Plasma Dart II Build Thread

Discussion in 'Scratch Built' started by neil_w, May 28, 2019.

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  1. Jun 30, 2019 #151

    mbeels

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    Make it a feature somehow, maybe put some detail there like a small vent, or light, or plasma fill cap....
     
  2. Jun 30, 2019 #152

    Nytrunner

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    That's the top fin now. since it's asymmetric
     
  3. Jul 1, 2019 #153

    neil_w

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    Top fin is already assigned as the one opposite the launch lug... fortunately, that was the one I screwed up. So it is indeed top.

    I did a last (actually, first) dry fit, and now she's ready for paint. Some rather unaccommodating weather is coming up, so this could take a while.
    final dry fit.JPG
     
  4. Jul 1, 2019 #154

    jqavins

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    Wrong. You are not no one.

    That too.
     
  5. Jul 1, 2019 #155

    neil_w

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    Fair point! :)
     
  6. Jul 2, 2019 #156

    neil_w

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    I had a near-disaster tonight. Faced with an unexpected painting opportunity after work, I laid down a coat of primer and put the rocket into it's drying rack in the shed. A moment later I hear a crash and see that our beach wagon, which was not in its usual spot, had slipped down and crashed right across the rocket. Expletives were uttered at high volume.

    Fortunately, it appears as if the only damage is that one of the antennae broke; that should be easy to fix. The paint is messed up in a couple of spots too, but no biggie. I'll let that coat dry, and then sand down as necessary and start again. Could have been much worse, but I did just lose a week or two of my painting schedule. I'm glad it happened after only the first primer coat, when starting again is easy.

    OK, maybe on every build I have to make *two* boneheaded mistakes...
     
  7. Jul 2, 2019 #157

    Bruiser

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    Sounds like something that would happen to me. I feel for ya, my friend.

    -Bob
     
  8. Jul 5, 2019 #158

    neil_w

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    Absolutely amazing that this was the only damage, other than a few areas where the wet primer got marked up.
    damage.JPG
    The antenna spike glued right back on with no issues. It probably won't be quite as strong as before, but under normal circumstances it shouldn't be experiencing any stress or impact. Just a bit of primer sanding and she's ready to go again. I'll probably add one more light coat of primer before my gloss base coat.
     
  9. Jul 5, 2019 #159

    neil_w

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    Creating this fin design with a combination of paint and home-printed decals requires some thought.
    upload_2019-7-5_11-41-36.png
    (Also I'm still not sure if the antenna spike should be white or black.)

    The final decal artwork will of course be much higher resolution.
     
  10. Jul 5, 2019 #160

    Nytrunner

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    I dont see any coat hangers, so I think you're doing alright
     
  11. Jul 5, 2019 #161

    neil_w

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    Too soon :eek:
     
  12. Jul 5, 2019 #162

    neil_w

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    Balsa Lamination Test Update

    Some time back I laminated two pieces of 1/16" balsa to check strength vs. other materials. I haven't done any formal strength test, but I did cut a bunch of test pieces:
    testpieces.JPG
    Note I cut two each of 3/32" and 1/8" balsa so I could paper one piece of each and compare to un-papered. haven't gotten there yet.

    Anyway, in lieu of formal test results (for now), here are some subjective impressions:
    1) After further consideration, the 2-ply piece doesn't feel too much different from the 1/16" piece, against the grain. The 3/32" is notably stiffer, and the 1/8" is in a completely different league.
    2) The 1/16" basswood feels about the same as the 3/32" balsa.
    3) Although the 2-ply laminate doesn't feel particularly strong in, it is equally strong in all directions, so I was able to cut the piece in the lower right with no problem. This is a fin that would normally need to be a 2-piece.

    So, if the 2-ply balsa isn't actually that strong, is it useful? I'm not sure. If definitely does open up the possibility of making one-piece fins, rather than piecing together jigsaw puzzles like I usually do. With regard to flight performance, solid balsa is clearly stronger against the grain, but even a complex multi-piece fin with highly optimized grain direction will have some flutter forces that apply in its weakest direction(s). So a fin that is equally strong in all directions might conceivably outperform (or at least equal the performance of) fins that are stronger in their strongest direction.

    At that point, I don't know how to go any further, because I can't realistically do any tests, short of building rockets with the laminate and pushing them until I find the "speed of laminated balsa". I admit there is some appeal in doing that (just a simple 3- or 4-FNC with a 24mm mount). If I flew more often, it'd be fun to do, but since my flying opportunities are few and far between, it's probably not what I would want to spend my time on.

    Anyone want to take up the mantle?
     
  13. Jul 8, 2019 #163

    jqavins

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    Maybe, but I've already gone one science project in the works.

    There was a suggestion earlier to support each sample by two ends and load it in the middle to failure, seeing both the breaking strength and the deflection relative to load before failure. If you don't have calibrated weights to add, you could use a small scale as the support for one end (and remember that the scale is reading half the actual weight, assuming the load is well centered) but for comparing one against another that doesn't really matter.
    They're antennae, so metallic.
     
  14. Jul 12, 2019 #164

    neil_w

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    After getting a first pass of my decal sheets ready, I did a test print and a fairly complete test fit:
    decaltest2.JPG
    This proved to be a useful exercise. In addition to giving me a sort-of-preview of the finished rocket, I found a few things I need to change and also learned what a challenging job this is going to be. Lots of custom-fitting, particularly for the fins. This is gonna take a few days I would guess.

    If nothing else I am *very* happy with the fit of the cockpit. :)
     
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  15. Jul 12, 2019 #165

    Nytrunner

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    Love the warp core. The rocket does look slick
     
  16. Jul 12, 2019 #166

    mbeels

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    Wow, that looks great. Has all the damage from the fall been repaired?
     
  17. Jul 12, 2019 #167

    neil_w

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    Pretty much. The broken antenna spike was really the main thing; there's a little bit of roughness in the area of the fix but not too bad. After doing my decal fit I laid a bit of medium CA into the rough area to fill it and reinforce the area. I think it'll be fine.

    The original primer coat was marred in a a number of areas; that was fixed with some sanding and a second coat of primer (and some more sanding). The primer coat is still not even in those areas but I don't really care; usually I don't apply primer at all (beyond the filler/primer) so anything that's there is a bonus. :)

    I did notice when fitting the decals that my repaired antenna points away from the center core a bit; not much I can do about that but also no biggie.

    Biggest challenge right now is finding opportunity to paint. Very humid stretch of weather. Tonight would have been perfect (have the house to myself) but it was pouring rain. *sigh*
     
  18. Jul 12, 2019 #168

    neil_w

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    Pondering a slight decor change in the rear.
    upload_2019-7-12_11-17-47.png
     
  19. Jul 12, 2019 #169

    mbeels

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    Hmm.... I think it will depend on what background it is viewed against. With the white image background, I like the top decor, but perhaps against blue skies or green trees, the bottom will contrast better.
     
  20. Jul 12, 2019 #170

    neil_w

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    upload_2019-7-12_11-23-54.png

    Yeah, I know the top is probably better, but the bottom would be somewhat easier. ;) Figured I at least needed to have a look.
     
  21. Jul 12, 2019 #171

    BABAR

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    Since your designs are both artwork AND engineering, the above kind of begs the question, "What is the background you are designing FOR?"

    Unless you are building for others, like Chris Mitchelson (@hcmbanjo), I am guessing you personally are going to be the person seeing this rocket the most. So are you designing it to be flashy on the pad, on the shelf, in the display case?
     
  22. Jul 12, 2019 #172

    neil_w

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    Well, it'll be seen in multiple contexts (the field, the air, my basement), but OR doesn't represent those options. Easiest screenshot is from the main window with white background. So that's what I usually work with, except for the occasional predominantly white rocket where I'll darken the background to show contrast better. But I'm just generally flinging ideas around; in many cases I just experiment with stuff and then try to assess. After staring at it for so long (i.e., months) I often lose my bearings.

    Earlier I was cleaning up my files and looking at a lot of discarded variations of this rocket. In at least three cases I said "that looks good, why didn't I build that?" but at the time I had a reason, even if I can't remember what it was. :rolleyes:

    There are good reasons why I don't do this for a living. ;)

    (BTW: it's "Michielssen", and yes it took me a while before I could type correctly that without referring back to his website)
     
  23. Jul 12, 2019 #173

    Nytrunner

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    Black is still the old and new black
     
  24. Jul 12, 2019 #174

    kuririn

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    Your rocket. Do what feels right. Yeah, you might feel different a few months down the road, but nothing you can do about that.

    OR.....

    Build two rockets.:D
    (FWIW I like the black trim and gradient between black and white on the fins).
     
  25. Jul 12, 2019 #175

    neil_w

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    To cover all the bases on this one I'd need to build about 10...
    I think I must concede that it is very hard to prefer the white edging over the black. I'll stick with the original plan. Just need to do more masking. :)
     
  26. Jul 13, 2019 #176

    neil_w

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    Got what looks like a better-than-average (for me) white base coat on today. No mishaps! I continue to beat the odds using Rusto 2x gloss white.
    white_paint.JPG
    (no, the rocket is not sitting in the grass, though it looks like it in the picture).
     
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  27. Jul 14, 2019 at 1:27 AM #177

    lakeroadster

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    Neil... your rocketry inspires me. Thanks for your detailed documentation, and your attention to detail.
     
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  28. Jul 14, 2019 at 2:27 AM #178

    neil_w

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    Thanks for the kind words. I am sincerely grateful that anyone is interested in following along on my long rambling builds. Without this forum I wonder if I'd even stick with rocketry at all, because no one I know in real life gives a crap about any of this. So it goes!
     
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  29. Jul 14, 2019 at 2:40 AM #179

    Nytrunner

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    And thatd be a shame as you've made some real craftsman's pieces over the years. You've got to stick with it till I have my L3 after all.
     
  30. Jul 14, 2019 at 2:44 AM #180

    neil_w

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    Don’t worry, you’re all stuck with me for a while. :)
     
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