This post deals with the topic of applying vinyl graphics to your model airplane or boat and will cover some of the basic techniques in preparation and application of the graphics.
An introduction to vinyl graphics
Graphics often come in two flavors: lettering cut from colored vinyl or printed and die cut artwork over a clear or opaque medium. Before we get into the “how to” of applying these to your model, it helps to have a basic understanding of the types of graphics and their suitability for your intended use.
Often delivered as weeded and masked (a real time saver) cut vinyl lettering is common in simple markings packages with fonts as small as 1/2 inch in height. Cut lettering has the advantage of producing the cleanest finished product with minimal weight gain to the model. Cut lettering is well suited to reproducing “N” Numbers, AMA member numbers, and simple markings. Cut lettering while produced from relatively affordable stock is a labor intense product. Some savings can be had by buying cut graphics at various stages within the production process. For instance, cut graphics can often be obtained in raw cut form ready to be weeded and masked by the hobbyist.
Cutting. The process involves CNC cutting each individual letter or character from a sheet of pre-colored adhesive and paper backed vinyl. The thickness, UV resistance, flexibility, and general longevity of the vinyl varies widely. For our purposes premium grade 2mil vinyl is most desireable as it is light, flexible, and offers the greatest resistance to UV fading and degredation. Specialty materials can also be cut such as AeroTRIM from StevensAero.com which is half again the weight of 2mil vinyl and has the advantage of being color matched to both AeroLITE and AeroFILM products. Local sign shops often charge by the letter for this type of product with prices ranging from $0.30/letter on up. While the CNC cutter makes short work cutting the actual lettering or artwork, the preparation of the final product and application can be labor intense.
Weeding. Using a sharp blade, the CNC cutter scribes through the adhesive backed vinyl leaving both the positive and negative elements of your design. The blade stops short of full penetration of the paper release backing. The cut/scribed art must now be “weeded” which involves using an awl or #11 hobby blade to tediously pluck away all of the negative components in the design (centers in the letter “O” or “A” etc…), leaving only the lettering or other design elements, to be transferred to your model, held in place by their adhesive back on top of the paper release backing.
Masking. A special low tack transfer tape (obtained from a vinyl sign supply shop) is now applied over the weeded graphics sandwiching the graphics between the paper release backing and the tape. This is no ordinary low tack masking tape as the tape is translucent which will assist with the final placement of the graphics to your model. The transfer tape has just enough tack to lift the completed vinyl art from the paper backing material, retaining the placement or spacing of the art, then apply and release the same graphics on top of the models surface. The application process will be discussed in detail later.
With the graphics cut, weeded, and masked the final art or decal is now ready to apply to your model.
Printed and die cut
While very complicated multi-color designs can be produced using cut and masked graphics, described above, the cost to produce these is often prohibitive. One solution to generating more complex art, affordably, is to print the design on top of either an opaque or clear vinyl or polyester adhesive backed sheet. The design is then die cut at a specified distance around the art leaving enough room that small registration errors will not cause the die to clip the actual artwork. As a hobbyist you have no doubt run across this type of graphic in the form of water-slide decal sets or adhesive backed decal sheets that either require you to cut the design out or are pre-cut with a custom die.
Printed graphics can be of great advantage and cost savings over a complicated cut and masked design, however, these printed graphics will feature a border and fill (area between the text or design elements) in the color of the backing material. This means that color graphics printed on a white medium will stand out like a sore thumb when placed on top of a colored surface (think sticker). Graphics printed on transparent materials are often no better as in various angles the light will reflect off the graphic differently than the surrounding model surface. Printed graphics do make great color markings such as “Rondels”, profile pilot figures, and detailed placards.
Thus, there’s a time and a place for both graphic styles in modeling and having some insight into how they are produced will arm you with the know-how to select the proper format giving thought to how and where the graphics are to appear on the final product.
Applying cut vinyl graphics
The following details the application procedure for cut vinyl graphics that have been weeded and masked with transfer tape:
Prepare your model by cleaning the area to receive the graphic with rubbing alcohol or glass cleaner and a lint free cloth. Good preparation will ensure that no dust, dirt, oil, or moth dung will spoil your finished product. Make certain the model is completely dry before applying masked vinyl art. Using a wet application method is not recommended.
Trim the cut vinyl graphic leaving about 1/8 inch of mask and backing material around the perimeter of the art. Now, with the cut vinyl graphic still masked and attached to the paper backing sheet, locate the graphic carefully on the model in the desired location.
Retain the graphic by applying a length of low tack painters masking tape across the middle of the graphic and adhering it to the model.
With the graphic held in place at the mid section, lift the masked transfer tape off the paper backing on one side of the artwork. Note that the vinyl art will lift off the paper backing and remain affixed to the transfer tape. Now use a pair of scissors to clip off the exposed paper backing material.
With the backing material removed carefully smooth the masked artwork back down along the model being mindful not to introduce any wrinkles. Remove the masking tape that held the art in position at the center of the graphic. Now lift the remaining side of transfer tape with vinyl attached from the remaining paper backing and discard the paper backing.
Once again, carefully smooth the graphic flat along the model surface. For larger graphics it may be necessary to work any air bubbles out from under the graphic or lettering using a squeegee. A business card works great for this purpose and does not risk scratching your covering work (vinyl sign shops sell a soft plastic squeegee designed for this task).
Complete the transfer of the vinyl art to your model by removing the transfer tape mask. Gently lift a corner of the mask and pull the transfer tape parallel along the surface to which the graphic was applied. By pulling the tape along and not up (as the case would be if you pulled the tape perpendicular to the work) the vinyl art is encouraged to release from the transfer tape mask and will remain in place on your model.
Don’t get too aggressive at trying to squeegee out any remaining air bubbles in the work, especially over open structures, as most (those that are not the result of dirt or dust) will disappear after a week of sitting in your shop. Bubbles in the finished work indicate that more care needed to be taken in preparing the surface (lint and dust free) and when initially placing the art onto the model after removing the paper backing.
Applying printed die-cut graphics
Printed die-cut graphics are as simple to apply as a sticker. These graphics do not typically come masked nor is it required to mask them. In the case of applying profile pilot graphics over wood, one would simply lift and stick the graphic. For applying graphics over covering film there are some tips that will make application more accurate and simple.
Prepare your model in the same fashion as above for cut vinyl graphics, however this time we will “float” the graphics into position using a wet application method. I use a quality glass cleaner (a few drops of dish soap in a shallow bowl of warm water works too) as my application fluid, however, sign shops stock a commercial application fluid just for this task.
Wash your hands as no one is interested in seeing your greasy finger prints lifted and on permanent display in the adhesive backing of clear decals. With the model, and your hands, clean and lint free spritz a bit of application fluid (glass cleaner) on the surface to which you will apply your graphic.
Use a clean #11 hobby knife to lift the graphic from it’s backing paper (Handling printed graphics on a clear medium with a #11 knife will further ensure that no greasy finger prints are made in the art).
Now spritz the adhesive side of the graphic with your application fluid (glass cleaner) and roughly place the graphic on your model. The graphic is now “floating” on the application fluid and is easily repositioned by sliding it back and forth. Position the graphic as desired then use a lint free cloth to blot the area around the graphic dry. After blotting up the application fluid reach for a paper business card and use this to squeegee out the remaining fluid from between the art and the application surface. The paper business card will readily soak up any fluid that finds it’s way to the edges of the graphic.
Leave the model and graphics to sit undisturbed for 12-24 hours.
An extremely fine tipped sharpie can be used to make reference marks on the model for placement of the vinyl art. Just make certain that these marks do not fall under the art where they may show through. Once the art has been positioned and applied the sharpie markings can be removed using a “Q” tip laden with rubbing alcohol or acetone (tested with AeroLITE, AeroFILM, and AeroTRIM – your mileage may vary with other brands of covering so we suggest a test on a bit of scrap material before trying this).