RIB PROTOTYPE CHARACTERISTICS
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DESIGN OF MID-SCALE MODEL
The mid-scale RIB model was designed to closely represent the geometry and fundamental stiffness characteristics of the 1/36 scale model that was successfully tested in the laboratory. An aerial view of this model is shown above. The basic geometry of the RIB System cross section, known as the "Double Delta," is shown below. The 1/36 scale model was constructed of a lightweight, rigid PVC foam board approximately 1/10th inch thick. An analysis of this model material, conducted by M.J. Plackett & Associates (MJP&A), indicated that the model material stiffness would be representative of a full scale stiffness equivilent to a corrugated 1/4" steel plate structure with a 4" by 4" corrugation pich. Using this as a baseline, full scale stiffness criteria for the mid-scale RIB section was developed by MJP&A.The mid-scale model was fabricated by Kepner Plastics Fabricators, Inc., Torrance, California . It consists of a combination of welded steel structure and closed cell foam floatation. The model is designed as a modular system capable of being assembled using simple hand tools on the beach at Currituck Sound.
MJP&A have provided technical assistance related to the design, planning, structural analysis and fabrication.
GENERAL REQUIREMENTS
The following general requirements for the mid-scale RIB model were identified:- The RIB sections should be fabricated in modules that could be managed and assembled using manual labor and simple hand tools.
- The model should be deployed in the test area using available FRF assets.
- The model should require minimal if any maintenance during the test period of sixty days.
- The model should be capable of being recovered as conveniently as possible without compromising the basic function of the system.
BASIC COMPONENTS AND MOORING DESIGN
Basic RIB System module (click to expand)
Anchoring Layout (click to expand)
- The RIB curtain consists of a welded steel structure composed of upper and lower triangles separated by a sheet steel web reinforced vertically and longitudinally with a framework of welded steel angle. A fabricated closed cell foam block is inserted in the upper triangle section of the RIB module to provide approximately 80% of the overall flotation. The RIB sections are constructed of 15 identical 10-ft long modules attached with special interconnect fittings to minimize stiffness discontinuities.
- The float or wave barrier consists of a closed cell foam filled vinyl tube that is attached to the upper triangle of the RIB section. The primary function of the float is to prevent waves from over topping the structure and to provide flotation of the structure.
- The nose wave deflector and mooring buoy. This is an independent welded steel float with special docking stations for receiving the port and starboard sections of the RIB and maintaining them at 45 degrees from each other.
- The port and starboard stern mooring buoy and docking station which provide the means of securing the stern of each section and anchoring.
- Intermediate mooring points are located at approximately 1/3rd of the length (50-ft at 1/8th scale) of the port and starboard RIB sections. The anchoring layout is shown above.