If you have ever been into a fiberglass shop you have probably noticed the smell of styrene and other volatile organic compounds (VOCs the feds call them) in the air. A few years ago in California laws were passed limiting VOCs. This meant that laminating a fiberglass hull with a wet laminate exposed to air became a thing of the past in the state. Other states have imposed similar restrictions on VOC emissions and the trend appears to be moving country-wide. To eliminate VOCs, other methods of laminating were sought and developed, and the one that has taken hold at TPI in Warren, Rhode Island, is the SCRIMP system. (SCRIMP is an acronym for Seeman Composites Resin Infusion Molding Process after Seaman Composites in Mississippi, which developed the process.)

For the reader familiar with vacuum bagging, the process is similar, but for those who are not here's a quick rundown. Unlike normal laminating methods, where layers of fiberglass cloth are laid on a mold and wetted out before being rolled, boats built with the SCRIMP process are laid up dry. In a typical mold the gel coat is sprayed on and the outer fiberglass layer, the core and the inner fiberglass layer are lightly glued in the mold. (The method can be used for both a cored and non-cored hull.) The entire layup is covered with a layer of peel-ply and a special SCRIMP cloth. On top of the SCRIMP cloth a vacuum bag is placed and the air is sucked out, putting the entire layup in a vacuum. Various hoses lead into the bag, and each hose is clamped until it is needed. Note that the entire layup is still dry.

When it is time to put the resin into the mold the hoses are simply dropped into a bucket of resin and the clamp on each hose opened as the resin is infused. The pre-accelerated resin flows through the hose and into the layup under the vacuum. The whole laminating process takes about half an hour, depending upon the size of the boat. The vacuum is held until the laminate is dry, and then the vacuum bag, SCRIMP cloth, and Peel ply are simply pulled off the molded shape. That's it. No voids, no drips and no mess, and non productive tool cleanup time. In the shop it was noticeable that none of the laminators wore protective masks and coveralls. The job was much cleaner than the former messy wet-laminating approach.

In Europe the same process is used to build 170-foot minesweepers, with significant savings in labor and materials over hand laminating systems. Using the SCRIMP method stringers and floors are built into the layup dry and wetted out when the resin is infused. This saves time and eliminates secondary bonding — a major plus for boats with lots of floors and framing. Another plus is the elimination of lightweight fabrics, cloths and mats. SCRIMP can use very thick fabrics, in some cases up to 120 ounces per square yard, although the more usual fabric is about 60 ounces.

Because the bagging and vacuum pressure is totally controlled during all phases of the process, the job can be repeated with an accuracy previously obtainable only with pre-pregs and vacuum bagging. According to the SCRIMP brochure, the navy has tested the method on laminates up to 6 inches thick and has found that voids cannot be detected using any of the current ASTM testing methods. (Typically a hand laminate may have 8- to 10-percent voids, while a pre-preg might have 2-percent voids.)

In terms of tensile and compressive strengths, SCRIMP, vacuum-bagged and autoclaved laminates are compared in the SCRIMP brochure using a 140-degree post cure. Tensile and compressive strengths are similar for SCRIMP and autoclaved laminates, while strengths for vacuum-bagged laminates is slightly lower.

The SCRIMP process is patented and SCRIMP Systems, Inc. is licensing users. According to various sources, the cost of a license is around $25,000, but that includes training for the licensee's workers and help in getting started. After that, the licensee pays a royalty on every piece laminated using SCRIMP. This means that SCRIMP Systems, Inc. could eventually end up getting a royalty on every piece of fiberglass molded in the marine industry.