In 2015, Eric Greene Associates was asked by Resolute Marine Energy to help develop preliminary design and manufacturing concepts for their innovative wave energy converter. The near-shore, bottom-mounted flap design was validated through sea trials off the coast of North Caroilina in 2009. EGA conducted a parametric study to downselect the optimum structural arrangement, material selection and manufacturing technology to support modular construction of the device. Laminate schedules, scantlings and interface design details were developed to ensure the device could endure extreme waves.
Carbon Fiber Radar Arch
In 2014, Eric Greene Associates was tasked by IAG Yachts of Zhuhai, China to design the structure for a carbon fiber radar arch to be fitted on their latest 140 foot megayacht. Working with longtime associate Tim Kings, who is the project manager for the newbuild, Mr. Greene developed laminate schedules and structural arrangments for the arch. The sandwich carbon structure was built by the expert composite craftsman at McConaghy Boats.
EGA also engineered carbon fiber deck beams to help IAG Yachts increase the interior headroom for King Baby, which to date is the largest composite yacht built in China. (photos by Tim Kings)
Union Station Bus Terminal Pavilion
In 2012, Compmillennia of Washington, NC built composite pavilions that were designed by Studio Twenty Seven Architecture and installed in the nation’s capital Union Station bus terminal. Eric Greene Associates provided the structural engineering for the composite construction, as well as detail design and building code compliance assurance. The unique design utilized Compmillennia’s expert craftsmanship and composites innovation to ensure a smooth installation, as seen in the video below produced by Eric Greene Associates.
Megayacht Helicopter Deck
In 2007, a megayacht builder approached Eric Greene Associates to develop a concept design for a helicopter landing deck that could be erected on an as-needed basis. The basic requirement was for the structural elements to be lightweight so the ship’s crew could handle the components manually. A system based on composite sandwich panels and pultruded beams was developed. The landing deck was required to resist helicopter landing loads, ship motions and accidental fuel spills that could create a fire hazard. Personnel safety considerations were also incorporated into the design. Modifications to foundation structure and mounting interface hardware were developed.
Composite Twisted Rudder
Ship rudders located behind large propellers experience a flow stream that varies in “angle of attack” from top to bottom. To better align the entire rudder with the water flowing by it, U.S. Navy hydrodynamics engineers have developed a rudder shape that conforms to this stream by “twisting” outboard in the middle. The goal is to delay the onset of cavitation-induced corrosion/erosion damage. However, this shape is very costly to build out of steel. Structural Composites in Melbourne, FL is currently building hybrid steel/composite rudders for a destroyer to validate construction methods and survivability.
Mr. Greene has served as Program Manager for the Composite Twisted Rudder (CTR) project since its inception in 2001.Responsibilities included securing over $5 million in project funding; integrity of structural design; full-scale testing and qualification; and manufacturing to U.S. Navy requirements.The project is directly supporting technology intended for the DDG-1000 platform.
Shock Mitigation for Special Operations Vessels
Eric Greene Associates collaborated with Hodgdon Yachts in the spring of 2003 to secure funding for the development of a composite MK V replacement boat with the goal of reducing impact loads experienced by Special Operations forces during mission transit. Eventually, Maine's congressional delegation secured $14 million through a series of earmarks over several years to complete the vessel. Conceptually, composite structures can deflect more than the current aluminum hull structure and therefore transmit less of the wave impact loads to its passengers. In addition to project conceptualization, Mr. Greene was involved in the preliminary material selection process and developed framing arrangements. Manufacturing and panel testing protocols were also developed for the project. The MK V.1, christened the Mako, is currently undergoing evaluation trials in Norfolk, VA by the Navy.
Megayacht Structural Fire Protection
Over the past ten years, Mr. Greene has supported the U.S. composite megayacht industry through consultation on structural fire protection systems.The background for this work was based on earlier support for U.S. Navy research and development projects to evaluate fire test methods and fire protection schemes to protect naval marine composite structures.
In addition to specific structural fire protection schemes, fire testing protocols and programs were developed to qualify composite structural systems subjected to fires.The advancement of structural fire protection schemes for large composite megayachts has made it possible to consider composite construction for vessels over 500 gross tons.
Marine Motion Control of Portland, ME has developed a patented technology that uses a gyrostat to stabilize the motion of large yachts and small ships.Most motion control methods rely on the vessel to be underway to make fin stabilizers effective.A gyrostat is a gyroscope mounted on gimbals so that the axis of rotation can tilt forward and aft. When the axis is tilted in the proper direction, a tilt-rate torque is developed that will offset the rolling moment of the vessel.
Eric Greene Associates developed the preliminary design and manufacturing concepts that would enable the gyrostat to operate at over 15,000 RPMs without creating a shipboard hazard.A geometry with two bearings was developed to reduce local reaction moments.
Manufacturing technologies considered included infusion and filament winding.Attention was paid to the need to have a finely balanced rotor assembly for safe operation.This work was performed in 2003 and 2004.
In the spring of 2005, Eric Greene Associates supported Atlas Hovercraft in their early development of composite structural concepts for hovercraft construction.Atlas Hovercraft, Inc. feels they are positioned to become the largest hovercraft design and manufacturing company in the world. Their air cushion vessels possess advanced features that overcome many of prior hovercraft shortcomings, such as low maneuverability, high maintenance costs and high noise.
Mr. Greene developed preliminary structural concepts for the novel hovercraft design.This included material, framing and manufacturing tradeoff studies for primary and secondary structures.A key focus was on strength, weight and production costs in order to allow Atlas to make hovercraft transportation economically viable for the military, commercial passenger service, and recreation markets.
Snow Center FRP Roof Panels
In the spring of 2005, Arabian Profile Company of theUnited Arab Emirates contracted with Eric Greene Associates to assess the structural design of roof panels they were building for the Snow Centre located in the middle of the desert.Composite panels were selected to help maintain the thermal difference between the interior “skiing” environment and the exterior heat, often in excess of 100°F.
Mr. Greeneconsidered loads from wind and personnel required to work on the roof panels.Structural details and manufacturing methods were evaluated to ensure that the design was safe for the intended use.Finally, quality assurance procedures were recommended for the project.
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The USS Constitution is the oldest commissioned ship in the U.S. Navy still in service.The Constitution set sail from her berth in Boston, MA in July of 1997 – her first sail in 116 years.The U.S. Navy’s engineering arm, NAVSEA, oversaw a host of structural and safety upgrades to make the sail possible for her 200th anniversary.The ship’s 60 officers and crew were supplemented by 70 naval reservists and civilians from the U.S. Navy Historical Center Detachment in Boston, MA.
Mr. Greene was fortunate to be on board during the July 1997 sailing to document the damage control drills carried out under the watchful eye of the NAVSEA Damage Control Group.Many dignitaries were present for the sail, including the Chief of Naval Operations and cruise commentator Walter Cronkite.Several news organizations had satellite video feeds of the event, yet Mr. Greene was the only photographer to obtain video from aloft in the rigging and below during damage control drills.This footage was edited along with some historical information about the Constitution in an early “desktop” movie program.Eric Greene Associates retains this capability to document projects in an edited video format.
Monolithic Composite Periscope Mast
Mr. Greene worked with the Advance Ratio Design Company (ARDCO) of Chester PA to secure funding to design and build an advanced composite submarine periscope mast for the U.S. Navy.Traditionally, these masts are constructed with an expensive Monel “I-beam” with mechanically-fastened composite fairings.Mr. Greene developed the concept design for a “monolithic” composite mast that utilized advanced composite materials to fabricate periscope masts with improved structural performance as well as reduced acquisition and life-cycle costs.
The structural “I-beam” and foil-shaped fairings are combined into a single structural element manufactured using the resin transfer molding process.The structural weight of the monolithic mast was half of what the incumbent design, helping to lower the submarine’s center of gravity.The monolithic design also eliminated the need for mechanical fairing fasteners.
This project was performed for Advance Ratio Design Company of Chester, PA and completed in May 1996.It was funded by the Small Business Innovative Research (SBIR) Phase II program under contract N00024-94-C-4177.
Structural Fire Protection for Navy Director Room and Helicopter Hanger
Eric Greene has managed full-scale fire testing for two U.S. Navy composite topside demonstration projects.The first was a Forward Director room on the DDG 51 destroyer.Northrop Grumman built a technology demonstrator at their El Segundo, CA facility.Since this is an unmanned space, an epoxy-based intumescent coating was used for fire protection.The completed technology demonstrator successfully underwent shock testing.
The second project was involved a composite helicopter hanger.This is a manned space and testing needed to be to standards outlined in DDS 078-1, "Fire Performance Requirements for Composite Materials, Surface Ships, Topside Structural and other Topside Applications." This required full-scale bulkhead and deck furnace tests, which were overseen and documented by Mr. Greene.
Technology Roadmap for Naval Composites Research
In 2002 and in 2005 Eric Greene developed Technology Roadmaps for Naval Composites Research to support the U.S. Navy ManTech program.The work was contracted by the South Carolina Research Authority.The purpose of the strategic plan was to identify technology gaps; plan ManTech projects to coordinate with platform insertion opportunities; define future composites applications; coordinate ManTech projects with other research activities to ensure fleet implementation; and to match ManTech research with Composite Consortium membership capabilities.The Composite Consortium consists of first and second tier defense contractors that utilze composite material to build weapons platforms.
After the Technology Assessments were completed, Mr. Greene presented his findings to the Composite Consortium in membership forums and print.The demanding performance characteristics of weapon systems have pushed military ships, aircraft and land vehicles to the leading edge of composites technology.Vital Navy needs in the areas of weight reduction, corrosion resistance, and signature reduction have been addressed over the last twenty years by the introduction of composite materials.The Technology Roadmaps have directed the path forward for research investments required be the navy
Joint Modular Lighterage System
The Joint (Army and Navy) Modular Lighterage System (JMLS) Advanced Concept Technology Demonstration program took place from 1997 through 2000. The JMLS was to provide configurable platforms to move supplies and equipment from ship to ship and from ship to shore.Mr. Greene supported Art Anderson Associates’ effort to downselect a “Champion Concept” JMLS composite flat end module prototype. The work was completed in July of 2001.
Included in the effort that Mr. Greene was responsible for was design concept, fabrication method and cost estimation.The JMLS system consists of multiple floating docks that are joined at-sea via a special linkage system.The connecting loads are quite high and engineering was done to ensure operability and structural integrity.
Composite Ventilation Ducting
The major problem with existing shipboard ventilation ducting is corrosion and the life-cycle costs associated with maintaining and replacing this ducting.The current galvanized steel or aluminum ducts have a shipboard life of 4 years due to corrosion from the salt/sea environment.This chronic problem has caused poor in-service performance, extended ship lay-ups, and is likely to continue aboard relatively new ship designs that use similar conventional materials and ventilation design philosophy. Mr. Greene supported Structural Composites effort to develop corrosion resistant, low cost, composite ventilation ducting manufacturing processes that feature integral fire, thermal and acoustic characteristics. Composite ducting offer a solution to the chronic problem of maintenance/replacement of corroded ducting.Composite ducts were built by Structural Composites and Boeing that were strong, quiet, fire retarding, non-corrosive, internally insulated, modular, easy to install and maintain, non-magnetic, and easily repairable.The demonstration installation of composite ducts on the USS Samuel B.Roberts (FFG-58) was completed in 1998.
Fire Performance of Composite Materials for Naval Applications
Mr. Greene served as Principal Investigator for a Small Business Innovative Research (SBIR) Phase II project awarded to Structural Composites under contract N61533-91-C-0017.The work was completed in November of 1993.A number of fire issues that have hindered composite structures within the U.S. Navy were investigated in this SBIR effort, including development of a five-year research plan; evaluation of flammability test methods; development of a novel structural integrity test; offgassing assessment; extinguishment evaluation; smoke corrosivity determination; and development of a Fire Data Management System.
Mr. Greene worked closely with naval researchers, scientists at the National Institute of Standards and Technology (NIST) and university researchers to coordinate fire research over a two-year period.The structural integrity test protocol was subsequently adopted by commercial ship and university researchers.
Mast Step Repair
The damage to this sailboat was first noticed on the hull near the forward end of the keel during an annual haulout. It was determined that compression loads from the mast caused the skin failure as the internal composites framing system was inadequate to resist the loads. A stainless steel assembly was designed to transmit mast loading to the hull via the existing composite stiffeners.
Redesign Engine Girder System
This boat experienced cracking in an aft transverse frame and in the outer hull laminate. Transverse frames were added to provide lateral support for the engine girders and the shallow transverse frame was stiffened with a carbon fiber cap. Mini bulkheads were added to improve the overall hull torsional rigidity.
Fiberglass craftmanship by:
Repair Disbonded Structural Grid
Many production composite boats use structural grids that are molded separately to stiffen the hull. These grids are attached to the inside of the hull using secondary bonding techniques. The bondline is not easy to inspect and the grid may not match the hull perfectly in all areas. This vessel showed areas of disbond that left a gap of up to 20 mm in some areas. A procedure was prescribed that involved removing old bonding material and preparing the surface for an epoxy filler with excellent bonding characteristics. The flange was then bonded to the hull using conventional tabbing procedures.
Fiberglass craftsmanship by:
Repair Internal Stiffeners after Grounding
This yacht experienced a severe grounding as evidenced by a blunt impression on the forward edge of the keel. There was no apparent damage at the keel attachment point but the interior stiffener system had multiple failures and delaminations. The full extent of the damage was revealed when the stiffeners were ground to the point of good laminate for the repair. The laminate schedule was designed to match the original scantlings and tabbing details were improved to increase the overall structural integrity.
Fiberglass craftsmanship by:
Longitudinal Stiffeners Repaired by Owner
This 1980s era racer/cruiser had been modified and repaired numerous times over her lifetime. The longitudinal stiffeners were discontinuous in many places, allowing the hull to distort to a "hogging" condition. This caused misalignment of the propulsion shaft, which exited the aft end of the keel. The internal framing system was redesigned and the owner laminated new stiffeners in place.
Repair Damaged Megayacht Sailboat Hull
A 110-foot sailing yacht sustained substantial damage to her hull beneath the waterline on the port side when she dragged her anchors and rested on coral heads for a tidal cycle. Although some interior skin damage was noted, no breach of the hull laminate that would allow water to enter occurred at the time. Eric Greene Associates was contacted to assist the repair contractor properly repair the hull by preparing material selection, laminate schedule and repair procedures. At the time of her construction, this yacht was one of the largest composite cruising sailing boats built. To meet the designer’s high structural expectations, a sandwich hull laminate 50% stronger than ABS requirements was developed. The skins consist of Kevlar/E-glass hybrid reinforcement (3/8”) vacuum bag hand-laminated with Shell Epon epoxy resin. The core below the waterline is 2” thick, made from two 1” layers of Divinycell H-130 PVC core. A 23-step repair procedure was developed for the project, along with detailed quality assurance and documentation procedures. Marty Ford completed the repair at Thunderbolt Marine in Savannah, Georgia.
Repair Boat Overturned During Hurricane Sandy
This racing sailboat was blown off her storage stands during Hurricane Sandy. The boat sustained substantial through-hull and interior water damage. Repair procedures, laminate schedules and repair oversight were provided to satisfy the new overseas owner that the boat was returned to her original structural integrity.