[Sonar] The powerboats strike back

[Ernest Brody]

I get to put my oar in also.  I suspect that whereas if you mixed it all up
you would not see any significant difference, the pH and oxidation potential
of the water at the first foot of water in the lake is more corrosive than
the general mixture.  This would be caused by the sunlight promoting
photosynthesis of algae in that first foot as well as oxygen mixed in by
wave action.  (I see this in another way, the sunward side of my boat has
more blistering at the waterline than the shadeward side.)  This would cause
more corrosion at the top of the chain and calamitous loss of holding power.

Ernest

-----Original Message-----
From: sonar-bounces at lists.wyc.org [mailto:sonar-bounces at lists.wyc.org]On
Behalf Of Shaina A Brown
Sent: Thursday, May 04, 2006 11:18 AM
To: Mark Kochendorfer; Thomas_M_Brown at bluecrossmn.com
Cc: sonar at lists.wyc.org
Subject: [Sonar] The powerboats strike back



Yet another thanks to all who helped to save Tally Ho! from certain death.

   In terms of material failure, Im sure there was some wear and fatigue
occuring on the bouy and pennant that contributed greatly to the failure.
But as I talked about with Steve this morning, I think the larger problem
is that the water is so diluted with fuel from powerboats that its
basically like puting a chunk of metal into a solvent bath...and this
speeds up the crack propagation and failure process ten fold. Any presence
of tramp ions in a metal grain boundary is devastating to the strength of
the metal. I bet that a simple pH test of Minnetonka water would scare most
of us off from swimming ever again. Fortuneately, we can all learn from
this mishap, and that Tally Ho! foundered into the safest place in the bay
that it could have.  In terms of a solution...I guess we will all have to
keep a closer eye and check on the corrosion and wear of each bouy
frequently. And for all those times that the powerboaters couldnt zip
through the channel at 50mph because of sailboats, the powerboats are
striking back...see you all at the club. Thanks,

Shaina

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