Froude for Thought
Getting Semi-Planing Hull Resistance Right

By

Dr Robert Ranzenbach

Donald L. Blount & Associates, Inc

The first step in having an efficient boat is to have an appropriate hull form for the intended vessel size and speed range. Most new recreational vessel designs today, with the exception of small outboard powered craft, fall into the non-dimensional speed range referred to as semi-displacement or semi-planing. While some people believe there are some minor technical differences in the terminology, we at DLBA believe they are one in the same. Living and operating in that range, there are a range of well known hull shapes and features that perform well.  This paper provides a great beginner’s summary into the technical nuances of what it means to be in the semi-planing regime, and discusses the design parameters, hull shapes, and appendages that can be incorporated to keep hull resistance low.  Tuning the vessel’s hull and propulsion system to have low resistance is good for both the environment and the wallet!

The article was published in the Yacht Report, please click on the image below to download the PDF.