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Pat Sparks BOMARC Build


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OK, the latest update, and the last one on the tail - I promise!


The first thing I did was take the previous print, and add a million effing supports:




I also laid out some spare empennage parts, just in case...


...but finally, I had complete success!






Sadly, though, the part turned out undersized!




How the George C. Scott that happened, I have no idea. But both the prints I did vertically are the same, whereas all the angled prints are the larger size. I can only assume that I got the scaling wrong for the last two prints. I'm not printing it again, however! Instead, I'm going to take the spare empennage parts I printed, and graft them on to the best of the previous prints.


Just the engine parts to go now (along with the launch tower).


Stay tuned!



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I'm pleased to report that the engine parts were (mostly) a great success!




It wasn't until I'd removed all the supports that I realised the central cone thingies came out a little warped:




I'm hoping that I might still be able to use them, since the warped sections are hidden inside the engine nacelles anyway. But lots of clean up work to do to find out!


I'm so glad Pat posted this image in his own thread, though:




Otherwise, I'd have no idea how these parts were supposed to go together!


Right, I'm off to do some sanding...



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Well done Kev. You are the master of perseverence.

A tough lesson but a valuable one going forward. 

Now you can choose to overdo the support points on future models if necessary which might prevent further failures.

Very much looking forward to seeing this all come together now.

Don't forget.....wear a mask ;)^_^:clap2: 


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Thanks, Guy. First and foremost I'm doing all this because Pat asked me to, so that he could see his designs materialise. But I also took it on as an opportunity to return to the 3D printing fray, and really try to work through the process and get past all the failures I was having. I'm not quite there yet, but I certainly feel like I've accomplished something. And while I now have all the basic parts to finish the BOMARC build, I still have to print the launch tower, which itself is quite a few components - so plenty more opportunities to hone my skills yet!



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Satisfied that I can use the parts I've printed so far to assemble a complete BOMARC missile, I've now moved on to printing the launch tower. This has quite a few parts, and I'm expecting to have quite a few failures, but I'm sure I'll get there in the end! Photos in due course.


Looking beyond that, I'm starting to think about how I might paint and finish this beast, but am not having much luck narrowing down a paint scheme. From what I can tell, early production examples were painted overall black with white extremities and silver areas on the fuselage. I'm not convinced I prefer this scheme, but am having trouble pinning down an alternative. Museum examples mostly seem white or grey, but no two are the same. In the absence of anything definitive for an alternative, I'll just do the black and white one, but would like to explore other options.


Anyone got any info?



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I've started working on fitting the separate tailplane pieces to one of the earlier tail prints where these elements had failed:




Pat had designed in some shallow holes for pinning purposes, but they didn't exist on the main tail section, as this was a complete unit that wasn't designed this way. So I drilled a corresponding hole for the rudder tip, deepened the one on the tip part, and cut a 3mm length of brass tubing to act as a pin. The only suitable drill bit I had was slightly undersized for the task (or conversely, the only length of brass tubing I had was slightly oversize), so I've had to force the fit a bit, and it's not particularly solid:




I also managed to get one of the holes slightly off centre, but it shouldn't be too noticeable on the finished model. I just need to repeat this process for the two tailplane pieces now.


In the meantime, here are the first set of prints for the launch tower:




They mostly came out OK, and certainly usable. Except for this part:




There's the one obvious wobbly bit, but there are a few more that you can't really see in the photos, so it's not usable, unfortunately.


If anybody's got any advice on how best to support an object like this for printing, let me know! For the record, this is what I went with:







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I've now completed the work on the tail section, but made a bit of a hash of it, and am not really happy with the results.




It's difficult to see in the photo above, but I managed to pin the tailplanes a fraction of a millimetre too far forward, and the leading tips are no longer perfectly aligned with their root fairings on the tail itself. The angle of the photo hides it a little, but it's really obvious to the naked eye. At least it's consistent on both sides!


I also made a bit of a mess on the port underside, with the drill bit shattering the brittle resin when it became too thin:




I've tried to patch it up with some black CA (the BSI stuff is the bomb!), but I'm not sure it's ever going to look good.


On top of that, I had the resin shatter while deepening the hole atop the fin, too, and the result is also a bit of a mess:






So while my plan was good, my execution left a lot to be desired (you'll notice that the tip of the lower rear-facing probe has also snapped off). And while I could probably patch it all up so that it's not really noticeable, the great benefit of 3D printing is that I don't have to! I can just print another one, so that's what I've decided to do. Had the previous one not been undersized, it would have been perfect, so I'll just try again, but with hopefully the correct scaling this time. After all, that's the point of the exercise! I am running out of printer resin, though...





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Well, it's not perfect, as there's some layer shifting in the lower (forward) portion of the outer tips, but nothing that won't sand out. The probes on the tailplanes are also slightly wobbly, so I'll either live with them, or graft a good set in from one of the other prints. I'm a bit leery about doing that after the previous experience, however!


In the photo below, you can just make out the layer shift:




And of course, lots of clean-up to do!




I used a mixture of light and medium supports, and probably should have mostly used the heavy variety. Overall, it's not as good as the one that came out undersized, but better than my Frankenstein version. Best of all, though: I finally feel like I'm gaining some semblance of control over the process.



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Watching your trials and tribulations had me contemplating the break down of IM kits.

Whereas the 3D print is a very large, complex chunk, IM manufacturers would create frets/trees/sprues of components that could be assembled to make the whole. 

Has anyone considered creating sprues of 3D printed components to avoid the failures often seen on large, time consuming prints I wonder?:hmmm:

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Thanks, fellas. These parts are indeed difficult to print, with many conflicting angles that defy simple support configurations. And unlike large miniatures with complex surface details, these angular, geometric shapes demand a higher level of printing precision and accuracy, which also increases the degree of difficulty. As far as configuring them with sprues, though: well, they'd have to be supported too!



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sprues as a necessity in injection moulding, as this is the way the hot liquid plastic is directed towards the parts.  It requires considerable design knowledge with regards to heat & cooling to make it work.

3D printing on the other hand is a bit like the printers of old - a layer is printed, then the bed moves up/down (depending on the type of printer) and a new layer is printed on top of that.  The supports on 3D printing are exactly what their name implies - supports for the freshly printed (overhanging) parts,  This support is needed because the hot plastic is cooled naturally (where cooling the injector moulds is done with fluids, hence much faster)

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19 minutes ago, Gazzas said:

Very nice. Kev.  I didn't know you had started the voyage into 3d printing.


Yeah, quite a while ago, actually. Had some early successes, but then reality set in, and I got frustrated and walked away from it for a few months. This project is not only my gateway back in, but also a terrific opportunity to learn and get better at it. I still have a 22" Eagle Transporter to print!


But here's a bit of a potted history of my output:










And these, waiting for paint:





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