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Showing results for tags 'scratchbuilt3d'.
I have been working on a 1/16 Boxer 8x8. As the Lance turret won’t be delivered until later this year, I’ve decided to move my CAD learning on to a new subject, the Bushmaster Protected Mobility Vehicle (PMV), in-service with Australia, Britain, The Netherlands, Japan, Fiji, and Indonesia. Measuring up a museum example, I’ve started drawing up & 3D printing the stowage bins. Drawing on lessons from printing Lance turret, I’ve decided to skin the most prominent surface with 1mm thick styrene to ease clean up & detailing. Part of the detail to be resolved was the exhaust grille - 40 slots on top & 36 triangular holes. After finishing the CAD, I asked a mate to print it on his resin printer. Turned out pretty well: Compared to the 1/1: Now on to the rest of the beast:
I've been posting this on ARC, but figured I might as well cross-post over here since the Britmodeller crowd is a little less jet-centric. Okay, so yes, I am scratchbuilding a 1/144 Zeppelin. LZ66/L 23 - a Q-Class Zepp - to be specific. Why this particular airframe? Because it was shot down by Lt. Bernard A Smart flying a Sopwith Pup, which I also intend to model. It should add an interesting story to the model and give a better sense of scale - you don't really realize just how massive the Zeppelins were until you see that iiiiiitty-bitty airplane beside it. In 1/144, it's about 4' long, 20" around. More than six square FEET of filling and sanding. Ask me how I know. I had briefly considered doing them both in 1/72, but the Zepp would have been 8' long, almost a foot in diameter, and I'm not quite that insane. (but, ohmygod would it would be sooooo awesome!) The build has its roots in a paper model designed by Thorsten Brand. http://jleslie48.com/zep/model_parts/Pclass_description.pdf http://jleslie48.com/zep/model_parts/ His model is a P-Class; the Q-class was a revised design that added an extra cell to the balloon for an increased payload and ceiling. My primary reference is actually just his P Class Description PDF. I ended up re-drawing everything in CAD for my plastic version. My basic game plan was fairly simple: Make a bunch of bulkhead sections (ribs) along the appropriate station numbers. Align these along a central spine, with reinforcing spars closer to the surface, then skin the whole shebang with styrene sheet. Step 1 in this whole process was to draw the balloon's profile in Solidworks. Thorsten's profiles list the station numbers (in metres), and the cross section shows the basic proportions. Dividing the profile into individual stations gave me the cross section at each location. I sketched out the cross section in CAD, then re-sized it to fit the height of the envelope at each station. For most of the balloon, this was a simple copy/paste/resize; at the back, I had to make some tweaks to match the tailplane geometry, where some facets blended out. The final step for the bulkheads was to add my spine and spar markings. A suitably sized layout was sketched (1/8" spar holes, 5/8" square spine), then copy/pasted in the middle of each bulkhead. I also took the time to make a sort of 'ruler' - a big ol' rectangle with the bulkhead stations marked off, eliminating the need for fiddly measuring come assembly time. With my 36 bulkheads sketched out, I now had exact widths of each skin panel at each station. By lining these up with the correct station spacing and going back to my profile, I was able to chop the profile into individual station sections and measure the exact length of the full skin panel, accounting for the projection - one of the handy features of Solidworks. This allowed me to set the bulkhead spacing accurately for the skin; it might be 5 scale metres between station 1 and 2, but because of the curvature it's 7 linear metres of skin (for instance). By plotting the width at each bulkhead, and the (actual) distance between each bulkhead, I had a guide for the skin outline. Then it was a simple matter of connecting the dots; using Soliworks' 'snap spline to points' feature gave me the exact curvature needed. This provided a 'master' skin panel, which was copied, pasted, and then it too was tweaked to match the tail geometry. It also gave me exact locations for each bulkhead, allowing precise location on the model. The last step was to trim off the tips of each skin panel. Aligning these perfectly would be a hassle, and I had other plans. Now, line up all 19 skin panels (in the correct order!), and the covering template is done. (profile for deriving all those measurements at top, finished skin below. The rectangle just above the skin segments is my spine template - just line the bulkheads up with the lines around the spine. The vertical lines on the skin sections again show the bulkhead locations.) The final step for the envelope was to make tailplane templates. This was a simple matter of tracing over Thorsten's drawings in CAD, then ensuring they were the correct scale dimensions. Templates finished. I also duplicated each bulkhead - I was using .020" styrene sheet - good for the flexible skin (and easy to cut), but a little flimsy for the skeleton. Doubling it up to .040" would give more rigidity. Next came print prep. The CAD templates were laid out and saved as .DWG files, then opened up in Illustrator (Illustrator won't open CAD files directly). My first step here was to offset the edges of the bulkheads, to account for the thickness of the skin. Next, I filled in the skin, bulkheads and tailplanes to give me precise cutting lines: cut right along the edge of the part (rather than somewhere in the middle of each line). Finally, the layout was tweaked to fit on 4 x 3' sheets and saved as PDF files, ready for printing. TL;DR: Math. Just lots of math.