Moebius' 1:72 Skipjack

You know, the first I'd heard of this kit was just the other day when I saw it on Squadron's home page. I guess it's been out for a few months already? I can't believe I hadn't heard of it before now. Would love to have one but I don't know where I'd put it.

I have the kit and she is HUGE. But so much more detailed and accurate than the old Aurora 13-inch kit that we all bought long ago. Funny thing. I don't see the reactor hatch anywhere!

I am waiting for the fittings kit. But I have the hull and sail taped together and sitting on my shelf.

Here's another look at the kit:

I am currently working on the base while I wait for the fittings.

- Leelan

modelnut

 Funny thing. I don't see the reactor hatch anywhere!

 

What reactor hatch are you referring to?  When major access to the reactor or its components is required, an access cut in the hull is made. There are access hatches (actually doors) to allow personnel to pass through the reactor compartment bulkheads but they are located inside the ship.

Look two weld lines aft of the sail join. There is the infamous and ficticious reactor access hatch put there for kids to see a "real" submarine's nuclear reactor. Most adult builders putty it over and forget it was ever there.

- Leelan

You are referring to the circular area aft of the cleats? You are correct in calling it ficticious, the reactor compartment is located closer to the sail. But it would still be cool for kids.

That's the one.

- Leelan

Here you go folks! All the juicy details on how Moebius' latest kit came to be in David Meriman's well-known cabal reports. In this first installment, David offers some background on Moebius' new 1:72 Skipjack & how it came to be.

Stay tuned, there's more to come.

Development of the Moebius Models 1/72 SKIPJACK Model Kit and its Conversion to R/C Operation, part-1

by David Meriman

A Report to the Cabal

Moebius Models has just released a plastic model kit of a 1/72 SKIPJACK class Submarine. I was the lead man on that project. A good history on the real boats can be had here, http://en.wikipedia.org/wiki/Skipjack_class_submarine

About two years ago I e-mailed the Moebius Product Development guy, Dave Metzner, suggesting they produce a 1/96 scale kit of the SKIPJACK class submarine. I figured, what the hell, the worst thing he will say is 'no'. Nope. The only thing he said was, "Too small. How about 1/72?" Holy-***! Hell yeah!

And the rest, as they say, is history. The guys at Moebius are constantly pestered by fan-boys to make kits of some off-the-wall-never-get-your-money-back subjects. I was mindful of that and respectful of their time and resources. On the other hand, I'm not some no-body off the street. My name -- and more significantly, my work -- proceeded me; I got my hearing because of who I am (pisses you off, don't it) and what I've done; I've paid my dues in this game and cashed in occasionally, like this job with Moebius.



This is the contents of the kit: an excellent set of Bob Plant instructions, complete with a painting guide; decal markings for all six boats of the class; clear parts for the four dead-lights and stern light; sail; appendages; propeller; and a complete array of optical and electronic periscopes antennas, masts, including a well detail snorkel induction-exhaust mast.

The hull comes in quarters. Two bow halves and two stern halves -- the bow and stern assembles joining at a very robust radial flange near the hull mid-point. The hull (and this was no mistake) lends itself to being built as an upper and lower unit that can be opened up if the kit-assembler wishes to r/c this model.



Just a sample page from the outstanding Bob Plant instruction booklet that accompanies the 1/72 SKIPJACK kit. This is a far cry from the bare-bones exploded-view sketch provided with earlier Moebius kits. A perfect balance of illustrations and text, in plain English. No 'chinglish' here! We all worked to keep the nomenclature of parts identified in the instruction on a pare with the descriptive words used by those who made and operated the real thing.



The man responsible for the box-art and instructions (and to no small degree the decal sheet) is Bob Plant. He's Moebius' 'Art' guy. I can not heap enough praise on the job he did on the instructions. Bob's work is in the tradition of the kits produced during the golden-era of plastic models kits, the early 60's to the mid-70's. If, after cracking the box on the Moebius Models 1/72 SKIPJACK kit you feel sweeping over you the joy you first felt as a kid doing this stuff it is due to Bob's capture of the look and feel of the old, good-old-days.

The box art on the first issue of this kit is a very well photo-shopped melding of a Dave Metzner build-up and Bob's dramatization of a boat underway on the surface. If there is a follow-up issuing of the kit, you all are in for a real treat -- the new box art will feature a dry-dock scene from a noted kit illustrator. Stay tuned on that.



The Moebius team worked long and hard to get the details right. An example are the main sea-water (MSW) suction and discharge gratings -- on the kit rendered as photo-etched (PE) stainless steel parts. Getting the attack and night periscope right was a battle. I spent several days researching the type-2 and type-15 scopes used by most of the boats of the SKIPJACK class. We didn't get it right till the second test-shot. This demonstrates the uncomplaining willingness of Frank, Bob, and Dave to get the kit contents right before committing to production.



The Chinese (through no fault of they're own) did not get it right the first time. The mock-up, grown in a 3D printer, was severally flawed -- the fault was mine, there were several pardoxes of form presented between the documents and scanning models I provided them. And even after making physical corrections to the mock up, once it was scanned, and that file used to cut the initial tooling, the test shots revealed the need for further refinements. We went through two test-shot cycles before all flaws were identified and corrected. Only then did Dave give the green light to start series production.

More on the work done to correct the mock-up and test-shot flaws later. Above are some of the orthographic and isometric drawings I prepared for the Chinese to help them get the scope heads right.



Nearly a decade before the Moebius project I had been operating a 1/72 SKIPJACK r/c model submarine -- a fiberglass (GRP) and resin kit produced by Scale Shipyard. The kit is one of the best quality articles that company produces -- the accuracy of form and detailing is high; the parts were warp free and no bubbles to fill. Nice kit!

However, GRP-resin kits are not for the common kit-assembler; they require a great deal of talent to clean up, lay-out, assemble properly, and to get operational. I know of only a hand-full of these kits out there working today.

Above you see my Scale Shipyard 1/72 SKIPJACK tooling around the fresh-water pond at Norfolk's Nauticus museum where our club, the Elite Fleet, puts on shows during the summer months.

The Scale Shipyard SKIPJACK's a dead ringer for the Moebius kit. It demonstrated to me that a mass-produced plastic model kit, if built robust enough, would be the perfect hull for the first-time r/c submarine driver: Maneuverable, fast, and lacking the brittle little bits and pieces of a WW-2 era submarine that invariably break off during handling and use; the SKIPJACK is the perfect r/c submarine for those with itchy transmitter fingers. Believe me, I know!



The SKIPJACK (all of my SKIPJACK's) is operated as a wet-type r/c model submarine: the hull and sail are free-flooding structures. The propulsion, control, and ballast sub-system elements are all contained within a single 3.5" diameter Lexan cylinder. That removable cylinder forming the brawn, brains, and displacement changing mechanisms that animate the model.



How many of you old-timer's remember this kit as a kid? How many of you stuck a motor in this 13" model and saw it chase across the pool only to smash into the other side with a sickening 'crunch'? Come on! I can't be the only one to have done this?

Oh ...you were the cherry-bomb type. Sorry.



Electronics have matured to the point where even that small Aurora SKIPJACK can be r/c'ed! Caswell Inc. provides a fittings kit to convert the little model to r/c and they also sell the Sub-driver and devices needed to complete the job. http://www.sub-driver.com/models/submarine-models/uss-skipjack-submarine/the-revell-skipjack-submarine-fittings-kit.html



And our 1/96 scale, GRP-resin-metal SKIPJACK kit. This was the size I first recommended to Moebius, but they preferred a larger, 1/72, sized kit -- something that would be in scale with the excellent Revell 1/72 Type-7 and GATO models. A good call in my opinion.



Prior to my assembly and use of the Scale Shipyard 1/72 SKIPJACK. I had produced and marketed a 1/96 scale GRP-resin-metal kit of the SKIPJACK which I've been selling now for nearly twenty-five years. Of course I've been driving this version of the Beast around forever! I've even produced r/c versions of the little Aurora-Monogram-Revell 1/230 SKIPJACK -- a model measuring only 13" in length. The 1/230 and 1/96 scale SKIPJACKS pictured above.

Yeah ... I'm Mr. SKIPJACK!

Development of the Moebius Models 1/72 SKIPJACK Model Kit and its Conversion to R/C Operation, part-3

By David Meriman

A Report to the Cabal:

1. Lead-man is assigned, research is completed, and documents and scanning models (optional, but desired) are scanned and reduced to a CAD file.

2. That file used to create a stereo lithographic 3D mock-up, or proof model, which is sent to the client for approval/correction.

3. The corrected mock-up is returned to the manufacturer with needed changes identified, the CAD file updated and converted to CNC code and, in a flurry of metal chips, the injection forming tools are cut, and clamped into a production injection forming machine.

4. The tool clamping system is fine-tuned after the factory tool-and-die guys examine the first shots out of the machine. They are informed by the physical condition of the shot: Does the machine achieve a complete fill of the tools cavities (temperature, pressure, and channel geometry)? Are the two tool halves in alignment (unregistered halves to a shots tree)? Is an even distribution of force applied throughout the flange area of the two tool halves during the shot (flash)? And do all the test-shot plastic parts fit without misalignment between them (machine cycle time)? After the clamping system is dialed in, cycle rate established, and other working parameters set good quality test-shots can be produced consistently. Samples are sent to the client for critique.

5. Corrections to the tooling are performed to satisfy the client identified errors found on the test-shot parts. This likely requires more cutting on the tool and may also involve weld build-up and re-machining.

6. Box-art, instructions, packaging, decals, PE and other tasks are reduced to production steps, and all items integrated into a complete kit, ready for a ride on a big container ship.

(The ideal -- most efficient -- source of manufacture is one equipped to perform all injection-forming, printing, PE work, and other tasks in-house. Unfortunately, no such facility exists in America today).

So, as far as Moebius is concerned, the test-shots received are for validation of fit, part quality, and accuracy between the prototype and the model the assembled kit is supposed to represent. The customer examines the test-shots and either OK's the product, or generates a list identifying the changes that need to be made to the tooling. Sometimes a test shot is handed out as a review kit to help chum the waters.

Several months passed till I got my grubby hands on a test-shot. The box arrived at our door with a thump. But to me, it was the sound of the last round bell of a 12-round fight I was winning on points but wanted a knockout. Ellie brought the box into the shop, plopped it on a worktable and gave me one of those patented side-wise grins, and handed over the box-cutter. Show time! I paused a moment to reflect.

Wanna know what happens to a group-effort when the lead-man gets it wrong? Let's see hmmm... Think, Plan-9 From Outer Space. Think, Titanic. Think, Edsel. Think, Little Big-Horn. Think, Hindenberg. And think, I-53.

Bad Ju-Ju when the lead-man gets it wrong. I slit the top of the box from China...

With an example of the first test-shot series in hand (at last some honest to goodness polystyrene to fondle) I bounced the dimensions and form of the kit parts against my documentation -- the primary source being the excellent Greg Sharpe drawing. You see a hash-marked area atop the upper hull where, for some unknown reason, the initial tooling produced a 'dip' just aft of the after deck flat. First gig identified. There would be more.

The fillet between the sail and the long, skinny diesel exhaust fairing needed changing. Also, the leading edge and trailing edge of the sail were found to be too blunt. More items for the Chinese tool-and-die guys to fix.



A remarkable example of excellent tool design and execution is the propeller: The Chinese made a spot on reproduction of the propeller master I sent them; the rendering of it, in polystyrene above, is a perfect twin. Of particular note is capture of the complicated curves in a tool that avoids high draft angle.

The solution our tool-makers came up with was to make the majority of the hub and blades as a single part, with the base of the hub -- those areas under the blades -- as another part. These two sub-assemblies fit together with a surprisingly tight fit requiring little filling by the kit-assembler. I am most impressed with how the Chinese solved the propeller part fabrication problem.



One of the things I did to the mock-up was to add the frames within the diesel exhaust fairing. That feature, now incorporated in the test-shots, came out fine. However, the outboard portions of the ribs that project down -- and seen through the long-running limber slit between hull and fairing -- were flush with the outside of the fairing. They should have been indented to the surface of the fairing by about a sixteenth-of-an-inch. I marked them, and added this item to the list of tool modifications.

The after end of the diesel exhaust fairing was too blunt. I added that to the list'.

Preparing the oversized artwork representing the SKIPJACK's MSW suction and discharge gratings. These went to China where they were scanned and that file used to produce the masking needed to make production stainless steel PE parts.

I'm old-school when it comes to drafting, no CAD for me -- you don't get totally involved in the project if you simply push a mouse around a drafting menu. No, dammit! In my world you get your hands dirty; you become intimate with the task; involve yourself physically with the work. That's the only way you can truly capture into you little brain all the nuances of the subject you're attempting to represent.

What the hell are we now, a bunch of mindless, automatons; only able to push buttons and respond to formulated stimuli?! I see no craft in computer aided drawing or machining! What's creative about punching up pre-ordained code? We don't have real Machinist's any more ... just over-paid bit-changers and chip sweepers.

(Picture me running in circles with my hair on fire!)

A quick look at just some of the photos used to help flesh out details as I worked the mock-up and checked the test-shots (yes, there were more than one set test-shots that ran the gauntlet -- we kept at it till things were as right as we could get them). All from my rather massive SKIPJACK folder. Research and adherence to the things research reveals is everything in this game.

I'm a reasonably skilled draftsman. Apprentice level, but adequate to my needs.

Unlike my Junior High-school peers -- the hoods, idiots, booger-pickers, and jock's -- who I had to rub shoulders with in shop class, I paid attention and enjoyed learning about and practicing the Crafts. And that training has served me to this day.

The first test-shot periscopes were elemental of form, not at all suitable for a model of the SKIPJACK's size. To help the Chinese work out better detailed periscope heads I prepared the above orthographic and isometric projections. The second test-shot came in with scope heads very close to what I illustrated. There were two types on the SKIPJACK. I've shown here the Type-15 'search periscope which featured a range-only radar antenna. Yeah, I'm a detail freak. I blame Ben Guenther!

Tappan Junior High School's shop class (mandatory for all boys) was divided into three sections: Wood-shop, Metal-shop, and Drafting. Wood-shop taught by a fellow class mates Dad, a rather handy fellow around the benches; Metal-shop taught by a tough little ex-Army booze-breath who really knew his stuff, and could weld anything to anything else; and the Drafting instructor was an old, skinny, well dressed, exacting, gentleman who took no *** from ANYONE (he managed, unlike other school staff, to keep the hoods in line).

How come I remember this ancient stuff but not my kid’s birthday?!....



Over the course of a three-month evaluation process we went through two test-shot cycles. The work above is from the second test-shot I got for examination. By this time, as two examples, we had refined the look of the two styrene optical periscopes and form of the PE main sea water suction and discharge gratings.

We all have Bill Rogers to thank for unearthing that photo of the MSW gratings. Nowhere else have I found a definitive look at those main condenser openings, unique to boats employing the S5W nuclear plant. Though the dry-dock picture is of a Polaris boat, it (as so many other American, and even one British, early nuclear powered submarines), like the SKIPJACK's, made use of the same S5W plant. So, it's a logical expectation that the MSW gratings seen on this Boomer were very similar to those on the SKIPJACK boats.

Anyone out there who can make a liar out of me? Let's see what you got!



Apprentice Rose inking out the decal artwork. There's something to be said for slave labor! I've found that staff productivity is directly proportional to the voltage applied. As the SKIPJACK work turned into a grind I noted that my Granddaughter had been getting into manga sketching big-time and was showing some talent. So, never one to waste an asset, I dragooned her into the shop to help me with the decal and PE graphics. She told me that she could punch it all out on a computer. Hell, no, I said. Regardless, she snuck out when I was involved in something else, got to the computer and took it as far as finding the correct fonts somewhere in digital-land. I put a screeching halt to that!

Here, recaptured, Rose -- an ankle chained to a leg of the desk -- is inking the decal artwork. 'What's with the attitude, Rose!? ... give us a smile!"

As with PE art-work it’s a good practice to render the decal art-work several times the eventual size of the finished product (PE or decal contact negative/positive). As the artwork images are reduced in the process camera -- or, these days, scanner -- image density increases and becomes 'tighter'. Rose is working to a five-to-one ratio if I remember correctly.

Development of the Moebius Models 1/72 SKIPJACK Model Kit and its Conversion to R/C Operation, part-4

By David Meriman

A Report to the Cabal:

This one's dedicated to my East Coast model submarine buddies, like Ray Mason, sitting in the dark, waiting for the lights to come back on and the water to depart. Hang in there, guys!

Parts one through four serve as preamble to the meat of this series, a detailed discussion -- an instruction manual, if you will -- on how to employ the Caswell-Merriman Moebius 1/72 SKIPJACK fittings kit to convert the static display plastic model kit to a practical, well running, and robust r/c model submarine.

I had little input as to how the kit was engineered. The only input I had was to ask that there be a longitudinally running, horizontal break between the hull pieces, be they two long ones, or the top and bottom halves divided into quarters. This to achieve a removable upper hull half to afford internal access for r/c versions of the model. I also asked that the hull pieces be of substantial thickness (3/32" the ideal); that the lower and upper hull halves or quarters be outfitted with internal stifening frames; and that there be provided a tight fitting system of pins and tongue-in-groove hull edges that would insure positive registration of the two removable hull halves. Other than that, the guys at the point of manufacture did all the engineering -- and what a wonderful job they did: a sturdy, well fitting, easy to assemble plastic model kit with the minimum of parts.

The mock-up SKIPJACK kit -- though fabricated in a 3D machine -- was broken down into parts and the parts indexed as the eventual kit would be. Inspection of the mock-up kit revealed that my wants had been incorporated. I was delighted as in this game you have to be ever mindful that the product is primarily targeted at the vast majority who will only assemble the kit for static display. Fortunately the things I asked for did not impact on the cost of the kit, so they were incorporated.

So, with my work for Moebius completed, I directed my considerable talents and good looks to service to the Caswell empire -- the design, fabricate, and packaging of r/c conversion kits needed by our customers who wish to turn the Moebius SKIPJACK into a well running r/c model submarine. Before the kits hit the West Coast I had completed all the fittings kit masters and tools, and was well underway with part production. I could do that as I made use of the second generation test-shot kit parts to give form to the masters that were conformal to the inside surfaces of kit parts. Masters were built up from test-shot kit parts (all the control surfaces) automotive filler, brass, plastic sheet, RenShape, foam-core PVC sheet, and white-metal castings.

Below is a visual presentation of the items that make up a Moebius 1/72 SKIPJACK fittings kit, along with a table below denoting the name and function of each item:

  
A stern planes and yoke
B rudders and yoke
C after Sub-driver foundations
D Sub-driver shock absorber
E forward Sub-driver foundation
F nest transverse bulkhead
G nest keel piece
H torpedo tube nest foundations
I torpedo muzzle bulkhead
J propeller shaft foundation
K propeller
L propeller shaft, bearings and coupler
M hull rudder hole blanking discs
N sail plane operating shaft bushings
O hull stand hole blanking pieces
P Sub-driver restraining strap foundation
Q sail planes and bell-crank
R sail-to-hull mounting foundations
S sail plane bell-crank shaft retainers
T sail plane bell-crank
U mechanical fasteners
V after radial flange
W forward radial flange
X upper hull securing screw and foundations

The first area I addressed as I went about the chore of creating masters was the stern. Specifically, the two-piece foundation needed to mount the propeller shaft bearings. I started by removing the strengthening rib and single longitudinal brace in that area of the two stern hull quarters. I CA'ed a half-circle sheet-plastic transverse damn forward and a blanking sheet butted against the after end of the hull, where the base of the propeller hub would fit. These dams to contain the thinned down filler used to give form to the foundation masters.

I waxed the inside of the containment to prevent the hardened filler from sticking to the styrene.

I thinned the filler with lacquer thinner till the mix was runny enough to insure a bubble-free fill of the stern areas with the gooey stuff. I mixed in a little hardener, poured and pushed the stuff into the stern areas and waited for the filler to cure.

Automotive filler will shrink a bit if used straight out of the can, Even more when you cut it with thinner. So, I was compelled -- after the two halves of the propeller shaft foundation master cured -- to pull them out, re-wax the interior of the hulls, smear un-cut catalyzed filler on the contact face of the masters, and smashed them into place, where they remained till the filler had hardened. The glaze I put on the parts made up for the shrinkage and produced a tight glove fit to their respective spots on the hull stern pieces.

The two halves of the filler formed propeller shaft foundations were marked out. Filed out those channels would form the bore through which two propeller shaft Oilite bearings would fit. Extreme care was taken to insure that the centerline of the two channels ran perfectly in alignment with the hulls longitudinal axis.



To make the reach of the long pushrod between the after end of the Sub-Drive (the watertight cylinder containing the propulsion, ballast, and control sub-systems) motor-bulkhead a simple one, I employed a partial bevel-gear linkage within the sail to translate the axial motion of the pushrod (mounted up against the inside of the upper hull) to the rotary motion, up within the sail, needed to operate the sail plane operating shaft. The masters of the two partial gear elements are seen here. A small cylindrical magnet within the eventual cast resin lower gear element engages a magnet at the forward end of the sail plane pushrod. A similar magnetic coupling at the after end of the pushrod produces a near slop-free linkage between servo and sail planes.

These masters, along with the others, would be de-greased, cleaned up, (pickled, if metal), primed, then used to make rubber production tools.

I needed solid foundations within the forward and after bottom ends of the sail through which securing machine screws would hold the sail down upon the hull -- permitting removal of the sail from the hull for sail plane linkage and snorkel induction head valve and float adjustment or maintenance.

The masters of those foundations formed -- like the propeller shaft foundation masters -- from thinned down two-part automotive filler poured into the area of the model part where the eventual model part would fit. Here I've formed the containment dams from oil-based modeling clay. However, with these, the last step was to assemble the two sail halves and hold them tight with masking tape as the last application of filler, applied to the outboard faces of the foundation masters, acted as an adhesive to form two solid foundation masters.



As I worked up the masters for the Moebius Models 1/72 SKIPJACK fittings kit, I developed the jigs, templates, and plumbing masters needed for production of a dedicated 3.5" diameter, SAS type, single-motor SD to handle the ballast, control, and propulsion of this kit.

I used my old, faithful Scale Shipyard 1/72 SKIPJACK model as the evaluation hull as I modified and eventually froze the design of the new SD.



I fabricated the stern plane operating shaft yokes and the rudder operating shaft yokes from brass rod. Here I'm checking the yoke masters as well as an assembled propeller assembly with mock intermediate drive shaft to check for non-interference of the control surfaces through they're full 35-degree travel up/down, left/right. Once all was found to operate properly, the yokes were removed, fillets built up with CA and baking soda, pickled, primed, used to make a disc type metal casting centrifugal tool.

Most of the masters are now in primer gray and ready to produce the production fittings kit tooling.



The first set of fittings kit production tools were made from relatively hard BJB Inc., TC-5050 silicon, platinum cured, room temperature curing (RTV) rubber. The relatively 'hard' rubber is best suited to hold the masters when the time comes to make duplicate tools or copy masters. More on that, maybe, at a later date.

This shows the four two-piece production tools used for resin part production. Note that the control surface cavities have been outfitted with brass operating shaft inserts, as well as brass rod mandrels in the torpedo launcher foundation tool, and a brass pivot pin in the 'accessories' tool. The inserts will be partially encapsulated in the hard resin and become operating shafts, pivot pins, and cylindrical bores.

With all inserts in place I spray in some Mann-200 mold release spray, dust on some talcum powder (a 'bubble getter'), assemble the halves of a tool, sandwich each tool between wooden strong backs, and clamp the assembly tight with rubber bands. Catalyzed resin is poured in through a single sprue hole where it is distributed to the cavities through a system of runners -- displaced air is routed out of the cavities through a separate vent-channel system. I'm a master at rubber tool design.

The Mann-200 keeps the polyurethane resin from sticking to or attacking the rubber (but not completely, these tools have a 100-200 cycle life before becoming too brittle for use). Talc acts as a wick to pull resin into portions of the tools cavity that otherwise would trap and hold air pockets, which evidence on the part as pinholes.

A fifth production tools, not shown here, is a disc-shaped tool that is spun in a modified blood separation centrifuge while molten white metal is poured in. Another virtue to the TC-5050 is its ability to handle low-melt metals of working temperatures below 600-degrees.

Most of the Caswell-Merriman 1/72 SKIPJACK fittings kit is fabricated from cast polyurethane plastic -- some of those raw shots seen in the center of the table. I remove the individual parts from the trees, machine back the stubs, and file off most of the flash. No attempt is made to de-grease the resin parts, I leave that for the customer.

This disc-shaped rubber tool is spun in a modified blood separation centrifuge as molten white metal (an alloy of Tin and antimony) is poured in through a sprue hole at the center of rotation. Rubber mandrels set within the cavities form the bores for the stern plane and rudder operating shafts. Another virtue to the TC-5050 is its ability to handle low-melt metals that can be poured successfully at a temperature below 600-degrees.

Once the yokes are snipped away from they're runners, the mandrels are pulled and each yoke is drilled and taped to receive the operating shaft retaining set screws.



The white-metal SKIPJACK propeller -- both the Moebius kit and the Caswell-Merriman r/c conversion fittings kit represent the original five-blade 'power' screw -- starts life as a gravity poured white-metal casting, which explains the long sprue on the center propeller. Tall to take advantage of the pressure head produced when pouring the molten metal into the screw cavity of the mold: the taller the sprue, the more hydrostatic pressure at the bottom of the tool, the more inclined the metal is to seek out and fill all cavities within the tool. Also, the tall sprue acts as a header in that it serves to provide make-up material should there be a leak across the flange face of the two tool halves.

Shrinkage is not an issue with white-metal -- which actually expands a bit during the state change from liquid to solid -- the Antimony expands in volume when it freezes.

To the left is a propeller casting with the excess sprue cut off on the band saw. To the right is a finished propeller whose excess sprue has been turned to the proper pointed dunce-cap shape. Note the assembled Oilite bearings and thrust washers, propeller shaft, stainless steel thrust washers, and Dumas style universal coupler. The screw is secured to the propeller shaft with a transverse 6-32 X 1/8" SS set screw.

David must have been up late writing this latest installment... :D

Development of the Moebius Models 1/72 SKIPJACK Model Kit and its Conversion to R/C Operation, part-5

by David Meriman

A Report to the Cabal:

A hair-dryer is not going to cut it -- you need an industrial strength hot-air gun like this one I got from Harbor-Freight (I LOVE Harbor-freight!). To avoid disaster, you must keep the gun in motion over the work, and to get as even a heat distribution to a hull quarter as you can.

Be warned: you fail to evenly heat the work and produce a hot-spot you will either punch a hole in the part or distort it beyond repair causing you to issue a primordial scream and stomp around in a blind rage.

Some fun, huh!



Believe it or not, it worked for me -- but then again, I've been doing this sort of scary :censored: for decades. There's a lot of burned, cut, sawed, melted, and stomped-to-death failures in my wake.

I simply held the work in one hand, applied the heat evenly, and when things got toasty (painful) I squeezed the hull into a proper half-round. Don't wear oven-mitts when you do this -- you're pinkies will tell you when things get hot enough.

A smarter way of doing this is to attach two wooden fences to a flat board, and jam the hull quarter between the fences, apply the heat, then let the work sit there till it assumes room temperature -- the smart-money is on that technique, not the hand-hold one.



Unlike resin and metal parts, polystyrene -- the plastic most injection formed kits are made of -- is a thermoplastic that lends itself to chemical and thermal welding: the introduction of heat or a solvent breaks the molecular chains, a characteristic of a solid, and momentarily changes the state of the material to a liquid or semi-liquid where, upon freezing or dissipation of the solvent, the new array of interlinking molecules cross over the seam line bridging the former gap, leaving a single item where there was once two. A fusion weld. The process is called cohesion.

And that's what the two solvent type cements above do. They melt styrene plastic. This is the preferred means of attaching styrene pieces to one another. The very thin solvent, applied with a brush, is used to soften the surface of the parts to be welded -- akin to pre-heating metal before effecting the weld. The gelled solvent cement, in the red tube, gives up its solvent much slower, giving you the time to apply it to one softened surface and mash it down onto the other, and work out any misalignments.

When you stick two or more pieces together by introducing a third ingredient that remains to anchor the pieces together, that's called an adhesive. CA, epoxy-glue, white glue, horse-glue, solder (yes, solder) and so many others are adhesives. No fusion here, it's the adhesives wetting ability, to get in close to the atoms of the substrate, that puts into play a mysterious (to me anyway) 'bonding force' between the parts and adhesive. Though, in some arrangements, mechanical tooth or physical interlocking of the parts can and will enhance the holding power of the adhesive bonded joint.

We'll use CA on this job to join dissimilar materials to one another -- situations where a fusion weld is not practical with street-legal chemistry.



If at all possible use the DuPont brand primer (Nason), paint (Chroma-Color), and clear-coat (Chroma-Clear) with flattening agent. You'll find this stuff at a local automotive refinishing supply house. Look 'em up!

Second choice is rattle-can paint from a box-store, something like Rust-Oleum or Krylon. But, decant the stuff and shoot it through a medium sized single-action air-brush/gun like my old trusty Paasche H-model seen above -- use the big tip and needle. Get cans of the primary colors, black, white, and primer -- the primaries so you can mix them up to get the colors you need (very dark gray, brick red, and international orange). And pick up low-tack masking tape and a color wheel.

Don't use hobby-store paint. It's all crap, that stuff is formulated to be safe, not good. You need a paint that has high abrasion, UV, and chemical resistance; and is flexible and has superior sticking power.

(You'll find nothing useful in today's brick-and-mortar hobby store but glue, blades, and magazines. The pimple-faced counter-person, likely some punk r/c racing type with metal studs and rings projecting from lips, lids, and ears; an un-cooperative, smart-ass, cash-register monkey more preoccupied with the timing of his next smoke-break than any technical or stock questions you need answers for. You dare talk to one of these dorks and all they can hear is a Charlie Brown, Whaa, whaa-whaa, whaa, whaa-whaa, whaa... ).

:censored: 'em!

Do your tool and consumables shopping at the box-store, auto refinishing house, Harbor-Freight, and the Internet.



You'll use an air-dry putty for scratches and low-fill seam work. I recommend the Nitro-Stan line. you can use it straight out of the tube (also available in cans), but you'll find that it's best applied with a brush, screeding blade (that yellow thing next to the tube of putty), or finger. When brushing it into tight unions cut the putty a bit with lacquer thinner, makes it flow better. The automotive refinishing supply house has it or something very much like it, likely 3M Red.

And get some two-part, polyester auto filler, like Bondo, for the deep seams and re-contouring work. I prefer the Evercoat brand. You can get that from the Caswell company. In fact, you can get just about all the tools, abrasives, and other consumables from that single source, http://www.caswellplating.com/

Yes, yes .... I'm a whore. Sue me!

Development of the Moebius Models 1/72 SKIPJACK Model Kit and its Conversion to R/C Operation, part-6

By David Meriman

A Report to the Cabal:

Marking Off, Test Fitting and Punching Holes

OK, you've culled out the unneeded Moebius 1/72 SKIPJACK kit parts; inventoried the fittings kit parts; degreased the resin parts; and scoured and sanded the hull, sail, and other appendages. Time to mark-off and open up the hull and sail holes. These holes needed to pass linkages, vent the hull and sail, permit flooding of the hull and sail, pass the control surface operating shafts, and to pass and accept the threads of screw fasteners used to hold the hull and sail assemblies together.

As the kit arrives to you the hull is broken down into four large hull sections or quarters, two upper hull quarters and two lower hull quarters.

With the exception of the resin blanking plugs, don't permanently glue anything together yet, though some of the below shots show assembled hull quarters. Do as I say, not as I do. Trust me, there's a method to the madness here. And you'll note in some photos that I have two SKIPJACK's in the shot. I'm not showing off. I do it this way to convey as much visual information as possible.

Fine. Let's get to work:



You want to check the fit, within the hulls stern, of the stern planes and rudders, as well as the running gear foundation.

An error we failed to catch on the test-shots was the too far forward positions of the rudder operating shafts. I corrected that by moving the center of rotation a bit farther aft to the cord of supplied resin rudders. However, you will have to relocate the rudder operating shaft hole, top and bottom.

Take the two stern hull quarters, identify the 3/16" diameter resin blanking pieces, and insert and CA each disc into a rudder operating shaft hole, leave a bit of the blanking disc standing proud of the hull so you can sand it to contour to the tight radius at that point of the stern. On the inside of the two stern quarters, grind flush the raised flanges of the former rudder operating shaft bores.

Back on the outside of the hull halves -- from the center of a blanking disc, measure 1/4" aft and drill a new 1/8" diameter rudder operating shaft hole, top and bottom. You're now ready to test fit the resin rudders and stern planes, running gear, and their associated yokes, pushrods, and intermediate drive shaft.



The function of the two white-metal yokes, that interconnect opposed control surfaces, is to provide clearance of the centrally running intermediate propeller drive shaft.

We're going to test-fit the stern control surfaces and running gear into the lower after quarter of the hull and get comfortable with how the two types of control surface operating shafts make up to the yokes; make up the pushrods to the yokes; and make up the intermediate drive shaft to the propeller shaft coupler. All this to check the components for fit and proper operation and to give you a good look at the assembly in operation (a chance to appreciate my magnificence) -- something you won't be able to do once the a stern-cone portion of the upper after hull quarter is permanently glued atop the lower after hull quarter.

The rudders are rather straight-forward in that the upper portions of those operating shafts are permanently encapsulated in the cast resin rudders with projecting end of each operating shaft running directly into a rudder yoke bore and made fast with a set-screw. The rudder operating shafts have machined flats, insuring non-slip alignment between the two rudders when made up to the yoke.

The stern plane operating shafts, through necessity, have to be removable from the stern plane pieces themselves. This because the outboard ends of the control surfaces fit within horizontal extensions that project aft and block a straight-in insertion of the stern plane with its operating shaft installed. So, I've made the stern plane operating shaft removable. Making up a stern plane to its yoke goes like this: a stern plan is held behind its horizontal stabilizer by masking tape; the stern plane yoke, with attached pushrod, is suspended within the stern with the aid of either a long hemostat or needle-nosed pliers; The stern plane operating shaft (it's flat oriented to present to the tip of the stern plane set-screw) is pushed through the hole in the center of the horizontal stabilizers outboard bearing, through the bore of the stern plan, and into the bore of the yoke till the outboard end of the operating shaft is flush with the outboard face of the horizontal stabilizer bearing; the operating shaft fully inserted, the stern plane set-screw is tightened (don't over-tighten or you'll strip the resin thread), keeping the shaft from rotating within the stern plane; finally, the inboard end of the operating shaft is secured to the yoke by tightening the yokes set-screw. You want to orient the stern planes cord line perpendicular to the yokes bell-crank arm.

Whew!

Oh ... and for the sake of scale, orient the stern planes with the operating shaft set-screws on the bottom, out of eye-shot.

Employing 1/16" diameter brass rod, make two pushrods, 7" in length, each with a Z-bend at one end. One pushrod makes up to the rudder bell-crank, the other pushrod makes up to the stern plane bell-crank. Later, the forward end of these pushrods will receive a magnetic coupler that will engage a counter-part that makes up to a SD pushrod and servo. Magnets are used to couple the two linkage elements -- no back-lash, no tools, no sweat. More on that later.

Two oblong holes, one in each of the bottom hull quarters, are intended to accept the stud of a display stand. Fine for static display of the model, but of no utility to those wishing to r/c the SKIPJACK model. Use the two resin blanking plugs to block those holes, as you did with the rudder holes -- then grind away the raised flange within the hull quarter over those blanking plugs.

Take the two resin propeller shaft foundations and, after grinding away the radial and longitudinal raised braces at the stern of the two stern hull quarters, test them for a tight fit. Keep the lower after hull quarter propeller shaft foundations in place for the next step, the dry-fit of the running gear and control surfaces.



Install the two rudders and two stern planes as seen above. And check for non-interference of control surfaces and yokes through the full travel (not to exceed 35-degrees left/right and rise/dive). Note how the intermediate drive shaft runs through the center of the rudder yoke and over the swing-arm of the stern plane yoke.

The intermediate drive shaft is a 8 1/4" long length of either .014" wall thick, 7/32" outside diameter brass or aluminum tubing with half a Dumas nylon dog bone insert into each end -- each dog-bone pined to the shaft with a transverse length of 1/16" brass rod peened at each end. You'll work out how much dog-bone half projects past the tube as you integrate the running gear with the SD.



You're going to saw away portions of the stern and bow from their respective hull quarters to establish a Z- type separation line between upper and lower hull sections. This is a long accepted hull access methodology popularized by r/c submarine pioneers, Dan Kachur and Greg Sharpe. This type break between the two hull halves provides for quick access (only one screw at the stern holds the hull halves together), is strong, and is less susceptible to flexing than a simpler horizontal break that runs completely around the bow and maybe even the stern

With the Z-break a single screw presses the after halves of the hull together as a radial capture flange forward works to press the forward halves of the hull together. To achieve this Z-separation you'll remove portions of the bow and stern and weld them to the opposing hull section. Confusing? Look at the pretty pictures!

Take the forward lower hull quarter and after upper stern quarter in hand and put the other quarter hull section out of the way so you don't grab one of them by mistake when you start marking and cutting.

Now, to mark the radial lines around the hull quarters where you will saw them free. Any number of ways to accurately mark off a radial line on a tapered body-of-revolution. But, the easiest method, presented here, is to take advantage of the internal stiffening ribs molded within the hull quarters, using them as both guide, and datum line from which to identify the distance from bow and stern to cut the bow piece and stern piece away. Study the above photo.

Load your compass with a Sharpie pen. Let's start with the forward lower hull quarter: Identify the second radial stiffening frame from the bow, that's our datum line. Set the compass distance between point and pen tip at 3" inches. place the point into the right-angle union between hull and frame. Careful to maintain the line between point and pen tip parallel with the hull quarters longitudinal axis as you move the compass laterally, mark a radial line into the inside of the hull quarter, that inked in line denoting the bow cut line.

Do the same for the after upper hull quarter. That datum frame is the one at the leading edge of the horizontal stabilizers. Set the compass so that the radial line established is 2 1/4" forward of the datum frame.

It's much easier to follow the cut line if it's on the surface of the hull quarter, so now you have to transfer the inner cut line to an outer cut line. Plug in a 100 Watt light bulb, and us it to back-light the interior of the hull quarter so you can see the internal radial inked in line through the translucent plastic. Pencil in cheat marks to the surface of the hull over the line you see through the hull. After enough points are put down to get an accurate indication as to the lines true form, lay down some masking tape, it's edge at the cheat-marks, and ink in a proper cut line to the outside of the hull using the edge of the tape to guide the Sharpie pen point.

Remember, cut off the stern of the after upper hull quarter, and cut off the bow of the forward lower hull quarter. Don't screw up! And don't cut these pieces off till later, we're just marking things off at this point.

Check twice and cut once!



Mark then drill or grind out the opening atop the two hull quarters. Above you see two SKIPJACK upper hull pieces, the one atop has its holes opened up. The lower unit has just been marked off as to hole shape, location, and size. Use new (sharp) drill bits spun at low speed. Styrene takes to the bit well, put keep the pressure light as you punch through. The indented round depressions on the sides (upper and lower) of the hull quarters indicate drill size to use. For holes larger than 3/32, start the hole with a 1/16" bit, this serving as a pilot-hole that better directs the cut of the larger bit that follows. When using high-speed cutting bits, do not let the bit stay in the work too long or the plastic will melt. Introduce the bit into the work in short, low pressure jabs.

Punch out 7/16" diameter holes in the centers of the six ballast tank vents on the forward deck flat. Do the same for the four ballast tank vents on the after deck flat. Don't touch the four big MSW holes on the after lower hull quarter after quarter hull section, those will later be covered by PE gratings.

The following hole locations are now marked off along centerline on the forward upper hull quarter. Measurements are taken from the projecting nib, marked 'datum' on the above photograph, just aft of the forward deck flat:

1. A square hole who's forward transverse line is 3/16" from datum, and after transverse line is 5/8" from datum. The longitudinal edges of this inked in hole are 1/16" inboard of the troughs that accept the indexing lips at the bottom of the sail assembly. Later the lower sail plane bell-crank gear will project through this hole.

2. 2 1/4" aft from datum is a 3/16" hole that will pass the snorkel head-valve tube down into the hull. If you use the Caswell-Merriman 3.5 Sub-driver unit, the SAS snorkel foundation piece will be used as a marking stencil to indicate where you'll drill 1/16" holes that will accept the self-taping machine screws that secure that foundation atop the hull, under the sail. That foundation piece seen atop the second hull in the picture.

3. 6" aft from datum is the first of three 1/4" holes that vent air in and out of the hull, under the sail and exhaust fairing.

4. 8" aft from datum is the second 1/4" vent hole

5. 10" aft from datum is the third 1/4" vent hole

Once you have marked out the holes that go under the sail, snip the two nubs (indexing pins, if you will) off the hull and at their former location, drill 7/64" holes. These will pass the 4-40 machine screws that hold the sail assembly down onto the upper hull. There is a third nub, back near the after portion of exhaust fairing, on the after upper hull quarter. Snip it off too, but drill no hole there yet.



Flip the forward upper hull piece and work on the inside now.

Open a long, narrow extension of the square hole you just put. This will eventually pass the pushrod magnet that makes up to the magnet at the base of the lower element of the sail plane bell-crank assembly. Note the orientation, and the side where you put in the new cut, and it's measurements. Now, grind away. The outboard longitudinal side of that the hole butts up against the raised portions of hull under the sail -- those raised portions accommodate the longitudinal indexing troughs atop the hull. The photograph shows how the linkage goes in there once all these preliminary operations are out of the way. Take heart .... you'll eventually get there, pal.



With masking tape, put the two sail halves together, time to open up the bottom of the sail to pass the bow plan linkage (mounted within the sail) and snorkel head-valve assembly (mounted atop the hull, but fitting within the installed sail). The upper sail has already been opened up, the lower sail has been marked off and is ready for hostilities. I forgot to indicate on the model the distance from the forward hole (both of them already provide as the kit arrives) to the forward transverse line of the hole. It's 3/16" from the holes center.



Tack-glue the forward and after resin foundation pieces within one half of the sail, then tape the other half of the sail onto it. With a Sharpie pen mark off the spot where you will drill a 3/32" hole and tap it for a 4-40 machine screw. Take everything apart and punch those holes and cut the threads into the sail foundation pieces.

Most apparent in this photo, at the base of the sail, at its perimeter, the plastic extends down into long-running lips that engage the deep troughs set within the top of the hull. The two 4-40 machine screws running up from within the hull into the resin foundations fixed in the sail make fast the sail to the hull, yet provide for quick and easy separation of the two for transportation, adjustment, or repair.



The many square holes you have to punch open in the bottom of the two lower hull quarters is done with drill, square files, and sanding sticks. The work goes pretty well if you take it easy and outline the inset gratings molded into the plastic with a Sharpie pen. Yes, you'll loose all that beautiful detail, but to be a practical r/c model submarine that works as a wet-hull type, you need to lose the flood-drain grate detailing. Get to it!

I suggest you punch out all the holes before sticking the hull quarters together, the parts are easier to handle when they are smaller assemblies. Note on the lower hull that I've also taken advantage of the engraved lines of the torpedo tube shutter doors to open those up -- that model will later be outfitted with six practical launchers.

A torpedo firing SKIPJACK is an option for you way-over-the-top r/c submariners. The nest foundation is provided with your fittings kit. If you go the hostility route, here's the weapon system you would need to make the local lake safe for Democracy,

http://www.sub-driver.com/torpedo-systems/torpedo-system-1-72nd-scale.html

and a technical paper on the system,

http://support.caswellplating.com/index.php?/Knowledgebase/Article/View/359/47/torpedo-launcher-instructions-172



Before installing the two sets of SD foundations, shock absorber, and SD Velcro strap foundation, it's wise to mark out a centerline to the inside of the lower hull quarters.

Examine the two sets of resin SD foundations provided. The smaller set goes aft and the cut-outs within those clearly defines where they butt up against a frame in the lower after hull quarter. The other, larger set of foundations fits against the forward face of the aftermost frame in the forward lower hull quarter. Note that the circular edge at the top of these foundations is not concentric with the circular edge at the base. On both sets of foundations the narrower portions of the pieces of the foundation halves meet at the bottom of the hull -- get that straight before CA'ing them permanently in place!

With the forward set of SD foundations glued against the frame, butt the after end of the shock-absorber (where the pin projects up) up against the forward face of the SD foundations. Center it, then using a ling pencil led, mark onto the hull where the holes will be drilled to pass the six securing 2-56 machine screws.

Remove the shock absorber and grind away a 1/2" wide, 3/8" deep channel down between the two halves of the SD forward foundations. This channel permits disassembly of the shock-absorber components, should that every be necessary.

The forward end of the strap foundation butts up against the after face of the forward most frame of the after lower hull quarter. (The tall end of this resin piece goes forward, the shorter end goes aft). Lay the piece on its side within the hull and mark off where you will punch two 3/32" diameter holes into the bottom of the hull, these will pass two 2-56 flat-head machine screws that secure the strap foundation piece to the lower hull.



Before drilling a hole, I push a pointed rat-tail file hard into the plastic, a sort of 'pilot-hole' that works to guide the drill bit as I open up the hole. Keeps the work centered.

Here I'm punching out 3/32" holes to pass the flat-head 2-56 machine screws that secure the SD shock absorber to the bottom of the forward lower hull quarter.

To the outboard side of the hull I will bevel these holes with a counter-sink bit to accept the flat-head screws that secure both the shock-absorber and strap foundation.

I would like to see a 688 get this treatment, too. Great posts, thanks!

Thank you for these posts!  I just got the Merriman/Caswell fittings kit in the mail today. Everything here will come in handy!

- Leelan

Nice.....very nice.  I'm impressed.....so very impressed.

Thank you, David.

Development of the Moebius Models 1/72 SKIPJACK Model Kit and its Conversion to R/C Operation, part-7

By David Meriman

A Report to the Cabal:

Bonding the Sail and Hull, Installing the Sail Linkage, and Attaching the Radial Flanges

Development of the Moebius Models 1/72 SKIPJACK Model Kit and its Conversion to R/C Operation, part-8

By David Meriman

A Report to the Cabal:

Securing the Internal Hardware and Structures

If you wish to equip your 1/72 SKIPJACK with teeth, I recommend the Caswell-Meriman weapon system. Each weapon system package contains one launcher (which can be configured for either mechanical or pneumatic actuation) and three gas propelled torpedoes/weapons. http://www.sub-driver.com/torpedo-systems.html

The fittings kit supplied nest foundation (torpedo tube foundation-H) is optional and is only used if you opt to include the ability to launch weapons. The nest foundation assembly -- in addition to its primary job of stiffening the bow -- is designed to accept and hold in perfect registrations the removable torpedo tube nest.

This picture shows to good advantage how the lower edge of the keep piece indexes the nest assembly longitudinally by engaging the forward frame and raised anchor well. Note that in this shot, the bow portion of the lower hull half has not yet been razor sawed away.



Time to glue the forward lower bow piece to the upper hull half. Note the pencil mark near the inboard and outboard edge of the upper hull -- marked off to indicate where to stop brushing on the thin solvent cement used to soften up both the upper hull matting edge and lower bow section mating edge. Once you get the mating edges gooey (it's a proper word ... look it up, damit!) the two pieces are assembled, more thin solvent cement was run into the seam where capillary action pulled it into the gap and the two pieces start to fuse together. To insure a tight seal, rubber-bands are wrapped around the assembly.



The inset flat heads of the shock-absorber and strap foundation screws on the bottom of the hull need to be secured permanently and faired to conform with the hull. A drop of thin CA adhesive is dabbed onto each screw head and left to soak in about a minute, followed by a sprinkling of baking soda which wicks up the adhesive and immediately cures to a solid -- an instant, hard filler ready for filing. The CA-baking soda filler is worked with file to conform to the curvature of the hull.

Note the CA work-station-caddy I've cut from a hunk of foam sheet -- keeps all CA adhesives, accelerator, glue mixing cups and open tray of backing soda handy for quick and easy use. When a CA gluing job calls for a mixture not too thin, but not too thick, I'll mix a bit of thick and thin CA into a cup and use a stick or rod (such as above) to transfer the adhesive to the work.

Development of the Moebius Models 1/72 SKIPJACK Model Kit and its Conversion to R/C Operation, part-9

By David Meriman

A Report to the Cabal:

SAS Theory and Preparing to Outfit the Sub-Driver

Above are most of the devices you'll need, all of them available from Caswell Inc. http://www.sub-driver.com/

1. 32000, 11.1-volt Lithium-polymer battery. Two of these are required, wired in parallel they provide enough capacity to run your 1/72 SKIPJACK all afternoon long.

2. Two sets of the Dean's connectors to make up the battery to your power cables, and to make up the motor-bulkhead devices to the other end of the power cable.

3. 10-ampere, DTSP toggle-switch and watertight boot

4. Optional 15A quick-blow fuse and fuse holder

5. 5-volt, 5-ampere battery eliminator circuit (BEC)

6. Sombra Labs SL-8 synthetic crystal receiver

7. MTronik's Marine-15 ESC

8. ADF, combined angle-keeper and fail-safe circuits

9. Lipo-Guard, to protect the Lithium-polymer battery against low voltage

10. Three mini-sized servos

11. Y type servo lead, to split and send the signal from the channel-4 receiver output to the LPB's motor pump controller (MPC) and ballast sub-system vent servo.



Four of the devices within the SD require hook-up to the battery directly, all wired in parallel to a common Dean's type plug that will mate with the plug made up to the power cables.

The four devices take battery power for the following services: send power directly to the propulsion motor after conversion to the correct polarity and amplitude (ESC); to sense battery voltage (Lipo-Guard), to protect the Lithium-polymer battery; to power the LPB's motor through the attached MPC; or to produce a regulated 5-volts required by the other devices (BEC), and do so at a much higher current draw than possible from the ESC's voltage regulator. With the exception of the BEC the devices connect, directly, or through one or more devices, to the receiver from which the intelligence you provide at the transmitter is conveyed.

On the left side of the devices pictured above is the power cable which originates in the forward dry space where its Dean's plug makes up to the battery, through a series wired mission-switch, to an optional fuse, where the cable then runs through the brass tube conduit through the ballast tank, into the forward dry space where another Dean's plug makes up and delivers battery power to the four devices, all wired in parallel with they're common plug.

The toggle of the mission-switch projects to the wet-side of the forward bulkhead and is made watertight with a flexible rubber boot.



This is how all the devices that mount onto the motor-bulkhead are hooked up to the receiver, either directly, or through other devices. The rudder (channel-1), sail plane (channel-2), and ESC (channel-3) plug directly into their respective receiver ports. The BEC also plugs into an unused receiver port, but only to apply power to the receiver bus, off of which the other devices draw their current. The receiver channel-6 port accept the lead from the angle-keeper side of the ADF, and from the ADF to the stern plane servo, the upper most servo seen above.

The receivers channel-4 port is for control of the SAS devices, and is deserved of a bit more discussion. The Lipo-guard plugs directly into this port. The Lipo-guard is directly connected to the battery cable, through which it monitors battery voltage. It's the job of the Lipo-Guard to drop the transmitted channel-4 signal -- simulating a 'loss of signal' condition should battery voltage drop to the critical level. When the Lipo-Guard drops the signal, the ADF's fail-safe circuit, which is next in line, takes its appropriate action which is to generate the pulse-length required to start put the ballast sub-system to the 'blow' condition, surfacing the boat. So, the devices connected to the receiver channel-4 port go like this, from the receiver: Lipo-Guard; fail-safe side of the ADF device; a Y lead to split the signal and send it along to the MPC of the LPB, and the ballast sub-system servo. Near the top of the above photo you see the Y lead feeding the ballast sub-system servo and MPC.

Four devices have to be hard-wired into the battery cable: the MPC (power to the pump as directed by the MPC); Lipo-Guard (voltage sensing); ESC (chopped current of appropriate polarity and amplitude sent to the propulsion motor); BEC (regulated voltage of a relatively high current rating to the receiver bus where the other devices draw their power).

Most, but not all devices have two sides to them: the receiver side, and the battery side. Observe correct polarity when you hook things up, or the magic smoke will be loosed.



Today's ESC's usually contain a low current BEC within them, but only rated for a maximum continuous current draw of 1.5 Ampere's. That's fine for what a reversible ESC's BEC is tasked to do for most model cars and boats: provide 5-volt power to just the receiver and one or maybe two servos -- in that case, 1.5-ampere's is plenty of capacity. But, in an r/c submarine, where as many as TEN devices are sucking off the receiver bus ... well, that's way too much of a load for the ESC's BEC. In a model submarine, even in the idling condition, the current passing through the receivers PC's foil is over 2-ampere's! When the servos are at work and pushing against a load (those watertight seals!), the total current draw of the system can spike system current draw to nearly 5-ampere's! Hence the need for a dedicated, high current BEC.

However, using a separate BEC, requires disablement of the ESC's BEC to prevent interaction between the two BEC's, sending transients along the receiver bus, potentially glitching the system. Disable the ESC's BEC by pulling the red-wire pin out of the J-connect at the end of the ESC's servo lead. Fold the metal pin back on the red wire, slip on a length of heat-shrink tube, and shrink it down with a hot-air gun this to insure you don't short the bare 'hot' pin against any system ground.

HEY! What's with the crazy text above?? To quote Servilius Casca in Shakespeare's Julius Caesar ; "it was Greek to me"