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New Mono-Hull Form Provides Ultra-Stable Drilling Platform A new mono-hull form having mo- tion characteristics almost equiva- lent to many semi-submersibles in operational sea states has been de- veloped and marketed by Waller Marine, Inc., a Houston-based ma- rine design and construction organi- zation. The concept, originally con- ceived and patented by F. Y. Mi- chael, utilizes a combination of small water plane with heavy damp- ing to achieve desirable motion characteristics that will allow a drillship, drilling tender, or offshore storage and production vessel to op- erate in sea states up to Beaufort Scale 6. The hull shape can be likened to a traditional vessel with upper and lower sponsons attached along its entire length. This produces a vessel having high displacement with cor- responding high deadweight, low waterplane area, and large deck area—elements that the designer strives to obtain with conventional semi-submersible design. Structur- ally, the hull can be simplified by using straight-line framing and de- velopable surfaces, complementing low fabrication cost techniques. The superior motion characteris- tics of this hull are derived from a combination of low initial GM and small water plane area, with added mass produced by the entrained water about the lower hull appen- dage. The result is a large increase in the natural period of the vessel in all degress of freedom, particularly in roll and heave, that produces a significant shift in the regular wave response curves toward higher mo- tion periods. Together with extreme hull damping, this provides for re- duced motion at normal periods of encounter along with reduced am- plitude. 2 'II E % • M Jr^ Lines Plan The natural period of roll for a drillship, for example, has been ex- tended 27.5 seconds—a condition that cannot be achieved by a drill- ship having a conventional hull form. Stability has not been ne- glected, as the small waterplane is large enough to allow reasonable weight movements on board with- out adverse heel, and the upper hull shape regains buoyancy and right- ing moments at larger angles of heel. 19 20 21 22 WAVE PIWIOD - 3EC0WDS GIBBS & COX INC. Naval Architects & Marine Engineers 1235 JEFFERSON DAVIS HIGHWAY ARLINGTON, VA. 22202 703-979-1240 119 WEST 31 STREET NEW YORK, N.Y. 10001 212-613-1300 6060 JEFFERSON AVENUE NEWPORT NEWS, VA. 23605 804-380-5800 REGULAR WAVE : HEIGHT =31.7 FT. PERIOD = iaO SECONDS LENGTH =I6. I HEIGHT MAX. WAVE SOPE -I I.I DEG. WAVE LENGTH =512 Relative Position On A Regular Beam Wave Surface Circle 122 on Reader Service Card BENDER BUILDS, CONVERTS, STRETCHES If You Can't Build New, Bender Will Upgrade By Lengthening Or Modifying Your Existing Vessels rna-m VTTjf" B ao 4 f • - 1BBEGULAR Y-JAVES / So ROLL MOTIOM Ao. P * / /V ° <,y~ - / 4 P J 20-a i iP e 12 !*• 1A IS Jl An "SIG. WNIt HE I6HT _ FT 1BEEGULAC y>o HEKVJE MT)T,OM 3J0 ZM- 3 tto- // ) 5> ^ e |2 lit >« u i f ± * Sib. VIAVE Htl&HT. FT Lengthening the Doc Tide and Darol Tide by 16 ft. For more information call JOHN R. LOGAN, General Sales Manager, or PETER MASCHKE in Mobile, and on the West Coast call JOE HENDRIX at (206) 282-9631 LENDER SHIPBUILDING & REPAIR CO., INC. Post Office BOX 42, Mobile AL 36601 Phone: 205/433-3673, Telex 505-457 MAIN DECK 11-,r Midship Section Circle 113 on Reader Service Card 92 Maritime Reporter/Engineering News
