I've seen one of the BDE Tashkent hulls. The person who was installing guns in it had to cut out one of the ribs because it was 2" center-to-center spacing, instead of 2" inside-to-inside. Not sure exactly how that happened, but it did. Overall though, that's exactly the sort of thing we'd want. The drawings of the Emile that the French gov't posted online are an excellent starting point. We can use the lowermost horizontal section as a baseplate (with markings for the ribs), and I even thought up a nifty way to use the vertical sections to accurately produce the impenetrable bow and stern (and even meet the Fast Gun impenetrable requirements). Webwookie, would you be willing to start digitizing the various profiles of ribs and horizontal and vertical cross-sections? If you could create a 3d model of the hull, that would be even better.
I can go ahead and start chipping away at it; however, if any of you can do a few of the vertical sections and export them to .dxf or .dwg, it'd greatly accelerate the process. The toughest part of the process is verifying the digitized profile from the CAD data against the French drawings. The best method I can think of is to print out each rib and overlay it with the drawings and tweak the lines until it's a sufficiently close match. Once we have complete profiles, it's a simple matter of using the CAD software to "loft" (not quite the same as lofting in the classical shipbuilding sense of the word) the rest of the hull model between the profiles. If you guys don't feel comfortable with taking a stab at some of the ribs, perhaps somebody could start creating templates for making the superstructure out of plastic sheet or plywood.
I used a home made light table to good effect on my first hull's drawings. I'm guessing a used digitizing pad at auction isn't costing what it used to? As far as CAD, I'm off for a dummies book. Have been flailing at Alibre and not getting anywhere. Mike Horne
I'm starting with the middle couple of ribs, working outward toward the bow and stern. Please be sure to post the number of the hull station you're working on if you do begin so tha we can ensure that we do not excessively overlap our work.
2" center to center (or forward edge to forward edge, or stern edge to stern edge - all are the same thing) is correct spacing for 1/4" ribs under NTXBG rules, and, as I understand it, many other clubs. Basically, 3" c-c for 3/8", 2" c-c for 1/4", 1" c-c for 1/8". Basically 1/8" per inch can be impenetrable rib. This amounts to 12.5% impenetrability in the penetrable areas. For what it is worth, to eliminate confusion where people might want to "stack" closer spaced, but thinner ribs where you have wonky curves, we specifically addressed that last year. Our current rule is: 1. Frames (Ribs) a. Frames (ribs) may be no thicker than 3/8 inch and on the bottom-most interior surface of the ship may be no higher than 1 inch above the bottom. b. For every 1 inch of ship's length the frames (ribs) are spaced apart, the frame may be 1/8 inch thick to a maximum of 3/8-inch thickness. For example, 1 inch space = 1/8 inch thick, 2 inch space = ¼ inch thick, 3 inch space = 3/8 inch thick; 4, 5, 6 or more inch spacing = 3/8 inch thick. Spacing may be mixed on the same hull. Example: 3/8” ribs with 3 inch spacing at middle of hull, 1/8” ribs with 1” spacing in the bow, ¼” ribs in stern with 2” spacing, but the larger space must be adjacent to the thicker rib (i.e., shorter spacing begins with a thinner rib). c. The hull area of the bow and stern may be made of any material provided the combined length of these two sections does not exceed 15% of the total length of the ship’s hull at the waterline and the ship does not have an unfair advantage as determined by the Technical Officer(s). This 15% does not include the thickness of the ribs. Rib thickness and spacing is covered above. Not the case for WWCC? By the way, yes I have a Tashkent kit I am building up - I believe it was $45. I like it. All issues in the building thereof have been caused by moi and haste and learning curve on experimental building techniques. I was sanding on the bow this afternoon. However, this is what prompted my earlier comment on using a CNC router to do the impenetrable bow and stern sections. For a ship with the beautiful bow of the Tashkent, getting it right is a lot of hand work for the novice. Cheers, Wreno
Does not your drawing software allow bitmapped overlays/underlays? Just put the import the TIF layer and draw on a layer above it. Pretty easy to conform the lines by, effectively, tracing. After all, the French files are already scanned. Then just scale in whatever scale you want. Or have I missed something? Oh, and fair warning - some cad software cannot loft the imported DXF's from some other software - treats it as meshes. I ran into that on the HMS Erin. Cheers, Wreno
Wreno, the WWCC requires that rib spacing measurements be made from inside edge to inside edge. So, for 3" spacing, the actual dimension of the penetrable window is 3" rather than 2.625". Interestingly enough, there was only one rib that didn't meet that requirement. All the rest were fine.
To my knowledge, no I don't believe there's a means of importing the tif into a layer; on the other hand, reverse-engineering a design from a scanned 2D drawing is something I haven't exactly done before either in the course of the time I've been working in Unigraphics. I've already scaled the French drawings to proper size so I'll probably poke around in the software tonight to make certain that I haven't overlooked any features that might otherwise be of value to this endeavor. --Update-- Aft ribs are fully digitized; when printed out, they are quite close to the profiles appearing in the French drawings. Forward ribs are roughed-out and simply need cleaning-up. I hope to have some sort of either solid or sheet model of the hull posted up at the end of tonight or tomorrow.
When I CAD-modeled the Mehoshi Maru, I couldn't just trace the ribs. Solid Edge does not have any ability like that. So instead, I measured xy coordinates for a bunch of points along each rib, then connected the dots. Getting the curves of each rib to line up was tricky, even for a simple hull shape like the Mehoshi. I also ran into problems CAD-modeling the bow and stern shapes. Some nuance about the shape, the number of vertexes I had, and the software I was using would not let me model the bow and stern. I could go from rib 1 all the way to rib 14, but I couldn't get the bow and stern. What I eventually did was use the ribs to calculate a bunch of horizontal cross-sections, then loft the shape between those. I hope you don't have to do something similar, but now you know, just in case you do.
I overlaid a grid on the source drawing to isolate key points. From there, I was able to create the rib profiles. The bow went quite easily when it came time to loft the surfaces; I suppose having once spent nearly two straight weeks of 12-hour workdays of working between ICEM Surf and Unigraphics resurfacing external sheet metal geometry on a car gives me a leg-up of experience. However, I'm currently stalled on the stern which is going to probably need additional splines for me to cleanly complete. After that, I'll go through the surfaces and check for tangency and gaps between adjacent surfaces and clean those up. If all goes according to plan, I'll have a sheet model of the hull, including prop shaft vectors, done sometime tomorrow. Once that's completed, I'll see about posting the data to the file manager along with a screenshot or two.
We now have the makings of a hull! Actually,the stern in the area right around the rudder and end of the skeg is still giving me a little bit of trouble to even get roughed-out so it'll be a little while longer before it's set to go. I'll upload an iges or step file model to the file manager as soon as it's ready.
Wow, Webwookie! That looks great! Ya know, you could start a little side business drawing up rib sections for people. I've got a few ships I would appreciate having better cross-sections for...
So much for waiting until I have the model perfectly finished with class-A surfaces. I've posted the preliminary iges model of the hull to the file manager, which you'll find here: Visit this site It's sufficiently accurate as-is that the more experienced people around here would be able to cut cross-sections of the model for ribs from which to build. Likewise, it's sufficiently ready that anybody so inclined can section the model to investigate options for rib placement. For anybody who'd like the file e-mailed to them, please drop me a pm and I'll send it right over. A few notes: 1. Not all primary surfaces are tangent to each other (0f the ones that are supposed to be) 2. The hull surfaces are not trimmed against the skeg/keel 3. The bilge keels are roughly modeled in with a square profile, not the tapered profile that would need to actually be used. 4. The surfaces are now "sewn" (each surface is a separate entity and does not necessarily perfectly intersect adjacent surfaces) 5. Only the foredeck is modeled (the main/aft deck should be easy enough to put in for anybody so inclined) 6. The deck surfaces and keel have not been simplified (both still possess their prototype curvature) 7. There may be "ridges" across some of the model surfaces (a result of not having yet corrected surface tangency or surface anomalies)
There hasn't been any activity in this thread for a few days but I'm still plugging away at the project when I can. I ran across a good resource for locating free CAD software (both 2D and 3D) so for those of you interested in being able to play with the data that we'll be yielding here before we have a finished product, you might be interested in taking a look here: Visit this site
Definitely. If it's ribs, keel, caprail, and deck, that can (at a general level) be done in a couple of ways. One would be to just project planes through the existing sheet model, display the intersection, and call it a day. Alternatively, I'm hoping to have the solid model wrapped up tonight; I'm planning to trim that solid model for a flattened main deck and can use cutting planes to evaluate rib options along with creating the templates for ribs, keel, caprail, and deck. If I recall correctly, the bilge keels are already suitable for creating 2D templates from which parts can be cut. Once we're a little further along, perhaps one of our existing vendors out there (Tugboat, you interested?) could mold fiberglass fore and aft impenetrable pieces that could be epoxied onto the wooden frame version of this design.
I think I am still stunned by the cad drawing. Impressive! Wookie have you given thought to as this thread builds, creating assemblies to add to the drawing for the various internal components? Motor mounts and blast shielding would probably cross all formats and variations well. Other parts may vary, but a layout and plans for all the guts might help the novices along too. In my experience, a hurdle for the novice builder seems to be that one, or all of the subprojects in the ship build is intimidating. If this thread creates a good how to with plans for a boat from start to finish... I think that would be a good thing Mike3
I shoulda gone back and read the first post... sorry. I have just seen one of the micro motors available from radio shack. Any thought on using two of the 6 volt version to propel this boat at big gun speeds? They are like way small But maybe a possibility for a destroyer. Mike3
Solid model data for a CNC cut plug of the Emile Bertin hull is located at the following location: Visit this site If anybody is interested in producing a fiberglass hull, the file can be directly provided to a shop that cuts high density foam (25lb or greater density recommended) to have the plug cut. I should have some more time later today and tomorrow to continue on building the model incorporating a set of ribs and a keel. At this time, I'm foregoing the fine-tuning detail of the model that would be necessary to make it possible to manufacture on an SLS rapid prototyping machine, mostly because I was quoted a price of ~$700 to make a Ready-To-Sheet SLS hull with the requisite glass-reinforced, impact-resistant resin.
As may be apparent, I've been far busier over the past couple of weeks than I had originally anticipated. Currently I'm planning to finish sectioning-up the solid model into the various components as soon as possible; after that's done, I'll create 2D drawings (probably .pdfs) so we can get a test-build of the hull design before jumping into the superstructure and internal systems. Is there anybody interested in being a guinea pig to build and document this "beta version" hull over the next few weeks?
