Displacement–length ratio

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. 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]

{\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

References

^ Rousmaniere, John. The Annapolis book of seamanship. ISBN 0-684-85420-1.
^ Eric W., Sponberg. "The Design Ratios" (PDF). Sponberg Yacht Design Inc.
^ Paris, Jay E. "Comparing Design Ratios". Sail Magazine. Retrieved 9 July 2020.

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[1] Rousmaniere, John. The Annapolis book of seamanship. ISBN 0-684-85420-1.

[2] Eric W., Sponberg. "The Design Ratios" (PDF). Sponberg Yacht Design Inc.

[3] Paris, Jay E. "Comparing Design Ratios". Sail Magazine. Retrieved 9 July 2020.

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See also

References