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September 21, 2007

High-Tech Boat-Building Takes Off


The Maverick Mirage HPX Tunnel was built using the latest fabrics and design techniques to achieve a strong yet incredibly lightweight flats skiff.

The fiberglass boat-building industry has undergone tremendous evolutionary changes in the past decade. Today, an increasing number of companies are building boats using the latest foam-coring materials and high-tech resins, glues and fabrics to increase strength while saving weight.

It wasn't always so. Those of you old enough to remember the early days of fiberglass boat-building will recall that back in the early 1960s companies like Bertram and Hatteras were producing boats with massive wood stringers and bulkheads, and hulls built of layer upon layer of glass. The old joke was that no one knew just how much glass you needed, so they would slap on a couple of extra layers just in case.

Lots of these early boats are still with us, of course, because they were built like tanks. The heavy hulls ran well in rough water, but were somewhat slow, wet, and not very fuel-efficient. That didn't matter in the mid-'60s, when gas wars drove fuel prices to as low as 30 cents a gallon, but all that changed with the Arab oil embargo of the early '70s. Fuel-efficiency suddenly became very important. Then, in the '80s, everyone decided they wanted their boats to be fast. Slow was out, and manufacturers rushed to find ways to lighten hulls without compromising strength.

Smaller boats had some of these same problems, too. Early fiberglass flats skiffs were heavy and drew too much water for extreme shallow-water fishing. And to get the speed one needed to travel across large bodies of water, higher horsepower outboards were hung on the transoms, thereby adding even more weight and exacerbating the problem. Fortunately, help was on the way in the form of space-age materials.

New Materials, Techniques

Maverick technicians add a layer of Kevlar hybrid to a Mirage HPX Tunnel hull being prepared for vacuum-bagging.
Maverick technicians add a layer of Kevlar hybrid to a Mirage HPX Tunnel hull being prepared for vacuum-bagging.

In the offshore world, companies like Hydra-Sports and Mako experimented with Kevlar in their hulls early on. Kevlar is a synthetic fiber developed by DuPont that is three times stronger than aluminum of equal weight, and 43 percent lighter than an equal amount of fiberglass, yet almost twice as stiff as glass. It also has more than ten times the impact resistance of 100-percent fiberglass.

Lightweight coring materials were also developed to replace wood as a structural material in stringers and bulkheads. High-tech foams arrived on the scene, offering very high densities and strength, at a mere fraction of the weight of wood. The combination of these coring materials and synthetic fabrics allowed builders to create lighter and stronger hulls.

Experimentation with new materials, techniques and technology continues, so we thought it would be interesting to check in with a company on the cutting edge of boat building. At this year's Miami Boat Show, one of the most talked-about new boats came from the Maverick Boat Company, known worldwide as a builder of high-quality flats skiffs. Maverick's new Mirage HPX Tunnel is a high-tech, tunnel-hull skiff built using the latest fabrics and coring materials, and the tunnel in the aft section of the hull allows the engine to be mounted much higher. A vee-hull version will be produced later.

Obviously, weight is a primary concern with a highly technical shallow-water skiff like this, and Maverick President Scott Deal says that the HPX Tunnel wasn't developed just for the sake of using new methods and materials. "Technology is not the end unto itself," Scott says. "Our ultimate goal was to build a shallow-draft boat that fishes well."

Birth of a Flats Skiff

We went to Maverick's factory in Fort Pierce, Florida, to watch an HPX Tunnel being built. Paul Ellig, Maverick's head of Engineering and Product Development, took us through the process step by step.

Ellig explained that the boat is built without a stringer system. Instead, layers of carbon/Kevlar fiber material and a Kevlar hybrid are used to create stiffness. Both carbon fiber and Kevlar offer outstanding stiffness without adding a lot of weight.

A gelcoated fiberglass skin coat is laid up first, and the strakes are faired out inside the hull with putty to create an even surface. Next comes a layer of 7 1/2-ounce carbon/Kevlar cloth, then another layer of 12-ounce Kevlar hybrid. The Maverick laminators use vinylester resin sparingly when laminating these fabrics to the hull to save even more weight. Ellig calls it "a stingy, disciplined lamination process."

A one-inch-thick Baltec closed-cell foam core is laid along the hull bottom, with 3/8-inch foam laid along the hullsides. Then one more layer of Kevlar hybrid is laminated into the entire inner hull. Between the high-density foam and the layers of carbon/Kevlar and Kevlar hybrid, a very strong hull with superior impact resistance is created, while adding very little weight.

Vacuum-Bagging Explained

As vacuum is applied, excess resin is drawn into the breather layer.
As vacuum is applied, excess resin is drawn into the breather ¿layer.

Ellig then vacuum-bags the whole thing to create uniform adhesion throughout the hull. A layer of smooth material known as a "peel ply" is laid evenly over the inner hull, followed by a more porous material called a "breather ply." The peel ply is super-slick and can be peeled off the hull even after the resin has dried. The breather ply allows air to move around beneath the vinyl bag to evenly distribute the vacuum pressure, and it also blots up excess resin as it is squeezed out.

The vinyl bag is wrapped around the hull and held in place with a special two-sided tape, then vacuum pressure is applied to the center of the bag. The bag sucks tight onto the hull, creating pressure that holds all of the laminated parts tightly together. The foam cores have small holes in them, and excess resin is squeezed up through these holes, through the peel ply, and into the breather ply, where it will be removed after the whole thing dries. The amount of vacuum pressure is critical because too little will not create a perfect bond, and too much will draw out too much resin, resulting in a dry laminate.

After the vacuum is applied, Ellig circles the boat slowly, checking the seam for leaks with an ultrasonic leak detector (no kidding). All leaks are closed off and the hull remains under vacuum until the resin sets, which usually takes about three or four hours.

Two transverse bulkheads add stiffness when the cap is applied (the HPX Tunnel has no liner), and the whole thing is glued together using space-age methacrylate adhesives such as Plexus or Weld-On. These super-strong adhesives do more than just glue parts together; they permanently bond them with an incredibly strong "weld." All hatches are cored with foam and laminated with carbon/Kevlar for stiffness, and the rod racks are glued in, adding additional stiffness to the hullsides.

Maverick further saves weight by heat-molding parts such as live wells and storage boxes out of high-density acrylic plastic instead of building them out of fiberglass. The factory's VOC (volatile organic compounds) emissions are substantially lowered too, which makes the EPA happy.

When finished, the HPX Tunnel hull weighs a mere 425 pounds. We tested the boat with a 50-hp Yamaha outboard and three large men aboard, and it hit 33 mph. That's impressive performance for a 17-foot boat powered by a 50. Plus, the boat floated in very skinny water. Poling the boat along the shallows of North Hutchinson Island, we went shallower and shallower until we finally grounded at the bow. A ruler showed the bow to be in five inches of water. The stern may have drawn slightly more, but not much.

Maverick is but one of many boat companies that are experimenting with new high-tech construction techniques, and others have no doubt developed different systems and combinations that work well for them - and us. As consumers, we benefit in many ways from the new boat-building technology. The new high-tech boats are light, strong, fuel-efficient, easy to trailer and easy to pole. But the biggest advantage is that they'll help us catch more fish, and that's what it's all about.For more information on the new Mirage HPX Tunnel skiff, contact the Maverick Boat Company, Ft. Pierce, FL; (888) SHALLOW; www.maverickboats.com