[Rhodes22-list] Major Ice Damage

[Roger Pihlaja]

Rummy,

Sanford Lake has a wide variety of different types of docks.  One can find
virtually any dock type ranging from floaters, to permanent structures on HD
pilings like mine, to docks built in sections that have to be removed every
fall & reinstalled every spring, to structures resembling one half of a
suspension bridge hung from cables led from massive towers on the shore.
All of these different types have their advantages & disadvantages.  Before
we bought our house in 1979, my wife & I rented another house on Sanford
Lake for about 2-1/2 years.  This rental house had the type of dock you were
describing in your post.  Every spring & fall, I had to get into bitterly
cold water & assemble/disassemble this dock.  Not only was this
uncomfortable & uncivilized; but, it limited our ability to use the
waterfront during the months when the dock was taken apart & the parts
stacked along the shore.

When we purchased our house, the property included a very crude set of steps
& a small permanent dock.  The dock was big enough for the 17 foot Van de
Stadt & MacGruer Siren sailboat we had at the time.  Not having to assemble
& disassemble that dock was absolutely wonderful!  When I built the
elaborate seawalls, steps, wharf, & pier in 1983 that you are all familiar
with from the posted pictures, I knew I wanted some sort of permanent dock &
it had to be sufficiently big to accommodate a Rhodes 22.  Yes, that's
right, that slip was custom designed for a Rhodes 22!

Engineering for ice loading requires the selection of a maximum design ice
loading using local knowledge of ice conditions.

By the time I built that dock, I had observed & kept records of 7 spring ice
breakups on Sanford Lake.  The largest ice floes I had ever observed coming
down the lake during the spring ice breakups were about the size of a bus.
Usually, these large ice floes were out in the middle of the deep channel;
but, I still assumed they represented the scale of the forces that had to be
dealt with.  So, I designed the dock to take a direct hit from an ice floe
2X bigger than that moving at 5 knots with an additional safety factor of 2X
.  For 21 years, this design worked just fine.  The ice floe that struck the
dock on Saturday was about 140X bigger than the design ice floe, moving at
about the design speed.  Besides the sheer momentum of such a massive
object, this ice flow was sufficiently large to span the deep channel in the
lake in front of my property.  The shear size prevented the east end of this
ice flow from moving any further east because of a shallow sand bar about
100 yards out in the lake.  Thus, the ice floe was physically prevented from
bouncing off my dock because there was nowhere for it go.  This geometric
affect dramatically increased the static & dynamic loads this ice flow was
able to exert on my dock.  In effect, the ice floe became a hydraulic
battering ram with the force of a 5 knot current spread across 100 yards of
surface area to power it!

Despite the damage to the wharf & pier, the coupling to the seawall did
function as a weak link.  The coupling failed exactly as designed, thus
preventing damage to the seawall.  I'd be in real trouble if the seawall had
ruptured!

We have a large commercial towing company in Sanford called Cole's Towing
Service.  When the weather warms up, I'm thinking I will have Cole's bring
one of their biggest tow trucks on site.  These tow trucks have lots of
strong cable & sufficient horsepower to right overturned 18 wheelers.  Using
this machine, we will drag the wrecked pier up onto the beach, pilings,
cement, and all.  Once on the beach, it will be a relatively simple matter
to cut the wrecked pier up into manageable pieces suitable for burning right
on the beach.  We will have "dock bonfires" for quite some time this summer!
This seems like a much faster & safer means of demolition than any scheme
involving cutting up the wrecked pier in-situ while it's still partially in
the water.

I won't know what kind of new dock to put in until I've had a chance to
survey the damage done to the lake bottom.  I can't wait to dive on those
pilings to see how they failed.

Roger Pihlaja
S/V Dynamic Equilibrium

----- Original Message -----
From: <R22RumRunner at aol.com>
To: <rhodes22-list at rhodes22.org>
Sent: Sunday, March 07, 2004 7:57 AM
Subject: Re: [Rhodes22-list] Major Ice Damage


> It kinda reminds me of why I moved South Ed. We lived on a lake in
Wisconsin
> where we all took out docks out every fall so we didn't have damage like
Roger
> now has to deal with. We built our docks in 10 foot secions with
adjustable
> legs that had a mud plate at the bottom to keep them from sinking. It was
a
> pain taking them out every fall and then putting them back in, but I
suspect that
> it would be easier than dealing with what Roger will in a couple of
months.
>
> Rummy
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