Report To The Cabal: A 1/48 SEAWOLF Pump-Jet, Part-6

Though I was commissioned to build only the PJ for a 1/48 SEAWOLF class model, I must say that of late I've been thinking of further exploiting this work by going ahead and making masters, tools and parts for a complete SEAWOLF class kit. Why not? ... the PJ is the majority of the work, the hull and appendages would be a cakewalk after that! And such an r/c submarine would be a natural for an eight-tube torpedo launcher! Hmmm ....

Not like I don't have enough things to do already!

Roger, Erich, Matt, CultTVman, Fred, and Mark, don't panic, you're stuff is next!

These are the five subassemblies that make up the 1/48 SEAWOLF pump-jet. On the left the forward and after sections of the just turned shroud (the holes are used to make up holding fixtures so I can still turn them on the wood lathe faceplate); to the right is the rotor sandwiched between the pre and post swirl stator subassemblies. Keep in mind that these are masters from which I will produce hard rubber tools; from those tools I cast the polyurethane resin model parts that go out to the customer.

A lot of effort was expended developing the 'Z' cut flange that interfaces the forward and after sections of the shroud master. The forward shroud half has the outer 'capture' flange, the aft section of shroud has the interlocking inboard capture flange. This radial tongue-in-groove attachment system assures perfect registration when the two halves are coupled and presents plenty of surface area for the screw fasteners in the model parts to pass, securing the PJ halves together.

Note that there is a lot of Evercoat filler used on the outside of the forward shroud half: I screwed up my layout when I cut out the Renshape 40 blanks -- they were slightly undersized at the forward area, that error revealing itself as I turned the master to shape on the lathe. Out came the filler! I'm such a dumb-ass sometimes! Evercoat saved my ass yet again!

What a knuckle-busting job that turned into!

The swing-over-bed of the pump-jet master was too large for my little Taig machine lathe. So I had to work the big shroud master on my nasty old wood lathe out in the shed in my back yard. Man! It's cold in there! I first made my rough cuts from the inside, then worked it to shape on the outside. Before splitting the forward from the after half, I first cut a groove into the outside. This groove would, on the forward half, secure a band of plastic sheet that would form the outer capture flange. The portion of the groove cut into the after half of the shroud would form the inboard capture flange.

Hey, confession is good for the sole they say, so here goes: Other than the foil sections, pitch and shape of the rotor and stator blades, this work is based on scaled up drawings of the Matt Thor pump-jet that accompany his 1/96 GRP sub kit. The shroud half securing system is his as is the geometry of the hubs and shroud. However, I altered the pitch of the rotor by making the pitch/diameter ratio unity, Matt's rotor (which had many more blades than mine) was of very fine pitch, and in the water, takes forever to get a good bite.

When you look at my pump-jet here, you're looking at Matt's work as well. Thanks, Matt!

A strip of polystyrene plastic sheet was stressed to a tight curl. The width of this ribbon a tad larger than the width of the groove cut out into the outside of the shroud master. The two shroud halves part at the center of the groove. Here I'm almost finished wrapping the outer flange piece onto the groove half of the forward shroud master. Once the ring was secured, it's outer surface was slathered with filler, which was then worked on the lathe. This work went surprisingly fast.

To continue inside and outside work of the assembled PJ master on the lathe I made up two sets of four brass straps. When working the inside of the PJ the outside straps were used, when working the outside of the PJ I used the inside straps. Note that during work up to and including this stage, the forward PJ half was still attached to the end-cut piece of Renshape 40 which in turn mounted with machine screws to the lathe faceplate.

As of last night (or was it early this morning?) here is as far as I got. The rotor is still a bit oversize in diameter, but the pre and post-swirl stators are good, tight interference fits to their sections of shroud. Today I march on with creation of the rotor ring, installation of the ring to the rotor, and machining of a groove within the after half of the PJ shroud to accept the rotor ring. The end is in sight!

Did I mention that I hate PJ's!?...