Inside Angle: Plumb Crazy

Vertical bows are all the rage, but are they functional? Bill Prince weighs in with this “plumb” assignment.

Flip through an issue of Power & Motoryacht from 2017 and you know what you won’t see? Fast powerboats with plumb bows.

But look through these pages or stroll the docks of any major boat show in the U.S. or abroad today and … they’re heeeeere. Wait … didn’t plumb bows on high-speed boats go the way of the dodo bird in the 1920s and ‘30s? That was a hundred years ago. What’s going on?

I offer ten seconds of history which may lend perspective. We all know where the bow is on our boat, but why is it called a “bow” and not just the pointy part? The word ‘bow’ is derived from Old Norse ‘bógr,’ or ‘shoulder’. The bow shoulders the waves on any boat, but it’s how well the bow shoulders those waves that matters. Makes sense, right? And this is where the evolution of the bow shape becomes the story.

Plumb bows on powerboats were largely replaced a hundred years ago for good reasons, but of course none of the people doing so are alive now to elaborate, which brings me here. Prior to World War II, relatively slow and stately motor vessels often had vertical bows which maximized waterline length for optimal displacement speeds. But after the war, marine engines became lighter and more powerful, increasing boat speeds. This led to the widespread development of the planing hull.

Shouldering the seas at new, higher velocities meant the shape of the bow had to change. This welcome evolution added the bow rake we’re all familiar with in a boat’s profile. The rake, coupled with the hull’s flare as it widens up near the deck, creates a progressive amount of reserve buoyancy as your bow begins to stuff into a wave at speed. The added bow volume in width and in length does wonders for keeping green water out of your boat and keeps your deck above water.

Now let’s talk about sailboats for just a moment. In the 1990s, sailboat design took an off-ramp. As a result of racing rule changes, the America’s Cup boats evolved into hulls with plumb bows for reasons entirely unrelated to the needs of fast powerboats with which you and I are most familiar. These new high-tech carbon fiber boats appeared on TV around the world, associated with luxury sponsors like Louis Vuitton and Prada. Racing atop hydrofoils, those boats literally began to fly. And they looked like the future. Boat buyers noticed.

This new fashion quickly spilled over to fast, open powerboats in Europe. The Italians are as concerned with fashion as anything—including function—so the proven advantages of a raked bow were jettisoned in the name of style. These “hipster boats” are proliferating now, leaving their new owners largely unaware of the nuances of their bow shapes..

Want a laugh? Pull up any YouTube “stuffing compilation” video from Haulover Inlet. You’ll see how the hipster-bow boats fare compared to their raked-bow sisters. Some of the shortcomings in seakeeping are shocking. .

But this fashion is hardly reserved for small, fast boats. The radical 390-foot motoryacht “A” styled by Philippe Starck (the same guy who designs trash cans and diaper bags you might buy at Target), has not just a plumb bow but a reverse bow. You won’t see it in the press photos but this bow shape is so impotent that the small ship requires a hydraulically operated “wave deflector” on the foredeck which the crew must deploy in rough seas to return green water to its rightful home.

My office shies away from vertical bows except where they’re historically accurate for a spirit of tradition new-build or for displacement-speed yachts. And the highest-quality American production builders have stayed true to their proven hull forms with proper bow rake and flare. You likely won’t be seeing a Viking, Pursuit, Grady-White or Cobalt with a vertical bow any time soon. Fashion is one thing, reputation is another.

So, sometimes, even important functional details like hull shape are merely influenced by what is perceived to be fashionable from a customer’s perspective. I have no doubt we will see other design elements from our seafaring past come back in style, only to fall out of fashion once again. Cannons, anyone?

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This article originally appeared in the March 2023 issue of Power & Motoryacht magazine.

Source: https://www.powerandmotoryacht.com/column/inside-angle-plumb-crazy