KEELS AND KEELSONS £35

A Side Keelson is shown in Figure 13 consisting of two bulb angles
riveted back to back with a plate fitted between them The inter-
costal plate is not shown on the drawing of the side keelson but it is
similar to that on the bilge keelson The horizontal flanges of the
two angle bars are riveted to each reversed frame and to a short lug
piece.

A Bilge Keelson is also shown in tie drawing. It is built up of a
series of vertical plates, one into each space, the ends of each plate
fitting tightly against the floors. The lower edge of this intercostal
plate is riveted to the shell plating by means of a short intercostal
angle. The word "intercostal" is derived from infer meaning .between
and costa a rib. The top edge of the intercostal extends a little above
the floors and is stiffened by two angles riveted back to back, the
horizontal flanges of the angles being riveted to each > ^versed frame

and to a short lug piece as indicated in the drawing

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Bilge Keels are frequently fitted on the outside of the bilge

strakes for about half the vessel's length amidships to act as anti-
rolhng chocks They consist usually of a rolled bulb section the
edge of which fits between the vertical flanges of two continuous fore
and aft angles. Sometimes one angle only is used; in any case the
section is riveted to the angle and the horizontal flange of the angle
is riveted to the bilge strake. Bilge keels also add longitudinal
strength to the vessel.

Fig. 15.—A Bar Keel.
Detail of a Bar KeeL—A, the bar keel, secured to the frame € by
the garboard strakes B, a further riveted connection being got by
heel piece & J? is the floor, D the reversed frame and E a lug piece.
In Figure 16 (i) the rivets 0 and C pass through the garboard
ptrakes B and bar keel A9 and (ii) represents a side bar keel, the rivets
holding five thicknesses together.