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7 Meter Rotational-Molded Craft: Powering, Maneuvering and Seakeeping Trials June – October 2010
Staples, MN – A Minnesota company has its 7m rotationally molded plastic boat tested by the Office of Naval Research. The 50 page report covers powering, maneuvering and sea keeping trials conducted in VA by the Combatant Craft Division.
By: Andy Stone
All calm- and rough-water trials were conducted with the craft in an operational displacement of approximately 4,860 pounds with an LCG 7.2 feet forward of the transom-keel intersection.
During calm-water powering trials Rotomold achieved an average maximum speed of 28.4 knots while the impeller absorbed an average of 236 shaft horsepower at an average 3,824 engine rpm. Average fuel consumption was 12.4 gallons per hour at maximum speed.
A-weighted sound pressure levels were acquired ear-level at the center cockpit position of the craft. All measurements recorded at speeds above idle indicated hearing protection will be required for exposures in excess of eight hours per day.
Rotomold accelerated to an average maximum speed of 27.6 knots in 28.7 seconds, covering a distance of 960 feet. It took an average of 13.2 seconds to decelerate, covering a distance of 220 feet. Rotomold accelerated to 20 knots in 11.8 seconds.
Turning measurements were conducted in the vicinity of Hampton Roads at maximum safe approach speed of approximately 26 knots. Turning diameters of approximately 8 boat lengths were observed when maneuvering to port and nominally 6 boat lengths when turning to starboard.
Sea keeping measurements were performed as the craft was operated in five directions relative to the prevailing sea at a nominal maximum safe speed of approximately 26 knots as determined by the craft’s coxswain. Significant wave heights averaged 2.8 feet, corresponding to a sea state two on the Wilbur Marks scale. The largest magnitude vertical accelerations were experienced in bow seas with the lowest accelerations experienced in stern seas.
The Rotomold craft’s performance characteristics have been evaluated for use as a Navy combatant craft. Potential issues and areas of concern have been noted, and recommendations made. It is expected that these test results will assist Navy and DoD acquisition programs responsible for procuring boats in evaluating the use of rotationally molded polyethylene technology for small combatant craft. The execution of the design and fabrication of the 7 meter boat by Stanley Widmer Associates and the performance trials conducted by the Navy completes the Navy’s science and technology activity for this platform. Stanley Widmer and Associates has listed the 7 meter Rotomold boat on the GSA schedule; it is available for purchase by Government customers.
The full report is available at http://www.widmerboat.com/
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About Stanley Widmer Associates, Inc. We Design, Engineer & Manufacture with Advanced Methods and Materials. Stanley Widmer Associates, Inc., founded in 1971, has offices in Staples, MN and is a leader in the Rotational Molding and Marine markets. More information about Stanley Widmer Associates, Inc. can be found at http://www.widmerboat.com