Producing Fiberglass Components
( The In-place Technique )

Introduction:

There are various methods of working with and producing fiberglass components for use in our hobby of model building. Some, of course, are very technical or complex while others are more simple or basic. There are many modelers asking just how to go about producing fiberglass components. Most avid modelers have some of the basic knowledge required to produce fiberglass parts in the conventional method of master or plug, female mold, and ultimately laminating or laying-up of the glass cloth with resins. Though this may well be the best time-proven method for producing any sort of fiberglass component with any sort of accuracy, it is too time consuming for many of the single or one-of components we may need for our models.

There are no doubts that components layed-up in a female mold, more often than not, produce the best-finished products. Let's consider an engine cowl for an example. Basically it is the outer shape or dimensions that we are interested in obtaining. Working with a female type mold to produce an engine cowl insures these outer dimensions, providing the original plug is properly sized and shaped. The interior of the cowl, so far as smoothness is concerned, is of little or no importance in most cases. That is, until the need arises to have the interior size or shape correspond to the fuselage so it may fit over or slide onto the fuselage. It then becomes very important that both the interior and exterior dimensions be held to a close tolerance and this then becomes another "bag of worms," which sends most modelers back to the hobby shops in search of another kitted model rather than trying his/her hand at scratch building.

If the model subject we select to do requires the engine cowl to overlap the fuselage by several inches, if you want the cowl separation line to be in a scale-like location at the firewall of the full-sized subject. Nothing, I think, can be more distractive on a model, than having a non-scale, additional panel or seam running around an engine cowl. Our engines, be it a small glow-engine or even a large chain-saw conversion engine, are nowhere near the scale length of any real aircraft engine and mount. So, it is a really rare occasion, on most models, to have our engines mounted on the scale-location firewall. Aside from being able to utilize some of the excess space forward of the scale-location firewall for radio equipment and fuel tank etc. it is much easier and stronger to just extend the model's fuselage to a point more convenient, under the cowl to secure our engine.

So as not to add any additional seams in the engine-cowl, it is best to just have the cowl overlap this lengthened fuselage. I hope to demonstrate just how simple and quickly the methods to produce all sorts of form fitting fiberglass components. I aptly named it the in-place technique. To simply describe the technique is that basically it's a method whereby some sort of expendable material is affixed in place, then shaped as required and. over this expendable material, resin impregnated glass-cloth is laminated to produce a removable fiberglass component. A release agent is employed to prevent the resin from adhering to the subject, over which the fiberglass part(s) are being fabricated. There is no guesswork involved as to how well the component will fit upon completion, since being made directly in-place (in-place), insures an exacting fit. The expendable material, in this case, the mold over which the laminating is accomplished can be, for example: wood, paper, and clay, wax, or most of the foam products like polystyrene (normally white and beaded) or polyurethane foam.

Basically, there are two types of resins mainly associated with the RC hobby industry. Most of the commercially produced RC items today employ the epoxy type resin as it is a more stable product for the most part. The other resin, and one more generally available to the modeler, is polyester resin. Of the two resins, polyester offers the lowest cost and the widest range of working latitudes as it applies to working temperatures and mixing ration with its catalyst, etc. The polyester-type resin is available in most hobby shops, packaged under many popular brand names. Most hobby dealers stock two types of this resin. One is labeled finishing resin, and the other is laminating resin. It is this laminating resin which is used for laying-up the fiberglass components. You can also use the finishing type with complete success. Before actually delving into the "How to . . . of " in-place fiberglass techniques. I would like to just touch a few bases on the materials themselves. First, as many of you know, polyester resins do not work well with polystyrene foam this is the white, beaded foam material most often employed for foam wing cores. The polyester resin will attack and literally melt this foam away unless it is somehow protected from contact by the resin. You can use beaded foam to make all sorts of fiberglass components over, but after shaping the foam, and to protect it from the resin attack, protect all the exposed foam with a thin coating of 5-minute epoxy adhesive. Epoxy resins or adhesives have no effect on the polystyrene foam.

The other foam product is polyurethane. This is a light tan colored foam and has a sandy, gritty feel to it. This material is immune to attack by either polyester or epoxy resins. Though polyurethane foam is somewhat easier to shape and sand, it must be cut or chipped away for removal. Polystyrene foam, on the other hand, can be almost melted away with a small amount of dope thinner, acetone. etc. Either type of foam boards or blocks are available at most local insulation distributors. Fall-offs, damaged or broken pieces, can be purchased very economically. Modeling clay or even common window putty, makes a very fine expendable material over which fiberglass components can be laminated. The side benefit here is that it is easy to remove after the required component is completed, plus being very easy to mold or shape. Stiff paper or card stock may also be used in conjunction with other expendables as you will learn later on. In working with any method of fiberglass lay-up, a most important item has to be the release agent.

The resins employed in fiberglass work are, in themselves, a very fine adhesive, and it is this quality which most modelers find objective in creating fiberglass components! Many modelers have ruined the female type molds because the release agent failed. There are many sorts of products at least 5 or 6 brands of wax for protecting molds. For those not familiar with P.V.A. (Polyvinyl Alcohol), about the best description of the product is like liquid Saran Wrap. The liquid is either brushed or sprayed over whatever area is to be protected from contact by the resin. When it dries, the P.V.A. produces a very thin protective coating. P.V.A. dries reasonably fast and generally one or two coats are sufficient. The P.V.A., is water soluble and therefore, is easy to clean up or remove. It can be applied over the best of finishes without worry. Though not a hobby shop item, it can be purchased from chemical supply houses. The smallest quantity I know of is in gallon lots, which would last a lifetime, or you may choose to split it up between a few fellow modelers and share the cost.

Now let's get into the actual process itself, and follow the procedures used to produce an overlapping engine cowl for the Grande-scale model airplane

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