3D Printing a Yacht Hull Mold
Thermwood recently printed several sections from a 51-foot-long yacht hull mold to demonstrate how only a single mold may be needed for the manufacture of larger vessels, such as yachts.

The printed sections of this test mold are made of carbon fiber reinforced ABS from Techmer PM. ABS was chosen because of its physical properties and relatively low cost compared to other reinforced thermoplastics.

Thermwood has already 3D printed a full-size pleasure boat master pattern which has been used to produce multiple production boat hull molds. While this demonstrated the value of additive manufacturing small boat tooling, much larger vessels, yachts for example, require a different approach. In these instances, since only a single mold is needed, it is desirable to print the mold itself rather than print a plug or pattern from which multiple production molds can be made.

To demonstrate to the industry how this might work, Thermwood printed a 10-foot section from a 51-foot long yacht hull mold. This rather unique mold design was specifically developed for additive manufacturing. It is printed in sections, each about five foot tall. These printed sections are then bound together both chemically and mechanically using high strength polymer cables into two mold halves. The two mold halves then bolt together to form a complete female mold for the yacht hull.

Each mold section has a molded in rocker. When the mold is fully assembled, it rests on the floor on these rockers. At this point, the mold can be rolled over to tilt about 45 degrees to either side, kind of like a giant rocking chair. This allows for easier access during the layup process. A set of molded wedges are clamped to the rockers to hold the mold in the desired position. Once the hull has been laid up and fully cured, the mold is rolled to level and the printed wedges are clamped to both sides, holding them level. Then the two mold sides can be un-bolted and slid apart to release the finished boat hull.

Certain thermosets will work directly on the ABS molded surface using just traditional mold release practices; however, other thermoset materials are based on solvents that can chemically attack the ABS polymer.

To prevent this, Thermwood has experimented with several protective coatings. While it appears that this approach will work today for certain thermosets, the ideal would be to develop a low-cost polymer that is chemically resistant to the other thermoset solvents and eliminate the need for a protective coating.

These demonstration pieces were printed and trimmed on Thermwood’s 10x10 foot LSAM MT, the smallest and lowest cost additive manufacturing system currently available. The entire mold section, made of four printed pieces, weighs 4,012 pounds and required 65.5 hours to print.

For more information, contact Duane Marrett, Thermwood Corporation, 904 Buffaloville Rd., Dale, IN 47523, 800-533-6901, E-mail: duane.marrett@thermwood.com. Web: www.thermwood.com.