Well you don't, but making a mold is very easy. You can make it from blue foam & some pieces of plywood, for example. What's wrong with that?
Or, you may modify the ribs to accept a thicker and higher l.e. but you end up using same amount of efford to make something not as good. L
That's what I would to, and I even have a foam cutter. Make a form with a plywood base the span of the airfoil, and the width of the (tapered) thickness, and plywood airfoil sections on each end. Glue a blue foam block in the middle, then carve away everything outside the plywood with a knife, then a rasp or Surform tool, then sandpaper on a long block when you get close. That will give you a mold for the LE. Blue foam is easy to work with, and much cheaper than balsa (which is how we used to do it).
Note that it is exactly like molding a top or bottom block, and it even looks like a really long turtleneck mold. But I would also point out that it doesn't have to be exactly correct. Just about anything with a similar curvature would work, and for years people have molded the conventional top/bottom sheeting by simply pre-curving it on another wing, or just wetting it and curling it so it will lay on the ribs more easily rather than forcing flat wood around it and holding it with pins until the glue dries. It also reduces the tendency toward the "starved horse" effect, although you can still get it from dope shrinking later.
The reason you do it this way is that you end up controlling the shape of the LE a lot better than just eyeball carving it. Ted was the first in the modern era to do it this way and later it was adopted by others who realized some of the airplane-to-airplane performance variations could be explained by how the LE was carved. I also made him put a stringer right at the LE because I didn't want to launch the airplane with just 1/16" balsa in there.
Brett
Topic: Thunder Gazer Build Help (Read 5248 times)