1/48 scale Type VIIC U-201 build

[Monahan Steam Models]

Nick, are those magnets in the bulkhead below your thumb?

Steve, good eye!

Yes those are magnets. At either end of the ballast tank, each bulkhead will have four magnets each and four stainless steel 1/8” alignment dowel pins. The end caps or bulkheads on the forward and aft WTC sections will also have four magnets and four dowel pin sockets to mate up to either end of the central ballast tank. This way the three main sections of the new version of the WTC can click together as if it was still one length of tube.

This version of the WTC keeps almost all of the original design work and component layout of the original WTC and is also identical in length. Besides being broken up into three separate modules, the only other changes made to the design was removing the bow plane and ballast control servos in the forward section. The upper and lower equipment shelves for both the forward and aft sections now also bolt to the new bulkheads that mate up to the central ballast tank. The equipment shelves now act as internal stays, keeping the end caps from blowing out of the cylinder ends from the piston trim tanks increasing internal pressure during use.

Also all the junk for the ballast control and dive plane linkage that was hanging off of and just below the forward trim tank is now gone. The ballast control and forward dive plane servos are now in the wet like the rudder and stern plane servos. Doing this eliminated the last two pushrod seals.

Nick

[SubDude]

Made some progress today on the new main ballast tank for this build.



The business end that houses the servo to control the main tank vent and emergency blow valve, along with the fittings for the LPB snort connection and LPB outlet nipple.



Still more work to do to finish it, but the cam that moves the main vent valve can be seen here on the opposite side of the aft ballast tank bulkhead. Using internal stays to keep the forward and aft ballast tank bulkheads from pushing apart. Outer cylinder just floats on bulkhead o-ring seals. Using super soft durameter 10 silicon for the main ballast tank vent seal.

Nick

Nick, are those magnets in the bulkhead below your thumb?

[Monahan Steam Models]

Made some progress today on the new main ballast tank for this build.



The business end that houses the servo to control the main tank vent and emergency blow valve, along with the fittings for the LPB snort connection and LPB outlet nipple.



Still more work to do to finish it, but the cam that moves the main vent valve can be seen here on the opposite side of the aft ballast tank bulkhead. Using internal stays to keep the forward and aft ballast tank bulkheads from pushing apart. Outer cylinder just floats on bulkhead o-ring seals. Using super soft durameter 10 silicon for the main ballast tank vent seal.

Nick

[Monahan Steam Models]

First part for the new ballast tank.

[Monahan Steam Models]

U-201’s main ballast tank is getting a major rework.

[Monahan Steam Models]

Manfred,

After reading your last post, I decided to borrow the Mrs. kitchen scale again to get some weights on this boat. The above waterline deck weighed 504 grams and the rest of the boat below waterline weighs currently 3910 grams so total weight 4,414 grams. So about 11.5% of the weight above waterline.

Some other figures for the fun of it. The WTC displaces 3,112 grams of water when the main ballast tank and trim tanks are empty.

The WTC weighs 2,134 grams. Main ballast tank holds 631 ml of water and each of the two piston trim tanks holds 100 ml of water.

The main ballast tank is definitely oversized and I am considering currently making a newer version of the WTC that will be 3 separate modules instead of one as it is currently. The overall project has evolved since I first started it. The big difference being the waterline cut. The current WTC was designed to be removed with a vertically split hull at the aft section, so a lot of the necessary controls, equipment and connections were incorporated into the design.

The waterline cut makes removing the current WTC very easy but what I am asking myself now is why bother removing the whole thing and disconnecting all the plugs and plumbing connections ever time? The main ballast tank can be one of the three new modules the should not need to be removed other than for servicing. The forward section of the WTC that currently holds all the pumps, torpedo launching electronics, sensors and other equipment with all of their plugs and plumbing also really does not need to be removed as often and can be another separate module.

The last section of the current WTC being the aft compartment is the power distribution and brains of the system. This is the only section that needs frequent removal to gain access to the batteries. Breaking the WTC up into these 3 separate modules would make it even easier to service the boat it seems.

As far as launching the torpedoes from one channel, I am using a device Kevin McLeod of KMC electronics designed called a TCP or torpedo controller pneumatic. It allows you to individually fire up to six bow torpedoes and four aft torpedoes with the use of a 3 position switch. The switch is normally kept in the center position which is also the launch position. Moving the switch either direction from center arms a forward or aft torpedo tube. After holding the switch in that position for one second, the switch is returned to center and launches that tube.

I found that it can be a bit tricky getting the exact sequence of timing correct for moving the switch to fire a tube so I wrote a sub program for the Arduino to use the same switch movement but have the program take care of the rest. Meaning if I move the switch on the remote either direction from center, I can hold it there for any amount of time but when I move the switch back to center the program kicks in and handles the timing and sends appropriate command to the TCP that it is looking for.


Nick

[MFR1964]

Nick,

I was curious how much my deck weights, 1184 grams, total weight of the boat 17000 grams, did some calculations and ended up with 7% of the weight, that 2% is much to low, my mistake, that launching from one channel, arduino?

Manfred.

[Monahan Steam Models]

Since I have separated the Arkmodel type VIIC hull at the waterline from bow to stern, it is very easy to weigh everything above waterline.

For those curious what everything above waterline roughly weighs, here ya go.



504 grams. I have not included handrails, deck gun or other small bits but those can be weighed separately and added to the total.

[Monahan Steam Models]

More completed forward launch tubes

[Monahan Steam Models]

Manfred,

Thank you for your help. It is good to know what this launch mechanism actually weighs now. Like you are doing, I am also now using one channel to pick and launch each of the 5 tubes.

As far as weight goes, I will need to check the ratio between the below waterline total weight at surfaced level verses the above waterline total weight of everything at surface level. Thanks for sharing that ideal percentage. I’ve done everything I could to stay true to the original design layout of these boats when it comes to the launch tube equipment and where that equipment was placed. Most of it is below waterline. I had to add 7 oz of weight to the forward section already to bring the WTC down. She’s getting heavy but most equipment weight is already placed down low and the cylinder has a lot of buoyancy dry. Close to floating this contraption, so it will be interesting to see where the cards fall.

Nick

[MFR1964]

Nick,

Now you know how much bouyency more you need if you don't use foam, as for firing, in the past i used a single servo with five switches, by turning a knob i could choose which tube i wanted to fire, there was a channel controlled relais between the wires, so i could set the switch, and fire by activating the relais.
This way i got away with the use of only two channels, now i'm using a multiswitch, one channel is split into 6 relais, much simpler to use.
One remark about weight, the stuff on top of your boat must not be bigger as 2% as the total weight underwater, this to counteract the pendulum effect when you raise the boat and when the wind hits your conningtower on the surface.

Manfred.

[Monahan Steam Models]

That is what i call a snapshot, nice!!!, how much does the complete contraption weigh?

Manfred.

Thanks! It is pretty fun to play around with pushing the temporary launch buttons.

Borrowed the Mrs. kitchen scale to weigh the complete contraption.
348 grams or 12.28 ounces.



Nick

[MFR1964]

That is what i call a snapshot, nice!!!, how much does the complete contraption weigh?

Manfred.

[Monahan Steam Models]

Dry firing tubes 1 & 3

https://youtu.be/MZe_W_vlmoM

[SubDude]

Insane Nick!! Looks like you are getting very close to a full system test. Keep that momentum going.