First and foremost, are these blades going to be flying? Or just static?Although I've never built my own blades, I have thought about it before and this is how I would go about it if I wanted to build my own blades. I also assume you have some knowledge of composite molding techniques parts as well as a lot of patience because you will probably fail a few times until you get the technique down. The first few attempts should be made with glass due to it being cheaper, however the blade roots and critical areas should be carbon or kevlar.It all starts with a quality plug. This part will take the most time since it has to be perfect in every way. Shape your blade the way you want it to look once finished and ensure the plug has a perfect finish and correct airfoil for your application. Full scale are usually semi-symmetrical or flat bottomed for increased lift. Your attachment points are also built at this stage. .Some blades have a balsa core such as V-Blades. Others have foam. If you will be flying these blades, I would make sure to bond a safety wire running all the way from the root to the tip to prevent the blades from throwing fragments. You will need a vacuum pump and bags, peel ply, and an absorbent medium to suck up all the excess resin once it's layed up. Ideally you would cure your blades in the vaccumm bags inside an autoclave or oven. (Heat lamps in an enclosed space would work also but you need to regulate the temperature)When laying up the blades in the mold, ensure that each blade mold sits on a scale so you have same-weight for every blade. This means making a mold for each one of the blades you plan to build. (4 blades+ 4 molds, etc) Use a known airfoil shape as a base. Full size helicopter blades usually have some form of washout built in but probably not necessary in a scale application.If painting the blades, paint them in the mold on top of the PVA and gel coat. When joining the 2 halves, use resin-impregnated carbon or kevlar tow to join the parts together. For weight, if you use any on the tips (more stability but more rotational mass) ensure it is bonded fully to the structure as well as the safety wire inside.Once the blades are cured and finished you would have to trim any excess fibers and ensure the seams are sound. Build some sort of test device to ensure that not only the blades are balanced by weight, but also the CG of each blade is in the same spot. Bolt your blades to a rotorhead and put it in a drill or bench-mounted motor with a shield around the whole assembly for testing. I would run the blades in a controlled fashion for several hours and check for delamination, excessive vibration, and out-of-track conditions.