Check out
https://www.flyingfoam.com/ . He has CNC hotwire foam cutting capabilities. I think 6' should be within his work envelope. Then put a light fiberglass or carbon skin on it. If you would rather do it yourself, buy the set of DVDs from
https://www.tailwindgliders.com/Video.html. Great videos. He covers bagging as well as hot wire foam cutting.
Thanks! This might work, or at least save me a lot of time. Looks like I could get 72" x 6" foam core airfoil constant chord for about $19 each (actually I think it would be two 36" pieces totalling 72 ", the cost quote is for a 72" wing span.) So four rotors for about $80 plus shipping (this is going to be my most expensive rocket, LOL!) Still would be worth it just in the time saved by having the airfoild built in.
Challenge: I would like to have the option of adding a flip out additional hinge rotor at the lateral/outer aspect of the span (A la "Whooper Flopper Chopper". This would require a very strong spar on the inner rotor AND a fixed hard "plate" at the lateral aspect of the span. I am at work now and can't draw this out, but will add a drawing later.
Start with a 72" x 6" constant chord foam wing, split it lengthwise at the apex/peak of the airfoil (probably a better word than this), and ran a length of, (say the mid airfoil width is 2.5") 2.5" x 1/4" balsa down the length, than added fixed 3"x6"x1/4" balsa plates at the hub and lateral margins to provide attachment points for the central hub hinge and the lateral swing hing (the swing out rotor would be a flat plate of 1/8" by, saay, 5" balsa about 36" long
0---- anyway, the BALSA provides the structural integrity . The foam provides the shape.
As for COVERING the foam, since this is not providing any significant structural strength, would MonoKote be adequate and lower weight penalty than carbon or fiberglass?
This would provide a total rotor length of almost 9 feet, little bit less due to the overlap of the hinges. Accounting for dihedral, would be looking at a rotor cone diameter of around 16 feet.
Again for those concerned about injuries from spinning rotors, I believe the air resistance from these large rotors simply will not allow them to spin very quickly. In fact, if it was spinning that fast, the outer 1/8" balsa flat plane rotor would shear off.
Again, continued thanks for the input. You guys are already pretty clear on the concept that I am very much a novice at this stuff.
Tom