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Boatbuilding Technology Keeps Getting Better

Michael Peters

Sightlines - March 2016

Freed from the Jello Mold

Boatbuilders are taking precision to the next level.

Bertram 35 mold

Over the years it has been plain to see that boats are getting more complicated. Each boat we design has a new set of standards that were only options a couple of years earlier. While the trend is pretty obvious, it has really come to light with our design for the new Bertram 35, which is meant to be an update of the iconic Bertram 31 Moppie, designed in the early 1960s.

I don’t really like to write about any specific design we are working on. But the new 35-foot Moppie is unique, because we compare everything we are doing to the original 31-foot design, so it is a real study in how much things have changed in the last 50-plus years. The new boat has roughly twice the power, twice the fuel capacity, and more headroom and accommodations compared to the original. These are the standard things of any modern boat, but what is most striking is how many more complex fiberglass parts are required. The 31 was built with roughly eight molds for the hull, deck, roof, flybridge, interior liner, and engine hatches, and the stringers were glass over wood and the cockpit was vinyl-covered plywood. By contrast, the new 35 requires almost 40 molds.

Take a look at fiberglass boats from the ’60s, ’70s, and ’80s, and you see trim covering every raw edge or joint. Fiberglass parts were put together with overlapping joints, called shoebox joints, and these joints ran around any two fiberglass parts that came together and were covered by aluminum J-trim or teak strips. Almost all decks and houses were taken from a one-part mold, which severely limited the designers to two degrees of draft on all molded parts. Aluminum-framed or rubber-grommeted windows were mounted through holes cut out of the featureless fiberglass cabin sides. Not much creative styling resulted from working within the limits of a single-part “jello mold” and the boat designs were often as exciting as a city bus.

Custom boats didn’t suffer from the design limitations of simple molding techniques and there began to be a distinct discrepancy in what could be built as a one-off compared to a production boat. About 25 years ago, this began to change with the influx of Italian designs, where the boats sported complex house sides, complete with deep overhangs and recessed, glued-in windows, with no nasty trim. It was impossible to see how these complex parts were molded, because all of the fiberglass joints had been eliminated by utilizing multiple molds and hand-finishing the gelcoat joints. Today, most modern production boats are done this way, which has allowed a revolution in styling.

On a recent visit to Marine Concepts, to inspect the tooling for the new 35 Moppie, I was a bit concerned about the complexity of the tooling we were developing compared to that of the original boat. As we walked outside, I noticed the cabin side mold for another manufacturer, complete with deep recesses and overhangs, which was only one of five molds necessary to fabricate the deck. I mentioned to Todd Biddison, our project manager at Marine Concepts, that I had guessed we weren’t the only ones to create new designs that required such complicated tooling. He said multipart molds are the new normal and have changed the game in tooling development. 

Tooling for a boat as basic as a center console is now more complex than what was utilized to build an entire yacht just a few years ago. The old industry standard was a simple deck hatch to a gelcoated bilge if you were lucky. Today, that hatch now opens to an insulated molded liner, and closes on its precision-routed gutter with an O-ring that seals perfectly against a squeeze-molded hatch liner that perfectly finishes off its underside. Multiply this philosophy over an entire boat and add the multipart mold technique to cast complex designs and you get an idea of how we have gone from eight molds to 40 molds.

The remaking of a classic points out how crudely simple fiberglass-boat construction was 50 years ago. The early fiberglass boats were very commercial by today’s standards and boaters would likely not accept them today. So now the designer has been freed from the jello mold. We will just have to see how many modern designs endure like some of their simpler predecessors did.

This article originally appeared in the March 2016 issue of Power & Motoryacht magazine.