During construction of the plane, there are some layups that are best done on the workbench first, then transferred to the airframe. These include ones that are installed in hard-to-reach places, those requiring a sharp line to match an exact shape (like when matching the canopy skin exactly to the canopy bubble), layups to fit odd shapes and sizes, and vertical layups. If you've used BID tapes, then you've already used the most common transfer method!
The process is simple and straight forward:
1. Make a paper template for the shape of the part being glassed. I usually mark out the centerlines, edges, and folds so I know where to position the layup on the piece being glassed. These pictures show the template being made for the outer layups for the canopy deck. In this case I was able to cut the fiberglass layup to the exact shape as to get a perfect edge with the canopy plexiglass without scissor trimming and without grinding away the fiberglass after it cured.
2. On the workbench, wet out the the fiberglass onto your favorite plastic, saran wrap, of foil. It's easier to wet out the cloth and squeegee out the excess epoxy while the fiberglass is flat on the workbench. You have more control of the epoxy. It saves time. It saves materials.
3. Place a second sheet of plastic, saran wrap, or foil over the layup. Tape the template over the whole thing. Mark out the outline of the template and transfer all markings for centerlines, edges, and folds onto the plastic for aligning the layup onto the part being glassed. In the picture on the left, I am cutting the edge that will fit against the canopy bubble. So I'm being very careful to trim exactly on the line transferred from the template. (The line doesn't show up well in the picture.) The second picture is of the templates used to close out the exposed foam on the insides of the canard cover.
4. Transfer the layup onto the piece being glassed. I do this by flipping the layup over and removing the bottom piece of plastic (because the top plastic has the markings on it). I hold the layup in close proximity to the part, I line up the reference marks, then apply the layup onto the part. I usually leave the top piece of plastic on the layup and stipple over it. This helps to "stick" the layup and remove a large majority of the air bubbles. The plastic also keeps the glass from moving around and going crooked on you when pressing the layup into corners and over varying shapes. If the layup is a complex shape (as shown in this picture), the plastic may not want to conform to the part. Don't force it just yet. Instead, go ahead and stick down all the flat surfaces first, then stick the curvy parts every 2 or 3 inches. After peeling the plastic off, it's really easy to stick the rest of the curvy sections in place. The picture on the right is an example of transferring a layup to a vertical surface, in this case the BL67 rib for the main wing.