Minimum Planing Speed
A HydroComp Technical Report
Report 113
Product link: NavCad,
SwiftCraft,
PropExpert
There
are a number of traditional 'milestones' that can be used to predict
the speed necessary for a boat to fully plane. You can expect
a boat to be on a plane above a speed/length ratio of somewhere
between 3 and 5, which nondimensionally is above a Froude number
(Fn) of 0.9 to 1.5. Similarly, a volumetric Froude number (Fv)
of 2.5 to 5 is often cited for minimum planing speed.
As you can see, 'critical' planing
velocities cover a broad range. Differing hull parameters  particularly
the aspect ratio of the planing surface  all affect the planing
performance and the ease with which a boat gets up on plane. Here
at HydroComp, we have worked up a ruleofthumb formula that has
shown good correlation with actual vessels. The formula is:
where k = 4.0 for feet and 7.2 for
meters, LCG is the longitudinal center of gravity from the transom
and B is the planing beam. This formula accounts for the efficiency
of the planing area due to the relationship between planing beam
and LCG.
