Mparker,

Sorry, I'm confused:

I'm not completely sure what the definition of the angle of a blade is - is it 2a? From the way your ascii art is drawn, I guess it is.

Another question: if you rotate your picture 90 degrees clockwise, is that the equivalent of resting the blade on its back with the edge in the air? I'm confused about what you call the width of the blade - is it the horizontal distance from spine to point, or is it the hypotenuse of your picture?

If it's the hypotenuse, I get why you use sin. I'm just not sure the width is the hypotenuse - I'd have thought sqrt((t/2)^2 + w^2) should be the divisor in the arcsin calculation.

Or am I getting it all wrong?

James.