Kit, Part-3

A Report to the Cabal:

The metal casting rubber tools (BJB, TC-5050 high-temperature RTV rubber) were
finished late last night and I just stepped out of the shop this morning where I've
been successfully casting metal propellers and detail fittings -- shaping up to be a
good day.

The first half of the rubber tools I'm making for the control surfaces, hatch,
periscope head, Camera WTC end-cap, and horizontal and vertical stabilizers are in
the freezer now and I'll soon be dressing those up for the second half of the tools.
These will be used for resin casting.

Things always take longer than I initially plan -- I was supposed to be done with
the tooling and resin and metal casting yesterday! Shit! Looks like today, Monday,
will mark the completion of those tasks.

Anyway, here's a quick look at yesterdays work: The midship horizontal control surface master was a very tight fit within its stabilizer master. I wrapped a piece of #240 sandpaper around the control surfaces leading edge and then cycled the control surface back and forth while pinned into the stabilizer -- all high-spots on the stabilizer were hit with the sandpaper and knocked down. I call this, 'conformal sanding' and is an old trick used to get parts to mate near perfectly with one another.

A better look at the 'lapping in' between control surface and trailing-edge of the amidships horizontal stabilizer.

The rudders and stern planes have pins up near the leading edge -- the center of rotation not far behind the trailing edge of their respective stabilizers trailing edge. However, the KAIRYU's midship planes are pinned well aft of the control surfaces leading edge, dynamically balancing them; they would require little force to position them, even in the face of a significant fluid flow. I think I know why: Perhaps these planes were positioned by a crewman directly through a linkage that presented him with little mechanical advantage over those planes. Hence, those planes were balanced.

I suggest that the midship planes (like today's sail mounted planes) were only useful in producing an 'up' or 'down' dynamic force, used for depth control. These surfaces directly controlled through a simple handle attached to an athwortship operating shaft which ran through the boats control room, much like the arrangement on the HUNLEY's bow planes. I would suggest that the Commander, either looking through his scope, or through the sails porthole, would be the one operating the midship planes to fine-tune the depth of his boat.

The other crewman aboard the KAIRYU (reports are that there were only two on board an operational boat) would likely operate the propulsion plant (diesel/ electric), steer the assigned course, and maintain the boats bubble with the stern planes.

The half-moon looking penetrations on all three control surfaces have something to do with how the Japanese connected the operating shafts within the control surfaces. I represented these very distinctive penetrations by drilling holes, then cutting a channel with a thin Dremel saw blade through the center of the holes, and inserting a thin gauge piece of plastic sheet to bisect each hole. Some putty and sanding and that took care of that. Note that I'm using photos of the actual prototype to pick out these and other details.

I used an intermediate tool, pulled off the Super Sculpy intermediate masters. From that tool I cast production masters (multiple copies being needed) of the cleat and exhaust pipe mounting brackets. I vacuum cast these items to insure no bubble voids collected at the bolt heads and tips of the cleat horns. Careful sprue, feed, and vent design of the production tools would permit the simpler, more productive pressure casting process to be used for casting of the kit parts.

After dressing up the production masters of the three brackets I assembled these, the gooseneck and flange plate masters with a length of aluminum tube to insure that everything fit correctly -- only once assured that I had practical masters did I commit them to the creation of the production tools.

You can see how well the hex-shaped extruded Sculpy did capturing the six facets of the 'bolts' that fit atop the flange plate and mounting brackets. Note how the goose-neck-to-pipe seam is hidden under the after most mounting bracket.

I have a standard moldboard (a wooden disc with hold down and sprue pins installed -- sized to fit my centrifugal spin-casting machine) I use when I create a new disc tool for spin casting. I simply lay on some backing clay to the moldboard, inset the masters in a circular array within, wind a masking tape dam around the circumference of the disc shaped mold board, and pour catalyzed RTV rubber to start the first half of the tool. But, before all that I mockup the array of masters on a piece of poster-board to get the spacing right. Once happy with the arrangement on paper I transfer the masters to the clay layered molding-board, mash the masters about halfway into the clay and tighten up the fit between masters and clay with a wet stippling brush.

I've placed a set of completed disc type rubber tools next to the work so you can appreciate how the completed tool will look and fit together (That tool dedicated to the production of white metal parts for a Matt Thor WW2 era Russian submarine model he's currently working on).

Two molds would be needed for metal casting and two for resin casting. The two circular mockups are for metal casting, the larger circle is for a 'disc' type tool used for centrifugal 'spin casting' of the many smaller detail parts needed to dress out the 1/16 KAIRYU model. The smaller, circular outline representing a gravity pour tool that will be used to cast the single propeller.

The two oblong tool outlines are for the two resin casting tools, needed to cast the periscope head, hatch, gooseneck, control surfaces and stabilizers.

The detail masters set into the clay backing atop the moldboard. You can get an appreciation of how a spin casting disc mold works by studying this shot: Not that the central sprue hole is the point where the molten metal is introduced once the centered tool is brought up to speed on the centrifuge. Centrifugal force directs the metal outward through the feed channels that radiate from the sprue outboard where the metal finally is packed, with considerable force, into the receptive cavities (those cavities of the tool formed by the masters you see here).

The two outboard tubes projecting up from the disc moldboard form bores in the eventual rubber tool halves that pass the securing studs that permit clamping of the took down tight onto the rotating bed of the centrifuge.

The propeller master set halfway into its clay backed moldboard. Note the discarded propeller master to the right. Under both items is one of the photos from the Wallace RC photo-packet that documents one of these boats -- very useful as I worked out the look and pitch of this particular propeller.

The masters set into clay backing preparatory to pouring the first half of the two-piece tools needed on this project. The dam that keeps the rubber in place till it hardens is low-tack masking tape, wrapped around the perimeter of the moldboard. The white line you see in the center of each tool is in actuality an acrylic rod ... the rod tends to capture and throw back the flash from my camera ... weird. Anyway, those acrylic rods form the major sprue channel through which the resin is routed to each cavity of the tool.

Granddaughter Rose pouring the second half of the spin-casting disc tool. It's vital to identify a practical mold-release agent, needed to keep the second tool half pour from permanently sticking, and ruining, the first half of the tool. In past times I've used a fifty-fifty mix of turpentine and Vaseline. Today I use silicon spray, the same stuff I use to help inhibit adhesion between rubber and cast resin parts. You can just make out some of the embedded masters stuck within their respective cavities of the first tool halve. To the right is the propeller master set within the first half of it's tool, ready to receiver rubber to form the second half of that tool.