BOAT HULL DESIGN 



2-23 



UNSUPPORTED TRANSOM 



INNERBOTTOM FLANGED UP 

 TO SUPPORT TRANSOM. 

 BOAT SHOWN CUT ALONG 

 CENTERL I NE 



VERTICAL BRACKETS TO BE 

 SUPPORTED BY LONGITUDE 

 NOTE: GUNWA E CARRIED INBOARD 

 ON TRANSOM 



d. HORIZONTAL SHELF 5UPPOPTING 

 TRANSOM. 



NOTE; GUNWALE CARRIED INBOARD 

 ON TRAN50M 



Fig. 2-18. Transom configurations 



in combination as illustrated in Fig. 2-18. Normally, in boats intended for higher power, a 

 narrow side deck or heavy gunwale strip will exist which may be carried around the corner 

 to reduce the span of the transom. If a permaneni inner bottom is provided, this may be 

 given a radius at the stern, and carried up the transom for support. The use of vertical 

 brackets,, which is common in wood construction, should be avoided in fiberglass construc- 

 tion unless there are corresponding stiffening members on the bottom. This is because the 

 toe of a bracket landing on unsupported shell constitutes a definite "hard spot" as discussed 

 in Chapter 3. One of the most common and most effective means of support for the transom 

 is the horizontal shelf located as close to the top of the transom as the depth of the mounting 

 bracket of the motor will permit. This horizontal shelf is usually used as a seat, or as the 

 bottom of a watertight well. Another method of increasing transom rigidity is to curve the 

 transom aft. The effect of any normal curvature is comparatively small, and it is felt that 

 the possible reduction in the transom thickness should not be considered. 



Decks: For structural design purposes, decks are divided into two types: weather decks 

 which may be subject to water loading and interior flats and cabin tops which are subject to 

 loads from personnel and equipment. 



For weather decks, including watertight open cockpits, a uniform, load corresponding to 

 2 feet of water is considered a good design value for most pleasure boats. For work boats 

 and fishing boats designed to operate at sea, a higher figure should be used. In boats with 

 small partial decks, as in runabouts and small sailboats, an alternative design loading may 

 be used, assuming the weight of a man concentrated at the center of the deck. A factor of 

 safety of four is suggested with either of the above loadings. 



