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There is some difference of opinion as to whether parts infused under reusable vacuum bags (RVBs) are the equivalent of those produced by Light resin transfer molding (LRTM). Arlington Heights, Ill.-based Composites One’s RVB expert Ashley Duncan says no. Like Light RTM, RVB infusion eliminates styrene emissions and reduces cycle time, but a sprayed RVB alone typically does not provide an engineered B-side finish: “If you need a gel coat finish on the B-side,” she says, “then a semirigid or rigid countermold is the solution.”

But Torr Technologies’ (Auburn, Wash.) president Greg Lindstrom asserts that in his experience autoclave-worthy silicone sheet goods can be processed to provide a cosmetic B-side, up to and including a Class A finish.

Rich Rydin of RVB system provider SR Composites LLC (Henderson, Nev.), however, has advocated for several years the use of a “floating caul plate” under the flexible membrane to achieve two-sided cosmetic parts as an alternative to Light RTM. Alan Harper (Alan Harper Composites Ltd. (Saltash, Cornwall, U.K.) adds that an RVB’s very high elongation and flexibility allows for variation in layup schedules, permits higher reinforcement loading than Light RTM and costs less than a rigid B-side mold.