THE buoyancy chamber of a pneumatic dinghy is roughly of ‘rubber inner tube’ form arranged around the wale or upper perimeter of the craft and when inflated the bow and stern ends are at a higher elevation than the midship section which is normally horizontal. The chamber is constructed of straight lengths of constant circular cross section each being joined to its contiguous members, the space curve of the contour of each joint constituting an ellipse. A requirement for the layout of the gores enjoins that the longitudinal scams of all portions should be outboard, continuous, rectilineal, and, as nearly as possible, in the relative positions they would occupy if the chamber were coplanar. A convenient plan by means of which this may be accomplished is to stipulate that the points of junction of the longitudinal seam lines of consecutive portions be in the plane containing the axes of assigned pairs of corresponding members and passing through the centres of the ellipses of junction of these members.
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