T&T: Overpowering a displacement boat

[Ed Bruette]

In a former life when I was the Harbor master for Pearl Harbor, the Navy
decided to homeport a small vessel there called SSP Kaimalino.  She was the
Navy's first Small Waterplane Area Twin Hull (SWATH) ship.  There were a
number of strange (at the time) things about Kaimalino.  She was driven by 2
GE turbines using huge multi-tier chain drives to a pair of CPP screws
mounted in the aft end of the 2 "pontoons".  She is 90' long, has a 45'
beam, draws 17' of water and exceeded 20 kts.  Kaimalino is stabilized using
canards and was rock steady in a state 5 sea.
 
A photo of Kaimalino with a helo on her deck can be seen at
http://www.coaps.fsu.edu/RVSMDC/cgi-bin/ship.cgi?id=KAIMALI.  A bit more
info can be seen at http://www.geocities.com/dthigdon/dynamics/sspbirth.htm.
 
The reason I bring this up is because I was reminded of her by an email I
received recently from a friend who used to work for Boeing at one of the
Seattle plants and I thought some of you might be interested in her.  
 
Many times on this list I've seen references to forcing a displacement boat
past its hull speed with the application of a "few" more HP but I never in
my wildest dreams would have thought anyone would exceed 40 kts. in a
displacement 38 footer!  Here's the quote from my friend's email.
 
"In the last photo you will note the APU in the tail of the 747.  I was
working for Boeing in the Acoustic Laboratory during the development and
testing of the 747.  One of the jobs I had was to take recordings of the
noise produced by the turbine engines from the various manufacturers who
wanted the contract to power the APU.  One of the tests was of an turbine
from United Teknowledgy.  They had mounted a turbine in a 38 foot yacht with
a displacement hull.  I have no idea why they did that, but they did.  They
hauled the boat to Lake Union so we could record the engine noise.  The
power train was the turbine (I never knew the power/thrust) which drove a 2
speed transmission which drove a variable pitch prop (I don't know the specs
on the prop).  The boat was operated by a UT engineer.  We took it out onto
Lake Washington where we ran the turbine up to a specified RPM and I took my
measurements.  At the test conditions the boat was doing a little over
twenty knots! A guy in what looked like an 18 or 20 foot ski boat could not
resist the challenge of showing us what speed was.  In a word, he lost.  At
a little over 40 kts. we left him in a hell of a spray (from the exhaust)
with his mouth wide open.  The engineer told us he was at about 35% power
but was concerned about vibration in the transmission.  We slowed to a
respectful 8kts and headed back into Lake Union where we put the boat to
bed."
 
I'd love to see that video!
 
Ed 
PT-38  "Makin' Do"
Poulsbo, WA