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Figure 5: Main induction valve bonnet. 
(Note 1-inch steel pipe which jammed under valve disk.)

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Work on the first tunnel, at frame 46, was started on October 22.  The divers
available had all done most of their diving in chasing lost torpedoes and were
consequently experienced in using a washing hose for digging out buried
torpedoes.  Tunneling was therefore the thing they knew most about, and no
special difficulty was anticipated.  A 2.5-inch fire hose with a 4-foot pipe
nozzle, at a pressure of about 40 pounds, was first used.  The progress for
the first day gave reason for optimism, but thereafter continued trouble was
encountered.  Instead of the soft mud in which the divers had ordinarily
worked, and which washed freely with a hose, it was found that under a thin
layer of hard sand and mud, there was a bed of hard blue clay mixed with some
sand in which the submarine was buried.  The consistency of the clay was such
that a moderate water pressure had no effect on it.  It was found impossible
to raise the pressure on the 2.5-inch hose, as the diver was unable to
withstand the reaction of the hose and lost control.  After the first day's
work, it was found imperative to raise the pressure to cut the clay.  To
permit this, the last length of fire hose was replaced by a 50-foot length of
1.5-inch wash deck hose with a pipe nozzle of the same diameter, and with this
reduced size the diver was able to hold a pressure up to 70 pounds, which
would cut the clay when the nozzle was held close against it.  With this
nozzle work was continued throughout the fall.

Another unpleasant discovery was the fact that the clay and the sand were so
heavy that, unlike mud, they refused to stay in suspension when cut and
settled again in the tunnel within a foot or two of the nozzle.  This feature
was aggravated by the small size of the water jet, which was unable to set up
any appreciable current in the tunnel as it advanced under the boat.  As a
result of this, the diver was compelled, after cutting ahead a little, to turn
his nozzle and wash all sediment backwards out of the tunnel.  Consequently
only a small portion of the diver's time on the bottom was spent in actual
cutting ahead.

Finally weather conditions through October and November were such that diving
was ordinarily impossible more than two days in succession, after which two or
three days might elapse before diving could be resumed.  It was found on
returning after each storm that the bottom currents had either partly or
completely filled the tunnel with heavy hard-packed sand, which had to be
washed out before any new cutting was possible.

The above factors, complicated by an insufficient and a decreasing force of
divers, prevented driving a tunnel through during the fall operations.
Several times success seemed near, with the divers approaching or even
touching the keel, but each time bad weather caused a suspension, and
practically all work had to be done over again when tunneling was resumed.

After the first three diving days, sufficient knowledge of the troubles
existing in sealing up and in tunneling was gained to make it evident that the
10 experienced deep-sea divers would not be able to finish the job before
winter set in.  An attempt was made to bolster up the force by using some of
the shallow-water men, sending them down in company with more experienced
divers.  This policy was tried out on October 28, but the results were
unfortunate.  The first man sent down failed to orient himself and did
nothing.  The second man apparently was paralyzed with fear, fell off the
submarine, and was found wandering on the bottom after having fouled the lines
of another diver.  This second man contracted a severe case of bends that
night from which he nearly died, and which kept him in the hospital for over
five months.  A third shallow-water diver sent down late that day wasted the
dive of his partner, who was compelled to put in his entire dive, keeping his
mate from being washed away by the current or fouling his lines, and
consequently accomplished nothing himself.

The experience of this day proved conclusively that the diving course at
Newport does not fit a man to dive in work of this kind.  In confirmation of
this fact, it was noted that of some 20 shallow-water divers present, none
desired to work on the job, all apparently realizing fully their lack of
training.  As there was now neither time nor opportunity for training these
men, it was felt that time did not exist for the small number of experienced
men present to complete

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Figure 6: Channel strong back securing motor room hatch.

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the job; by the middle of November this was seen to be a certainty.  However
it was determined to do as much as was possible while the weather permitted.

To seal off the motor room, Eiben and Wilson entered from the engine room and
closed all necessary valves including the ventilation valve.  Later they
closed the motor room door and sledged down the dogs.  To discharge the water,
the drain valve in the forward bilges (pl. 1) of the motor room was opened,
there being a nonreturn valve on the bilge suction.  In the engine room a
valve bonnet on this drain line was removed so that water could be forced from
the motor room to the engine room but not in the reverse direction.  To admit
air, Kelley and Anderson removed a bolt through the top of the motor room,
tapped out the bolt hole, and secured a 0.75-inch connection for a blowing
hose.  To prevent blowing open the motor room hatch under internal pressure,
an external strong back was made and bolted down over the hatch, as shown in
Figure 6.

On November 7, the air was put on the motor room to test it out.  Considerable
water was expelled, when air started to blow out the ventilation main in the
superstructure.

Inquiry of the "S-51" survivors disclosed the fact that the drain valve on
this line in the motor room was defective and could not be effectively closed,
though they had not previously reported this trouble.

To remedy it, the motor room door was opened, the drain line disconnected, and
the valve (1.25 inches) sealed with a pipe plug.  The door was resecured after
considerable difficulty, on November 15, and on November 18 another attempt
was made to blow the motor room.  After the water had gone down a few feet,
the air started to escape through the ventilation valve, which was reported by
the divers to be chattering like a relief valve with the air being released in
gusts.  This valve was closed and secured by the internal locking gear, but
this locking gear, even when set up to the limit, was unable to hold the valve
on its seat against a few pounds pressure.  Nothing further could be done with
this compartment during the fall operations.

The second compartment attacked was the C.O.C.  To seal this compartment
required the substitution of two salvage hatches for the regular hatches in
the conning tower and the gun access trunk, as the original hatches were
unable to hold an internal pressure.  There was further required the closing
of numerous valves inside the C.O.C. and the closing of the two doors leading
to the battery room and the engine room.

As a preliminary, the hatch on the gun access trunk was opened as previously
described.  The hatch on the conning tower was open at the time of sinking.

Handling the salvage hatches presented a new problem.  Each hatch was made of
steel plate 1.25 inches thick, with a heavy strong back and bolt running
through it, and with a long length of 4-inch suction hose attached to the
underside about as shown in Figure 7.  Each hatch weighed around 700 pounds
assembled.

After a rehearsal on the "S-50" it became evident that the hatches could not
be suspended from the surface while the divers endeavored to install them, as
the up-and-down motion was too much to allow the divers to work.  It
consequently became necessary to provide a means on the submarine boat over
each hatch for handling it.  For the conning-tower hatch a heavy oak timber
provided with an eyebolt was secured over the bridge where it plumbed the
hatch cover and the hatch itself was handled by a half-ton chain fall secured
to the eyebolt in the timber; using this rig the conning-tower hatch was
hooked onto the chain fall after it had been lowered in the bridge inclosure
and was installed and set up by two divers, Frazer and Smith, in one dive.

Having secured the conning-tower hatch, another long oak plank was attached
across the timber already in place over the bridge, with the end of the new
timber projecting forward of the bridge enough to plumb the top of the center
of the gun access hatch.  With this rig in place and the chain fall ready, the
hatch was lowered from the surface boat, guided down by

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Figure 7: Engine room salvage hatch. 
Practice on "S-50". (Note 4-inch hose.)

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a line secured to the side of the gun access trunk.  As the hatch neared the
submarine it was dragged over by the divers, who entered the suction hose into
the trunk and fed it down until the hatch was landed when the surface line was
let go by the divers.  The chain fall was then hooked into the strong back
bolt and the hatch was thereafter handled from the chain fall by divers.
Considerable difficulty was encountered with this hatch in getting it
adjusted, on account of the slope of the submarine boat, but this hatch was
also successfully installed by Frazer and Smith in one dive.  However, it
appears that the exertion of handling this heavy weight while plumbing the
hatch was such that Frazer strained his heart and it was discovered that
further diving by Frazer was out of the question.  (Gun access hatch, fig. 8.)

With both hatches in the C.O.C. sealed up, the next attempt was to close the
doors.  Two divers entered the battery room and went aft along the passage to
the crew's quarters toward the forward C.O.C. door and found the passage
blocked by mattresses and bunks.  An attempt was next made to enter the C.O.C.
through the after door from the engine room.  The first pair of divers who
tried this entrance were unable to squeeze through.  The second pair of divers
on the same attempt had to quit because four underwater lamps burned out on
them during one dive while inside the submarine boat.  A third attempt to
enter this door, made by Wilson and Eiben proved successful.  The two men got
part way in the C.O.C., cleared away a bunk which had washed into the C.O.C.
from the battery room forward, and then found a clear though congested passage
through the remainder of the C.O.C.  By working forward they reached the
forward C.O.C. door, which was found jammed with wreckage but which was
cleared and closed by the divers.  The necessary valves to seal up the C.O.C.
were next closed by the same pair of divers.

On a previous dive the divers noted that one of the air banks showed about
2,000 pounds of air in the C.O.C.  An attempt was consequently made to open
all the Kingston valves in the main ballasts, using the master controller in
the C.O.C. to operate the air motors at the individual valves.  The divers
opened the master control, but none of the air motors functioned.  As a result
of this the Kingston valve for No. 3 port tank was opened by hand from the
C.O.C. and the Kingston valves for ballast tanks 4 and 5, port and starboard,
which were accessible from the engine room, were opened by hand from the
engine room.  None of the gear for operating the Kingston valves on the
remaining ballast tank were accessible from the inside of the boat, due to
wreckage.

Having opened the Kingston valves on port ballast tanks 3, 4, and 5, on the
next dive Wilson entered the C.O.C. again and adjusted the valves on the air
manifold so as to blow down these three ballast tanks, using the ship's own
compressed air.  Another diver was stationed outside the submarine to observe
the discharge from the Kingstons.  Air was turned on all three tanks at once
and the gauge inside the boat started to drop in pressure immediately.  The
diver outside noted that a stream of muddy water was being discharged from the
Kingston in each one of the three tanks.  The tanks were blown for about 30
minutes, when the air on the gauge inside the ship dropped so low as to render
further blowing inadvisable.  All air valves were closed and the diver came
out.  None of the three ballast tanks had commenced discharging air, so none
of them were dry.  It was estimated that all of them were from one-half to
two-thirds blown down.

A rubber hose was found through the after door of the C.O.C. running from a
connection in the engine room to the ice machine located under the deck in the
C.O.C.  As this hose prevented closing the door, it was cut by the divers and
gagged on both sides of the cut.  The divers then closed the after door on the
C.O.C. and dogged it down.

A hose for blowing the C.O.C. was secured to the connection provided on the
salvage hatch already installed and air was turned on the C.O.C.  After
building up a pressure of 3 or 4 pounds in excess of the bottom pressure at
the point of discharge, air started to blow

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Figure 8: Gun access salvage hatch in position. 
(Note air connections.)

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in gusts from the C.O.C.  It was evident that in spite of being locked from
the interior the ventilation valve in this compartment was operating in the
same manner as the valve in the motor room.  As this occurred at about the
same time - that is, late in November - nothing could be done during the
remainder of the fall operations.

About the middle of November divers worked in the engine room on the fuel-oil
manifolds, setting the valves and rigging air connection to blow the contents
of the fuel-oil tanks, of which there were two groups, one forward and one
aft.  The after group of oil tanks were blown first, the contents being
discharged through a hose led to the surface.  It was found that the after
group contained nothing but water, all of which was blown out until air was
discharged.  The connections were then shifted to blow the forward group,
which was done a few days later.  From the forward group of oil tanks there
was discharged first water, then oil, and finally water again, until air was
discharged.

Late in October an attempt was made to lower the first pontoon.  Divers passed
reeving lines of 21-thread manila under the stern of the submarine, which was
clear of the bottom.  On these as guide lines there were hauled heavier
manilas and then two 1-inch wire lines.  The pontoon was to be lowered with a
15-fathom shot of 2.5-inch anchor chain hung from each hawse pipe, each chain
being held at the top of the hawse pipe by a heavy bolted clamp similar in
design to those used on the "F-4".  The wire hauling lines were secured to the
lower end of each one of the chains.  The pontoon was to be lowered from the
surface, using a 6-inch manila line at each end.

Flooding of the pontoon was started as in previous practice with these
pontoons on the "F-4" and the "U-111".  The pontoon sank until it was
practically awash, when it tended to submerge one end first.  Some time was
spent in juggling with the vent valves and the air connections on each end of
the pontoon in an endeavor to level the pontoon and make it go down
horizontally.  This was not successful, as whenever the pontoon was made heavy
enough to submerge as a whole one end always dropped first.  As no more time
was available for holding the pontoon at the surface, the weather getting
worse, the pontoon was finally permitted to flood until it had negative
buoyancy and was then lowered over the side on the 6-inch lines.  As the
pontoon went down a few feet it grew heavier and it became quite evident that
the 6-inch lines could not hold the weight.  To prevent the lines from
breaking, an endeavor was made to pay them out fast; but in spite of this,
first the line on the after end and then the line on the forward end of the
pontoon broke in quick succession; later it was found that the pontoon had
descended to a depth of about 50 feet when this happened.  The pontoon
thereafter fell freely to the bottom.  Fortunately the "Falcon" was being held
clear on one side of the submarine and the pontoon landed away from the
submarine about 50 feet on the starboard quarter.  The hauling wires with
which it had been expected to guide the pontoon in position against the
submarine had slacked off and fouled themselves around the submarine.  After
some days' work these wires were finally cleared and the pontoon was blown dry
and brought to the surface.  It was evident that the methods previously used
in lowering and handling pontoons in shallow were not applicable in the open
sea.

The "Falcon" proceeded to Narragansett Bay where, in shallow water, using
another pontoon, an attempt was made to lower evenly.  It was again
demonstrated that as soon as the pontoon had taken in enough water to
submerge, between the loss of external water plane and the free water surface
inside the pontoon (the pontoon at this time being two-thirds full of water),
it retained no longitudinal stability, and the slightest inclination toward
one end or the other would cause that end to drop and the water on the inside
to flow to that end and make the pontoon go down one end first.  Two solutions
seemed possible; one was to allow the pontoon to flood completely at the
surface and provide means of lowering it which could stand the full load of

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40 tons.  The second was to discover at what point the pontoon had taken in
sufficient water to reduce its internal free water somewhat and consequently
its lack of stability.  If the pontoon were held reasonably level by the
lowering lines, one end would not have a tendency to float up while the other
end dropped and took all the load.  It was felt that if such a condition could
be found the pontoon could be flooded to that condition, the flood valves
closed with the pontoon slightly submerged, and the pontoon then lowered.
After some calculation and considerable experiment in Narragansett Bay, it
appeared that with a negative weight of the pontoon of 10 tons the internal
free water plane was sufficiently reduced to make the pontoon reasonably
stable provided it was not permitted to exceed a moderate inclination.  To
handle the weight of 10 tons there was required a large factor of safety for
dynamic conditions and for the probability of exceeding the designated weight
while flooding.  It appeared that nothing less than a 12-inch manila line
would be satisfactory.

By this time it was too late in the season, however, to do anything further
about lowering pontoons alongside the "S-51".

Meanwhile the mate to the first pontoon lowered, which had been moored to the
buoy near the wreck on the day of lowering the first pontoon, was torn away by
a bad storm and washed ashore about 30 miles away on a beach in Buzzards Bay.
An independent expedition was sent out on the "Sagamore", which after some
difficulty managed to pull the pontoon down the beach and float it again,
where it was taken back to Newport.

After the middle of November the weather became so bad that diving was
possible only at infrequent intervals and the water became extremely cold.
From the 21st of November until the end of the month diving was impossible
altogether until the 30th of November when an attempt was made to dive.  On
this occasion, of three divers sent down two had to be hauled up because their
air hoses froze up with ice from the moisture in the air being pumped down to
them and completely cut off their air supply.  At the same time only 4 divers
out of 10 who started the job were still in good condition for work.  It
appeared that operations could not be continued successfully.

An attempt was made to hire civilian divers to augment the force, but only
three men were found who were willing and qualified to work on the job, except
those of the wrecking company which had handled the rescue operation
originally, and the latter were not employed.

Considering the unsuitability of the weather, the impracticability of being
able to work more than 1 day in 10 or 15, and the lack of divers, it was
decided, on December 6, to suspend operations for the winter and all vessels
of the salvage squadron proceeded to their usual stations.  The mooring buoys
were removed by the Lighthouse Service and two marker buoys, one can buoy and
one lighted buoy, were left to mark the position of the wreck.  The pontoons
were left moored to the docks at the torpedo station, Newport.

Before the shallow-water divers who were attached to the "Falcon" temporarily
were detached and sent to their permanent stations, all of them, about 20,
were put in the recompression chamber on the "Falcon" and the pressure was run
up to 80 pounds, being the equivalent of about 180 feet depth of water.  As a
result of this pressure test, it was found that 12 of the men were capable of
standing the pressure and appeared suitable material for deep-sea divers.

The diving personnel on the "Falcon" scattered to their regular stations with
the exception of the few men who were kept at New York to overhaul diving
equipment during the winter and with the exception of Chief Torpedoman Kelley,
who was retained as an instructor for the diving class which was immediately
started, using the 12 men just selected.

During the months of December and January these men were given daily work in a
diving tank at the navy yard, New York, where they were required to use air
tools of every description and do various jobs under water on pipe joints,
cutting out rivets, and handling weights, the idea being to make the men
thoroughly familiar with tools under water and to get them into

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the habit of working under water without conscious effort as regards the
proper adjustments of their diving rig.  In the meanwhile a series of
experiments was also carried on looking toward the development of a
practicable under-water cutting torch, the torch previously available for use
by the Navy having failed to operate on every occasion during the fall
operations when it was tried.  The torch experiments were carried out under
the direction of Lieut. Commander Edward Ellsberg, who at the same time took
the diving course with the other shallow-water divers.

Meanwhile considerable attention was given to the method of rigging the
"Falcon" for lowering pontoons, and a careful mathematical investigation was
made of the stability conditions of a pontoon while being flooded on the
surface and while being lowered.

At the end of January the members of the diving class were considered
sufficiently trained and were sent to the south to join the "Falcon" again for
the purpose of actually diving in deep water.  Unfortunately, the operating
schedule of the fleet was such that during the first month that these men were
aboard the "Falcon" no opportunity whatever arose to permit them to dive.  As
a result of this condition the men were all returned to the navy yard, New
York, about the middle of March, where their training in the tank was resumed,
followed shortly by diving in the basin of the navy yard where, on account of
the mud bottom and the opacity of the water, diving conditions were somewhat
harder than in the tank.

About the middle of April the diving squadron was reassembled at the navy
yard, New York, and all equipment which had been landed was taken aboard.  All
divers were recalled from their permanent stations and rejoined the "Falcon".
The total diving force with which the expedition was equipped at the start of
the spring operations was 25 men, of whom 10 were the original divers, 12 were
members of the new diving class, 2 were divers from the fleet not previously
available, and 1 was the yard diver from the navy yard, Boston.

The "Falcon" sailed from the navy yard, New York, on April 23, 1926, and
proceeded to Narragansett Bay, where the next three days were spent practicing
on sinking a pontoon in deep water.  It was found that the calculations were
correct and that a pontoon flooded down to a negative weight of 10 tons could
be lowered slowly to the bottom, held at any depth desired, and finally placed
in any position required before actually landing.  The total time taken in
lowering the pontoon could be indefinitely extended, and in practice a pontoon
was held for periods of over 30 minutes.  By marking the 12-inch lowering
lines with distinctive marks, at each fathom of their length, it was possible
to maintain the pontoon in a horizontal plane at all times during lowering.
To accommodate the wire hauling lines which were required around the submarine,
the bulwarks of the "Falcon" were cut away in two places on each side and new
steel chocks made on the "Vestal" were installed.

At the same time all members of the new diving class were given an opportunity
to dive in 130 feet of water and work on the pontoon as it was landed on the
bottom.  The new divers all passed this test in deep water satisfactorily with
the exception of one man, who had trouble clearing his ears and who was unable
to stay on the bottom as a consequence.

The underwater cutting torch was also tested out on the bottom in deep water
satisfactorily, a steel bar 3.75 by 3.75 inches in section being rapidly cut.

Having made sure that practicable means of lowering pontoons was available,
the "Falcon" sailed on April 26, 1926, from Newport for the scene of the
wreck.  Arriving at its approximate location it was found that the two marking
buoys which one week before had been sighted in proper location and close
together were now separated by a distance of over 5 miles.  As the weather was
hazy at the time, it was not possible to determine by sights of lighthouses on
the horizon which buoy was correct, if either of them was.  An attempt was
made to get radio compass bearings from stations in the vicinity, but these
plotted about 3 miles away from each buoy.  Assuming that the more northerly
buoy was probably correct, sweeping was started by the "Falcon" in its
vicinity, but no results were obtained that day.

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The next day the "Vestal" arrived.  With clear weather it was possible from
the high bridge on the "Vestal" to sight three lighthouses and get an accurate
fix of the northerly buoy.  Compared with the original fix of the wreck
obtained last fall, the wreck appeared to be about one-quarter of a mile west
of the position of this buoy.  Sweeping was consequently concentrated in this
area, using grappling hooks.  Late in the afternoon of the second day, one of
the grappling hooks made a hard strike and a diver descending the grappling
line found himself on the deck of the submarine.  The grappling line was
immediately cast loose from the grapnel and made fast to the submarine, after
which the "Falcon" replanted the moorings in the same locations as during the
fall operations.  An inspection of the submarine boat showed no change in
position from that when last sighted in November.  The vessel had not settled
any deeper in the bottom nor changed her list or trim, nor had there been any
silting up around the hull.  There was a slight marine growth over parts of
the hull, but no great amount.  Diving was prevented by rough weather during
the next few days, but on the 30th of April, 1926, the weather was fair and
the "Falcon" took position for lowering the first pontoon on the port quarter
of the "S-51".  Divers passed two small reeving lines under the stern on which
were hauled through heavier manila lines and then a pair of 1-inch wire lines
for hauling.  These wires were secured to the lower ends of a pair of chains
suspended through the pontoon hawse pipes, the chains being held on top of the
pontoons by bolted clamps.

Unfortunately, just after the pontoon went awash and before the flood valves
had been closed, a splice in the wire strap holding the forward lowering line
opened up under no special strain, and as a result of this accident the
pontoon tore free and sank to the bottom, end on.  As before, the "Falcon" was
holding herself a little clear to port, so the pontoon in landing hit the
bottom about 30 feet outboard of its designated position.  The next day this
pontoon was lightened up on the bottom by blowing out some of the water and
was then hauled over to its position against the port quarter of the
submarine.

The wire hauling lines, having pulled the chain under the submarine, were rove
through the hawse pipes of the second pontoon on the surface and this pontoon
was then lowered on the two wires as guides.  This pontoon was sunk somewhat
lighter than intended, with the result that it landed alongside the submarine
standing on its end rather than horizontally.  As a result, one of the chains
unrove through the hawse pipe.  The matter was rectified by lightening the
pontoon and bringing it to the surface, after which it was resunk.  The second
time it went down evenly and landed in the horizontal position as intended.

The torch was then used for the first time in actual work on the job.  The
chains were hauled through the pontoon hawse pipes for a predetermined amount
after which a stud in the link just above the hawse pipe was burned out of
each chain and a nickel steel toggle bar 40 inches long and 3.75 by 3.75
inches in section was slipped through the chain and locked in position by a
long half-inch bolt on each side of the chain link.  (See fig. 9.)  When this
had been completed, the lowering lines were cast loose and the hauling wires
were burned free of the chain and taken up.

Meanwhile work was recommenced on the forward tunnel at frame 46, using the
same size hose and nozzle as during the fall operations.

A special inclinometer was made and taken down by one of the divers to measure
the heel of the ship.  A measurement was taken just forward of the conning
tower and it was found that the "S-51" was listed over exactly 11.5 degrees to
port.

Work was now commenced on lowering a pair of pontoons on the bow, and reeving
lines were passed under that part of the bow which was clear of the bottom.
The forward reeving line, however, slipped out three times from under the ship
owing to the rise of the forefoot.  To remedy the situation Chief Torpedoman
Kelley went down with the torch and reaching down 2 feet through a hole in the
deck burned in half the wire holding the mushroom anchor.  This

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Figure 9: Bow pontoons. (Note nickel-steel toggle bar through link, 
locked in position by 1/2-inch bolt each side.)

----------------------------------------------------------------------- Page 27

dropped the anchor from its place under the keel forward until it rested on
the bottom, and in this position its shank, which still protruded into the
hawse pipe, formed a trap behind which the next reeving line was passed and
which prevented any further slipping out of the reeving lines.

A pontoon was then rigged and lowered on the starboard bow in the same manner
as those at the stern, and later in the same day another pontoon was lowered
on the port bow.  This was the first instance in which two pontoons were
lowered in one day.  These pontoons were secured by the divers in the same
manner as those at the stern.

During a storm early in May which came up during the night while the "Falcon"
was lying moored over the submarine, one of the tugs, the "Iuka", drifted down
on the "Falcon", and in getting clear the "Falcon" was compelled to cut most
of her mooring lines, while the "Iuka" fouled her anchor in the bow pontoons
on the "S-51" and was then forced to slip her cable.

As a result of this, when the storm cleared considerable work was necessary to
clear the fouled anchor and chain, to replace the descending lines which had
been carried away, and to recover the lost mooring lines.

On May 11, 1926, after the longest dive made, up to that time, 2 hours and 20
minutes, Eadie and Wilson working from opposite sides of the submarine both
managed to drive their tunnels down to the keel of the submarine.  Eadie
pushed his foot under the keel to the other side to which Wilson secured a
small line which Eadie hauled back with his foot and the first line was thus
passed.  A second reeving line was then pulled through, tied to the first
line, and the two lines cleared of each other.

On this same day 16 divers made a dive, being the maximum number of divers who
went down on one day during the entire operation.  On the next good day
preparations were made to sink a pontoon on the port side abreast frame 46.
Manila lines, 4-inch, were rove through the tunnel as hauling lines for the
1-inch wires.  The wires were hauled down and secured to the chain hanging
from the pontoons at the surface as usual.  However, when all was in readiness
and the 4-inch lines were hauled in to pull the wires through, one of the
4-inch manila lines was cut in half by the starboard bilge keel of the
submarine when apparently running freely and without strain.  The remainder of
the day was spent in an endeavor to recover an end of this line but
unsuccessfully.  Meanwhile the weather changed and in a heavy sea the pontoon
alongside became a serious menace and had to be cast loose from all lines and
towed away.  The next day it was found that one wire reeving line was fouled
on the bottom and had to be cleared.  To replace the line which had been cut
it was necessary for the divers again to work through the tunnel and push a
new line through, this time with a small pipe 8 feet long as a lance to carry
it through under the keel.  After some difficulty this was accomplished and a
new 1-inch wire was rendered through.  About 7 p.m. work began on sinking a
pontoon on the port side.  The pontoon was lowered successfully and was held
at a point about 30 feet above the bottom, where the chain should have started
to render through under the keel; but in spite of the maximum pull that could
be given on the hauling wires by the "Falcon", the chain failed to render.
Two heavy manila hawsers, 6-inch and 8-inch, were then secured to the wire
hauling lines, and the ends of the hawsers sent over to the "Iuka", which was
anchored about 100 yards broad off the beam, with the idea of getting a flat
hauling lead which might make the chains render more easily under the keel of
the "S-51".  The "Iuka" heaved on both lines with her quarter-deck winches but
without result.  A diver was sent down to inspect conditions on the bottom and
found the pontoon in its proper position about flush with the deck of the
submarine and with the two wires on the opposite side of the submarine leading
out flat and taut toward the "Iuka", but no chain was through under the keel.
The diver came up and the "Iuka" then started ahead on her main engines
gradually working up to full power, but in spite of this she was unable to
haul the chain through.

          45129-27--3

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The "Iuka" then slacked off the 6-inch manila line to get her entire hauling
strain on the 8-inch line.  After about five minutes under these conditions,
the 8-inch line parted, throwing the entire strain suddenly on the 6-inch
line, which also parted.  As nothing more could then be done, the pontoon was
lowered the remainder of the way to the bottom.

During the following two weeks various methods were tried to haul the chains
under the keel, including the placing of tapered wood blocks under the keel as
fair leaders.  Various attempts were made to clear the first link from the
keel with crow-bars and several more attempts to haul the chain, using the
"Iuka" to haul.  In every instance whenever a strain came on the chain the
first link would be brought hard up against the angle of the box keel, which
hung about 16 inches below the hull, and the chain would then bind securely
and could not he freed.  Owing to the close quarters, a diver having to work
in a small tunnel and in an extremely difficult position, the divers were
never able to clear the chain.  Finally, after the last attempt at hauling had
resulted in tearing the quarter deck winch out of the "Iuka", it was concluded
that a different method would have to be used, and the pontoon was brought to
the surface, together with the chains.  Having done this, the position of the
wire hauling lines through the tunnel was carefully checked, after which the
chains were removed from the pontoons.  The eye of the first wire hauling line
was shackled in to the end of one of the chains, using a Boston design
detachable link for a shackle.  Over the end of the wire was then fitted a
special steel cone which gave a smoothly faired surface from the 1-inch wire
around the outer diameter of the first link, with no angles to catch on the
box keel.  With this rig the first chain was independently lowered and passed
through the tunnel under the keel without difficulty, where it was equalized
with the same amount of chain on each side of the hull.  The second chain was
lowered in the same manner.  There being no pontoon to contend with at this
time, the divers were able to work on the bottom while the chains were being
lowered and to guide the chains through the tunnel.  Having secured the
chains, they were then held up as shown in Plate 3, and a pontoon was lowered
on the port side until it was about 20 feet clear of the bottom, in which
position a pair of divers went down on the pontoon, checked its location, and
then rode the pontoon the rest of the way to the bottom.  Here the divers cast
off all lines and inserted and secured the locking hers.  The mate pontoon,
meanwhile, was brought out from Newport and was lowered and secured the same
day.

This method of handling the chains and the pontoons was seen to be
considerably superior to the manner in which the pontoons had been handled
before - that is, with the chains lowered with the first pontoon.  The reason
for the original rig was that the only means of securing the chains in the
hawse pipes of the pontoon was by means of a steel clamp made in two halves,
weighing about 300 pounds, and secured by four 1.5-inch bolts.  Such a rig was
extremely difficult to handle and probably could not be secured without
auxiliary rigging in the way of chain falls or lines to the surface.  In
shallow water, where a diver could work all day, such means were available.
In deep water, where his time on the bottom was very limited and extreme
exertion was likely under the heavy pressure to affect him unfavorably (as
actually happened in the case of Frazer), it was considered best to cut this
work in half by securing the pair of chains to the first pontoon by making up
the clamps on the surface, leaving only the work of clamping the chains to the
second pontoon.

However, when the use of the torch made possible the removing of studs and the
insertion of a locking bar at any desired point, it became possible to
eliminate the clamps.  This was first done only in the case of the second
pontoon of each pair, but was obviously applicable to both pontoons, and the
further use of clamps was wholly discontinued.  It might casually have
appeared that all studs might have been burned out on the surface originally,
but there was considerable danger in such a practice of the chain kinking up
if the studs were missing while the chain was being handled under the
submarine boat, and as such a kink would insure

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the parting of the chain in a load, it was considered safer to burn off the
studs where wanted, rather than taking a chance on burning out a large number
to insure getting an open link on the hawse pipe.

Early in the spring operations, on May 11, 1926, work was started to seal off
the ventilation main leading to the C.O.C., the engine room, and the motor
room.  The motor room was first attempted, as the ventilation main leading to
this compartment could be most readily reached of the three compartments.  The
deck of the submarine just forward of the motor room was removed, and the deck
beams covering the ventilation main were then burned clear by Chief Torpedoman
Kelley.  Work was then started on unbolting both flanges of a section of this
12-inch main for the purpose of blanking it off on the motor room side.  After
some days all the bolts were removed from the after flange, but several of the
bolts in the forward flange were practically inaccessible due to their
location close alongside the engine air induction valve.  After several
attempts by divers to get at these bolts, it was determined, after an
inspection by the salvage officer, that there was no need to unbolt both
flanges.  Consequently, a wire line was tied around the pipe near the unbolted
flange and on heaving from the "Falcon" the pipe was torn out of the ship, the
forward flange breaking off the pipe while the unbolted flange came clear.
The joint left in the ship was then scraped clean by divers and a new blank
flange, which was immediately made, was securely bolted on.  (See figs. 10,
11, and 12.)

After blanking off the ventilation main to the motor room, air was turned on
to blow it dry, and divers reported a good stream of water being discharged
through the nonreturn drain line into the engine room.  After blowing about
half an hour, a stream of air bubbles came to the surface over the forward end
of the motor room.  A diver's examination showed that a butt in one of the
upper strakes of the shell on the starboard side was open over a sixteenth of
an inch (the vessel was single hull throughout the motor room) and a steady
stream of air was escaping from a length of about 2 feet at the upper portion
of the butt.

It was evident that the leak was due to defective workmanship originally, as
there was no evidence of damage or strain in that vicinity.  Apparently a
poorly fitted and wide-open butt had been made tight by splitting the edges of
the plates and bringing the feather edges of the two plates together.  Between
corrosion and an internal pressure part of the feather edge had now given way,
causing a bad leak.

To remedy this, Eadie and Eiben were sent down with strings of lead wool made
by twisting together lengths of fine lead fuse wire.  They calked this lead
wool into the open butt until the space between the two plates was completely
full, using ordinary hand wood calking tools for the job.  Eadie then took a
standard air-driven chipping and calking hammer and, using a fuller, proceeded
to recalk the plates themselves in the usual manner.  This calking job was
complicated by the fact that each time the trigger was pulled the stream of
air escaping from the hammer set up such a cloud of bubbles in the water that
it was no longer possible to see the work clearly and the diver had to be
guided by his sense of touch and general skill.  When the air pressure was put
on the compartment, the part of the butt which had been recalked was found
tight, but new leaks had developed over the remaining length of the butt (as
is usual even in surface work) and Eadie was compelled to recalk the entire
butt with the air hammer.  This effectively stopped all leaks in this
location.

In this calking job, the surface air pressure was kept at 150 pounds.  The net
pressure at the hammer was between 80 and 90 pounds, taking account of hose
friction.  On examination of this job later with the vessel in dry dock, the
calking could not be distinguished from the other calking done while the ship
was building.

Air was again turned on the motor room and the water driven down a few feet
farther, when another stream of air bubbles appeared, this time near the stern
of the submarine and aft of the motor room itself.  On a diver's examination
of this new leak it was found that about

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Figure 10: Section of 12-inch air supply line to motor room, 
removed by divers.

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10 feet from the stern there was a large dent in the top of the boat in way of
the tiller room; in this dent one rivet was completely pulled through the
shell and the adjoining rivet was partly pulled through.  Air was escaping
freely from these two places.

The tiller room was a small compartment abaft the motor room, connected with
the latter by a manhole about halfway down the bulkhead.  It was evident that
this manhole was open (which was not known definitely before) and that the air
in the motor room, having driven the water down to the level of the top of the
manhole, was now escaping via the tiller room leaks.

To seal the leaks, a lead plug was cast to the size of the open hole and
fitted with a tapered oak cone driven into its base to act as an expander.
When this plug was inserted in the hole, the wood plug brought up against the
frame bar inside, and resulted in spreading the lead plug inside the hole
while the lead was being hammered down by the diver outside.  The result was a
firmly secured flush lead plug which was entirely tight and proof against
jarring loose or being torn away by towing lines during later salvage
operations.

To seal the partly pulled rivet (the rivet itself was solid and in no way
loose) the diver drove soft pine plugs into the open parts of the countersink
so that the wood was firmly jammed in; then trimmed the wood off flush to
prevent lines from tearing out any of the wood filling.  This rivet showed
pinhole leaks afterwards through the pine, but they were of no consequence.

The reason for the dent in the shell was never definitely discovered.  The
location was far removed from all collision damage and could not have been a
result of the submarine hitting the bottom.  It is believed that one of the
vessels engaged in the original rescue operations dropped anchor over the
"S-51" and that the anchor landed on the stern, dented it in, and bounced
clear.

The work of sealing the motor-room leaks was completed early in June, and the
pressure again applied; No further leaks appeared on the outside of the vessel
in the vicinity of the motor room, but when the water level inside had been
forced down to the point where it reached the shaft stuffing boxes in the
bulkhead between the engine and the motor rooms, air started to escape in
considerable quantity through the stuffing boxes into the engine room.  At
this point, the motor room was about two-thirds dry.  It was only by sending
all the air the "Falcon" could supply into the motor room that it was possible
to drive the water lower; the moment blowing ceased, the air below the shaft
lines would escape and the motor room refill to this level.

Inquiry of the officers on the "S-50" brought out the information that on all
submarines it was impossible to keep interior shaft stuffing boxes tight as
the vibration due to the close proximity of the engines quickly wore the
packing to a considerable clearance.

No attempt was made to tighten up the stuffing boxes, as they were practically
inaccessible to a diver; further it was considered that when the engine room
was sealed up and blown dry, air leakage around the shafts would be of no
consequence.  If, however, on this job the engine room, instead of the battery
room, had been the bilged compartment, this leakage around the shafts would
have been a serious matter.

Having sealed up the motor room ventilation valve by blanking it off,
consideration was given to the same procedure for the ventilation valves in
the engine room and the C.O.C.  The main engine air induction valve, having
had its bonnet previously removed in the process of closing the valve, was
quickly sealed from the outside by bolting a steel strong back across the
valve body and pressing a heavy oak block firmly down on top of the valve disk
to hold it on its seat.

The battery exhaust valve which discharged into the engine room and the
ventilation supply valve which opened into the C.O.C. presented different
problems.  Both valves were closed by their internal locking gear, but it was
now known that this was ineffective.  It appeared possible to get at a section
of the battery exhaust main in the superstructure and

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Figure 11: 12-inch supply pipe to motor room
 sealed by cover plate installed by divers.

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blank it off, though with more difficulty than in the case of the motor room.
The line to the C.O.C., however, was so covered by other pipes and buried
inside the structure of the periscope shears as to be practically inaccessible
for blanking off from the exterior of the boat.

A start was made on removing the deck over the engine room, to get at the
battery exhaust main at the same time as work was proceeding on unbolting the
ventilation main to the motor room.  The latter operation, while successful,
took so much time that work was suspended on the engine room and a search made
for methods requiring less diving.

It was noted that each one of the compartment ventilation flapper valves had a
1.25-inch drain valve screwed into its body just above the flapper disk.  In
the case of the motor room, such a drain valve had previously caused
considerable trouble by leaking and had to be plugged.  It now appeared that
through these drain-valve openings a cement mixture might be injected into the
ventilation-valve bodies on top of the closed flapper valves, which on
hardening would permanently seal the valves closed.

To carry out this scheme, a special elbow, to get into a confined space, was
made on the "Vestal" to suit the drain-valve connection in the C.O.C.  This
was tried on the "S-50".  The door from the engine room to the C.O.C., which
had been closed during the fall operations, was undogged and reopened after
some difficulty (the gasket stuck).  Eadie, Wilson, and Eiben then proceeded
to install the cement connection, but found conditions on the "S-51"
sufficiently different to prevent installation, as less clearance existed on
the "S-51".  After modification, the fitting was finally installed, but with
great difficulty, as the water in the C.O.C. was so black from particles in
suspension and from dead water throughout the winter that, even with a
submarine lamp, vision was possible not over 6 inches, and the work had to be
done by sense of touch in a cramped space.  Conditions were so bad that the
lamp itself was invisible unless held within 6 inches of the diver's
faceplate.

Meanwhile experiments were being carried out on the "Vestal" to determine the
best cement mixture.  The primary requisite was to obtain a cement that would
harden under salt water; the secondary problem was to obtain a cement mixture
that would flow freely through 250 feet of 1.25-inch-diameter hose, pass
through a number of valves and fittings, and that would still not be too
liquid to set firmly.

Several brands of standard Portland cement were experimented with, but their
hardening qualities under salt water, except in very thick mixtures, was
extremely poor.  A special bauxite cement, furnished by the Atlas Lumnite
Cement Co., was tried and found to be extremely satisfactory.  A neat mixture
of two parts of this cement to one part of water by volume was found to be
thin enough to insure flow, while its setting properties under salt water were
excellent.  The use of Lumnite cement in this proportion is strongly
recommended for all future salvage jobs where cement is required.

For injecting the cement, the "Vestal" made a steel tank tested to 200 pounds,
with a quick-opening handhole on top for filling, test cocks on the side for
determining the cement level, and a discharge connection tapering from 3
inches to 1.25 inches at the bottom.  Using 200 feet of hose leading to the
bottom of the sea into a piece of 12-inch pipe, a full-scale experiment was
carried out on the "Vestal" to test the apparatus and the mixture, the cement
being forced out by 150 pounds of air pressure on the tank.  About five hours
after injection, the pipe was hauled up and the cement was found already to
have set moderately hard.  It was kept submerged in salt water and by the next
day had set solidly.

The hose and the apparatus were taken to the "Falcon", where the divers ran
the hose inside the submarine and connected the last short length to the
fitting on the C.O.C. ventilation valve.  When all connections had been made,
the cement was mixed on the "Falcon", and two charges forced through, being
about four times as much cement as was required to fill the valve body.  The
divers then uncoupled the hose section near the C.O.C., sent up the remainder
of the hose, and a few days later closed and dogged down the door to the
C.O.C.