This will be a step by step process to do a standard wing (balsa sheeting, carbon sub spar, and foam core). Additional processes like LE caps, TE caps, composite skins, etc… are a little above this process.

1. Core preparation- The foam core needs to be prepared for sheeting. All internal structure, like wing tube and spars, need to be installed and sanded flush with the foam surface. The foam needs to be sanded smooth (no ridges) and filled if necessary. Vacuum the surface when done to remove all the dust.
2. The sheeting now needs to be prepared. The sheeting will be joined and sanded before placing on the core. Get the ridges off, but don’t spend too much time getting a perfect surface. The bagging will require sanding after! Cut the sheeting so that an overlap of ½ in is at the trailing edge, ¼-3/8 in at the root and tip, and 1/4 overlap at the LE. Any more will result in crushing, any less makes alignment tough.
3. Mark the sheeting with an "in" and an "out". VERY important.
4. In order to prevent crushing from unsupported areas, mark any holes in the cores on the "out" side of the sheeting. The marks will be used to align the metal plates over the sheeting to give support for those areas.
5. Prepare the carbon fiber for use. I use a triangle located on the "thick" portion of the wing. Not necessary, but helpful. Also use a ½ in thick piece of CF on the trailing edge for surface rigidity and ding protection.
6. Lay one saddle bed on a flat surface.
7. Lay the bag on the saddle bed. Seal one end of the bag to the length that you need.
8. Make up 2 breather cloths. To do this use the roll of paper towels. 3-4 sheets (still connected) and folded will provide a path for the escaping air. Make a top and bottom. Place the bottom into the bag.
9. Time for a DRY run!!! VERY IMPORTANT!!!!! Follow the steps below, but DO NOT USE ANY EPOXY!!!!
10. Time for the epoxy. Mix up about 4 oz of epoxy. Better to have too much than too little. Place one skin side "in" up. Spread on the epoxy. Spread on a lot at first. The color of the sheeting will darken slightly when "done". Spread the epoxy throughout. Now scrape it all off!!! It is amazing, but the end result should be a surface with no visible epoxy, but will be tacky (slightly) to the finger. Event then a little more scraping should be done.
11. If using CF, place the CF on the sheeting in the place needed. Spread epoxy on the CF. The vac will help to pull the epoxy through the CF, so wet it out then scrape off.
12. Repeat above for the other sheeting.
13. Place the core between the two skins. Secure with a couple of pieces of tape.
14. On the outsides, tape the plates over the marks on the sheeting. Tape helps hold them in place.
15. Open bag and insert "sandwich" into bag. Place other towel cloth on top of the wing
16. Place the top saddle on TOP of the bag. Using a couple of weights, hold the core/saddle in place.
17. Place a peel ply "breather" over the vac attachment, and run it to the wing to provide a patch for the air. Peel ply is used in case any epoxy is on the valve, then the valve will not clog.
18. Seal the bag end. Hook up vac and start to pull vac.
19. While the vac is starting, align the core in the bottom saddle. Make sure that everything is straight. Align the top saddle as well. Place enough weights on the saddle to hold the core in place.
20. Once most of the air is out of the bag, turn pump off. Should be at 1 in mercury or less! Starting at one corner of the bag, pull the bag sharply away from the wing. This prevents any wrinkles from occurring and causing problems. On the leading edge, the skin should not be crushed, but instead be pulled together. Push the bag between the skins if necessary.
21. Turn the pump back on! Set it for 4-6 in of mercury for white bead foam. 4 is adequate. For blue or gray foam, 15 in can be used, for spider foam 24 in can be used.
22. Once the vac is achieved, remove the top weights. The bag will now prevent movement, so the weights are not needed. Taking a ruler, make sure that the wing is straight. It will be, but why not be sure? If needed, turn off pump, open bag, and reset the core. Shims are sometimes needed for cores that are warped to begin with. VERY important step.
23. You did do a dry run right?
24. After 24 hours, turn off pump and remove the wing. If you did this right, then there will be a good wing! A little sanding and you are done. Don’t worry about if epoxy seeped through skins, this is normal. Just sand it out. The trailing edge should be trimmed and sanded if necessary. If CF was used a sharp TE can be created by sanding the balsa down to the sheeting.
25. Repeat for other wing.

Why to bag a wing?

There are a variety of reasons. Most important is the ability to create a uniform bond between the skin and core. The vac also places WAY more pressure than possible with weights. A pull of 1 psi on a 1000 sq in wing will require over 1000lb of weight!

Another advantage is the ability to use less epoxy. The better bond between the two requires less epoxy to do the same job. Hence less epoxy and less weight

Finally the ability to use composites such as CF and fiberglass. It is next to impossible to get a good CF layup when using weights alone. The CF will not be compressed enough to create a good secure matrix. End result is a "dry" layup and a weaker wing than if no CF was used!