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WHAT IS CA?
CA or cyanoacrylate, is actually acrylic plastic. CA’s cure (or polymerize) when pressed into a thin ﬁlm in the presence of a slightly alkali environment. The only trigger it requires is the hydroxyl ions in water, which is convenient since virtually any object you might wish to glue will have at least trace amounts of water on its surface. In general, ambient humidity in the air and/or on the bonding surface will provide the proper pH to initiate cure in a few seconds. The best bonds are achieved when relative humidity is 40% to 60% at room temperature. If the surfaces to be bonded are excessively dry or are acidic, the curing can be much slower or not happen at all. Most manufactures will agree that depending upon humidity, CA’s may take as long as 24 hours to achieve full cure. As a point of interest, gel and thickened CA’s are produced with additional components to induce various levels of thixotropic or gel qualities.
Only use a little! CA glue needs room temperature or higher to cure. Place the pieces together and drip a small amount of glue on the edge of the crack. Capillary action will draw the glue down into the crack. Use acetone or nail polish remover to remove unwanted glue.
White glues, like Elmer’s, bond by solvent evaporation. The solvent in Elmer’s allpurpose school glue is water. When the water evaporates, the polyvinylacetate latex that has spread into a material’s crevices forms a ﬂexible bond. Super glue, on the other hand, undergoes a process called anionic polymerization. Cyanoacrylate molecules start linking up when they come into contact with water, and they whip around in chains to form a durable plastic mesh. The glue thickens and hardens until the thrashing molecular strands can no longer move.
CA glues do have a lot of shear strength. CA glue can be used to “tack” a part in place while epoxy or other glue hardens. CA or super glue comes in several forms, such as gap ﬁlling, and thin or thick. The term “thickness” as it applies to CA relates to the amount of dripping associated with the glue, thin CA runs a lot, gap ﬁlling CA expands when drying “ﬁlling” in gaps. All CA’s will cure only with an air tight joint! The absence of air causes the glue to set. CA glue will not work well on porous material and any joints that are not near perfect. One way around this problem is to use a spray hardener that will “set” the glue when applied. This hardener is a MUST when using CA on wood.
Once a bottle of CA glue has been opened, it is important that it be kept upright and not exposed to extreme heat or cold, and most especially, dampness or water. Find a glass or plastic jar with a tight ﬁtting lid. Use the change-a-tip package to replace the tip that comes on the bottle with a change-a-tip cap and stopper. (Available from Rockler Woodworking Supply http://www.rockler.com/ﬁndit.cfm? cookietest=1&page=10562. It is recommended that you place used replacement tips in a small bottle of Acetone for storage and cleaning.
Place the CA glue bottle in the jar along with a dry pack, which will have a blue color to the package and seal the jar. Keep an eye on the color of the dry pack. It will change to a pinkish color when it has absorbed all of the moisture that it can. When this happens, place the dry pack in a microwave for a couple of minutes. It will dry out, the color will change back to blue, and it can be re-used. You can place more than one bottle of the CA glue in the jar.
It is extremely important not to place either a CA accelerator or de-bonder in this jar with the CA glue. If any type of leak were to develop in these products, it will ruin all the CA glue in the jar. This procedure will maximize the life of your product. Do not store CA glue in the refrigerator. The normal moisture in the refrigerator will ruin the glue. Properly stored CA glues will last a long time.