Big Gun Predreadnought: IJN Mikasa

After a marathon 7-hour-long wood-cutting spree, the Imperial Japanese Navy's sixth 1st-rate battleship, Mikasa, was finally laid down. The Mikasa has been on my drawing board for more than two years, so when the time came to cut, I knew exactly what to do. subdecks, ribs, decks, and keels have all been cut. Below, you can see my first test-fit assembly at home, and my planned internal layout using my laser-cut cannons and a 4-oz CO2 bottle. The mighty Prinz Eugen looms large in the background, but Mikasa has a much more impressive ram bow

Here's another look, this time at the stern. A few details worth noting include:
1) cutouts where the casemates go. They are very close to the deck, and so are tricky to do in a traditional wooden hull. More details on that in a later post, probably next week.
2) propshaft supports. I already know the exact internal layout, so I know where the shafts and motors will go, and built supports directly into the hull to ensure their alignment and strength.
3) built-in braces, bottle/battery mount, supports for servo tray in stern. As I mentioned earlier, I've been planning this boat for a long time. With that much time, not planning these in would be embarrassing.

 

Now that's a ram bow!

 

That is one thing I love about warships of that era, even the parts that normally could not be seen have the most lovely lines.

 

Iwill upload my Mikasa plans collection once I figure out how to upload files again. It's got several different battleships from the 6-and-6 plan fleet, and a bunch of photos of the museum, models, and history that helped me plan the build. I also included various CAD files I used in planning, and for the laser-cut cannons. The important stuff is photoshop files, though, containing the exactly scaled plans that I used. The side profile is unfortunately not accurate, so I had to overlay several other side profiles from other sources to get a correct shape. The result is very accurate, but also somewhat confusing. The rest of the plans are very accurate. My top view even has different layers showing how the superstructure stacks up.

I chose to use joinery not for any strength, but to make the tumblehome hull more accurate. If I had simply placed the subdeck and deck on top of the ribs, like I do with other hulls, the ship would have had a knuckle at that seam, that would have been hard to sheet. In this particular case, I oversized the subdeck and used joinery to locate the ribs, so I can sand the subdeck to exact shape later. The deck and ribs are perfectly scale, however. I'm still not a big fan of joinery on non-tumblehome ships, though, especially after yesterday. All those notches are a pain! I'm planning the Mikasa to be my showboat, to be as historically accurate as possible and to have as much detail as its bitty predreadnought hull can handle. I'll have to be careful not to overload it with shiny brasswork right now, the debate rages between doing the pre-war version with its bright colors, plentiful air vents, and huge masts, or the Tsushima-strait version with its easier-to-maintain grey and smaller masts (but more rigging, squee!)

 

I would say do the period of historical significance, Tsushima, even though I love the Victorian paint schemes.

 

Wow, 57mb... maybe that's why. I'll see what I can trim out to reduce the size. Bit busy this weekend, so I'll probably do that on Monday.

Nick, the Mikasa will be using a pair of 3800mAh 7.2v NiMH sub-C packs. That is more than enough power for a Big Gun battleship, especially one of this size. They will go on either size of the CO2 bottle, sandwiched between the vertical supports you can see on the two amidships ribs.

Today I will cut the rails for the water channel and glue most of the framing together, then tomorrow Mikasa goes to her first show! It's Wooden Boats on Parade in San Francisco, and Mikasa will be strutting her stuff next to the finest ships in the SF Model Yacht club (some of which are over 100 years old!). Together with the transparent laser-cut cannons, she will be an excellent visual demonstration of Model Warship Combat technology.

 

That looks great! Looking forward to seeing it in person. Are you planning to have it ready for combat next year?

 

Almost done putting the bottom on, now. I will take some more photos once that is complete. This build is moving right along.

 

Haven't gotten much done recently, due to efforts refitting Prinz Eugen and Tegetthoff. I'm almost done putting on the bottom, though. I am wrapping the bottom in 1/64" plywood. Once that's done I will lay down a single 3/32" plank on either side to make a no-xacto-cutting bottom edge. In the photo below, you can see my progress on the bottom. You can also see what I'm planning to do for the anchor decks. I saved the cutouts from the subdeck and deck, and wrapped a 3/4" wide strip of 1/64" plywood around them. The idea (as shown in the photo) is that I can then re-insert the pieces into the subdeck, using the strip of plywood to hang them down at the correct level, and sand to fit. Unfortunately I made a boo-boo and put the plywood on the wrong way, so they fit upside-down. I can still peel off the plywood, but I'm focusing on the bottom right now.


Above is my planned layout, with parts placed in approximately correct locations. In the very bow you can see the front gun, with accumulator going forward. After fiberglassing the bottom, I will need to knock out the bottom of the rib there, so I can fit the gun in lower. Lower guns means longer barrels (thus more efficient), and room for a depression servo. That's right, I'm planning this little baby to have both rotation and depression.
Next you can see the batteries and CO2 bottle. Right now I have a compact 4oz bottle there, but there is room for larger. I hope to test-fit a 5oz and a 7oz next week, and I'll take whatever fits. The batteries are standard RC car packs, and they go on either side. The batteries hold the bottle centered in the boat, and the bottle keeps the batteries from shifting. This whole center area almost snaps together, it's such a nice fit. No worries about shifting ballast here.
Just aft of the batteries are the shiny objec... I mean motors. One pair of high-efficiency, high-performance maxon A-Max motors in shiny silver cases. These two babies will move my ship at speed for less than 2 amps, and plenty of torque to go with it. Hopefully they'll get me up to speed for less than 1 amp. Between the motors (and underneath the end of the CO2 bottle) is the pump. I don't have it yet, but I can actually fit a BC small pump there. The only question is brushed or brushless, and I won't decide that until the next Naval Budget Review.
Finally there is the stern gun and stuffing tubes. As with the front gun, the back gun will be as low in the boat as possible in order to fit longer barrels and a depression servo. This one is extra-important, because it is my anti-torpedoboat gun. If any cruisers or destroyers decides to get adventurous, this is what I'll use to fend them off. It'll also be my primary weapon against battleships for the first 6 months of Mikasa's career. Once they learn to fear it, of course, I'll start using my front gun more to chase them down while they run away

 

That picture of the bottom reminds me of the photo of the over turned hull of Majestic off the Dardanelles

 

Good day sir, any news on this magnificent ironclad?

 

Yes indeed. It's just about time for more photos. I've finished wrapping the bottom, but still need to do a little cleanup before fiberglassing. I'm also making progress on the casemates. I'll see if I can take and post a few tonight.

 

I just ran an endurance test with the Mikasa's laser-cut cannons. The purpose of this test was threefold:
1) find out how many shots I could get off with 3.5oz of CO2.
2) find out whether or not the acrylic magazine would stand up to the stress of continued firing.
3) find out how reliably the laser-cut magazine design loads.

The first part of the test ran into problems immediately. There was an air leak where the air nipple threaded into the accumulator. Since I only had one full 3.5oz bottle, I had no choice but to continue the test. Any results would be lower than I could expect in combat, after I sealed the leak, but I still wanted some numbers. So with Gascan holding a towel over the cannon, and me operating the test rig, we opened fire. One shot every four seconds, at 130 PSI from a 4cu.in. accumulator. Ten shots later, we checked the magazine for damage. No cracks, or any other indications of failure. Twenty shots later, another check. Still good. At about the 50-shot mark, the magazine ran dry. Still no signs of damage, and the CO2 bottle was frosty but still going strong. Test two, successful, test three, successful, still gotta complete test one. So we kept going. Finally, at seventy six shots, the pressure started dropping. The next shot was noticeably weaker, a clear indication of an almost-empty CO2 bottle. At that point we called it, safed the system, and sat down to discuss the results.

As I mentioned earlier, the first part of the test was inaccurate, since the cannon being tested had a pretty serious air leak. Despite the air leak and the cold weather, I was still able to get 76 full-power shots off. Each turret holds 117 rounds (58 volleys per turret, 116 total for the ship). So I fired more than half of Mikasa's maximum ammunition capacity from a single 3.5oz CO2 bottle, with a big air leak. I'll be getting a 5oz bottle from Strike, just to be safe, but I think a 3.5oz will actually carry enough air once I seal up those leaks.

The second part of the test, checking for damage, was also quite successful. I half expected the laser-cut acrylic to crack within the first few shots. However, nearly one full magazine-load later, there was no indication whatsoever of damage from firing. The only question that remains to be seen is how well they stand up to years of punishment, and that will simply take time. And... if they break, so what? laser-cut ABS magazines are only slightly more expensive, albeit uglier and not transparent.

The third part of the test, reliability of magazine loading, was also surprisingly successful. I used very simple, flat feed ramps on one of my two turrets, and this is the cannon I tested. A simple flat feed ramp is much easier to manufacture, but there were concerns about reliably loading rounds into the breeches. In my test, this was not an issue at all. You can hear whether a cannon is firing a round or a blank. I heard when the magazine started firing blanks, and when I checked, the magazine was indeed empty. Not only that, the number of shots was very close to half the number of rounds in the magazine (it is a twin turret, after all). Furthermore, this test was on a flat, level table with nothing to stir up the ammunition. In a moving ship that is rocking and rolling and rotating and firing, I expect loading to be even more consistent.

All in all, the test was a complete success. I am continuing forward with filling and sanding the belly of the beast in preparation for fiberglassing. Construction continues at a good pace. I expect to have this ship on the water for Maker Faire 2011.

 

I haven't worked much on the Mikasa recently, but this weekend I finally kicked into gear again. So that means progress photos!
The basic hull is already together, so I've been working on the casemate guns and started epoxying the hull. The casemates presented quite a challenge, since they are supposed to be exactly 1/4" below the deck. The deck is 1/8" thick, and the subdeck is 3/8" thick. This left two easy options: go 1/8" low and put them below the subdeck, with tech officer approval, or go 1/8" high and go directly into the subdeck. Either way would not be historically accurate, however, and I refused to accept that. Instead, I chose a third option: go into the subdeck, then lower the casemates by 1/8" so they're correct. You can see in the 1st picture that there are a number of triangles along the subdeck where the casemates go. Those are where I fitted 1/8" spacers to get the casemates down to height. You'll also notice that I added in the anchor decks. These are probably one of the most unnecessarily complex features ever put on a battleship. They don't help the anchors at all, they don't make storage or handling or deployment of the anchors at all, and they are a pain in the *** to use. However, they add to the funky predreadnought look and add extra impenetrable area, so I just had to have them. I will be filling in the accurate details later.
With the casemates now at the correct height, I then had to build the features themselves. On the VUs, I carved them out of solid wood, then added half-round dowels to make the gun shields. These splintered and failed very easily, so this time I decided to do something much stronger. I'm using quality 1/8" ply for the angled sides, and using 1/4" fiberglass tube for the gun shields. The gun barrels will be carbon fiber. To prevent the fiberglass tube from failing spectacularly, I am planning to fill them with epoxy when I install them. The 1/8" ply has also been carefully positioned and placed so that it holds the fiberglass tube inside the barbette, preventing it from falling out in battle. You can see a clear example of how this will work in the second photo. I still need to find a better way to cut the fiberglass tube, as you can see by how horrible my test piece is. Cutting it by hand is inaccurate and irritatingly inconstant, and I've gotta make 14 identical parts. I think a mini cutoff saw plus a work stop will work, so I'll be asking around my local club if I can borrow one.

 

I used the same method for making casements on the HMS Erin. It looks good, though a pain to put together.

Very nice build so far! Love the wood work.