Definition of Aspect Ratio

[Kevin Murray]

OK, I tried a search. It seems that calculation it is a no brainer.

But I don't know how. :o :o :o


SO,..... What is the definition of aspect ratio.

I know that it is the ratio of span to chord but I would like to be able to measure/calculate it.

Thanks.

[steve lewin]

I'm not sure I see the problem. As you say it's the ratio of wingspan to chord. Measure the span, wingtip to wingtip (e.g. 60"), measure the chord, front of wing to back of wing (e.g. 10") then divide span by chord 60/10 = 6. Aspect ratio = 6.

If the wing is tapered it's the average chord you want
i.e. (chord at root + chord at tip) / 2

Steve

[BMatthews]

That's the way I've always done it too. But in a few books I've seen it as sq(Span)/Area. So for your example this is 60sq'd or 3600/600= 6. Not sure why the fancy method but perhaps it has more to do with odd shaped semi-elliptic stuff and all that. Span/Chord works fine for me though.

[steve lewin]

That's an interesting way of looking at it. If you know the area that gives you the average chord without all that fuss of trying to work it out for elliptical wings etc.

Area = span * average chord

so the formula is

Span squared / Area
= (Span x Span) / (Span x Average chord)

I wish I'd thought of that ;).

Steve

[Sail 'n Soar]

The "fancy method" is easier to use when calculating the aspect ratio of a more complex planform wing than no or straight taper. How do you calculate the average cord when you are calculating the aspect ratio of a triple taper or eliptical, etc., planform wing? It is also easy to use when comparing models from published specifications. They almost always give wing span and area, and most often skip wing cord information.