moment of inertia

[dionysis]

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

[BrettM]

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

[dionysis]

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

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.

[dionysis]

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

[BrettM]

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]

[dionysis]

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