stability

2015.11.09

What is the connection between soft ride and stability?

Any planing boat can be made softer, even without changing the deadrise angle. The beam is an important parameter here. If the beam is decreased by 10%, vertical accelerations will be decreased by about 20%. However, the boat will also lose side stability by more than 10%.

Petestep can make this design dilemma easier. If a boat uses a Petestep hull, it can be wider, have the same vertical accelerations and significantly increased side stability. Or, it can be just a little bit narrower and with a decrease in vertical accelerations by half, while having the same stability.

Why does my boat become unstable at high speed?

The faster a V-bottomed boat travels, the higher out of the water it planes. When the wetted beam becomes too narrow, depending on weight, center of gravity, bottom and propeller, etc, the boat will start to heel back and forth to port and starboard, unless you are a skilled driver and can counteract these motions. The traditional approach to counteract this instability is to place large spray rails at the side of the wetted area to act as support wheels. This might slightly improve stability, but it will make the boat much harder in waves.

Petestep deflectors act as much better “support wheels”, without contributing to a harder ride. And you will not need to counteract the rocking motion by steering.

2015.09.15

Deadrise angle

Deadrise angle, or V-bottom angle, is the transversal (sideways) angle between the horizontal plane and the v-bottom surface. A large deadrise angle, e.g. 24 degrees, makes the boat ride softer in waves but less sideways stable and more fuel consuming.