Neil_W's half-baked design thread

Discussion in 'Scratch Built' started by neil_w, May 8, 2017.

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  1. Jan 2, 2020 #961

    mbeels

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    Happy New year to you as well!

    Oi! I really like it! I like how the angles of the fins reflect the angularity of the transitions.
     
  2. Jan 2, 2020 #962

    kuririn

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    If it came from the same species as the Alien Invader, shouldn't the fins be more curved with cutouts?
     
  3. Jan 2, 2020 #963

    neil_w

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    Yes, which is why this design (so far) is definitely *not* that rocket. I started off thinking "Alien Invader" and ended up with a rocket with a bunch of sharp angles.
    :facepalm:
     
  4. Jan 2, 2020 #964

    neil_w

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    Maybe could start with something like this instead for the "real" Alien Dreadnought?

    upload_2020-1-2_11-21-20.png

    Never mind availability of suitable plastic nose cones to hack up.
     
  5. Jan 2, 2020 #965

    kuririn

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    Personal preference: I like my rockets curved.
    Just like my women. (Old politically incorrect joke).
     
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  6. Jan 2, 2020 #966

    neil_w

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    Brings to mind an even more politically incorrect joke from Airplane, which I shall not quote here. :)

    I've certainly done my share of curvy fins but sharp angles are fun sometimes as well. But for sure, an Alien Invader spinoff must be curvy.
     
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  7. Jan 2, 2020 #967

    BABAR

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    On a different thread, people were talking about the origin of the term "grain" for high powered motor segments. Grain being distinguished from vegetables (non seed part of plants) and fruits (which are ripened ovaries.) Your congoining white tail piece kind of looks like a ripened ovary.
     
  8. Jan 2, 2020 #968

    neil_w

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    Aaaaaaand there goes that one. :(
     
  9. Jan 2, 2020 #969

    neil_w

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    By accident I made invisible fins in OR.
    upload_2020-1-2_17-20-4.png
     
  10. Jan 2, 2020 #970

    kuririn

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    Hey, I think you've found a way to show clear fins.
     
  11. Jan 2, 2020 #971

    Tobor

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    Okay, I'll bite...
    How did you do that?

    On a side note. On New Year's Eve, I was fiddling with a rocket in OR's 3D view. I accidently did some combo of consecutive left and right most clicks which then allowed me to drag the light source. It was neat being able to change the orientation of the rockets shadows and such. So, my question is, did I discover an undocumented feature, or did I uncover a bug?
     
  12. Jan 3, 2020 #972

    neil_w

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    I have no idea. Well, actually I do, but I haven't tried to verify it. It's not very useful, but interesting nonetheless. :)

    Feature. Click and drag the right mouse button to move the light source.
     
  13. Jan 3, 2020 #973

    Nytrunner

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    Thats glare flashing on two fins 180 apart right?
     
  14. Jan 3, 2020 #974

    neil_w

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    Not glare I think, it seems that the edges are visible but not the surfaces.
     
  15. Jan 3, 2020 #975

    jqavins

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    My suggestion is this: keep the back side small.
    1. Go back to the starting point.
    2. Run the two side tubes all the way through the bulge and cut them flush on the forward side. These will be tube fins for pitch stability.
    3. Add four elliptical fins perpendicular to the plane of the plane of the three tubes for yaw stability. They might be nestled in the tube valleys (my first thought) or standing up (and down) on (under) the outer tubes.
    I like the guns on the forward part of the aft bulge, but they should be pointed slightly outward so they're not aimed at the forward bulge. Similar guns can be placed on the aft part of the forward bulge, while parallel guns are placed on the forward-forward and aft-aft parts. And then some more, smaller ones on the tube in between, pointing perpendicular to the axis, so the whole thing is positively bristling with fire power. You did say "Dreadnaught", didn't you? Enemies should dread facing it.
     
  16. Jan 6, 2020 #976

    neil_w

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    I believe this is buildable if one is sufficiently motivated and/or masochistic. I think it might even fly.
    upload_2020-1-6_9-14-23.png
     
  17. Jan 6, 2020 #977

    jqavins

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    I'm sure it could be made to fly. And it's probably not even that hard to build, with a straight central tube and a bunch of eccentric rings (i.e. not-exactly-centering rings). And yes, I use the word "eccentric" advisedly.
     
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  18. Jan 6, 2020 #978

    neil_w

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    Only two hard parts that I can think of would be:
    1) Attaching a new shoulder at an angle to the nose cone (or just 3D-print it and call it a day, but I like hacking balsa).
    2) Attaching two of the fins (shown in the picture pointed at and away from the viewer) at a rather severe cant on the fin can.

    My original vision for this rocket had a smaller number of jagged cuts between the tubes, and another jagged cut through the fin can including the fins, which could be cool. Theme was going to be something about tectonic fault lines. Couldn't be bothered to try to render that given my limited CAD skills though.
     
  19. Jan 7, 2020 #979

    afadeev

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    I would add:
    3) Plumbing ejection gasses to the nose cone to pop the chute.

    If you add a central body tube to nest the segments, it will solve the structure integrity, MMT, and ejection charge issues, as well as problem #1.
    It would, however, add a requirement for a lot of custom offset centering rings. Which could be fun to design and spec, but way less fun to fabricate.

    With the number of open cylinders acting as de-facto fins, I wonder if the aft fins are at all necessary.
    I also wonder where the CP for this model will end up, and if OR calculates it correctly.

    a
     
  20. Jan 7, 2020 #980

    neil_w

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    As designed in CAD right now it has a stuffer tube running top to bottom. Each offset segment touches one side at the top and the other side at the bottom. Therefore there would be no airflow through them. Actually the offset centering rings would block off airflow as well.

    Those rings would be a laser-cutter job for sure, even *I* wouldn't dare to hand-cut all those things. :)

    I would just model this as a 4FNC, maybe with a larger equivalent BT diameter. Then a "heads-up" launch. :D

    [EDIT: To be clear, I will not be building this rocket under any circumstances; discussion is purely academic. It'd be fun if someone did though]
     
    Last edited: Jan 7, 2020
  21. Jan 7, 2020 #981

    BABAR

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    Gonna need bigger fins.
     
  22. Jan 8, 2020 #982

    jqavins

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    One could make the four fins in four different shapes too. Or the same irregular quadrilateral shape, but each with a different edge as the root. Cut them all with their proper grain orientations, but underneath paint no one can tell.
     
  23. Jan 27, 2020 #983

    neil_w

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    I've been doing some planning work for the Blackfish build. It's pretty straightforward but with a few wrinkles, mostly involving the pods and those stupid (but nice looking) rings on them. Anyway, I tried a color change so I could use the same paint I'm using for the Skywriter:
    upload_2020-1-27_8-58-45.png
    Looks OK, but the white lettering doesn't contrast against the Golden Sunset as well as it does against the orange.

    I then realized that those color-matched noses on the pods are incredibly annoying from a painting point of view (they are the only place where that color paint would be needed.) Just yesterday I was commenting on a gallery thread about how a face card color scheme should never force the builder to color-match a paint to the decals. I would love to take my own advice here, but I haven't liked any alternative decal-only design nearly as much as this one. Suggestions welcome. Note that the pods are almost 100% nose and tail cone; there's only .5" of BT5 connecting them, and much of that is hidden under the ring. So any decal scheme would need to be compatible with application to the compound curves of a nose cone.

    I'm also a bit worried about survivability of the pods on landing. The tail cones really stick way far back, and *will* take a landing impact. But having already purchased the nose cones for it, and really liking the appearance, I'm reluctant to change. Very strong mounting to the fins will be a requirement, but it'll have to be a surface mount.
     
  24. Jan 27, 2020 #984

    mbeels

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    I like the pods, they are what really makes the appearance of this rocket interesting and unique. Do they have to be surface mount, though? Could they be all-the-way-through-the-wall mounted? As in: through one side of the pod, and glued to the inside of the other side of the pod. That would allow for at least a fillet on the inward side, and a surface joint on the interior of the outward side.
     
  25. Jan 27, 2020 #985

    neil_w

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    The pods will be solid balsa is the problem. I'm going to have to cut each shoulder down to .25" so they'll fit back-to-back in the .5" BT5. Cutting a slot through the finished assembly would allow for an incredibly strong mount, but I don't know how to cut a slot like that, at least not with sufficient accuracy. Any ideas?
     
  26. Jan 27, 2020 #986

    afadeev

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    You need either a completely different contrasting color for the lettering (red?), or reverse fading of the letters to preserve contrast: yellow letters on black background (front), fading into black letters on yellow background (aft) ?


    A decal on a compound curve would be EXTREMELY challenging.
    You could, however, just dip the tips of the pods into trays of yellow paint. That would give them nice contrasting (Rudolph-style) noses, with minimum complexity.

    Alternatively, and if you really want to go nuts, you could insert blinking LEDs into the nose-cones of the pods, and change the contrasting color hues based on the time of the day/night, your mood, or artistic preference du jour.

    Then they *will* detach ;-)
    If you glue them really well to the fins, they *will* detach together with the fin that takes primary landing impact. Maybe make them detachable on purpose, via some clip-on attachment mechanism?

    Alternatively, you could source FG fins, and epoxy pods to the FG main fins, and TTW fins to the body.
    This will make it tail heavy, but strong enough to survive any landing (could just fly on a streamer, then ;-).

    a
     
  27. Jan 27, 2020 #987

    neil_w

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    Some thing are not bad but you could definitely not color the tips that way.
    I do not. :)

    “Thank you”.

    That’s an interesting thought.

    Seems I have two choices: try make them (along with the fins) extremely strong, or else make them detachable or even breakaway.

    Must think about this.
     
  28. Jan 27, 2020 #988

    mbeels

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    Ah, I see, that is trickier. If I were to attempt it, perhaps this is how I'd go about it. After cutting down the shoulder to 0.25", and before gluing anything, cut notches into the nose cones. Most of this cut would be with the grain, the bottom of the notch could be cleaned up with a square file. Then, cut out the width of the fins from the 0.5" long BT5. I'm not sure how long I'd make the tabs, somewhere between 0.5" and tip chord of the fins.

    But the new breakaway idea is an interesting one....
     
  29. Jan 27, 2020 #989

    neil_w

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    Great minds apparently think alike; I had a nearly identical thought after my last post. The only tweak I would make is that I would keep the slots (and the fin tab) confined to the .5" shoulder area; I'd rather not be messing up the exposed part of the nose.

    If I then made those fins from basswood, I'd have a pretty strong assembly. Strong enough to survive a landing? That would remain to be seen. :) I'll have to see if I can afford the extra weight back there.

    The fins of course *will* be TTW in mounting to the airframe.

    It's also a pain, and would mean having to go looking for at least one pod after each landing.

    I wish I could think of a way to change the design to make it less vulnerable, but I don't have any ideas at the moment. Certainly, there have been plenty of rockets with pods out the back, maybe I'm worrying a bit too much.
     
  30. Jan 27, 2020 #990

    mbeels

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    I bet the rocket will be fine, you've got a nice grassy area to launch with a very soft surface. (Although Alcubierre has suffered some damage)

    A design change you could consider is rear eject, that would bring it down nose first. And also let you have a seamless front end.
     

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