We're unsinkable, too
The following letter from Mirage Manufacturing. builder of Great Harbour Trawlers, appeared in the November 2004 issue of Soundings Magazine.
I was both delighted and disappointed by the September article "Unsinkable boats, exceptional safety." Delighted because a serious boating journal was touting the obvious advantages of boats that can't sink, disappointed because the article failed to mention Mirage Manufacturing, which has been building unsinkable trawler yachts since 1997, when we launched our first Great Harbour 37. We now offer three models, the GH37, the N37 and the GH47, which displaces 70,000 pounds but will not sink.
As your article noted, materials play a major role in constructing an unsinkable boat, and indeed our use of Nida-Core, a honeycombed plastic coring material, is a major factor. Our hulls are solid fiberglass up to the rubrail, but above that the super structure is made with Nida-Core to add stiffness as well as buoyancy and insulation against both sound and temperature.
The coring material, however, is just one of two factors. Nearly every full displacement trawler yacht on the market is based on a hull form that is round-bilged like a beefy sailboat. The designers of the Great Harbour trawlers took a less traveled road, and that led to several technological breakthroughs, one of which was positive buoyancy. Instead of the familiar sailboat hull, naval architect Lou Codega and Mirage President Ken Fickett based the Great Harbour hulls on those of offshore tugboats--beamy, hard-chined and inherently stable.
Form stability eliminated the need for ballast, and solid fiberglass is a couple ticks on the scales shy of being neutrally buoyant, so that left only the ship's machinery to pull her to the bottom. Our use of Nida-Core easily overcomes that pull. And while we have not done the saw-it-in-half photo op of some of the small-boat manufacturers, we believe that single Nida-Core part, the boat's rooftop, would standard twin engines across Buttermilk Bay (Mass.)
More conventionally, our 15-year-old sportfish line is also unsinkable because of high-density foam coring of the hull. This was demonstrated in dramatic fashion when one of our customers thought that he could land a 1,200-pound shark on a 6,000-pound vessel, and swamped 100-miles off New Jersey. Not only did the crew survive those shark-infested waters, but the vessel was recovered and put back into service.
Whenever we see notions of seaworthiness debated, we have ruefully noted the omission of unsinkability as a factor. This silence is because most manufacturers of larger vessels, particularly trawlers, have taken a path that makes it impossible for them to achieve unsinkability. This is not a condemnation; those builders have looked at the marketplace and put a higher premium on aesthetics. We don't blame the builders; we blame their customers for failing to see the advantages as described in your article.
Twin Screws vs. Singles
Shoal Draft vs. Deep Draft
Form Stability vs. Ballast and Stabilizers
New "Fishtail" Rudders
Space Age Core|
Boat Core Materials