We have studied for a new type of Spar-Buoy boring derrick, which required to cope with two exceeding conditions, namely (1) increasing loaded weight of boring machine parts and materials for increasing boring depth, and (2) a increasing current velocity to about 4 knots.
We have studied two models, (1) double float type, and (2) larger diameter of float for increasing buoyancy, in order to utilizeparts and materials of the existing spar-Buoy boring derrick for economical choice.
We have performed numerical analysis and model experiments for two type model, and prototypes were designed and put to practical use.
