Displacement–length ratio

Ship measurement

The displacement–length ratio (DLR or D/L ratio) is a calculation used to express how heavy a boat is relative to its waterline length.[1]

DLR was first published in Taylor, David W. (1910). The Speed and Power of Ships: A Manual of Marine Propulsion. John Wiley & Sons. p. 99.[2]

It is calculated by dividing a boat's displacement in long tons (2,240 pounds) by the cube of one one-hundredth of the waterline length (in feet):[3]

D L R = d i s p l a c e m e n t ( l b )   /   2240 ( 0.01 × L W L ( f t ) ) 3 {\displaystyle {\mathit {DLR}}={\frac {{\mathit {displacement}}(\mathrm {lb} )~/~2240}{(0.01\times {\mathit {LWL}}(\mathrm {ft} ))^{3}}}}

DLR can be used to compare the relative mass of various boats no matter what their length. A DLR less than 200 is indicative of a racing boat, while a DLR greater than 300 or so is indicative of a heavy cruising boat.

Displacement DLR
ultralight under 90
light 90 to 180
moderate 180 to 270
heavy 270 to 360
ultraheavy 360 and up


See also

  • Sail Area-Displacement ratio

References

  1. ^ Rousmaniere, John (October 1999). The Annapolis book of seamanship. Simon and Schuster. ISBN 0-684-85420-1.
  2. ^ Eric W., Sponberg. "The Design Ratios" (PDF). Sponberg Yacht Design Inc.
  3. ^ Paris, Jay E. (31 May 2018). "Comparing Design Ratios". Sail Magazine. Retrieved 9 July 2020.


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