Looking to build a custom battlewagon?
Maybe it’s time to consider a jig boat.
Photos Courtesy of Ritchie Howell
A five-axis router is used to cut the frames that are laid out and become the jig.
I’ve heard many boaters tell me that someday they’d like to build a “Carolina” boat; they consider it the ultimate fishing machine. What I’ve gleaned they mean by that is they’d like to construct a sportfisherman with wicked flare for knocking down head seas and have a sexy yet muscular profile. (On the practical side, these composite-material boats are lighter than conventional fiberglass ones of similar size and so require less horsepower—and therefore less fuel—to push them across the water.)
But there is no absolute Carolina boat. The builders who create these functional floating pieces of art employ a variety of construction techniques. For the purpose of this article we’ll be focusing on jig-built (cold-molded) Carolina boats. (Look for a future article on the plank-on-frame-built version.) So if you’re thinking about building a custom Carolina sportfisherman—and there are myriad qualified builders from which to choose—here are a couple of construction options to consider, as described by the men who do them.
North Carolina-based Craig Blackwell has been building powerboats and sailboats for 38 years, but he’s best known for his sportfish vessels. A transplanted Midwesterner, he got his start back in the late-1970s following a five-year apprenticeship with Michigan’s Gougeon Brothers, purveyors of West System™, which involves the use of proprietary epoxies in the construction and repair of boats.
Cold-molded boats start off upside down and are flipped during the build process.
Even as many custom builders embrace Computer Aided Design (CAD), Blackwell prefers to adhere to traditional boatbuilding skills. This builder starts by hand-lofting each vessel, which, in brief, means he makes to-scale drawings of each. To effectively do this requires a three-dimensional mental picture of the completed design. Blackwell starts by taking three measurements: one for the boat-to-be’s transom; a second midway up the hull; and a final one forward of amidships. “From these simple dimensions,” he explains, “I can lay out frames.” The builder places these frames at precise intervals to create a basic outline or “jig” around which he will form the boat.
Yet despite his traditional technique, Blackwell says that at some point he’ll usually consult with a naval architect. For instance, he recalls one project that required prop tunnels. Without prior experience in creating and incorporating them into one of his boats, Blackwell turned to naval architect Darren Roop to help work on the design.
Jig construction requires that a boat be built with the hull bottom facing up using a process called cold molding. Blackwell’s technique involves shaping by using an underlayment of three layers of diagonally placed three-quarter-inch, four-foot-wide sheets of okume plywood, which is used primarily for its shear strength and puncture-resistance.
Three diagonally placed layers of plywood sheeting provide strength.
As he works up to the hull sides, he reduces the sheets to about two feet wide and eventually down to six inches, depending on their location. Coring materials such as CoreCell are also employed in areas like the deck to add strength without increasing weight, but there’s no fiberglass reinforcement between the layers of plywood. When completed, a Blackwell-built hull will measure around two-and-one-quarter-inches thick, which he says provides the strength necessary for the kind of open-water duty his boats typically experience.
At some point after all this work is complete, a jig-built boat must be removed from its shed, picked up via a crane, and flipped right side up. Before this, the hull has already have received four layers of 18-ounce fiberglass cloth and resin atop the plywood. (Blackwell prefers fiberglass cloth over fiberglass mat because he says the mat continually soaks up resin, which results in increased weight.) Once it’s flipped, all of the frames that created the jig and helped form the shape of the boat are removed, leaving just the fiberglass-plywood shell. Because it’s so strong, there’s no need for the wide transversals that are typical of a plank-on-frame or fiberglass boat, so there’s more interior space. Blackwell admits, however, that plank-on-frame boats can have a lighter scantling schedule because those frames add strength.
With the sheets in place, each hull is then impregnated with layers of fiberglass and resin.
This builder’s boats also receive four layers of fiberglass cloth over the keel for added safety. Once all internal bulkheads are in place, the rest of the layout is up to the owner.
Another jig-build specialist is 25-years-and-going-strong custom builder Ritchie Howell, who says that while he’s lofted boats in the past, he now employs modern CAD technology and cuts all of his boats’ jigs on a five-axis furniture router. “A man can’t loft a boat by hand and get it [more accurate] than a CAD design,” Howell says confidently.
He explains that his reason for building with jigs and cold-molded plywood is that the end product is stronger than steel. In addition, he points out that the epoxy used takes about a year to completely cure, and with a cold-molded jig boat everything is comprised of solid sheets with little room for flexing compared to some other custom build methods that use individual strips of wood (i.e. plank-on-frame), which he says may allow for more movement and could result in a less-than-fair finish.
Like Blackwell, Howell starts with large—four by eight—okume plywood sheets for the hull bottom, plus pieces as small as 16-inches wide for other areas. Like Blackwell, he places three diagonal layers in the hull bottom, but unlike his peer, adds fiberglass mat between each layer. Howell agrees with Blackwell that mat holds more resin but says it also “keeps the glue from running.” A Howell hull ends up about an inch-and-a-half thick, and the builder claims you can whack his boats with a hammer without penetration. “It’s about puncture-resistance,” says Howell.
Note that boats like Blackwell’s and Howell’s are not limited to traditional inboard propulsion. Custom jig-boat builders like Paul Spencer, Jarrett Bay, and others now offer a variety of pod-drive-propulsion options too, creating a unique blend of the traditional and the high-tech. And of course, these Carolina boats possess a look and personality that’s timeless no matter what’s under the skin. PMY
This article originally appeared in the May 2011 issue of Power & Motoryacht magazine.