CONTENTS

1. Abstract
2. Deadweight Restrictions of Catamarans
3. Five Key Ingredients for optimal Strength to Weight Ratios
1. High Modulus Epoxy Resins
2. Fabric Impregnators
3. Vacuum Bagging Technology
4. High Strength Fabrics
5. Lightweight Structural Cores

ABSTRACT
The integration of high performance composites into new hull shape designs for power catamarans will provide for commercial and utility workboat applications that are: more efficient, more stable, more sea kindly, safer, roomier and faster.

The evolution of high performance composite technologies (i.e. high modulus epoxy resins set in high strength fibers, laid up over either side of a light weight structural core material) offers exciting possibilities when used in twin hull construction.

DEADWEIGHT RESTRICTIONS of CATAMARANS
Typically, a twin hulled vessel's limiting disadvantage has been what is called its deadweight restriction. After a point, as displacement increases, optimal speed and efficiencies decrease, restricting the practical ability to load the vessel. The fabrication of a catamaran hull using high performance composites and advanced processing can make available a significantly lighter platform when compared to the traditional polyester fiberglass hull. Obviously, if the static weight (dead load) of the vessel is minimized, the dynamic loads (live weight, cargo) can increase enhancing the efficiency of the vessel at greater loads, and/or allow for a reduction in the power plant requirements of the vessel.

Aside from the deadweight restriction, catamarans are a superior hull shape for most applications. The practical advantages of the hull shape are significant enough to make the production of utility power catamarans a viable alternative to traditional design concepts. The obstacle of the vessels deadweight restriction can be overcome with the use of the high performance composites as the building material. Simply put, twin hull design criteria calls for the lightest possible building material. High performance composites, done properly, offer the greatest strength to weight ratio. As in the aerospace industry (another weight sensitive arena which utilizes high performance composites), the high mechanical properties of the materials justify their use despite their higher costs. Even though these materials cost more per pound when compared to the traditional polyester laminates, far less material is used to build the same hull. Costs can also be minimalized due to the introduction of new production technologies to the shop floor that increase productivity. We believe the value of the proposed vessels will exceed their cost to produce.

Five Key Ingredients
To reach the optimal strength to weight ratios for the panel, the goal on the shop floor is achieve high fiber to resin ratios in the laminant (by weight) since the strength of the laminant is determined by the fiber content, not resin content. The resin needs to only 'wet out' the fabric and displace all air voids. Any additional resin is excess, (excess resin = excess weight). It is possible to achieve a fiber to resin ratio of 60/40 in the new composites compared to the typical 30/70 polyester lay-ups. There are 5 key ingredients to the fabrication process that must be optimized to achieve the goal of a strong but light product

1. The use of a high modulus epoxy resin.
The higher mechanical and toughness properties of these resins allow for leaner resin content without sacrificing strength. Also, epoxies give high bond strengths to core materials. The long 'open time' of the resin allows for extended process times of up to 8 hours before cure. This affords the complete assembly of complex laminants at one time and within a single vacuum bag, increasing shop floor efficiencies and product quality. The resin is post cured at 140 degrees F after the hull is finished to achieve the high mechanicals.

Epoxy is spread evenly throughout the fiberglass material as it passes through the wheels of the impregnator.	Lightweight structual core is layered with the impregnated fiberglass.

3. The use of a lightweight structural core.
The core provides for hull stiffness. The stiffness of a material is a function of the cube of its thickness. This means a cored laminant ("sandwich") will be as stiff as a solid glass laminant of the same thickness, but not as heavy. A complete cored laminant will act much like an 'I beam'. When deflecting loads are applied, one skin will be in tension, the other in compression. A good core material will have high shear strengths and will withstand the post cure temperatures.

4. The use of stronger fabrics.
Stronger fabrics such as S Glass, Carbon fiber, and Kevlar give the necessary strengths in less plies when compared to the standard E Glass. Less fabric use also means less resin use, again making a lighter laminant. Equally important to fabric type is the orientation of the fibers. The laminant should be engineered so that the orientation of the fibers accommodate the anticipated loads on the structure. Finally, a tightly stitched fabric is preferable over a loosely stitched fabric.

Finishing touches are made to the laminated panel to prepare it for the vacuum bag.	The green vacuum bag is stretched across the entire panel and sealed around all edges before the suction is started.

5. The use of vacuum bagging technology.
The importance of vacuum bagging a complex laminant with core materials cannot be overestimated. A vacuum bag compacted laminant will easily save 30-50% of laminate weight over the same materials laid up by hand with only the viscosity of the resins to hold the laminate together until it cures (requiring more resin). A vacuum will debulk the laminate and ensure that the individual plies contact each other without puddles of resin between.