Applying Oratex is a relatively simple process. Since it is non-toxic and not messy, you can even do it in your living room! It’s just a matter of gluing it down and then shrinking it tight. What follows is a summary of the procedures involved. A more detailed manual will be shipped with your order.
All contact surfaces must be completely free of any grease, oil, dirt, wax, silicone or other contaminants. When working with glossy surfaces such as powder coating or gloss paint, the surface must be scuffed to provide tooth for the adhesive to adhere. Scotchbrite works well for scuffing most surfaces. Because Oratex is so durable, an unprotected wooden airframe could easily begin to deteriorate long before the fabric even begins to show wear. For that reason, all wooden surfaces should be painted or varnished (per aircraft designer’s recommendation) and then scuffed or lightly sanded to ensure adequate adhesion. Steel and aluminum should be primed.
Two thin coats of adhesive are applied to both the underside of the fabric and the contact area of the airframe. Both surfaces are coated with two coats of adhesive; no more, no less. Be certain to use adhesive that has not reached its expiration date and be sure to use enough adhesive. Do not skimp! After the glue has been applied, it must be allowed to dry completely. The glue will not adhere if you don’t let it dry completely. Depending upon temperature and humidity of your work environment, a thin coat of glue will dry in about 45 minutes. Do not apply the second coat of glue until the first layer has dried completely.
Once the adhesive has dried completely (and thus turned from white to clear) the fabric is secured to the airframe with non-abrasive clamps, such as spring clamps with rubber coated tips. Special tools are not required to cut the fabric. Good scissors, pinking shears or a sharp knife all work well. Leading edge seams overlap 4 inches, and trailing edge seams overlap 2 inches.
It is important to get the fabric as tight and as wrinkle free as possible when you glue it down. This is particularly important information for those of you who are experienced with other fabric systems, because Oratex does not shrink quite as much as some other fabrics. Just take the time to make the fabric as tight as possible on the glue down. It will make the shrinking job easier, and the end product will look great! Do not follow the advice of those that have experience with the old legacy systems. Their procedures do not work with Oratex.
The adhesive is activated by heat, and pressure is required to ensure that the adhesive layers fully penetrate each other and air pockets are avoided. The surface of the fabric is rubbed with a hot iron set at about 100°c. This will melt and trigger the adhesive. As the adhesive reaches 70°c the melting will trigger the glue activation. As the glue melts, good pressure is applied with the iron to force the glue into good contact with the fabric. As the iron is moved forward to a new area, the melted glue behind will set in about 10 seconds. It is imperative that the fabric does not move while the glue is setting up. The heating is done with either a digital heat gun or a digital iron, both available to purchase from us.
Once the adhesive has fully cured it will have a much higher melting point. It will still melt before the fabric melts (250°c) allowing for removal if necessary. But the melting point will be high enough to withstand any environmental exposures—for example, an airplane that is painted black and placed in the hottest desert on the hottest day.
Once the adhesive has had sufficient time to set (usually 24 hours, longer in a cold environment) it is time to shrink the fabric. Apply heat with your hot air gun (never more than 250°C) and shrink the fabric until taut and wrinkle free. Before you begin shrinking, test your heat gun on a scrap piece of fabric. If you have the proper temperature, the fabric will not discolor or be damaged even with the nozzle close to the fabric. Better to check this on a scrap than on a wing! This is easy with our tools, as they have precise digital temperature controls. If (when you glued the fabric down) you stretched and clamped the fabric to be as wrinkle free as possible, a minimal amount of shrinking with the heat gun will be required.
The finishing touch is the final application of heat, using your flat iron. For this final shrinking, do not press down on the iron. Hold the iron “weightless” and wave the iron back and forth over the unsupported surfaces. Light contact is all that is needed. Use a single thickness of paper towel under the iron, with the iron set at 160°C. Once the shrinking is complete, your fabric will have a taut and smooth finished surface.
All seams must be covered with finishing tape (pinked edge or straight edge may be used). Tapes come with glue already applied to one side. In addition to the glue that is already on the tape, glue must also be applied to the fabric seam itself, otherwise there is the possibility of air bubbles becoming trapped at the seam joint. To avoid this potential problem is simple. Just be sure to apply a line of glue that is about 1/4 inch wide, and in three layers. Do not go overboard. Keep it narrow so that it does not come out at the edges of the tape. Remember, all you are doing is preventing tiny air bubbles from forming at the fabric joint, where the edge of the top layer of fabric is. The glue also makes the seam look good, as it hides the edge of the top layer.
Be sure to apply reinforcing tapes to the fabric before rib-stitching/lacing or pop riveting is done (or whatever primary method of attachment the original aircraft design specifies). Then cover with the finishing tape. If your design calls for rib stitching, the finishing tapes will go over the stitching. If it calls for rivets, the finishing tapes will go over the rivets. Just as you applied extra glue to the fabric seam, you also should apply extra glue to the reinforcing tapes (and rivets or rib stitching) to prevent air bubbles under the finishing tapes. After the finishing tapes have been applied over the ribs, apply the leading and trailing edge tapes. Leading edge tapes must be at least 4 inches wide, trailing edge tapes must be at least two inches wide. Tapes are available in one-inch increments.
Note: Be sure to provide for drain and ventilation holes. Because Oratex is airtight, ventilation holes are necessary to allow for air expansion as the airplane gains altitude. Condensation must also be vented and drained!
Be sure to use the Oratex wax for future maintenance and ease of cleaning. There is a special cleaner concentrate as well.