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RE: Stack Strakes

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I suggest leaving some slack in the wire ropes to let them bang into the 
stack to provide impact dampening.  We use impact type dampeners 
extensively on lighting poles.

Ray Minor

-----Original Message-----
From: seaint-seaosc(--nospam--at) [mailto:seaint-seaosc(--nospam--at)] On 
Behalf Of Harold Sprague Sent: Friday, February 01, 2013 5:32 PM
To: seaint-seaosc(--nospam--at)
Subject: RE: [SEAINT-SEAOSC] Stack Strakes

I have tried almost anything to avoid helical strakes myself.  All of MY 
previous efforts to avoid bar stock helical strakes failed.

If your client is serious, you will have to run 3 ropes in a helical 
pattern. I have never tried wire rope, but you will have to anchor it and 
support it at intervals to keep it from banging into the stack.  The 
potential problem is in the aspect ratio of the wire rope.  To get the 
profile required to mitigate vortex shedding will take a pretty big wire 
rope.   The equivalent weight of the wire rope will be significant.  I am 
not sure if you would want to run a CFD model, but I have a contact (Mike 
Porter) that can do that for you for a reasonable fee.  THE expert in 
vortex shedding is Bob Belvins.  But I use Mike to do CFD modeling for me. 
You might run this concept by Dr. Blevins first.

It took me a significant and expensive learning curve.  I have a source 
that became an expert on bending bar stock into helical strakes.  I used a 
guy in Chicago for making the strakes.  After some hiccups, he built a 
section of stack and check fit each strake before it shipped.  We welded 
clips on the stacks and attached the strakes to the clips to avoid a 
problem with differential thermal growth.  For my application, the

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