Building a pair of Deutschlands

Ahoy folks! Kotori's Big Gun Battleship Shipyard began construction today on two new Deutschland class battleships.


It's a huge mess of laser-cut wood, 3d-printed plastic, and assorted other bits, but eventually this will become a pair of mighty predreadnought battleships. Since nobody else has been documenting their builds, I figured I should record mine. I'm still in the middle of assembling the two hulls, so it'll be a little bit before I get to post any major construction pics, but I'll at least give you all an overview of the plan.

Like all PDNs, the Deutschland gets 3.5 units. I am a very offensive person, so I intend to use 3 units of cannons and a half-unit pump. Right now I'm planning for twin sterns and a bow sidemount, but that may change in the future. Since this is a very high-tech build, I also intend to equip it with as much 3d-printed hardware as possible, including BIC cannons (or variants thereof). Propulsion will be a single geared 550-size motor. I'm not sure if I'll go brushless or not, that may end up as a future upgrade. Batteries will be 7.4v 2S LiPo, and CO2 will be supplied by a super-fancy 4oz CO2 bottle with 1/4 turn valve. And unlike my Scharnhorst, these beauties will be equipped with electric solenoid firing systems. Ideally there will be just one servo in the entire boat, everything else will be waterproof ESCs or waterproof solenoid drivers. This thing should be waterproof enough to pour the water out after a sink and immediately resume fighting.

Well that's it for now. It's time to start the next print.

 

Is there any way to get copy of file for deutschland

 

If I haven't mentioned this before, I am a Fast Gun noob. I've built dozens of Big Gun warships in the last 14 years, but have very little experience with the intricacies of Fast Gun construction. So rather than a step-by-step set of building instructions, I'll be using this thread to document my progress and ask fast-gun-specific questions like this: for those of you who've built this class of ship before, should I be concerned about weight? I need to decide how to build the bottom of the ship, and I have a couple of options.

1) I could wrap the underside in 1/32" ply, then pour cement filler to form the water channel. This is a popular method of doing water channels when additional weight is needed down low, and also can form snug fits around heavy, low-mounted components like batteries, CO2 bottles, etc. If I need the mass, or stability is an issue, this method would be preferred.

2) I could fill the spaces between the ribs with balsa to form the water channel, then sand the outside smooth and fiberglass it to form the bottom. This is lighter weight than the cement filler method, but could limit how low I mount heavy objects like batteries. Also looks much nicer than the cement filler method. If mass and stability are good enough without extreme precautions, I would much prefer this method.

Thoughts? Comments? I have materials to do either method, just gotta pick one.

 

I built my predread King Edward using the balsa block method. I routed an inset for the batteries to sit a little lower in the hull. To make weight, I glued a couple pound block of lead on the bottom of the hull. Very very stable. Pics on my build thtead.
I'm not a fan of concrete filler.

 

You can do without the servo if you really wanted to. I made up a rudder assembly using the old TD throttle board, since it had built in end stops that could be wired to micro switches, that are used as end stops. It worked great, had immense torque. The only thing it did not do, was auto return to center, you had to steer the opposite direction to center the rudder. Took a bit to get used to, but it was very fast in changing direction. Just a tad bulky, would only work in larger boats with some room in it.

I purchased one of these kits, still in the box, been busy building my new Bismarck, not sure what I'm going to do with it yet. Will look forward to the build, might get me going on it someday, but the Kumano needs some rebuilding yet before Nats, new stuffing tubes, and a Nagato that Rick K gave me, that needs rebuilding over the winter.

 

Well then. Balsa blocks it is. Looks like the shop is going to get a lot of sawdust this weekend. Next question: batteries? What would be an appropriate type and amount of batteries for this boat? Here's my initial thoughts:
Assume pump current draw of 22A (stinger motor), drive current draw of 8A (brushed 550)
Assume run time of 10 minutes
30A * 1/6 hrs = 5 AH minimum capacity
Is that a reasonable set of assumptions?
Battery-wise, I think a pair of 2S LiPo batteries of roughly 3000-4000mAh each, in parallel. Mount them on either side of the CO2 bottle, for easy access and low center of gravity. I could go with a single big cell mounted centerline, but that risks interfering with the CO2 bottle or electronics, or putting the battery all the way forward which makes for awkward access and bad weight distribution. I could also go with some of those 10AH LiFePo cylinder cells I've seen people using.

 

Pink foam (because it is cheap and easy to form), then I box the void and pour in 610 urethane foam from Alumilite. The 610 is more expensive than pink foam but will flow into all the small spaces and fill them solid with closed cell foam that can be cut and trimmed without water ever getting in. Balsa block is not closed cell and will turn into a sponge and degrade (read Kon-Tiki) after a little while.

 

I've done balsa before, and I've done plywood wrap, but I've haven't tried foam blocks. I've also never seen well-epoxied balsa go bad. I have seen several non-waterproofed hulls rot and disintegrate, though. What exactly is the concern there, cracks forming on the inside allowing water seepage, or cracks forming on the outside?

 

Progress Report:

View: https://youtu.be/ZOaAl9Reneg

 

Are those kits from Rcegnr? Look good.

 

Nope, these kits were courtesy of Greg Mcfadden. As is this cannon:

View: https://youtu.be/WmbQGjAVBhg

 

They remind me a lot of Marks kits. Very nice either way.

 

Oh yeah, I forgot to mention. The cannon Greg designed is super-low-profile. It barely hangs less than half an inch below the deck, and entirely fits within the barbette.

 

Ahoy folks! This build is not dead! I finally have some time to work, and I've got a LOT of progress to report.

The hulls are now assembled, fiberglassed, and waterproofed. The cannons are printed, assembled, acetone-washed, and tested. The remaining hardware is coming together fast. So here's an overview:


Up forward, you can see the 3d-printed forward casemates, the BC main control board, the forward sidemount cannon, and the solenoid valve to fire it. The sidemount can be switched from side to side, and I have not yet locked it down yet. Only battle experience will show which side I prefer.


Top view, amidships. Here you can see the basic centerline layout. Aft of the bow gun is the 4oz CO2 bottle. Then comes the BC pump, then the main drive motor and reduction gears. Two 2S Lipo batteries will power the ship, one on either side of the water channel. Between them they will have 6ooomAh, and I have plenty of room for more and bigger batteries if needed. Stern gun solenoids will go on either side of the reduction gears and drive motor. The opening in the stern deck, just aft of the stern cross-brace will hold the solenoid test switches. Three switches for three cannons.


Here you can see my largest time-sink so far: the Stern Guns. These are based on the BIC 3d-printed cannons, but are a lower-profile design in order to fit in the low stern of the Deutschland. It took around 20 hours of CAD modeling and over a dozen test prints to get a good working design, but now I have a fully functional cannon. The twin mount fits smoothly inside the barbette, and eventually I may add a pivot servo to swing the guns 15 degrees side to side, opposite the rudder.


And here is a side view. As you can see there is very little height available. It may not be immediately apparent, but these cannons are significantly shorter than the original BICs. The reduced height does mean a shallower slope on the ammunition tube, but it's still enough to ensure proper feeding for stern guns with minimal down-angle.


A close-up of the propulsion systems. A five-bladed 1.5" prop and a 3 sq.in. fish-tail rudder. I do need to trim the prop hub down for the rudder to fit. There is also a pair of 3d-printed drag props included in the kit, but I have not installed them yet.


As I continue forward, I do have several questions about the build. First, I have no indications about where the stern casemates are supposed to go. These are ready to be installed, but I don't know where exactly they are supposed to go. All the way aft, against the stern hard area? All the way forward, against the aft-most rib? Or somewhere in the middle? None of the build instructions cover this detail.
Also, for those who have used the BC main control boards, do these already have a waterproof coating, or is that something I need to do myself?