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Constructing the floatation & weights: |
Floatation material:
This page will show you the "how", not the
"why". For an explanation of trimming, please
click here.
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Finding the blue
floatation foam proved hard, but finally a hardware store a bit from
me had it! (At $24 each...)
The brand is "Floormate TM",
by the Bow Chemical Company". It's normally used for silencing
floors, but since it does not soak (while
expanded polystyrene
does), and since it's hard and has a very fine structure, it's
perfect for the job. |
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The first piece
was cut by hand, and shaped to fit above the water tight modules,
under the surfaced waterline, and inside the top of the submarine.
The idea is that the floatation material is to reside in the top
half of the sub only, thus making a high center of positive
buoyancy, and thereby offering a very stable submarine. The missile
deck is quite a bit above the surfaced waterline, but I'm pretty
sure that this will do the trick. |
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Here the
prototype is fitted to the lower half of the submarine, showing the
future location and orientation.
The idea is to make a lot of these blocks, making it possible to fit
more or less (thus adjusting) when trimming the submarine in the wet
dock shortly.
It is vital that the floatation material is below
the surfaced waterline! This explains the flat top if the unit. |
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This image shows the floatation
piece fitted in it's actual future location: Inside the (inverted)
top half.
The white "bottom" if actually the missile deck.
By lowering the prototype info water, I found that one piece of
these dimensions displace app. 110ml ( 0.23 pt )
of water, and on a
scale I found that the weight of one is app. 3g ( 0.1 oz )
The positive buoyancy pr. unit is the app. 107g ( 3.7 oz ).
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This setup is for the crowd, and
shows the cross section of the hull. The outer brown hull holds the
inner transparent tube used for the watertight compartments, that
rests on the bulkheads.
The floatation foam sits from the center line of the main brown hull and
app. 50mm ( 1.97" ) upwards, all the way to the surfaced waterline.
The watertight compartments are all 10mm ( 0.4" ) off center,
pulled down a bit, to lower the heavy parts. (Thus lowering the
negative center of buoyancy a bit. The further apart the negative
and the positive center of buoyancy is, the better. They do,
however, need to share the same vertical axis.) |
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The bow and stern area is free of compartments, so in these areas the foam will not have the inner arc, and will be longer.
This is the bow section. The hole allows air to escape easier and prevent instability.
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This is the aft section. It was a bit tricky to make, as the prop shaft, rudder push rods, zink anode, and the support bridge required some tracks to be cut in the flotation foam. Again, holes allow air easy escape.
Next is to put all of the components into the hull, and lower it all into the test tank, and then trimming by placing the floation blocks one by one, until the trim is perfect. |
Weights:
The submarine will need some dead weight as well, and
here's what I came up with. The two rods are actual shafts from a
Zerox-mashine, and the combined weight is 1252g. (2,76 lb) They are
mounted as low as possible, but raised a little bit from the hull, thus
not resting on the inner hull wall. Holes in the fixtures ensure that
water can escape when taken out of the water, and was made by placing a
McDonald straw under the wet, thickened resin. Resin does not stick on
straws, so they could be pulled out afterwards, leaving nice, round
drain tunnels.
If you look real careful on the picture to the right,
you can see my mark on the hull edge "CL" (Center of Length) The center
of weight and of cause also the center of positive buoyancy, is app. 2"
in front of the center of length. This should make the sub easier to
turn, once all of the components are done.
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