Sep 12
Fiberglass Molds – Multipiece Benefits
posted by: Steve Jones in Uncategorized on 09 12th, 2017 | | No Comments »

I just finished building a new mold for a 1/10 scale radio controlled car. One of the great things about making radio controlled car bodies out of fiberglass is the detail and the undercuts that can be formed using multi-piece molds. The realism is much greater than that which can be found in a vacuum formed body.

Multi-piece molds are always necessary for building three dimensional objects – whether those objects are hobby related or not. With the exception of very simple molds, multi-piece molds are almost always required or at least preferable. The obvious reasons for the use of a multi-piece mold are driven by the ease of extracting your parts from that mold. Molds that are very deep are difficult to lay-up parts in and can be very difficult to pull your parts out of.

The draft angle of your plug is a major determining factor that will determine the need for a multi-piece mold. Smaller parts may require no draft angle while larger parts that are deeper than 12 inches will require a draft angle of up to 5 degrees.

Automotive parts other than hood scoops, fender flairs, spoilers, etc are often done with one piece molds. Larger parts, such as doors, hoods, entire bodies and the like are almost always done as two piece molds.

I was looking at my first and main Fiberglass Mold Manual in which I outline the procedures for building a simple one piece mold. The funny thing about this manual is that the project that I follow in this manual ultimately required 3 separate one piece molds. A project requiring 3 separate one piece molds can also be labeled as a multi-piece mold.

Multi-piece molds do give many benefits to the builder, but there are a few drawbacks. Multi-piece molds do produce a flash line that must be dealt with. Flash lines require filling, sanding and refinishing. Flash lines are created by imperfections in the edge of the mold and in the general alignment of the pieces of the mold. In my opinion flash lines are a minor trade off for the many benefits of a multi-piece mold.

Happy Glassing