Converting the Totalimmersion, 31" long NAUTILUS static resin kit into a practical r/c submarine, Part-3

A Report to the Cabal:

Recently Bob Martin presented photos of a like designed 31" Nautilus kit produced by Scott Brodeen, a kit that Bob built up into a fantastic looking static display piece, complete with salon interior and practical iris window closures. You have to see this to believe it! got to, http://www.rc-sub.com/nautilus.html

I was amazed to note that there seemed to be more than a chance similarity between the kit I'm working, produced by Lee Seiler, and the static display kit finished recently by Bob - that kit produced by Scott Brodeen. I'm not clear what the relationship, if any, is between Mr. Seiler and Mr. Brodeen.

Anyway ...

After examining Bob's work, I've decided to retain the break between upper and lower halves of the hull as provided with the kit. In both type kits (are they the same kit?) The upper hull possesses the two big horizontal strakes, which act to all but obliterate the seam between the two hull halves when joined together. Simplicity itself. And keeping the split as provided permits complete access to the interior when the upper hull is pulled away from the lower hull -- you can see this as I perform the internal work needed to turn this static display kit into a practical, fully capable r/c submarine.

This is the work on the resin 31" long NAUTILUS model as of last evening. Work accomplished since the last Report included the installation of two WTC saddles (foundations), drilling of a WTC alignment indexing hole through the ballast tank, creation and test fitting of the propeller shaft pitch teeter-totter, and tightening of the tolerance between gimbal ball and socket halves. I've also decided to leave the model hull halve separation flanges as they are on the kit: the model split along a horizontal plane along the mean centerline. What made up my mind on that was seeing how Bob Martin made use of the same hull split system used on the Scott Brodeen NAUTILUS kit; how it was possible to incorporate the big Saloon windows -- this split even accommodated the salon windows and lamps without presenting any obvious separation lines.

The two WTC foundations were plotted out on a single thick piece of RenShape 40 Pattern Makers polyurethane foam, then cut out on the bandsaw. Before gluing the foundations into the hull with epoxy (mixed with cotton waste to make a no-run thick paste). The interior of the hull, where the foundations would attach, was roughed up with #38 sandpaper to knock off any mold release remaining from manufacture and to give tooth to help insure a good mechanical bond between the RenShape 40 and resin hull.

Atop each foundation I inserted a 1/16" brass wire that was bent to a hook, used to secure the rubber bands that hold the WTC in place. If you look carefully through the Lexan you can see the 1/16" brass indexing pin, set within the bottom center of the forward foundation. That pin holds the WTC from either rolling or moving longitudinally within the hull.

Here I've installed the pitch teeter-totter, the device that translates servo axial push rod motion to propeller shaft pitch angle changes. The center of rotation of the shaft is, at the center of the gimbal ball. The transverse brass pin running across the hull (teeter-totter fulcrum point) is temporary, it will be replaced by a non-obstructing clevis as I finalize the installation.

My initial study sketch of the teeter-totter device is the post-it-note at the right (a doodle performed as I had some coffee at the local IHOP at 3am one recent sleepless night). Last evening, as I rethought the construction of the device, I sketched another version, to the left: A simple brass sheet and wire assembly that soldered together quickly and worked the moment I fit it into the model.

Isometric sketching like this as well as orthographic plan creation and reading is a vital skill set for Model Builder, being our predominate means of modeling a concept before committing to creation of the 3D item itself; such sketching permits refinement of design and catching function shortcomings and interference with adjacent device. Most of a models device creation and installation chores are done in the mind, then checked by sketch renderings on paper, then finally, the item made, installed, and checked for correct operation.

Another look at the pitch teeter-totter device. The 'U' shaped wire does not directly engage the propeller shaft. Instead, it applies force to an Oilite bearing surrounding the propeller shaft, reducing interference friction between teeter-totter and the spinning shaft. This teeter-totter, oriented as it is, cases the propeller shaft to rotate about the pitch axis and thus will control the bubble of the boat; the means by which the boat is controlled in depth.

An identical teeter-totter unit, oriented ninety-degrees from the unit seen here, will position the propeller shaft about the yaw axis to turn the boat. The same push rod that works the yaw axis of the propeller shaft will connect to a bell-crank on the single rudder, this to enhance the turning rate of the model submarine.