moment of inertia

hi all,

I need to know the moment of inertia (second moment of area) of a naca 0012 section, for structural purposes. Anyone know it Thanks in advance.

Cheers, dionysis

 

Um... Dimensions? or you could get it from any self respecting cad package...

 

24 inch long and 2.88 in wide. got to buy myself one of those selfrespecting things, thanks

 

Use builder's rule

I wrote a simple spreadsheet which used a series of triangles for just this sort of problem, and it was very simple, though I don't have it around any more.

Just add up area, centroid and self I of a series of triangles comprised of the origin, the ith point, and the i+1th point. All the formulas for a triangle are in any handbook. If you are consitent about which way you go around the triangle, the orgin can be anywhere, as it will subtract tnegative areas automatically.

 

I see what you mean. I will have a go. Thanks

 

This is what I get, but you should satisfy yourself by other means that it is right. This data is for the complete section,
Units are mm etc.
X-Section Area 30219
Centroid 259mm from leading edge
Ixx 9169473 mm^4


Other data which you probably won't need but the above was extracted from.
Area: 30219.4681
Perimeter: 1241.0065
Bounding box: X: 0.0000 -- 609.6000
Y: -36.5760 -- 36.5760
Centroid: X: 259.0364
Y: 0.0000
Moments of inertia: X: 9169473.1270
Y: 2637530313.3132
Product of inertia: XY: 0.0000
Radii of gyration: X: 17.4192
Y: 295.4305
Principal moments and X-Y directions about centroid:
I: 9169473.1270 along [1.0000 0.0000]
J: 609807741.7375 along [0.0000 1.0000]

 

Now this is certainly a complete reply! Kinda nice to have a self respecting. Thanks Brett.