At this point I am about one and a half hours into the actual build. All parts fit to the tolerance I am prepared to deal with when I finish this model, nothing had to be re-cut, sanded down, or remade. This is a perfect example on what CAD will do for the scratch build process. Almost unbelievable, especially when looking back on earlier models.
The Mystery of Airfoil
Designing an airfoil seems like a daunting task. For real designers I bet it is. For me, I don't have to worry about having the fastest craft, the best endurance, or even razor edge competition. I simply need something that works. That being said, I can make a good approximate to everything listed above. And even still, what I do may not be better then something like a simple KF airfoil. I do know that it will work, and has given me great performance. So I begin by cutting out the plans.
After they are cut, I use the classic Sharpie method to apply the pattern to the roofing tin I'll be using for my template.
The line is traced and then numbered as such:
...And this is where I called it a night. Not bad for a single nights work. This took me longer to write up then it did to actually get to this point, so here's a plug: For more information on cutting foam, hot wire cutting, and general foam construction check out Keith Sparks' Book, Building with Foam. It's a good read, excellent reference, with a low cost theme. I highly recommend it as I've learned quite a bit from it.
Day 2 Airfoil Continued...
I had considerable time to spend on this warbird today, but spent a considerable amount of time spinning my wheels. It really wasn't until the evening when I actually cut out the templates and wing blocks. Sandpaper was used once they were cut to smooth out the edge. I've found that once you can run your finger nail over the edge, without feeling any snags the edge is ready for the wire. Keith goes into good detail on how to cut wings in his book, but here is another good source that seemed to fill in some of the gaps.
Continuing with the hot glue theme, it's easy to apply these to the wing block. First a line is drawn onto the block so that each template is lined up properly, washout could be applied by adding a twist, but I don't want it here. There is one other good idea, as the wire will slow down if it touches the glue, so I trace out the template onto the block and use as little glues as possible, keeping it from the edge. It's now ready to burn out.
And that's the idea behind the wings, don't expect the first one to be perfect, don't be afraid to throw out, and they will get better as you make more. It's impossible for me to describe the best way to cut from here, and exactly what will work for you, but there is enough info here to get a running start. Whatever you finish with, it's best if both wings are symmetrical, as surface differences do make a difference.