Since I have some time to wait for my ABS enclosure to arrive, I thought I could start modeling my next ship. What do you think it is??
Correct!!! I guess I'm doing something right! The ship did have a bulge... do you think the model is too bulged? I am drawing straight against the plans... Can you take a screenshot of what you are seeing, so I can double check that area is correct?
It looks more buldged than most Lutzow models I've seen, if it were my model I would decrease the buldges by about 50%, from the screenshot you shared it almost looks like a monitor. I've taken a few nasty rams in my Lutzow, despite having more modest buldges, so going down a bit on the buldgeyness would lower ram susceptibility a bit
If you're planning for Big Gun, you'll want to eliminate the bulge entirely. Just draw a straight line from the outer-most part of the bulge to the deck rail. The thicker balsa wood (3/32", three times thicker than what Fast Gun uses) has difficulty making complex shapes, and the knuckle-edge between bulge and hull creates a weak point that, unlike armor belt edges, isn't supposed to be reinforced in any of the Big Gun rulesets I am familiar with. NTXBG rules may be different. The simpler hull shape also makes sheeting significantly easier, which is an important consideration if you plan to battle aggressively. Um... I'm also thinking about cannons. This ship is going to need triple 7/32" cannons, which I do not yet have modeled. My next patrol is coming up soon, so I will not be around for the next 3-4 months. I should be back on land by March-April time frame. When I get back, I'll have several months of proper off-crew to design, build, and battle to my heart's content. Until then, I won't be able to do much. I'll see about getting you some design notes and pictures, though.
FYI, to me, your hull looks "right" as in "scale", but scale doesn't always work best on boats. As others have said, for Big Gun, you probably want to smooth those out so that you can sheet them with the appropriate balsa. Or (quickly looks at the NTX rules) consider a ship that isn't so slow. It turns out that speed does matter rather quite a bit.
I am always intrigued by the different ways we all go about designing hulls in CAD. Looks like you are using surfaces.
I'll just drop these here. This is a cannon magazine from BDE back when they were in business. The original cannon base had problems, so I built my own, but the magazine itself is fantastic. It was all CNC machined from aluminum and PVC, although pretty much everything can be 3d printed today. Between these photos and the twin cannon I posted for the Mikasa, there should be enough info to design and print your own triple 7/32" cannon. Like most Big Gun cannon magazines, this one is constructed in layers. The bottom plate is aluminum, and has CNC-cut holes for either a triple or quad setup. The rotation mechanism is a custom-made ball bearing, that works for an aluminum bottom plate but would destroy anything 3d-printed. I would recommend using a normal rotation bearing instead. Next up is the manifold and breeches. This is a two-sided plate. The bottom side is the manifold, approximately 1/4" deep with as few obstructions as possible. #4-40 setscrews from the aluminum bottom plate stick up into this area, and set the height of the rounds in the breech to ensure proper operation. The top has the ammo ramps and breeches. These use a clever stair-step method of sloping the ramps that is very easy to do with a CNC mill. The last short length is cut with a drill bit, but the stair-steps do cover most of the ramps. You'll also notice a spot for o-ring seals between the barrels and the ramps, and a lip to align the magazine ring that holds the barrels. As for the cannon base, you can use a modified version of the Mikasa cannon base. It will need some modifications, though. First, the accumulator should be about 1/5 to 2 cu.in. per barrel, so around 5 to 6 cu.in. The copper T's will not work. But you can get some aluminum tube from Mcmaster Carr that has the same OD and ID, and comes in a variety of lengths. The other thing is that, in general, you want the airflow cross-section to be the same (or shrink) as it flows from the accumulator to the barrels. That maths out to about 1/2" (13mm) ID for the air path through the buna-ball valve, with a 5/8" or larger buna ball. The rotation bearing will also need to be bigger, to accommodate the larger air path. The Mikasa cannon was designed for two 7/32" barrels, and this is going for more. This particular cannon has a triple-stack of ammunition, which can be rather tall. The Deutschland is somewhat limited on internal height, so you'll probably want fewer layers on a larger diameter magazine. For the bearing, you'll want something along the lines of these: View: https://www.amazon.com/gp/product/B07HTBLC2G/ View: https://www.amazon.com/gp/product/B082PS5HHN/
yup. I sketch the outline first, then the ribs, then I loft the skin. For Deutschland, I abandoned the “thicken” tool and drew an inner and outer skin, then stitched it to a solid. Compared to Surcouf it was a LOT simpler and controllable. I’d love to see how others do it?
This surprised me! I’ve seen the Indians style cannons on the other NTXBG boats. I also had a set on a borrowed Alsace back in the day. After seeing the efficiency of the fast gun canons PLUS the ability of 3d printers… I’m not sure why I can’t scale up that design? Have you tried it?
Oh.. no one wants to see how I do it. I do not follow the KISS principle. i sketch out the outline, every rib at station, create guide rails, solid loft, sketch hard area and rib pattern, cut that, make new sketches for every rib to carve out the inside, loft all of those to cut the solid to shape…. While some people can knock out a hull in a few hours, it takes me most of a day. That said I am a stickler for hull shape. I will spend hours relofting a part and changing guide rails until I am happy with it. I will obsess over the STUPIDEST of details (like the hull torpedo tube on Derf.. or making sure the outer prop “wings” at least look correct..)
Once you have a system it isnt bad. I can control the rib shape and cut in water channel in one go. But that is MY method. And I’m… special. I WISH I could do it faster but every time I have done a faster method, Ive spent more time backtracking to fix things I didnt like.
If you only look at gas per trigger pull, then Big Gun cannons look pretty inefficient. But on a gas-per-round basis, well-built Big Gun cannons are not far behind Fast Gun cannons. One of my test cannons (twin 7/32") fired 166 rounds using exactly 5oz of CO2. At a steady rate of one trigger pull (two rounds) every six seconds until empty, in my winter-cold garage. That's about 33 rounds per oz. under worst-case conditions. Fast Gun cannons will do between 40 to 60 rounds depending on airflow. Then you've got to consider scaling factors like how much larger the magazines get, or how hard it is to rotate Fast Gun cannons. I can easily pivot a Fast Gun twin, triple, or even quad cannon through a 30-degree arc. Maybe as much as a 90 degree arc, 45 degrees to either side. But trying to smoothly cover a full 270-degree arc? Not really practical with more than a single barrel Fast Gun style cannon. The impracticality of it just hasn't given me any reason to try upscaling Fast Gun hardware. I remember reading about someone trying it years ago, and IIRC his results were less than satisfactory but I don't have any performance numbers for it. @darkapollo that's the same method I use. Draw the ribs, loft a solid, then separate lofts for the interior. I include both the interior and exterior on the same set of sketches, but it's very similar to what you do. Takes time but I like the results.
... and we have windows. I can def'n see the concern with sheeting this! I'll smooth it out after talking with NTXBG members. Please double check any mistakes on the math.
So, each club is different, I'm not sure what format you're building to (big gun?). You do have the correct number of ribs for fastgun (15% of total area is allowed to be impenetrable, subtract 2" for bow 1" for stern, remainder divided by .375 for ribs = 12 ribs) however most would probably run a 1/4" rib. It does look like the bow area could be a bit big for fast gun? (maximum 2") Also, in fast gun, you'd be allowed a 1/8" stringer along where that bulge meets the rest of the hull. It'll be almost impossible to get balsa to transition from the straight hull to that curve without it. See attached paint pic for the stringer. Also, you can fill in that little notch in your second to last window, just bring that stern subdeck straight across to the rib. You've got a little stress riser in that location now the way it's modeled. Loving it so far
