How Boston Whaler Builds Boats

A conversation among Whalers
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How Boston Whaler Builds Boats

Postby dtmackey » Wed Jan 09, 2019 8:17 am

This video may help answer some questions on how Whaler builds boats.


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Location: Michigan, Lower Peninsula

Re: Open or Closed Cell Foam in c.1979 Boat

Postby jimh » Wed Jan 09, 2019 6:31 pm

DT--the presentation on youTube you have pointed to is very interesting. It reveals some further details of the construction process of which I was unaware, specifically the paste of resin and chopped fiber applied to one of the two components of the Unibond hull to ensure a good bond when the two parts are joined.

I have visited the Boston Whaler plant in Edgewater, Florida, and was afforded a tour of the plant. I wrote a detailed article with illustrations about that experience, and published it at


Because of the time of day when we were on tour, we did not get to see the process of the hull and liner being married together and the introduction of the foam. (The first shift had done its last boat, and the second shift was just coming on duty and had not made it first boat yet.)

In the present-day facility the creation of the foam is done under much more controlled conditions that in 1979. As seen in the recorded presentation (but not too well explained), a rather sophisticated machine controls the foam "shot" to a predetermined amount for each model of hull. The narration track is a bit misleading, as the material injected by the machine is not a foam, but rather a liquid mixture. The reagents in the mixture undergo a chemical reaction that turns them into a foam, filled with encapsulated bubbles, which expands significantly. It is important to note that the tightly clamped mold halves resist the expansion of the foam, helping to maintain the density to a higher weight. At the same time, intentionally designed vents in the molds, along with a setting of the mold forms at particular elevation angles, helps to distribute the foam throughout the empty space between the hull and the inner double-bottom hull liner. The hulls remain in these mold sets, and the foam is allowed to set and harden for many hours, before the newly joined hull are separated from the mold. The result is a very high consistency in manufacturing of the Unibond hulls.

Although my article does not contain any motion-picture elements, it does have a considerable amount of information and detail about the method used to construct Boston Whaler boats, so I would not hesitate to recommend reading it to learn more about how Boston Whaler boats are built.