[Courtesy of Jeff Naber, nxtdoor "at" webzone.net, June 1999]
I started bagging wings about a year and a half ago and have had excellent and immediate results. No bragging, but I tend to be a good craftsman and work well with my hands. (Its my brain that doesn't work as well). This I feel has helped with my immediate success. I suggest the first thing one does when starting to bag is read everything you can get your hands on regarding bagging. Also, listen to others you know of that have had success and ask questions. I also suggest Geo. Sparr's bagging video from Aerospace Composites. It will give you a visual representation of the process.
Make sure you have decent, correctly operating equipment. The vac pump, your bags, mylars, gloves etc.
Once you feel confident you understand the process, practice on a few wing panels to start. This will give you an idea of what it is like to work with the mylars, glass, epoxy etc. This will help you develope a technique for the process. Be prepared to forget something while you are bagging. It happens. I lay out all my materials before starting so I don't have to remember anything like the kevlar for the hinging after the wing is in the bag(its happened).
I feel one of the most important items you will work with is the mylars. Get good mylar and more than enough to work with for your project. Make sure you have a good release agent. Make sure you wax the mylars several times prior to using. Cut the mylars so when joined at the trailing edge with masking tape they are held back from the leading edge about 1/8". This allows the mylar to wrap the leading edge at all the taper joints and lets the glass wrap fully around the leading edge. When cured the glass that has wrapped the leading edge is easily cut away with a razor blade. It also reduces the sanding required to final sahpe the leading edge. If you use mylars that run past the leading edge, you have excess epoxy seepage between the mylars at this point that creates a problem to sand.
I cut my own cores with a feather cut. You can buy yours if necessary. Make sure you sand the cores with 400 grit paper to get all the ridges out and the joints where the tapers are. Smooth now means smooth later.
Paint the waxed mylars. I have had good success with Krylon colors. I will be trying epoxy soon. Should work fine. Don't go overbored with the paint. Use just enough to create opaqueness. I don't generally paint the bottoms. This will add about 2 oz. per panel. I use a fabric paint purchased at a local art store made by Badger of airbrush fame. I spray the glass, and the core bottom both. This is a latex dye and is very light when dry and creates very deep colors.
As far as the layups are concerned, I have bagged mostly Super V 100's and 2m's so far. I use spyder foam(extruded polystyrene) and no spars. I use triangles of carbon top and bottom. The carbon is 2.9 oz. unidirectional fabric. On a 9" root chord on top, I am using a 6" wide base triangle the extends to the tip. I also add a second triangle about 1/2 the length of the panel on the top. The big triangle on the bottom extends out to about 2/3rds the panel length with the second one about 1/3rd. Based on the winch tests I have done, this layout gives minimal bend with full pedal launches on the strongest winches. This is basically a copy of what Mark Levoe uses on the V's he has sold. I
I use 3.2 oz. plain weave fiberglass, single layer over entire wing with a double layer out from root end about 6-8 inches. I also put to layers on the leading edge prior to bagging the panel. This is done with a 1 1/2" bottom layer and a 1" top layer. Lay the strips out and spray with 3M 77 contact adhesive and stick to the leading edge and wrap around. This will stay in place up to and through the bagging, and also gives you something to sand to.
Lay out your mylars that are taped at the trailing edge over a wide expanse of newspaper. You will be scraping the epoxy off the glass on to the paper later. Lay the glass on the mylars. I cut my glass about 1" greater in size all the way aournd the mylars. Get all the wrinkles out and straighten the grain of the cloth. Put on your surgical gloves. I mix up about 3-4 ounces of West systems for each panel. This is more than you will need. First I brush the leading edges and work the epoxy into the cloth with my finger. Set a side. Pour the epoxy on the glass which is over the mylars. Using a credit card or squegee, move the epoxy around until all the glass is saturate and has a wet look. Now, start scraping it all off. Your goal is to scrap til you can't get anymore off. Excess epoxy wil cuase bubbling I have found. I guess its due to the heating in the epoxy while it cures. Lay out your carbon, kevlar etc. and do the same on the newpaper. Now lay your carbon in place on the glass one at a time and scrap them into the glass making sure all air bubbles are out. Do same with Kevlar hinges.
Once this is done,(about 10-15 minutes) lay the core on the mylar and fold it like a book. Set on the trailing edge of the mylars and push the core towards the trailing edge. Now put in your prepared bag. I pull the bag down once and then let it vent. I then lay the core in the bag onto the shucks and weigh them down with a piece of 1/2" glass(nice and flat. I should mention a flat table is very important.). I then pull the bag down again in the shucks. This insures the core forms to the shucks. Without doing this and just setting the core on a table by itself while bagging will flatten the camber in a core. Leave for at least 24 hrs.