CarbonReinforcing

Carbon Reinforcing

SAFETY NOTE: C/A glue emits noxious fumes when it cures, which can be very irritating to the mucus membranes (eyes, nose, throat, etc.). The fumes will also condense in the immediate area of the glue joint, leaving a white film around the glue joint. This may wipe off easily, or not, depending on the surface material. ALSO: Remember never to use C/A on polystyrene foam, as it will dissolve that type of foam.

Here is a pair of elevon blanks for a half span version of a Trick RC Zagi-THL, called the "WingTip". If you click on the still image, a larger version should open to allow greater visibility of detail. The blanks are made of low density balsa. The elevons are 1/8" (3mm) by 3" (7.6 cm) balsa sanded to nearly a point along the trailing edge (TE) and wiegh 4.8 grams per pair after sanding. To strengthen the wood against splitting or breaking where the control horn is attached and at the tip, raw carbon fiber (CF) is glued on by hand. The image on the right shows some carbon fiber (CF) tufts laid across the grain and glued down with slow kick or gap filling cyano-acrylate (C/A) adhesive. The CF is prepared on clean wax paper by holding one end of the tuft while a bead of C/A is draw along its length and then squeegied into the fiber with one pass of another clean piece of wax paper. Chill the glue first to gain working time, and don't take too long before sticking it to the wood because it may decide to start curing anyway. At the control horn end, or inboard end of the elevon, a double wide tuft is used to strengthen the control horn mounting. Make sure you put these inboard tufts in line with the push rod path.

One trick to learn is how much glue to use. Too much glue starts adding weight quickly, which defeats the purpose of our light weight elevons to begin with. Too little glue and the fiber will not be encased in the glue matrix or stuck to the elevon. These images show the CF tufts after gluing to the balsa wood elevon. each image has another similar one linked to it that you can open just by clicking on the visible image. The glossy black areas of fiber are where not enough glue has been used. That is the surface of the fiber before gluing. The more grey matte finish is the fiber that has been glued enough. The glossy black unglued areas can be hit with a few drops of fst kick Cyano-Acrylate (C/A) and then held under a clean piece of wax paper (quickly!) to finish up the unglued areas of the fiber tuft.

Here the CF tufts are completely glued, without excessive glue spread on the wood around the CF. You can also click on these images to get more similar ones or bigger versions of the same ones. When applying the CF tufts to with wood with gap filling (slow) C/A adhesive, be sure to align them quickly and then hold them down firmly while the elevon is on a clean flat surface. The glue will warm noticably when it cures. When the heat goes away it is done curing and you can let it go. Then it is best to leave it alone for an hour to help make the wax paper peel off more easily. Next, check for missed areas that need a drop or three of fast kick C/A glue. Glue these areas and repeat the clean wax paper press routine, being sure to let cure completely. At this point the excess CF hanging over the leading and trailing edges (LE and TE) of the elevon may be trimmed carefully with a sharp knife, such as a new #11 hobby blade or a new safety razor blade. The elevons shown here gained only 1.1 grams from the addition of 3 carbon tufts on each surface, or 12 tufts total for the pair of elevons.

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