Defense Technology International - March 2008 - (Page 28)

DISPATCHES MAINE MARINE MANUFACTURING GLOBAL HULLFORM HEAVEN Composite boat may reduce injuries from wave acceleration PAT TOENSMEIER•NEW YORK he U.S. Navy has designed a speedboat for special operations that may mark a turning point in the materials it specifies for surface craft. The vessel is called the Mark V.1. It is almost an exact reproduction, in composite material, of the Mark V Special Operations Craft, an 82-ft. aluminum boat in service since the 1990s that is typically used to insert and retrieve the Navy’s SEAL commando teams. The hullform and deck of the Mark V.1 are unitized structures made of a high-tech material: inner and outer layers of epoxy resin reinforced with a woven carbon-ﬁber fabric and foam Navy raiding boat has a tuned hull design to reduce shocks from high-speed operation. T hullform signiﬁcantly reduces impact shocks on crew and passengers from high-speed transit. The aluminum Mark V, with top speed in excess of 50 kt., exposes those on board to impact forces of up to 20g from wave acceleration. As the boat clears the top of one wave it increases velocity and hits another with greater force. Depending on how rough the sea is, passengers and crew can experience wave-acceleration impacts every 5-7 sec. Though there are shock-resistant seats and other damping features on the Mark V, injuries often result, notably to the back and feet. “These a ect a crew’s health and readiness,” Hess says. U.S. OFFICE OF NAVAL RESEARCH Unitized composite hull weighs less than aluminum counterpart. core—a design that’s more likely to be found in an advanced ﬁghter plane than a patrol boat. While the Navy has used composites in vessels for years, it usually doesn’t specify such high-tech materials. “This is the ﬁrst time that the Navy hasn’t used an o -the-shelf composite,” says Paul E. Hess, Mark V.1 program manager at the O ce of Naval Research, which directed the design. “We rarely have the opportunity to try a new [material] technology that results in a boat.” The Mark V.1, nicknamed Mako, will be used to determine if a composite 28 The Mako will be tested against the Mark V in the Atlantic this summer. Hess says the data, including a costbeneﬁt analysis, will be available to the acquisition community so they can make informed decisions about boat designs for special operations. The choice of composites was inspired by an experimental boat called Stiletto that is made of carbon ﬁber-reinforced epoxy. Stiletto was built three years ago for a program initiated by the Pentagon’s O ce of Force Transformation, to experiment with designs for littoral missions (DTI November/December 2005, p. 14). Hess says that Stiletto’s success with the material brought epoxy and carbon ﬁber into the materials equation for Mako. “Carbon ﬁber and epoxy are expensive and di cult to work with, but yield a higher-quality structure and are new options for the Navy.” Composites permit the Mako’s design to be tuned for improved shock resistance. This is largely a function of the epoxy resin, which is a natural damper. Though both boats are nominally the same, the Mako’s hull has some features that reflect the use of composites. Among them are a thicker frame and more robust keel than in the Mark V. The hull is also thicker, owing to the inner and outer composite layers and foam core, which improves sti ness and strength-to-weight ratio. The hullform and the deck were fabricated by a process called vacuum-assisted resin transfer molding. Beneﬁts of the closed-mold process include even distribution of the foam core’s cellular structure, which improves structural performance. After fabrication, the deck and hullform were mated, essentially creating a two-piece boat. One beneﬁt of the design is that the Mako is about 5,000 lb. lighter than the Mark V, which displaces 57 tons. Despite design di erences that stem from materials used, the Mako is virtually identical to the Mark V. The aluminum boat has twin 2,285-hp. MTU 12V396 TE94 engines and a pair of Kamewa K50S waterjets, carries 16 passengers and ﬁve crew, cruises at 25-30 kt., and has a range of more than 500 naut. mi. The Mako was launched on Jan. 11 by Hodgdon Yachts of East Boothbay, Maine. It was built by an a liate, Maine Marine Manufacturing in Portland, which was formed in 2004 to pursue military contracts. The Mako is the company’s ﬁrst job, says CEO David Packhem. The boat was transported to Norfolk, Va., in February to ready it for sea tests this summer. I AviationWeek.com/dti DEFENSE TECHNOLOGY INTERNATIONAL MARCH 2008 http://www.aviationweek.com/dti

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Defense Technology International - March 2008 Contents Sweden Cancels SEP; Israel Launches Imaging Satellite; Geotextiles Secure Ammo Dump U.S. Navy Taps Neural Architecture Software to Assure Job Satisfaction Shrapnel-Like Pieces of Reactive Materials Increase Explosive Force of Bombs Technology is Rapidly Closing the Gap Between Sensors and Shooters Italian Army Program Aims to Develop a Fully Networked Land Force Political and Military Uncertainties Plague U.S. Defense Budget Democrats Put Pentagon on Notice Over Spending and Policy at DTAR Conference Russian Combat Vehicle Protects Tank Formations from Anti-Armor Weapons European Battlelabs Use Simulation to Verify Technologies and Stretch Defense Funds Malaysia Accelerates Fleet Modernization to meet Long-Term Goals U.S. Navy Says Composite Raiding Boat May Reduce Injuries From Wave Shocks Seeing Isn’t Believing When it Comes to Deciphering Funds for Secret Projects Advances in Sensors and Propulsion Make Torpedoes Ever More Lethal FAA is in No Rush to Approve Rules that Let UAVs Fly in Civil Airspace USS Truman Carrier Strike Group Patrols a Rough Neighborhood 24/7 U.S. says Sino-Russian Space Disarmament Plan is Riddled with Pitfalls Hyperspeed Projectile; “Sound Cloak” Hides Subs; Improving Nuclear Forensics Dutch Air Commodore Theo ten Haaf Analyzes the Impact of Rotary-Wing Operations One Soldier’s War is a Behind-the-Headlines Look at Russia’s Campaigns in Chechnya Black Budgets are Huge and Growing, and Often Conceal Amazing Failures

Defense Technology International - March 2008

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