Splitting the hull,
and fitting bulkheads:
The very first step in this process,
is to put the hull into water. Allow the hull to roll, and settle. Now,
using a permanent marker, mark the top most part of the hull. Why all
this? Well.. since we have made this hull from epoxy and glass fiber, no
matter how careful we have been, then there will be a little more
resin here and there, than in other places, giving it an uneven balance.
Why force our self to use weights and flotation material compensating
for this later, when this small step does the job for us?
Ohio hull splits right at the middle (Between black and brown area).
Very very carefully
draw a line around the main part of the hull at
the exact middle!
At the bow, follow the outline of the sonar dome and travel over the
hull, leaving the entire sonar dome as part the lower half.
At the tail section we need to go across the top and to the other
side as well, leaving all rudders fitted to the lower half. (This is
the only way we can ensure proper rudder control, and fixture) This type
of cutting is called a "Z" cut. Then, using a thin cutting disk,
separate the two halves all the way around.
There are a number of reasons why I did
not choose to make the sonar dome a part of the upper half, though it
would mean that the cut would travel under the hull, thus making it
harder to spot. Leaving the dome on the upper half would:
- Make it harder to put down the top half when removed,
- cause the forces from any impact to be absorbed by the lighter half of
the two hull parts,
- complicate the front most MBT and bow thruster pump orientation,
- make an unbalanced hull when sailing without the top in test
||Splitting the hull
along the length IS pretty tricky. I drew a line with a marker, and
build the setup in the picture.
The sledge holding the drill could slide, and the hull could not
move anywhere in the box it was sitting in. The sides of the box was
shaped to match the shape of the hull, so the aft and bow end also
could be cut using the rotary cutting disk. Be careful not to run
the disk too hot, as this might damage the epoxy / PVC.
Not in picture: Below the rear end of the drill, there is an
aluminum bar supporting the drill to a firm hold, as it's very
important that the drill can not get out of alignment!
||After cutting the
whole thing, and using a knife to cut the foam within, the two
halves came apart. I haven't seen the inside mockup for about two
years, so this was a rather big step.
The wooden stick served as a guide back when there was nothing else
to guide the mockup's, keeping them aligned along the center axis.
||After digging out
expanded polystyrene, the hull finally looks
like something that will end up being a sub, and the last stretch of
the project can begin. Now it's time to put together all of the
components produced for the last many many month.
The duct tape that formed a membrane between the mockup and the
resin let go real easy, so the removal of the mockup's was done
quickly. (Still the small white balls was all over the hose
||A close look of the
aft section. This area will house the aft MBT later, and shortly
I'll fit the rudders and dive planes as well.
The edge around the entire cut need to be filed and in two spots
repaired, as the disk did wobble a bit. However, I'll wait with this
until the two halves are more stable, so I can get a better view of
where I need to take action.
||I had to see how it
looked with all of the WTC's in it, missing is only the not yet
constructed pressurized air system / tank. I also got into thinking
about how to fit the WTC's. The original idea with a series of disks
forming walls, holding the WTC's need to be altered a bit, since the
brown PVC tube bents slightly after cutting it, making the sub too
thin at the middle. In other words, both the top and the bottom half
need to be supported into right (round) shape.
||This might give the
impression of a lot of waste space, but keep in mind that the air
system including the air tank is still not produced. There will still
be some space to spare though, and I'm thinking about making a third
WTC for periscope control, bow thruster pump, receiver, and some
Next I'll drill a series of drainage holes in
the very bottom of the sub. The diameter of these holes should be
app. 0.2” (5 mm), and close to 2” (5 cm) apart. They should all be
aligned down the center line, so that they are placed in the lowest
place possible. (As this is a "wet hull" sub, the hull is flooded
This completes the splitting of the main hull, and now
it's time to fit the missile deck.
||Take the missile
deck, and temporary put on top of the sub. A line
is then drawn around it, and then the missile deck section is
removed yet again. Now a second line is drawn inside the outline,
and the area left is cut out. The distance between the two lines
should be such that the main hull sticks app. 1/4" (6mm) past the
inside vertical edge of the missile deck. This enables us to glue
the missile deck on to the mail hull, without the glue strip being visible from
the out side.
||First we need to
cut out the part of the main hull which is under the missile deck.
We need the space for stuff, and we need to reduce hull weight as
well. Another reason to cut this section of the main hull, is that
it allows us better control of any entrapped air.
The electrical jig saw proved to be perfect for this job, but the
blade did run rather hot! Besides that, I have noticed that cutting
resin and fiber cloth really wears down the cutting tools.
This blade was dead afterwards..
||Here's a view of
the finished job, and all three major hull parts (main hull upper
and lower part, and the missile deck).
The weight removed from the top half of the main hull by cutting out
the area below the missile deck was app. 1/3.
||Detailed view of
the aft end of this step. Next is to fit the hulk heads in the top
half, and prepare for missile deck fitting..
Notice that the hole in the top half of the hull follows the inside
outline of the missile deck. At the ends, it'll be clued straight
on, but down the side (along the "crack"), the glue line is some
what further up, why the hole shows this in it's outline.
Well...yes. It's a look down the hole for the sail, seeing the very
bottom of the sub about 19 cm (7½ inch) below missile deck surface.
The hole down there is one of the drain holes, of which there are
Notice the reinforcements of the gathering between the main hull
tube, and the green-like bow part. It's split at the very bottom
allowing water to drain undisturbed.
||This is a look
inside the top half of the main hull with the missile deck
test-fitted on, seen from the bow.
Notice the hole for the sail in the missile deck, and the aft end
app. 188 cm (74 inches) away!
It's a boomer all right...
Now let's make and fit the bulkheads..
serve two purposes. First is to stabilize the hull, and second is to
work as a mounting bracket for the WTC's
and MBT's later on. The material chosen for this task, is a 10mm
(0.4") thick plexi glass sheet. (Seen on the picture with the
protective coating still on one side, and the marked up surface
It's a tricky material to work, but when done right, it's strong,
light, and relatively inexpensive. The disks was cut using a plate
cutter, and afterwards the inside hole was cut. Notice that the
inside hole for the WTC is off center, this is so in order to lower
the center of
balance to be below the center axis of the sub. (Thus giving upright
||The inverted top
to the right shows the completed bulkhead tops that go into the top
half of the hull, thus stabilizing the structure. When these are
fitted, then the missile deck can go on.
This image shows the original bulkheads, made of plexi glass. Later
these was replaced by some made in a plastic kind of material. Plexi
glass is just to brittle, I found out.. the hard way.
Fitting the bulk heads are pretty
straight forward. The two long aluminum bars on the sides of the upper
hull part, ensures that the hull part will have the right width
afterwards. The small aluminum pieces that the bulk heads are standing
on, ensures the right location of the bulk heads. The masking tape just
holds it all in place, until the resin has cured.
Remember to rough all the edges prior to gluing.
This image shows the indexing plates
that will extend down and into the bottom half, when the sub is
They also serve to add strength to the structure, right at the gathering
between the brown main hull pipe, and the green self-made part.
Why are the indexing plates not in the bottom half? Well.. this way
they'll even serve as legs when the top is put down somewhere, ensuring
that the edges of the upper hull part are kept intact, and clean.
The original bulkheads were of plexi
glass, but it proved too brittle in the end, so a mold was made from
them, and new ones was cast in a plastic-like material.
The mold was made by putting the nicest of the original ones in a box,
and pouring silicone over them. After curing, the mold was used again
and again to produce all of the bulkheads.
Back at the dock, brass brackets was
made by hand, to go over the modules and support the modules as well as
The funny "fork-shape" at the lower end allows hoses and wires to run
next to the weights.
Left: Notice the holes in the
bulkheads. They will support the push-rods for the rudders. The
tunnel in the middle will support hoses etc.
Right: This gives a nice overview of the fitted bulkheads, allowing the
weights to sit at the very bottom. The "fork-shape" allows hoses and
wires to run next to the weights through out the sub, front to back.
Left: A view of the fitted bulkheads towards
the bow area, and at the fitted air tank.
The two bulkheads closest to the camera are for the MBT1. (Later removed)
Right: This shows the WTC2 and the MBT2 (Later removed) at their places, resting in the
bulkheads, and with the brass bracket in place. (But not bolted yet)
NOTE: The number of bulkheads was heavily reduced in the stage two rebuild because the dive system was changed from two ballast tanks to one, central ballast tank.
The bulkheads all have a small brass
nipple with an M3 thread inside drilled into the top. This allows the
brass bracket to mount.
The H shaped support bracket holds firmly around the bulkheads. The
space between the lower end of the bulkheads matches the width of the
support brackets bottom piece, thus locking it.
NOTE: The H bracket is
not glued to the bulkheads, but to the module. This is for illustration
The H bracket is glued to the module,
and now the module is ready for the final piece of mounting: The brass
bracket. The brackets was made from the same tube as the modules them
self, as it proved strong and just flexible enough.
Here the brass bracket hold the
module, missing is only the M3 brass bolts.
This method gives a strong and secure fit of all modules. They can not
slide, turn, or rise out of their bulkheads. Water, hoses and wires can
pass, and the hull is supported as well.
Notice that the very top of the H bracket arms grasp the brass bracket