Converting the Total immersion, 31" long NAUTILUS static resin kit into a practical r/c submarine, Part-4

The last couple of months I have been working on converting this hollow cast resin static display Disney NAUTILUS into a practical r/c submarine.

Yesterday the client came around to pick it up, take it home and detail and paint the thing. Later he'll bring it back for a final trim after I install a different battery. Propulsion and control power currently comes from a standard AA NiCad battery pack designed for receiver, servo service only. Even with this rather anemic power supply, I got ten-minute run times in the pool. Not bad.

The trimming in the kiddi-pool went quickly and I went through three battery packs playing with the submarine. I had a blast with it. Even Ellie got in some stick time with the model. The tilting propeller provided very responsive pitch and yaw control. Speed, all things considered, was pretty fair. The ballast system, a restriction valve installed in the blow line, delivered a metered squirt of gas with each command of the stick; I had enough fine control of the ballast system as to permit me to actually hover the model.

Believe it or not, this little Disney Nautilus -- as configured now, with the yawing propeller coupled to the swinging rudder -- can describe a submerged circle within the confines of the ten-foot diameter kiddi-pool. Not bad, not bad at all.

My involvement with this kits structure is minimal -- it's the client who will do the detail and painting work on this little resin kit of the Disney NAUTILUS. My area of responsibility, recently discharged, was to work up a WTC, outfit it to get it operational (ballast, pitch, yaw, and throttle control), install the WTC into the hull, to work up a mechanism to angle the propeller in pitch and yaw, to link the rudder to the propeller yaw linkage, and to trim the model with fixed weight and foam to make it stable on the surface and submerged.

Other than the need to make a glove-fit for the propeller ball bearing, install two WTC saddles, and to get the two hull halves to fit tightly together, the only other structural thing I did to the resin kit was to open up the square holed flood-drain ports in the bottom of the hull. No vent holes needed atop the hull as the two open hatch points permitted quick bubble escape from within the floodable hull. As it turned out the grill work represented in the center of each flood-drain hole was very thin and easily busted out with Moto-Tool and files.

The completed mechanisms needed to get this static model kit working as a realistic, practical, and easy to maintain r/c submarine. This model features NO active control surfaces other than the rudder. All pitch control is effected through the tilting propeller, yaw control through the tilting propeller and the coupled scale rudder.

All the linkage seen at the stern is dedicated to the job of translating the axial moving servo pushrods to the required propeller shaft angular displacement -- up and down for pitch control, left and right for yaw control. A component of the propeller yaw linkage is a translation arm that drives the single rudder. A bit of experiment determined the best ratios of coupling between yaw motion of the propeller and rudder.

Note the big hunk of lead bolted into the forward lower portion of the hull The upper hull has a huge piece of foam attached within it, over the weight -- the net change in the models total buoyancy is near zero, but the amounts and position of the two ballast elements produce a rather tall metacentric height; hence making the boat very stable in roll and pitch. Always endeavor to make your boat as statically stable as possible -- the maximum amount of fixed lead weight low, and countering buoyant foam high.

We see the after face of the WTC's motor bulkhead. Near the top, left and right are the two servo pushrods projecting through 1/16" watertight seals. Dead center on the bulkhead is the foundation and 1/8" seal for the direct-drive propeller drive shaft (which connects to the propeller intermediate shaft through a flexible piece of plastic tube). Center to the right is the equalization valve (modified tire-valve) The Yellow antenna wire originates from a lug dead center, bottom.

The linkages attach to the WTC pushrods through modified wheel-collars. The WTC motor output shaft makes up to the intermediate drive shaft with a length of tube (forming a poor-mans universal joint) -- all this makes WTC installation and removal from the hull a twenty-second operation. Other than the two rubber bands that secure the WTC onto the hull saddles, there are no other mechanical interfaces between WTC and hull.

Here you can also see the pushrod that connects the rudder to the yaw linkage within the hull.

Neat prop, huh? Made that sucker in about two hours!

Fabrication of the propeller began by turning the hub on the lathe. Fortunately for me I have a rather massive collection of source material on the Disney NAUTILUS. I used the detail drawings the effects miniatures propeller to guide me as I made the little wheel for this tiny r/c model.

Since I was using a little Graupner 380 sized electric motor, direct drive, it was important to minimize the loading this propeller would present -- I endeavored to make the pitch of the blades very fine: The motor would be permitted to spin relatively fast, yet not be loaded to the point where it would overheat.

A neat thing about this submarines stern design is that there is enough clearance fore and aft of the propeller disc to permit me to tilt the scale propeller a full five-degrees left-right, and up-down. Neat! Thank you, Mr. Goff. How did you know?

Close-up of the milling machine cutter (a Dremel cutoff wheel) near the hub, which is mounted in the chuck of the rotary table. The only operation required once everything had been setup was to move the X-slide in a measured amount to make the cut, back out, then rotate the table seventy-two degrees, and repeat those steps till I had five perfectly symmetrical slits cut into the hub, ready to receive the brass sheet propeller blades.

The key to getting things right on a soldered-blade-to-hub type propeller is to achieve the correct spacing, angle, depth, and uniformity of cut to each slit that will accept the root of a brass sheet blade. The principle tools in achieving this is a tilt table, a rotary table, and a milling machine. The cutter used here was a thin blade carbide cutoff wheel, a Moto-Tool accessory.

This was a chance to teach Rose some basic shop practices as well as a practical application of mathematics: I informed here that a common measurement of the parts of a circle is a division of the circle into degrees, each 1/360 of the whole. Telling her that I needed to cut out five equally spaced slots around a circle. With only a little coaxing, she figured out that if we divided 360 by five, then we would have to rotate the table 72 degrees to get the five evenly space slots cut into the propeller hub. Know that she rotated the chuck the appropriate amount after I milled in each slot. The rotary table has a degree scale on the rotating head and an indexing mark on the bed.

Not bad for a eight-year-old little girl.

With bandsaw and some hand tools I had the required number of brass sheet blades ready for soldering in no time. At this point I've bored an 1/8" propeller shaft hole in the hub and have mounted it on this simple blade assembly jig. Note that there is a sandpaper backed marking stencil, from which I scratched an outline into a length of brass sheet.

Rose test fitting one of the brass sheet blades into one of the five slots cut into the side of the turned brass hub. All I needed to do now was to come up with some kind of holding fixture to secure the blades out straight, ready for soldering to the hub.

Normally I make a more-involved-than-necessary blade holding fixture when doing this sort of work. But ... it was two in the morning, I was tired, pissed off, and wanted something to hold those blades level while I applied solder. And, I wanted it NOW! Such is the stuff of inspiration. Uncured PVC is Sculpy! this clay like material does not get soft and fail with heat. Not at all It hardens! So, I used Super Sculpy to position the blades around the turned hub. Perfect!

Slightly charred, but none the worse for wear, the Super Sculpy 'holding jig' after soldering had been completed. Sometimes stupid simple is the way to go.

Initially I tack soldered each blade to the hub with a big soldering iron, not yet a complete wetting between blade and hub, but enough adhesion provided to let me check symmetry between the blades. Tack soldering permitted me the option of breaking, with ease, an offending blade and to reposition it and tack again. Once happy with the rake and spacing between blades I applied more acid flux, then blasted the work with a mini-torch -- this permitted the solder to flow completely between blades and hub grooves, completely wetting all surfaces with solder, assuring a very tight adhesive bond between all parts that make up this five-bladed propeller.

Little fillets of solder also formed at the gaps between blades and hub, obviating the need for any fillers later. All this propeller will need is a good cleaning in lacquer thinner to knock off the flux, and an acid dip to pickle, rinsing, drying, then primer.

Ellie got us one of those ten-foot diameter kiddy pools ... allegedly for our grandkid, Rose. Actually, it's my test tank. Here Rose takes a few moments from doing laps to help me trim out this little NAUTILUS model. It's my practice to determine the amount and location of buoyant foam needed by first rubber banding hunks of the stuff to the outside of the model, moving the foam blocks around and changing the amount till the model (with a flooded ballast tank) assumes proper submerged trim: boat resting on an even keep with just an inch or less of submarine structure sticking in the air.

Rose holding up the model, ready to hand it off to me so I could take it back into the shop where I would transfer the foam to the inside of the model, completing the final trimming chore. Note that at this point the only fasteners used to hold the four major structure (lower hull, upper hull, superstructure, and wheelhouse) together. The client will come up with a more elegant solution, I'm sure.

Now, with everything working, the customer took charge of the TI NAUTILUS model so it can be detailed, painted and weathered. After that he will give it back to me for final trimming and installation of a larger capacity lead-acid battery to replace the pissant little battery currently being used.