PWMdk,
I agree with your calculations. I went to the same website and found your calculated values different from the website.
I have a very strong feeling that we are missing something; they are calculating using something more than the basic formula of AR= Span/MAC or (Span)2/area. Just to confirm my thinking, I calculated with both the above equations and found out that using span/MAC the value is actually 8.46 (as calculated by you) rather than 9.16.
I went on to calculate using (Span)2/area. Theoretically it should give the same result but I got 7.91.
This proves that these calculations on the website are based on a formula that includes something beyond the basic formulae. What? I have no idea.
Last edited by Guru8904; 16th Nov 2015 at 16:21.