HOT-25: Chief Scientist Report

Chief Scientist: R. LUKAS

Personnel List

Roger Lukas, Chief Scientist
Dale Hebel
Ricardo Letelier
John Dore
Terrence Houlihan
Marc Rosen
Jef Snyder
Chris Winn
May Ver
Alfred Adam
Jim Christian



Summary

HOT-25 was conducted on R/V ALPHA HELIX.  ALPHA HELIX departed from
Snug Harbor at 0930 HST on 8 April 1991, and returned approximately
1430 on 11 April.  The return was one day early because the GOFS
drifting sediment trap array was not deployed (see below).

The weather was very good, with light trade winds prevailing.  There
remained a swell from the previously strong trades, and the swell
caused occasional excessive rolling of the vessel.  This resulted in
breakage of some gear, as detailed below.

With the major exception of the sediment trap deployment, the cruise
achieved all other scientific objectives.  A total of N CTD/rosette
casts were made at station ALOHA, and 2 were made at the Kahe Point
station.  The GOFS primary productivity cast was made, and the in situ
array successfully deployed and recovered.  Several net tows were made
for students working in the GOFS component of the program.


2  Problems

2.1  PITS spar buoy

A port-side deployment of the drifting sediment trap array was tried on
HOT-25 instead of the stern deployment of HOT-24.  During the final
stage of the deployment of the array, the surface spar buoy swung into
the side of the ship breaking off the weighted end.  There was no means
to repair this damage, so the array was recovered and the deployment
abandoned.

The proximity of crane to the port rail forces the crane to a near
vertical position to work close to the rail.  This results in a long
scope which, along with the propensity of the ship to roll, results in
excessive swinging of the suspended objects.  There is no way to
prevent swinging as there is no way to get opposing tag lines
outboard.  A starboard side deployment will allow a reduction of the
scope from the crane, minimizing the swinging on rolls.


2.2  HOT Winch

The Markey winch which has been used by the HOT program was overhauled
in the UH Marine Center shop prior to HOT-24.  This overhaul was
requested by the PIs as the winch had not been serviced since at least
last fall.  The scope and quality of this overhaul appears to have been
inadequate in light of problems experienced on both HOT-24 and HOT-25.

On HOT-24, the coupling on one of the hydraulic hoses failed during the
first lowering (weight test), disabling the winch.  New hoses were
installed prior to HOT-25.  Several serious failures occurred during
HOT-25.  Fortunately, the winch operators (ALPHA HELIX crew) noticed
these problems in time to prevent further damage and possible injury.
The ALPHA HELIX engineer repaired all of the problems with the
exception of the feed rollers on the level wind which were serviced by
Rosen.


2.2.1  diamond gear/shuttle

During the first lowering (winch test with weight only), the winch
operator noted that the sides of the grooves on the diamond gear were
being cut as the level wind shuttled back and forth.  After retrieving
the weight, the shuttle was taken apart, and the shuttle gear was
observed to be frozen.  Upon disassembly, it was obvious that the
surface of the piece was corroded (rusty) and that the lubricating
grease had combined with the rust to make a very thick paste which
caused the gear to freeze.


2.2.2  level wind sheave

During a subsequent cast at the HOT site, the center sheave in the
level wind mechanism started to come apart.  The winch operator
fortunately noticed an unusual noise and discovered that the bolts
holding the two halves of the sheave together were backing out, and the
wire was falling down into the bolts.  Again, the ship's engineer fixed
the problem.


2.2.3  gear lever

During the deep cast to 4700 m, the gear lever popped out and the winch
began free-spooling when the rosette package was only 200 m above the
bottom.  The winch operator responed rapidly by applying the mechanical
brake averting damage to the CTD and possible hocking of the cable.


2.2.4  level wind feed rollers

At the same time that the diamond gear shuttle was being repaired, it
was noted that the feed rollers on the level wind were also frozen.
These were disassembled, cleaned and lubricated.  The problem was
similar to that described above for the shuttle gear.


2.3  Rosette ring

The aluminum rosette frame had been modified by the Engineering Support
Facility prior to HOT-25 by welding aluminum struts holding an aluminum
ring to the frame.  This was designed for use as a grappling hold
during deployment and recovery operations.  Several welds failed during
one recovery operation, with the result that jagged ends of the ring
and bars were swinging around above the deck because the tag lines then
slipped off.  The rolling of the vessel at the time was not extreme.
Inspection of the welds by the Chief Scientist indicated that they were
of poor quality.