Vic Dura wrote:
On Wed, 17 Aug 2005 15:34:52 -0400, "CL (dnoyeB) Gilbert"
wrote Re 4 x 12:


Edwin Pawlowski wrote:

"Duane Bozarth" wrote in message


Why would that be? There's no more (and maybe less) material
(neglecting the effect of an additional 1/2" (say) ply which would add
some additional resistance.


Putting to different pieces together acts the same way, sort of like a
torsion box. Same as a 1/2" dia. tube is stiffer than a 1/2" rod.



Say what? I disagree. Further a 1/2" tube should not be stiffer than a
1/2" rod.


No, the tube is *stiffer* than the solid rod of the same material.
Our Strength of Materials teacher in 3nd year engineering went through
the math/physics for the proof and I remember being stunned by it. But
it was clearly correct as I recall.

Sounds like an urban legend to me. Kinda like hot water freezes faster
than cold water.

The wikipedia says stiffness is a measure of resistance to deformation.
Solid rod resists deformation more than a hollow rod. It makes no
sense that boring out a steel rod would make it stronger. How thin
should I make it? The thinner the stronger? And the opposite is true
too? The more I fill it, the less stiff it becomes?


--
Respectfully,


CL Gilbert