Step 3: Cut the balsa pieces
Since there are so many parts, I have labeled the first picture with how I'll refer to the bits throughout. The hardware is labeled in the Tools & Materials step.
On a large piece of paper, draw three 'bone' shapes X, Y, Z. The important dimensions are the lengths from the middles of the hinge holes. I put masking tape over the back of the paper before I cut out the patterns; this made them much easier to trace onto the balsa.
bone X:
top hole to middle hole: 12-3/8 inches
middle hole to bottom hole: 6 inches
bone Y:
top hole to middle hole: 18-3/8 inches
middle hole to bottom hole: 6 inches
bone Z: top hole to bottom hole: 6 inches
and it should be about as long, overall, as bone Y
Trace the patterns onto the balsa, two of each. You should be able to fit 2 pieces per balsa sheet if your bones are shaped like mine (or smaller). Using the Xacto knife, cut the pieces out (a very small, fine saw would probably also work but my jigsaw just tore up my test sample). A good technique for this is to trace the lines several times, cutting deeper each time. Ripcuts are very easy; crosscuts are slightly harder as the balsa tries to compress. Cut only a little deeper each time. Don't worry too much about accuracy, once the shapes are cut out in general it's easy to carve the edges down as if you were whittling.
Lay each pair of identical pieces out with the pattern on top and line them up well. Drill pilot holes where you marked the hinges.
On a large piece of paper, draw three 'bone' shapes X, Y, Z. The important dimensions are the lengths from the middles of the hinge holes. I put masking tape over the back of the paper before I cut out the patterns; this made them much easier to trace onto the balsa.
bone X:
top hole to middle hole: 12-3/8 inches
middle hole to bottom hole: 6 inches
bone Y:
top hole to middle hole: 18-3/8 inches
middle hole to bottom hole: 6 inches
bone Z: top hole to bottom hole: 6 inches
and it should be about as long, overall, as bone Y
Trace the patterns onto the balsa, two of each. You should be able to fit 2 pieces per balsa sheet if your bones are shaped like mine (or smaller). Using the Xacto knife, cut the pieces out (a very small, fine saw would probably also work but my jigsaw just tore up my test sample). A good technique for this is to trace the lines several times, cutting deeper each time. Ripcuts are very easy; crosscuts are slightly harder as the balsa tries to compress. Cut only a little deeper each time. Don't worry too much about accuracy, once the shapes are cut out in general it's easy to carve the edges down as if you were whittling.
Lay each pair of identical pieces out with the pattern on top and line them up well. Drill pilot holes where you marked the hinges.
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Here's the link to my work in progress: http://www.instructables.com/id/Steampunk-version-of-Rachels-articulated-wings/
If you're making this, I'd love to see pictures, and any advice or improvements you may have worked out!
Check out Step 5 (http://www.instructables.com/id/SDNED6MF82EXL84/), the last 3 pictures which are of the lower shoulder hinge. The balsa-to-dowel hinges are made just like that, only the balsa piece is used instead of the wrapped copper strap. The pictures there should be pretty clear (they show a metal piece instead of a wooden dowel but it's the same function).
If you're making this, I'd love to see pictures, and any advice or improvements you may have worked out!