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Re: Stack Strakes

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       Thank you for your response.  As always, it's very valuable.

The idea of using wire rope for strakes is my own idea; my client is not even aware of it.

I'm on side with all of the items you've pointed out. For 8" and smaller pipe the wire rope size would probably be tolerable; for larger diameters all bets are off. One concern that I have and that you did not raise is corrosion. The possibility of corrosion may mandate the use of galvanized wire rope.

Anyway, you didn't reject the idea out of hand. I think I'll consider this one a bit more and, perhaps, do a bit more research before I present the idea to my client.

       Thanks again, Harold.


H. Daryl Richardson

----- Original Message ----- From: "Harold Sprague" <spraguehope(--nospam--at)>
To: <seaint-seaosc(--nospam--at)>
Sent: Friday, February 01, 2013 3:31 PM
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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