Building An R/C KILO, part-3

And with this third part I conclude work on the r/c KILO till other jobs are finished off (thunderous applause from Erich, Jonathan, Fred, and Roger).

Other than this kit not very faithfully following the form of the Russian KILO class submarine, there is one major flaw -- a fit problem, probably originating from tool distortion in the press.

When fit together, there's a major longitudinal and transverse bowing of the upper hull half when it's pressed down upon the lower hull half. If the kit is assembled as a proper static display piece only, there is nothing to prevent a very pronounced inward dip between the hull halves; the ideal is a cylindrical hull, but the warped upper hull piece causes a 'figure of eight' bowing at the hull halve union. Fortunately, a circular union is restored when the WTC is installed, its stout cylinder insuring that the upper hull will distort to correct circular section when pulled down tight over the WTC. Further, the installation of an auxiliary ballast tank back aft acted to further stiffen the hull. So, now, the little 1/144 KILO has a very good indexing at the upper/lower hull seam when the hull halves are assembled.

Not indicated on the kit are the many flood/drain holes that need to be punched into the lower hull. I just 'winged it' and punched in an array with the aid of my handy-dandy-wonder-Chinese manual milling machine. How did I ever get along without this thing?!...

When I first got this milling machine I punched a bunch of 1/4" holes into the bed and taped them to accept 1/4-20 bolt thread. Here you see a couple of all-thread studs screwed into the bed. At the top of each a bolt a nut is tightened down to push a strongback, which compresses the KILO lower hull half down hard on the bed (a long piece of sandpaper glued atop the bed insures a non-slip surface). A new (sharp!) 1/8" end-mill cutting bit does the dirty work here. Always segregate your cutters: one set for metal, another set for plastics.

Indexing the X and Y slide hand-wheel dials insured accurate and consistent hole size and distance between holes. Once the securing setup was done, hole punching went very quickly. This is a surprisingly tight machine for the four-hundred and some dollars I paid for it at Harbor Freight. Love this machine -- tight gibbs, but way too much backlash in the worm gear slide drives.

Once I had the WTC put together I assembled it into the KILO's hull and started a series of dunkings in my granddaughter's kiddi-pool. The thing could be trimmed properly with foam and some weight for submerged trim, but I found that it sat way too low at the stern in surface trim. The only solution (I could not move the WTC aft in this hull) was to build in place, from styrene sheet plastic, an auxiliary ballast tank. Open at the bottom it works in unison with the main ballast tank --this trick achieved by running an 'equalization tube' between the two tanks. Here I'm installing a half-round piece into the center of the tank-top. This needed to make room for the propulsion shaft. Wherever possible I prefer to weld plastic together instead of bonding it with an adhesive. Cohesion is a proper welding of the two pieces and produces a much superior bond than does adhesion.

Note that within the upper portion of the WTC's ballast tank I've installed a contoured foam 'filler block' This reduces the floodable volume of the tank in the area that would be normally above the waters surface in surface trim -- this reduces the amount of Propel gas expended to empty the tank. Note that buoyant foam has also been added to the bow of the upper hull. So far, as it's trimmed now, the little KILO has a pretty fair metacentric height and exhibits good roll stability submerged and surfaced. The WTC-2/KILO is secured by four 2-56 machine screws that run through the bottom of the hull.

Test fit of the drive-train. The kit propeller is bored to accept a 1/16" shaft, so I simply run the shaft up to the motor extension shaft and couple the two with a length of 1/16" i.d. rubber hose: the poor-man's universal coupler! Note how the shaft runs above the trough I built atop the auxiliary ballast tank. Note also the watertight seal bodies for the four servo pushrods that project. I'm just showing off here, I'll only drive the stern planes and rudder, the two other pushrods will be taken out and those holes blanked off before I make this thing operational. I was going to drive the bow planes as well, but I found that I need to take out the fourth servo to make room for the damned APC-4. Such is life, compromises, compromises ... Man! This is going to be one neat pool-toy!

OK ... enough playtime. Back to my paying (and very patient) customers.

David,