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“Between perpendiculars” (BP) is a naval architecture term used to describe the length of a ship. It refers to the distance between the forward perpendicular (a vertical line intersecting the forward side of the stem at the waterline) and the after perpendicular (a vertical line intersecting the after side of the sternpost at the waterline).
This measurement excludes any projections such as the bow sprit or the overhanging stern. It is a fundamental measurement in ship design and is often used in specifications and naval architecture drawings to denote the ship’s size and proportions.
See
- Length between perpendiculars