Re: Does an ovoid or a spheroid shape have greater structural strength?

Shyam,

Thanks for writing.  First, I must say that your intuition is correct--a 
ovoid/egg shape will be stronger across it's length, but not as strong 
across it's breadth relative to a sphere.  But, when you say, "How much?" 
then you must ask the question, exactly what size is it?  

If you have a sphere and an ovoid of the same volume, thickness, and 
material, the ovoid is going to have to be longer than the sphere in one 
direction and thinner than the sphere in another direction to maintain the 
same volume (using the same volume is the only "fair" way to compare 
different shapes).  Thus, as you said, it will be less strong in the 
direction that got thinner, and stronger in the direction that it got 
longer.  But if you want to know how much stronger/weaker, you need to know 
 how much longer/shorter is it relative to the sphere.  You also need to 
know what kind of loading is being considered?  Axial, torsional, uniform 
pressure, etc.?  

In the case of uniform pressure, the ovoid would be weaker.  A sphere is 
esentially the optimal shape for a pressure vessel, so any other shape will 
be weaker.  To find out the exact difference for other loading cases, I 
would suggest using a finite element analysis.  There are many software 
packages available to do just FEA, and many CAD packages now days are 
also capable of FEA.  If you have access to software capable of finite 
element analysis, it should be fairly simple to constuct a model of a 
sphere and an ovoid (or multiple ovoids of various dimensions) and subject 
them to varoius loading cases to see exactly how much stronger or weaker it 
gets.  You may even just try modeling a simple 2D circle and an oval (or 
ellipse) to give yourself an idea without having to construct a 3D model.  
Hope that helps you.

Your Mad Scientist,
Mike Scannell