Hull Joint

Posted: 7th December 2012 by Nate in U-52
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The two hull halves will be attached together via three bolts.  I started by drilling two holes in the keel of the forward hull.  Since this part of the keel was made from wood, two brass tubes are pressed into the holes and CA’d into place.  This way, the inner wood surfaces will be protected against the water.

As for the other side, I epoxied a strip of styrene above the keel and drilled two other holes.  Two nuts are then CA’d into place.

The top joint uses a similar design, a section of brass tubing was also glued into the styrene to prevent the plastic from being stripped bare by the bolt over time.

On the bow section:

More later!

Ballast Tank Switches all Wired Up!

Posted: 28th July 2012 by Nate in U-52
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Time for another update!

I’ve soldered the switches responsible for turning the ballast tank pump on and off and controlling the direction of the water flow.  In particular, the switches for filling the ballast tank has an additional micro-switch connected.  The latter is wired in the NC (Normally Closed) position and will be opened by a lever swinging up and pressing on the blue button.  The lever itself will be raised by the flexible rubber bladder filling up, this will prevent the bladder from being overfilled and blowing up inside the WTC!

Additionally, the ballast pump leads have also been wired up, along with the RF noise-suppressing capacitors:

The pump will be connected to the ballast tank switches via a standard Futaba servo connector (visible in the first picture).

Main Switch and Bow Servo Unit – Completed

Posted: 24th July 2012 by Nate in U-52
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On to the bow!

I decided to have a main switch to turn all of the boat’s functions on and off, for simplicity.  The switch is located along the main power line going from the battery to the ESC, which in turn powers the receiver and all of the servos.

First, I CA’ed the bow servo supports to the endcap and then epoxied the switch in the middle.  Extra epoxy was also applied to the servo supports to provide extra strength:

With the servos in place:

The left servo will control the torpedo firing mechanism whereas the right one will provide control for the bow diving planes.

Front view of the endcap, the rubber bellow seals for the pushrods will go over the aluminum tubes:

To make the switch waterproof, a rubber cap is screwed over the toggle lever.  Silicone will be applied around the cap later on:

More later!

Stern Servo Unit and Propeller Shaft Support

Posted: 24th July 2012 by Nate in U-52
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Hey all, its been a while!

I’ve completed the stern servo unit which houses the aft diving plane and rudder servos, along with the ball bearings that will go around the propeller shaft.

As usual, I started by cutting and gluing the styrene pieces together.  Below is the box that will house the two servos, they will be laid flat on top of each other:

Next, two semi-circles were cut, these will house the ball bearings:

With the bearings in place:

The whole setup will be attached to the endcap with two bolts, their corresponding nuts are first CA’d to the endcap:

The styrene circle will be epoxied over the inner endcap.  The holes in the endcap match the diameter of the propeller shaft seals.  The holes in the styrene circle are smaller and are slightly larger than the propeller shaft.  Once epoxied to the endcap, this will provide a back support for the shaft seals to rest on, so that they don’t pop into the WTC:

The setup secured into place:

To provent the servos from falling out, a styrene bar is bolted over them:

The ball bearings are also held in place by styrene braces, here is a close-up of the bearings:

Skipjack Ahoy!!

Posted: 15th April 2012 by Nate in Uncategorized
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There is a new submarine model on the horizon!  Moebius Models have posted pictures of their upcoming 1/72 scale USS Skipjack kit:

At 1/72 scale (over 40″ or 1m long), this will be a BIG sub!  Big enough to RC!  Needless to say, I will be grabbing one of these babies on day one! :D

The folks at Moebius have informed me that the kit is due for a June release, so I know what my next project will be when my U-boat is done!

Stay tuned for more updates soon!


Early Spring Update!

Posted: 23rd March 2012 by Nate in U-52
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With the weather being unusually nice the past few days, I’ve decided to prime the hull!  After washing the bow and stern sections with some soapy water, I let the hull air dry overnight.  Before priming, I masked some key areas such as the torpedo door hinges and spring, top bow section bracing, and the areas around the bow/stern joint where holes for the securing bolts will be drilled.

After building the stern servo tray, I will patch some spots on the hull and sand it smooth.  Hull details such as saddle tank vents and weld lines will be added next.

More to come!

U-boat Mega-Update #2

Posted: 26th February 2012 by Nate in U-52
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Time for another update on the project!  The following post chronicles the progress made during my Christmas vacation and the past week.

I started by gluing the two PVC endcaps that will make up the joint between the bow and stern WTC sections.  Looking at the profile of the Type VIIb U-boat, you can see that the hull curves upward as we move towards the stern.  Therefore, I decided to split the WTC into two sections:

The bow section contains of the following:

-Ballast tank servo-valve and switches
-Forward diving plane servo
-Torpedo control servo
-Main drive motors

The stern section will contain:

-Ballast pump
-Servos for stern control surfaces

Because of the curvature of the hull, the stern WTC will be slightly more elevated than the bow.  The endcap joint that will connect the two sections together is shown below.

You can see that the stern endcap (left) is slightly offset because of the hull curvature.  I later reinforced the joint with more epoxy.

Next, the holes for the motor shafts are drilled, along with larger holes you help secure the motor can:

The motors themselves are secured together with styrene sheets and four bolts:

Here are the motors test-fitted on the bow part of the endcap joint, before the two endcaps were glued together:

The black bolt will secure the styrene motor support to the endcap.

With the motors secured, I soldered the supply leads, along with the RF noise suppression capacitors:

Turning now to the stern section, I attached a piece of styrene to hold the Velcro that will support the ESC and drilled a hole that will allow the ESC and ballast pump wires to pass through:

The ESC is a Tamiya TEU-103BK designed for dual motors, from my monster truck.

Yup, that’s a lot of wires!

Next, I built the bow diving plane and torpedo control servo supports.  These were fabricated using thick styrene sheets and brass square tubing.  Hinges at the bottom will allow me to install and remove the servos after the supports will be glued to the bow WTC endcap:

To remove the servos, I simply have to undo the bolts and flip the rear support pieces down!

Finally, I began to tackle the ballast tank section.  Originally, I had intended to use a sealed-ballast type setup similar to the ones used on the Sheerline subs.  To do this, I had modified a windshield-washer pump and a medicine bottle to serve as a ballast tank.  However, after some testing I discovered that at 7.2V, the pump only had enough strength to fill the ballast tank to about 70% full, this was due to the air being compressed inside the tank while water was being pumped in.

After doing some research on E-bay,  I was able to obtain a nice gear pump and a blood pressure cuff bladder to convert this to a flexible ballast tank system:

The great thing about this pump is that it is able to pump water at a sufficient pressure with as little as 2.4V of input!

I then built the pump support frame that will be attached to the endcap joint.  The black piece of plastic was obtained from motor cover of the windshield-washer pump, which happened to fit the gear pump motor perfectly:

The pump was then fixed to the endcap joint with two bolts:

The completed propulsion/ballast pump module!

In a flexible ballast system, a valve is required to prevent the flow of water from the rubber bladder to the outside when the pump is not running.  The outward flow of water is mainly due to the elasticity of the rubber causing the bladder to deflate and also because of the increased interior WTC air pressure when the bladder is inflated.  With an idea in mind, I proceeded to build my servo-actuated valve.

The concept is very simple, a servo with a stainless steel roller will pinch a flexible rubber tubing (connected to the bladder) in the neutral position, preventing the water from flowing out of the the bladder.  To activate the pump, the servo will simply rotate one way and flip a DPST switch on.  At the same time, because the steel roller is also part of the servo wheel, the pinch on the rubber tube will be released due to the wheel’s rotation.  To reverse the pump flow, the servo simply has to rotate the other way and flip another DPST switch on.

The parts that will make up the servo roller mechanism, I obtained the steel rollers from a scavenged printer.

The roller all assembled, the bottom roller spins freely between the two servo wheels, whereas the top two rollers are glued to the plastic and will be used to flip the DPST switches on and off.

Installed on a Futaba S3004 ball-bearing servo.

The servo supports are fabricated and glued onto the component tray.  There is a clearance of approximately 3mm below the bottom roller to accommodate the rubber tubing.

To hold the servo down, I built a upper styrene deck.  This will be threaded through the upper steel WTC support rod.  At the same time, it will also house the two AA batteries that will power the pump.

The servo support mounted on the component tray with the AA battery holder in place.

Now its time to build the DPDT switches!  I was lucky enough to find these micro-switches at my local electronics surplus store.  The little plastic tabs can be easily pressed down by the servo rollers.

A bit of superglue and styrene later, I have two DPST switches!

The switches are assembled onto the upper servo support, from the underside you can see how the servo will activate each switch by rotating one way or the other.  In essence, the whole setup behaves like a DPDT switch.

Now its time to put everything together!

With the rubber tube in place, this is the neutral or pinched position.

The battery is a 7.2V NiMH 6800MAh, should provide plenty of power and runtime!

As you can see, I’ve modified the original bow component tray by shortening it down.  Removing the steel support rods around the ballast tank gives the rubber bladder more capacity while making the system very modular!  I can essentially use this unit in any 3″ WTC with a pump-based ballast system.  The completion of the ballast tank control module is a crucial part and a major milestone of this project.  The next step is to install the prop shaft and linkage seals along with building the stern component tray.

Thats all for now folks!  Hope you enjoyed reading!

U-boat Mega-Update #1

Posted: 18th September 2011 by Nate in U-52
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Its been a while!  Since my last post, a lot of progress had been made:

1) Bow section:

Built a lip to help how down the upper bow section

To secure the upper bow section, I drilled out and installed a nut inside a styrene brace.

A bolt will pass through this fixture .

Upper bow section secured!

Bow flood holes on the hull and bow section have been drilled.

At the time the hull master was built, I did not have access to schematics that showed both the port and starboard profiles of the boat, so I assumed that they were identical.  As a result, two anchor cavities were hollowed out…  I had wanted to keep this arrangement since it made my boat look unique but ultimately decided to fill in the port side cavity for scale.  I also sanded down the lower bow section to make sure that the torpedo doors could open and close smoothly.

CA’ed a thin styrene sheet to the upper deck and sanded it down.  Some flood holes will be drilled out after priming.

2) Midships:

To prevent hull flex and to add rigidity, I built a series of hull braces that will be glued between the saddle tanks.

Here’s the above installed.

Also added a few more on the bow…

…and the stern.

The joint between the bow and stern halves was also sanded to avoid leaving a gap when both sections were assembled, I also spent a few days sanding the saddle tanks and hull to make both sides symmetric.  Had I put in more effort when the hull master was being built, I wouldn’t have had to sand off some of the styrene plating to make the contours symmetric.  Lesson learned!

3) Upper Deck:

The upper deck was cut from ABS sheets, flood holes were drilled out, and both sides were held together using styrene braces.  The ABS was heated with boiling water to make it more flexible.

Partly completed stern upper deck.

The deck sections will be attached using two sets of nuts and bolts, I’ve drilled out the holes necessary and reinforced the joints.

4) Hull as of Today:

Here are some shots of the boat with the upper deck and conning tower installed, all that is left is to finish the stern deck, make the bow-stern securing mechanism, lightly sand the whole hull smooth and then it’s off to priming!

That’s all for now folks!

Torpedo Doors

Posted: 9th June 2011 by Nate in U-52
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Progress has been made on the torpedo doors.  The mechanism is inspired by MFR’s excellent torpedo build here.  In short, the doors will be kept closed by a spring in-between them and opened by a servo pulling on two strings.

The torpedo doors and pieces from the bow section were glued on two miniature hinges

The parts were then glued to the bow section along with a spring that will hold them closed.  Two strings are glued to the inner side of the doors and will run to the servo that will pull them to open the doors.  To close the doors, the servo simply needs to be in the neutral position, at which point the spring tales over

Another shot of the upper bow section.

Watertight Cylinder Cont’d – Component Tray

Posted: 21st February 2011 by Nate in U-52
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Hello all

After gathering the necessary materials, I decided to build the forward Electronic Component Tray.  My design is somewhat “European” since in addition to a styrene platform and bulkheads, aluminum threaded rods will be used to reinforce the whole setup.  From what I have seen, this design seems to be very popular amongst modelers in Germany and France.

The aluminum rods were cut into the appropriate length, nuts will be used to secure them to the bulkheads

Next the styrene bulkheads were cut and sanded

Holes to be drilled for threading the rods  through are then drilled.  Here, the access space for the main battery has also been marked

Finally, the bulkheads were threaded through and secured using nuts.  Also visible here is my main ballast tank, namely a HDPE medicine bottle

The 7.2V battery fits nicely!

In addition to the two main bulkheads, I also fabricated a middle support bulkhead and platform to house the servo-activated flood valve

Close-up of the support braces.