUSHING 

 STRENGTH 



SANOWICH CONSTRUCTION 



CABl N TOP Wl TH LOW 

 DENS I TY CORE / 



JL 



BULKHEAD OR 

 TRANSVERSE WEB 



Fig. 3-35. Alternate Cabin Top Mast 

 Step - Aluminum 



Pulling Loads 



Fig. 3-36. Alternate Cabin Top Mast 

 Step with Recess 



The principles involved in developing foundations to resist pulling loads are, in some 

 respects, similar to those discussed for the pushing loads. The load must be spread over 

 a large area to avoid high local stress. The direction in which the load will be applied is 

 very important. In some cases, particularly standing rigging connections, this can be very 

 accurately established. In other cases, such as, mooring cleats and so on, it is dangerous 

 to assume that the loading direction will always be the sensible or obvious one. Granted 

 that lines should run from the cleat to the chock and from there over the side, they may not 

 always do so. The foundation should therefore be designed on the basis of line directions 

 which are physically possible, rather than those which are considered customary. The 

 amount of load to be applied to a foundation of this type may be considered on one of two 

 bases. Either the normal line pull is arrived at by some service or operational criterion 

 and the foundation designed to withstand this load with a substantial factor of safety, or the 

 breaking strength of the line is applied and the foundation is designed to withstand this load 

 with a small factor of safety. The basic requirement is that the loading line should break 

 without causing permanent deformation of the supporting hull structure. Considering this, 

 the use of the breaking strength of the line is preferred and is the most commonly used 

 design criterion. 



