Disney Nautilus - 1:77 Scale

[He Who Shall Not Be Named]

make your pictures bigger. As sized now they convey little useful information.

[Johnny Depth]

Yeah, I don't know what the problem is. This image is either too big or too little. That's why there are 8 attachments. Not doing anything different from the other ones. I'll try again.
Thanks!

[Johnny Depth]

OK, That's better.

[He Who Shall Not Be Named]

Now we're cook'n with gas. Nice work.

David

[Johnny Depth]

Thanks!


Springs on Hatch Hinges

I had some trouble with getting a nice strong fit with a couple of Hatch Hinges, namely the dorsal fin hatch and the ventral hatch.
Then I did some research into the hatch hinges in the movie and saw that they had springs which counterbalanced the weight of the hatch. So I decided to imitate this by wrapping a small brass rod around a drill bit that had the same diameter as the hinge rod. And of course the wrapped hinge has to fit between the two arms of the hatch. This gave the entire hatch a more "real" look, but the real benefit was that the entire hinge was larger and that meant that the hinge could be custom fit into the original hinge mount. And the larger size meant more area to apply glue resulting in a stronger hinge.

[redboat219]

Any photos of your WTC and "hidden" rudder linkages?

[Johnny Depth]

Hidden Rudder Control

My goal was to have my finished Nautilus be as exact a replica of the Disney movie version as possible. So for rudder control I wanted to avoid any visible external linkages. After researching several options I came up with the following solution:

In short, a spindle.

Drilling the Hole in the Lower Tail For the Spindle

On the lower hull where the rudder pivots there is a bump-out or box which is probably intended to house, on the "real" Nautilus, the guts of the rudder control. I used it for the same thing.

The "rudder box" on the model is about 1/4" square.

1. On the top of the rudder box I scratched an "X" from corner to corner to locate the exact center of the box.
2. Next I used a 1/16" drill bit to drill a 1/2 inch long hole straight down through the center of the rudder box. The shaft of the spindle is 1/16 inch.
3. Then I used a 7/32" drill bit to drill a hole for the body of the spindle down just above the bottom of the rudder box, using the 1/16" hole as a guide. Since the rudder box is only 8/32" wide, I chose the 7/32" drill bit to allow a bit of hull material on either side of the hole. Being a cylinder, the only place where the hole is closest to the surface of the rudder box is at the middle of both sides. The rest has plenty of material around it.

The image above shows that I also tried drilling the 7/32" hole first and then drilling the 1/16" hole using a lasercut acrylic donut and a cardboard template as a guide.
In another approach I used nested brass tubing as a guide for drilling the 1/16" hole. Whatever works.


Fabricating the Spindle

I purchased a 7/32" diameter brass rod from K&S Precision Metals.

Using a drill press I did the following:

1. My first task was to drill a 1/16" diameter hole through the exact center of the brass rod. I used about a 1" long length of the brass rod. This is so I could later chuck it into the drill press for Step 2. I secured a block of wood to the bed of the drill press and drilled a 7/32" hole through it. Theoretically when I drilled the 1/16" hole it would be at the exact center. Didn't work very well in practice. Something about the drill press. I used a center bit to start the hole. When I drilled the 1/16" hole, the hole at the top was centered but the hole at the other end, not so much.
2. Next I chucked the length of brass rod into the drill press.
3. I cleaned up the end of the rod by pressing it onto a metal file and then sandpaper.
4. I decided to make the height of the finished spindle about 3/32". So at the approximate midpoint of that 3/32" length I cut a rounded groove using a file. Maybe a triangular groove would have been better. The groove only had to be deep enough to accept the thickness of the "rudder cable".
5. Then I cut that part off just above the 3/32" mark, chucked that and cleaned up the cut end with a metal file and sandpaper.
6. To prevent the rudder cable from slipping in the groove, I used a 1/32" Dremel drill bit to drill a hole. Well let's put it this way; if it was a clock face the 1/32" hole was drilled between 11 AM and 2 PM.
7. Did not secure the shaft in the spindle yet because some future fitting is required.

So the idea here is that the 1/16" shaft will shoulder any stress put on the spindle so that the main body will not bind, or at least not bind as much.

Next Step is How to Get the Rudder Cable to the Spindle.

[He Who Shall Not Be Named]

THIS is clever stuff, sir.

[redboat219]

Me after converting imperial measurements to metric.

[Johnny Depth]

THIS is clever stuff, sir.

Thanks very much!

[Johnny Depth]

How to Get the Rudder Cable to the Spindle

The idea is to run a line from somewhere inside the lower hull to the Rudder Spindle. You have to drill a hole.
My target for the end of the hole (referring to the image below) was just below the box that surrounds the lower attachment point of the Prop Guard. At that point it is a straight shot through the fin to the middle of the Rudder Spindle. The origin point inside the hull would be determined largely by the thickness of the hull along the path.

To guide a drill over that distance I created a jig consisting of a length of aluminum tubing with an interior diameter of that of the drill bit. And because of the length of the hole, I had to use an aircraft length drill bit of 6".

First I created a mold of the exterior of the hull from the tail to the end of the skiff. Having that, I could determine how to orient the drill bit guide and where the hull was thickest.

The mold was made using Micro-Mark 1-to-1/Rapid 4 Hour Cure RTV Silicone Rubber.




I started with a 1/16" aircraft length (6" long) drill bit. The tail fin had a piece of aluminum (I think) embedded in it. I was concerned that the metal would deflect the path of the bit so I changed to a 3/32" bit in the hope that the larger drill would be less likely to deflect when it hit the metal.


The casting was done using Easy Cast Clear Casting Epoxy. It's a two part casting resin. You are supposed to mix equal volumes of both parts. I had not had very good success with this in the past due to slight differences in the volume of both parts. The result was always tacky and in some cases sticky.

Luckily, I had an old Ohaus balance beam scale with a max of 50 grams with a resolution of 0.01 grams. I found the density of each part, Resin and Hardener, on their respective Safety Sheet. Knowing the density, I could calculate the weight of each part to achieve equal volumes. No more stickiness or tackiness.

The mixtures I used were as follows:

For a "large" amount…

16.20 grams Resin
13.50 grams Hardener

For a "small" amount…

10.80 grams Resin
9.00 grams Hardener

TIPS:

1. Measure both parts into the same container.
2. Measure the Resin first. It is heavier. The Hardener will float on top when you add it. If you add a little too much Hardener you can carefully remove some from the top using a toothpick or Qtip.
3. Don't worry about bubbles. The more important thing is complete mixing! As it cures it shrinks a little and forces out the bubbles. Incredible.
4. The mixture gets hard after 24 hours, but I always leave it for 48 hours just to make sure.

So now you have a casting of the hull with an aluminum tube sticking out of it. Let's call it Cast B. So the next step is to make another cast, call it C, of the inside of Cast B, so that you end up with a casting that fits in the hull and has your aluminum tube sticking out of it. So Cast C is what you use to guide your drill bit.

Drill the Hole

If you didn't measure the desired length of the hole, do it now. Mark the distance on the aircraft=length drill bit.

Place the Casting C, the one with the tubing embedded into it, into the hull. Insert the aircraft length drill bit, and begin to drill. I used a power drill but because the plastic shavings have no where to go because of the length of the bit, you have to drill a little then pull the bit out and get rid of the plastic shavings and go again over and over till you reach your desired distance. If you didn't break through the hull, you were successful. You won't know if you hit your target till you make the Trench.


Finish Assembling the Rudder Spindle

Then the spindle should be assembled. The 1/16" shaft should be inserted through the hole in the spindle and out the bottom to the bottom of the 1/16" hole drilled into the hull below. The top of the spindle should be about 1/8" below the top of the hole so that the spindle could be covered over and hidden completely with only the shaft sticking out.

Once the position of the spindle body on the shaft was determined I soldered the shaft in place at the top where the center bit made an indentation using Stay Brite Silver Solder and Flux. The top of the shaft was cut off at about 1/2" to provide good penetration into the Rudder itself. The Rudder will be attached later.

Route Out the Trench

The Trench in the Tail Fin will complete the connection between the hole that was drilled, above, and the Rudder Spindle.

So the next thing to do is route a 1/8" wide trench between the spindle hole and the box that surrounds the lower attachment point of the Prop Guard. With any luck you will find the end of the hole you just drilled. You have to find that end. A plastic straw, the kind you use to stir your coffee, or a metal tube, which would add strength to the tail fin, is then placed in the trench. It must be lined up with the hole leading into the hull. Eventually you will glue down the tube in the trench and then putty over it to hide it.




Thread the Cable

I initially used a 6 pound test monofilament. Monofilament because it had the reputation of being tough. But I wasn't sure what stress might be put on the monofilament (and I still don't) so I bumped it up to 12 pound test. I also tried 20 pound test but it was too stiff to be useful. During a test it seemed that the monofilament was being stretched. This was not good. So I looked for a line that would not stretch but was very strong. Believe it or not, I ended up using Kevlar thread. Worked great.

You start threading at the hull end. Pull the Spindle out of the cavity if it is still there. Run the monofilament down to the Rudder Spindle cavity. Then run the line through the small hole in the Spindle. To prevent the line from slipping in the Spindle during use, you tie a half-hitch in the line at that point and snug it up so that it doesn't sit higher than the groove that was cut in the equator of the Spindle or else it would bind. Then to keep the knot from loosening, you put a little CA glue on the knot.

Then you thread the line back through the hole and back into the hull and set the Spindle into its cavity and take up the slack.

Then what? You tie the line directly to the horn of a servo.

[redboat219]

Great technique!

[redboat219]

How are you set up for pitch control, dive planes or tilting prop?

[Johnny Depth]

How are you set up for pitch control, dive planes or tilting prop?

None whatsoever. In the movie it seemed that the Nautilus was engineered to rise or fall in horizontal orientation.

[Johnny Depth]

Rudder Cable Connection to Servo

In my first version, I screwed a spare Servo Horn to the midline of the lower hull, elevated about a half inch with a Servo Horn attached at the top. I tied the Rudder Cables to that Servo Horn. Then I used a conventional 1/16" push rod to connect the servo inside the WTC to the free-standing Servo Horn. There was too much play in the linkages so I abandoned that approach. I had always wondered if connecting directly to a Servo located outside the WTC would work. So…



First I had to figure out if and where the servo, a TowerPro MG90S Mini Digital servo, would fit. That was just a matter of trial and error.

I used a laser cutter to make an acrylic servo mount with 4 holes for brass bolts to secure it to the hull.

Then I made supports for the servo mount using J-B Weld PlasticWeld Plastic Repair Epoxy Putty. In order to embed the brass bolts in the putty and align them perfectly with the holes in the servo mount, I secured the bolts, upside down, in the servo mount using one nut underneath the servo mount and one above the servo mount. By tightening up both nuts, the bolt was firmly secured. Then I applied the putty under the servo mount and around the bolts and against the hull. So far that has held just fine.

Next I threaded the Kevlar line, one through each side of the the servo horn, and tied it with a slip knot. To hold the knot in place I put a small drop of CA glue on each knot. The line was not as taut as I wanted it, but then it finally occurred to me that I could elongate the bolt holes in the servo mount and move the entire assembly back to tighten up the line.

In the first versions of this assembly I had tied the rudder cable to the holes in the horn farthest from its center. In testing, I had the strangest pulling problem on the lines. It finally dawned on me that that by tying the lines to holes on the servo horn that were the farthest apart the servo horn was describing a circle which was much larger than the Rudder Spindle. Effectively I had the servo pulling on the Rudder Spindle farther than it could go. So by threading the rudder cables closer in to the servo horn center, I eliminated the pulling problem. So maybe it wasn't the monofilament stretching that was the real problem after all and I didn't really need to switch to the Kevlar line.

Attach the Rudder to the Spindle

Drill a 1/16" hole about a half inch deep in the rudder to accept the top shaft of the spindle. Make absolutely sure that the rudder is oriented exactly over the knot that was tied on the spindle. Then it can be epoxied into place.

Final Note

Because of the way the rudder cable attaches to the spindle, the actual range of motion of the rudder is greater than 180 degrees. In practice, the range of motion is determined by the servo.