Dynamics of Launching

Using the components of weight and buoyancy with the specified frictional coefficients (water, grease and chain drag) in the equation of motion describing the vessel's progress down the ways, the speed at each interval of travel is estimated. McNeil's energy method, together with the total distance travelled before stopping (that means, McNeil's general energy equation) is used to solve the equation of motion. The difference in speed between each interval of travel determines the acceleration or deceleration over that interval and hence by summation the total time taken can be derived. The program terminates the calculation when the speed is zero, that means, the motion has ceased. This is estimated by a parabolic fit through three values of velocity.

A table and graph is produced detailing the instantaneous velocity, elapsed time and instantaneous acceleration as the vessel progresses down the ways. The calculated and available travel before coming to rest and the maximum velocity attained during launch, are also reported.

The pressure required to prevent the ship sticking (that means, not starting to slide) is calculated using an empirical formula based approach. First the static pressure is calculated as follows:

Where the length and width of the sliding ways relates to the area in contact with the fixed ways. The minimum allowable pressure that is necessary in order to ensure the ship does not stick is calculated using the following formula (for metric units):

where , measured at midships (this is calculated by Calc from the slipway information supplied). If the static pressure is less than the minimum required pressure, a message is printed that states that the ship is likely to stick.