[Rhodes22-list] Major Ice Damage

[Peter Thorn]

Roger,

Very sorry to hear about your ice flow dock damage.  Your story detailing
all the thought and preparation that went into building it to begin with, at
least to me, is very interesting.  I really do appreciate engineering
elegance, and especially your particular type of it.

However, if your dock was built of "old" pressure treated wood (CCA), please
don't burn it.  The arsenic and copper fumes from a fire fueled by this wood
would be deadly.  Once those poisons become airborne, you would have no
control over where they could end up.

PT




> 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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> >
> >
>
>
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