At 10:55 AM 1/19/99 -0800, Mike Taylor wrote:

Yes, that is what happened.

This "squat" is well known in the world of high performance racing
displacement monohull sailboats.  That is why at the dock you see such a
large difference between the LOA and the WLL, as both the bow and stern
sections are cantilevered out on both ends above the water.  In light winds
where hull speed is not a constraint, this minimizes the wetted area in the
water.  In heavy winds, the boat squats down into the water simply because
it is an upside down airplane wing.  This results in a greatly increased
WLL, and therefore also increases the hull speed.

A number of years ago, a full displacement monohull sailboat ran into
trouble that required a tow in Tampa Bay.  A passing tug offered a tow.
This tug had enough power so that it could pull the sailboat at an S/L
considerably higher than 1.4, which would have been about the normal "hull
speed" for this boat.  The result is that it squatted down and sunk.

At 01:59 PM 1/19/99 -0500, Mike Tellup wrote:

I've bounced a full displacement boat off the bottom in a similar situation.

That is also another thing that is often called "squat."  It is not a very
precise term.  :-)

In the case of Bernoulli type squat, the whole hull will settle down into
the water.  In the case of this bow wave type squat, the bow raises as it
tries to climb the bow wave and the stern squats.  In the case of the bow
wave squat, you might draw less water in some circumstances, since the deep
forefoot of the hull will rise a little.  The problem is that both types of
squat are normally occurring at the same time on small displacement power
boats.  The only way to know how your boat will perform is to go try it.
Trying to scale down from the QE2 will not give you any meaningful
information, especially since you will find quite a lot of variation between
one boat and another of about the same size.

For a true trawler, which is to say one designed for commercial fishing by
dragging a trawl through the water with massive amounts of power, it is
pretty much impossible to exceed an S/L of 1.4 by much at all.  The reason
for this is that it will squat down and simply displace more water if you
try to apply enough power to make it exceed hull speed.  So then more power
does not add speed, but only displacement.  This is something to think about
for the folks who are talking about work boat conversions.

This is the standard I used some time ago on the TWL, when I suggested that
even a Krogen was actually a semi-displacement boat, since it can be driven
past hull speed by at least a little with a fairly small amount of power.
If you look at the difference between a commercial trawler and a Krogen
hull, then you will begin to see what I'm talking about.  In my estimation,
Mr. Krogen was about the most talented naval architect to ever design and
build a recreational trawler, in that he was able to make his boats squat
differently from a true commercial trawler.  In fact, he makes them squat
more like a semi displacment boat.  The bow will climb the bow wave a
little, but the stern has enough buoyancy to prevent squatting very much at
all.  At the same time, he has greatly minimized the Bernoulli squat by the
shape of the bottom.

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Arild comments

The suction effect also works sideways but there  seems to be  two
different effects.

Lake freighters in the St. Lawrence  river system are restricted to certain
speeds due to the limited keel clearance.  Downbound and upbound speed
limits are different since the  speed of the river current has to be taken
into consideration.
In addition there is  something called bank suction. It was mentioned in an
earlier post.
However, bank suction also works with a stationary vessel.  I was on board
a 34,000 ton bulker  docking at a steel mill in Hamilton Ontario. I watched
the captain put the vessel alongside and slide in against the wall without
use of tugs or even the bow thruster.  Later I asked him  how he did it.

He said "bank suction"    Then he explained.  The freighter is essentially
a square box in cross section. Whe you place  such a vessel alongside a
wall  about six feet away  with about a foot or so keel clearance,
hydrostatic pressure on the off side  pushes the  hull against the wall.

As proof you can  replicate the effect with  a piece of wood floating in a
sink or basin. As the piece of  wood gets near the edge it will suddenly
move more quickly and "stick" to the  wall of the basin.
I always attributed this  to the surface tension  which is proportionately
larger  when dealing with tiny models but he demonstrated  that it works
even with  34,000 tons.
Most lake freighter captains  pride themselves on never  using tugs for
docking or undocking.

Cheers

Arild