resistance

2015.11.09

What is the connection between soft ride and fuel consumption?

A boat can be made softer in waves in a variety of ways. However, each method leads to other effects:

  • Less beam (decreases stability, increases hump speed and limiting space)
  • Adding weight (linearly increasing fuel consumption)
  • Increasing deadrise angle (increasing fuel consumption)
  • Using Petestep technology (decreasing fuel consumption and quieter ride)

Decreasing the beam is often not a good idea because decreased stability and space is never desirable. To achieve a reduction of vertical acceleration (hardness of ride) by 30% using conventional technology by adding weight or increasing the deadrise angle, around 50% more energy is required and hence, 50% more fuel consumption.

Petestep technology always gives a boat a significantly softer ride, and/or significantly lower fuel consumption. We can make a boat ride over 30% softer, while also reducing the resistance by 5-10%. Compared to a boat with similar softness using conventional technology, resistance is now reduced by over 35%.

2015.11.06

Resistance

The resistance, or drag, is a physical term for a force wanting to counteract the motion of a moving object. In planing boats there are four main resistance components

  • Frictional (viscous) resistance from wetted surface area
  • Induced resistance, the cost of lifting the boat out of the water
  • Aerodynamic resistance, air resistance on the hull, deck, superstructure etc
  • Appendage resistance, form and frictional resistance on sterndrives, gearhouses, rudders, etc

Wetted surface

Wetted surface is just what it sounds like. Every bit of the boat that has contact with water creates friction at speed. At high speed, the friction dominates as the major resistance component. A larger wetted surface means higher friction, which means a higher resistance, leading to higher fuel consumption and less top speed.

On a planing boat, there are two types of wetted areas. The pressure area, which makes the boat lift out of the water, and the spray area, which is undisired and only creates friction.

Petestep hulls remove as much of the spray area as physically possible on a planing boat, thus reducing the wetted surface and frictional resistance to a minimum.