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[Towertalk] Strength of fiberglass.

To: <>
Subject: [Towertalk] Strength of fiberglass.
From: (
Date: Thu, 28 Feb 2002 16:11:20 -0600
WRONG !!!   (see below)

The maximum shear stress Tau (max) for a hollow tube is

Tau (max) = 16 Mt x D / pi (D^4 - d^4)  ...  (4th power of D and d)

where D is the Outside Diameter 
         d  is the Inside diameter
         Mt is the bending moment (I presume)

It is clear that the greater the wall thickness, the greater the
which is maximum when d = 0  (solid rod).

NOTE:  MOST of the strength comes from the outer region of the tube
and it is more 'effective' from a strength vs weight standpoint to go to 
a larger diameter thin wall tube than to increase the wall thickness.

When d = 0.5 D,  
Tau = (1 - 0.0625 ) Tau (rod) = 93.75% of the strength of a solid rod.

When d = 0.75 D,
Tau = (1 - 0.3164) Tau (rod) = 68.36% of the strength of a solid rod.

Tom  N4KG

On Thu, 28 Feb 2002  "Randy Williamson" <> writes:
> Solid is not stronger than hollow as it was explained to me its about
> surface area. What would be interesting is carbon fiber and epoxy 
> resin over a round mold.
> Randy
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