That was quick, Wouter!
Even the definition of 'planing' is controversible.
From "a boat travelling faster than its stern waves",
via "lifted by dynamic forces that are larger than static forces (bouyancy)"
to "lifted to the water surface by dynamic forces".
Most planing boats produce some waves, hence even for planing, there may be some wave drag.
My impression being a non-expert trying to interpret what I find in books and on the web, an ultrabrief version is that 'semi-planing' is "static lift being larger than dynamic lift, with separation of water from the stern/transom" or "the transition between displacement mode and planing mode".
See this thread
http://www.boatdesign.net/forum/archive/index.php/t-2347.htmlwhich contains referances.
If you search "semi-planing" on Google, you will find many ads and stories on vessels and military ships using the term semi-planing.
E.g.:
http://www.globalsecurity.org/military/systems/ship/semi-planing.htmIf 'planing' is imprecise, then it is not possible to produce an exact definition of 'semi-planing'.
Stein
