# displacement to planning?

Discussion in 'Hydrodynamics and Aerodynamics' started by rolexer, Feb 27, 2013.

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### rolexerJunior Member

Hey!
I find it hard to understand how the displacement transferred to a flat effect. Know that the force down (on the boat) becomes too large and the resulting will be a lift. Do not fully understand why?
Anyone know?

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### rolexerJunior Member

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### jehardimanSenior Member

All boats are supported by the pressure of the water on the skin of the hull. In the static condition, i.e. speed is zero, this is just the static water pressure and follows Archimedes' principle. As the vessel gains speed, the pressure on the hull changes in accord with Bernoulli's principle. In some places the sum of these pressures (static and dynamic) increases, in some places it decreases, both dependent on the shape and angle of the skin to the inflow velocity.

Planning occurs when the vessel is mostly supported by the dynamic pressure. The vessel is said to "rise up" onto plane becuase the sum of the static and dynamic pressure is greater than the staic pressure and the vessel is physically "lifted" out of it's static position. This occurs due to the shape of the hull as it moves through the water. Some hull shapes will never plane, i.e. the hull remains supported by the static pressure, and my even "sink" because the cause the sum of the static and dynamic pressure is less than the static pressure, thereby providing less support for the hull in the water.

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### alan whiteSenior Member

Good definition of planing.

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