If OceanPlanet is cold molded...

[jonsailr]

i.e. layers of diagonal veneer set in epoxy, what is the construction type of the old Jet 14's., or the old Thistles?

I know they are molded plywood, but is my memory playing tricks when I want to think there was some heat involved in the molding process? What were the glues used for those boats?

What is the correct description of the construction type for these molded ply boats from the late 50's and early 60's?

Thanks,

Jonathan
--
I am building my daughter an Argie 10 sailing dinghy, check it out: http://home.comcast.net/~jonsailr

[Todd Bradshaw]

I've always heard it called "hot molded" but there might be other names for it.

[Thorne]

From - http://www.sculleyboatbuilders.com/const_coldmold.html

Arguably, the best resource for modern boat construction and repair is a book entitled "Gougeon Brothers on Boat Construction: Wood & West System Materials." The Gougeon Brothers (pronounced "Goo-jan"), were pioneers in the use and implementation of synthetic glues in boat construction, and parts of the book highlight their methods:

"Laminating techniques depend on adhesives. Over the years, methods and technologies used to laminate boat hulls have at least in part developed around the specific requirements of glues. Different adhesives require different amounts of clamping pressure and different cure temperatures. Some require tight fits, while others can span voids. These factors in particular have determined the history of laminated hulls.

“Early laminated hulls were made by hot molding – the process by which much plywood is made today. This technology developed rapidly during World War II when steel was in short supply. Adhesives then available required heat – often in excess of 300 degrees farenheight, hence the name hot molding – and frequently, 75 pounds-per-square-inch of pressure to bond properly. Laminating was complicated because large autoclaves were needed to provide these temperatures and pressures. Capital investment for pressure vessels and molds was very high, so hot molding remained strictly within the economic range of ‘Big business.'

“For 10 to 15 years after the end of World War II, some leftover hot molding equipment was used in production runs of various sizes and types of boat hulls. Luders 16 and Thistle class sailboats and small Wolverine outboard-powered runabouts are examples of hot molded laminated hulls. Just as the autoclaves and tooling were wearing out, the fiberglass boat industry came into its own with lower production costs and a more marketable, lower-maintenance product. Hot molded hulls couldn't compete against this combination, and soon the industry died out.

In the early 1950s, adhesives, which required neither heat nor pressure, came onto the market. Hot molding gradually gave way to cold molding. Cures could be reached at room temperature with contact pressure, so the expense of pressure vessels was eliminated. A simple mold or form and staples were all that was needed to hold laminated parts together as they cured. Since a minimum number of tools and little capital were necessary, small builders could practice the laminating procedures, which had been limited to large enterprises."