Producing Fiberglass Components
( The In-place Technique )

Construction:

Photo 1: The fuselage is completed and sanded to its final contours. The working centerlines are well defined and that portion of the extended fuselage, onto which the finished fiberglass cowl will actually overlap (back almost to the cabane struts), is protected with strips of masking tape. The strips of masking tape are butted together, rather than overlapped, on installing. The masking tape used here became almost totally transparent due to its color match with the balsa wood, and does not show up too well in this photo.

Photo 1

Photo 2: Polyurethane foam blocks are tack cemented to the firewall. Working centerlines are extended onto the foam blocks with a felt tip pen.

Photo 2

Photo 3: Paper templates (part of the actual plans) are used to mark out the general outlines of the cowl.

Photo 3

Photos 4, 5, & 6: The foam blocks are worked and shaped toward the ultimate contours. The foam is easily sawn. cut with a sharp knife, or sanded to shape. The Stanley brand Sure-form Files work well also. If an area is undercut, dented, or nicked, etc., a bit of spackling compound can be applied to correct the condition.

Photos 4

Photos 5

Photos 6

Photo 7: As this cowl requires a returned lip at the front air intake opening, the foam block is carved to produce a recess, so as to receive the laminating material. The final sanding of the foam is done with fine grit sandpaper to bring the foam flush with the masking tape which is protecting the wood fuselage. With the sanding completed and all the particles of foam removed with a vacuum cleaner, the masking tape is given two coats of P.V.A. No P.V.A is applied to the foam.

Photo 7

Photos 8 & 9: The glass cloth is then resined into place. For this cowl, three layers of 1-1/4 ounce cloth will be applied. The number of overlapped joints is kept to a minimum. After the second layer of cloth was applied and cured, the entire cowl was rough sanded to reduce the bulge of the overlapped fabric and any other lumps and bumps which may have developed. In the actual application of the glass cloth, avoid any excess use of resin. The fabric need only be thoroughly wetted. Excess resin only adds weight, not strength. The strips of butted masking tape applied to the fuselage are now quite visible.

Photos 8

Photos 9

Photo 10: The laminating is completed and allowed to cure for an hour or so. It is then sanded again to a smooth finish. When sanding (wet sanding works best) the completed component, do not worry about sanding through a layer of cloth. Before removal, the entire component be given a coating of resin only to seal any fabric which may have been exposed by sanding. I have found that if any areas are left where the glass cloth has been exposed, in time, these areas will actually show right through the primer paint and finished paint job as well. The cowl is now ready for removal. To make removal of the polyurethane foam easy, I use a stiff piece of music wire with a small ninety degree hook bent onto one end. Used in an electric drill, the revolving wire hook digs out the foam with ease. Had this foam been of the polystyrene type, a bit of acetone would make its removal even quicker.

Photo 10

The completed cowl. To remove the cowl from over the masking tape on the fuselage, a thin section of a hack saw blade, with the teeth ground off, is slipped between the fiberglass and the masking tape to break the bond of the resin and the P. V. A. applied over the masking tape. The excess fiberglass is trimmed away after removal.

Photo 12: A few embellishments, panel lines, screws, rivets, etc., and some pain finish the project. Now you may well ask how long did this process will take? Approximately it wil take a little over four hours in total time. One yard of glass cloth was used along with six ounces of polyester resin. The cowl, as you can understand, is a perfect fit onto the fuselage. It has to be, of course, it was produced "in-place." The thickness of the masking tape used to protect the wood fuselage was the same thickness as the ultimate covering and finish applied to it a few days later. If a thicker finish material was planned, then another layer or two of masking tape could have been applied before shaping the expendable foam block. Removal of this foam core block was very easy on this particular cowl design because of its generous intake opening. But, bear in mind, that it does not take a very large aperture to insert the music wire hook to chew-up the foam into small particles. The interior of the fiberglass cowl is a bit rough on completion, but a bit of sanding on that portion, where the foam was, and a coat of paint hides all manner of sins . . .This technique, with variations, can be used on all sorts of model items. The very large wing fillets (Photo 13) for the Quarter Scale PT-19A were produced "in-place" over modeling clay and card stock on already finished surfaces. The P. V. A. release agent protected the finish from adhesion with the resin.

Photo 12

Photo 13

Photo 14: The complex stabilizer fairing made of fiberglass is from the same model and same method, only in this case, regular window putty was the expendable media over which the fiberglass was laminated.

Photo 14

Photo 15: Illustrates the cowl for the PT-19A. This cowl is the product of two techniques. The front nose bowl was layed-up in the more conventional manner of: wood plug, finished, female plaster mold, etc. A small recessed flange was left at the rear edge of the nose bowl, which later became homogenous with the "in-place technique" that produced the very large rearward section of the cowl. This cowl is over 15" deep and it was made right over seven separate sections of foam fitted and shaped over a rather complex engine mount. This cowl also overlaps the basic fuselage by several inches.

Photo 15

Photo 16: Still another "in-place" cowl. This one ,is from the Quarter size Stinson Voyager. The nice part of having these cowls overlap the fuselage is that they are so very well supported, due to the closeness of fit. that only a small screw or two is needed to keep them in place. I have only shown here the rather large cowls. This does not indicate nor mean that this method only works on big models.

Photo 16

Photos 17 & 18: Illustrates the fiberglass fairing to secure the windscreen. The expendable materials for the mold are a section of thin aluminum sheet only taped in place right on the fuselage and a piece of styrene sheet taped onto the aluminum at the proper angle. Again, P. V. A. is the release agent used to allow easy removal. A bit of trimming, some sanding, and paint complete the project. This neat little fairing takes less time to produce than it does to describe. You will have to admit that it add that touch of class to the model, aside from being very functional in holding the windscreen in place. The screws are decorative only.

Photos 17

Photos 18

The "in-place technique" not only works for our models. I can think of all sorts of fiberglass parts such as framing over a clear canopy, hatch covers, gear-leg fairings, nacelles, wheel doors and covers, antenna fairings, hinge covers, and on and on. The list is only limited by one's imagination. These are only ideas for our models. These can be carried further into full-sized aircraft. How many more items might there be for boats, cars, and all sorts of prototype work in general? In describing/demonstrating my "in-place technique" for fiberglass, it is my hope that the next time you ponder a new model subject, the thought of having to produce an item or two in fiberglass no longer will be viewed as: too troublesome or difficult. I close with a word of caution: When working with the materials described here, please read, heed, and follow all the manufacturer's instructions and recommendations.

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