Planing in Extreme Conditions

By Donald L. Blount and Jack Funkhouser

When you think about high speed craft, like the two projects SeaForce 410 CC and the CFD simulations for Scout Boats, one question that should flash through the designer’s mind is: “Will she become airborne?”  This is an important question to know the answer to as it significantly increases structural loading on the hull structure and other components.

Design accelerations for dynamic supported craft are non-linear, which means that they don’t increase in a predictable way as sea state increases. This is because of two factors: 1) not every wave in a sea way is the same, and the larger ones will be quite a bit larger than the average, and 2) once the vessel launches from the waves, the impact upon re-entry can be exponentially higher than normal accelerations.  Understanding if item 2 will occur, will enable to design to select appropriate design accelerations for the hull and onboard equipment. Recognizing the need for this knowledge, DLBA developed an evaluation technique based on model test data of a range of high speed hull form.  The results of this effort are captured in this paper a simple technique for determining if a vessel will become airborne.