Triple Vee

Discussion in 'Scratch Built' started by jqavins, Oct 17, 2019.

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  1. Oct 17, 2019 #1

    jqavins

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    jqavins

    Joseph Avins TRF Supporter

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    I've been pushed into starting on this: The design isn't really finished and I"m open to suggestions. This thread will be an open forum for ideas for a while and then will morph into a build thread.
     
  2. Oct 17, 2019 #2

    mbeels

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    It seems to me like a good candidate for through the wall fins, that interlock with each other. From the file it looks like they could pass tangentially against the motor mount tube. The body tube could be slotted all the way to the bottom to slide over the fins, and the centering rings could butt up against the fins, one on top and one on bottom. Just thinking aloud how I'd approach it.
     
  3. Oct 17, 2019 #3

    jqavins

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    Joseph Avins TRF Supporter

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    Nice idea, for next time. For this one the fins as shown are part of what I've already ordered.

    For next time, if one does the math right one could use the internally formed triangle to support the MMT within a custom rolled BT, no centering rings necessary. A forward one would be needed as a bulkhead if one would use motor ejection. Still, the back end could be left open to show the structure.
     
  4. Oct 25, 2019 #4

    jqavins

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    Joseph Avins TRF Supporter

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    OK, some progress. First, I decided to extend the V motif all over the rocket. The paint job will involve upward and downward wedges and the nose cone will have a V-shaped waste.
    upload_2019-10-25_12-40-53.png
    Also, I'll use a two motor cluster, canted to form another V. I did the calculation for the angle between two BT-20s, tangent to each other at the forward centering ring and tangent to the BT-60 body tube at the aft ring, the rings 50 mm apart. I got only about 3½°. So I might want to go up to BT-80 and/or push the rings closer together.

    I won't get to do all that in RS until at least Monday, so pictures on or after Tuesday.
     
  5. Oct 25, 2019 #5

    neil_w

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    This thread reads as if it's starting in the middle of the conversation. Which design is this?
     
  6. Oct 25, 2019 #6

    mbeels

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    See Joe's link in his first post, he started a build thread for the Triple Vee that he introduced in his half-baked thread. I think that makes "half-baked threads" a thing here.
     
  7. Oct 25, 2019 #7

    neil_w

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    Thanks, I completely missed that link up top. That is why I got in the habit of bold-facing all my links (actually that was original a suggestion by Gary Byrum, which I decided was a good one).
     
  8. Oct 26, 2019 #8

    jqavins

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    Joseph Avins TRF Supporter

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    Not a bad idea.

    And it's not my half naked thread. It's everyone's, except Neil. ;)
     
  9. Oct 26, 2019 #9

    neil_w

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    Ummm...
     
  10. Oct 26, 2019 #10

    jqavins

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    Joseph Avins TRF Supporter

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    Uh, yeah. Well, it's not that either.
     
  11. Oct 26, 2019 #11

    mbeels

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    Boy, a few minutes after 5 pm on a Friday, and this place gets a little (or a lot) wilder :)
     
  12. Oct 26, 2019 #12

    kuririn

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    Looks like a Very Visionary, Viable, and Versatile design.:D
    As for the motor tube nesting between the "triangle", are you sure you're not related to Jim Flis?;)
    His Whatchamacallit, Doodad, and Thingamajig have what he calls "fin jig" technology.
    Automatic alignment and centering of the tube.
    Maybe long lost son?:p
     
  13. Oct 26, 2019 #13

    kuririn

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    I thought we were talking about baking?
     
  14. Oct 26, 2019 #14

    jqavins

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    Joseph Avins TRF Supporter

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    And what's wrong with baking while partially undressed?
     
  15. Oct 26, 2019 #15

    kuririn

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    That could be...………...painful.
     
  16. Oct 28, 2019 #16

    SDramstad

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    especially bacon.......
     
  17. Oct 28, 2019 #17

    jqavins

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    Umm, yeah; anyway...

    More pictures tomorrow as promised. Until then, this thought: the name I've chosen, Triple V, naturally puts me in mind of Guy Fieri's Food Network shows, which he refers to as "Triple D" (for Diners, Drive-ins, and Dives) and "Triple G" (for Guy's Grocery Games). So I though I might pack a Guy Fiere bobblehead inside on his own little parachute.
     
  18. Oct 29, 2019 #18

    jqavins

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    BT-80 upsize complete. I didn't need to lengthen it or increase the fins size at all for stability, due to the added weight of the scaled up solid balsa nose. I like the L/D look better this way. I may still want to bump up the fin size as they are not so visually prominent as they originally were; the fins are the point here, so I certainly don't want them to seem understated. Opinions?
    Triple_Vee_BT80.jpg
    The blue in the main length of the body tube is supposed to be the same as the blue between the fins. One is the RS built-in color and the other is an applied texture. In their respective programs they have the same color (0,0,255) but then RS treats them differently. I haven't got a tenth of the experience using textures that it would take to fix this. (What I'll probably have to do is redo the texture graphic to cover the whole tube and not use the built-in color at all.) So for now please use you imaginations to see the blue fin can blending seamlessly into the blue wedges.
     
  19. Oct 29, 2019 #19

    neil_w

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    I agree the fins look much too small there. Weird about the blue.
     
  20. Oct 29, 2019 #20

    mbeels

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    I like the V-shaped waist in the nose cone, and I like the idea of the twin canted cluster (a-la Deuce's Wild). I also think that the fins could be a larger. Even if they're not needed for stability, it would further help the appearance.

    I haven't played around with textures or colors much in Rocksim, but I think I recall that there were two coloring options, one was the base color of the material, and the other was something related to the lighting, so it changed the reflected highlights. It kind of looks like Rocksim is using a different color lighting for your texture.

    Do you have a plant yet for how to make the V-shaped waist in the nose cone? Turn down a balsa cone?
     
  21. Oct 29, 2019 #21

    jqavins

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    Joseph Avins TRF Supporter

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    Yeah, the lighting stuff is sufficiently complicated that I've never wanted to take the time to master it. And I'm sure that's somehow the root of the problem.

    The nose cone will be turned on a lathe, either from a cone to start with or, more likely, from a block of balsa. I think. It might be feasible and less expensive to make it out of three off the shelf pieces, a cone and two transitions, just as it's built in RS. I'll have to do some investigating.

    And it sounds like we're agreed on upsizing the fins. That'll let me core out the nose and reduce the weight, so it may well result in a performance improvement.
     
  22. Oct 29, 2019 #22

    Nytrunner

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    Triple V sounds like it needs three motors
     
  23. Oct 29, 2019 #23

    mbeels

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    Yes.... yes it does....
     
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  24. Oct 29, 2019 #24

    jqavins

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    Damn you, sir! Now I have to do another redesign.
    upload_2019-10-29_15-21-19.png
    That puts about 28° between the tubes if the rings are 40 mm apart. Which is not a whole lot less of a V angle than I get with just two.
     
  25. Oct 29, 2019 #25

    neil_w

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    That would be très bien.
     
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  26. Oct 29, 2019 #26

    boatgeek

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    I would guess that Rocksim/OpenRocket won't full capture the drag of the V notch in the nose cone. I don't have anything to back that up, it just looks like a spot where unpleasant drag will happen that is hard to account for numerically. Assuming that's accurate, I'd want to fly on a healthy stability margin to reduce chance of surprises. I'd personally shoot for 2 calibers, but I fear weathercocking a lot less than skywriting. Also, it's not like this is optimized for high performance. :)

    I'm also in favor of three motors. If nothing else it makes all of your fins the same as they all either hit or miss the motor mounts the same way. Naturally, this comes with thoughts about reliability and flight under 1 or 2 motors if you have ignition failures.
     
  27. Oct 29, 2019 #27

    jqavins

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    Joseph Avins TRF Supporter

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    All the fins are the same no matter what, as they do not go through the wall. Reliability is an interesting question, as getting one failure out of three is (obviously) more likely than one failure out of two, but then getting at least two lit is also more likely.

    When I was working on it last night I verified that one (discontinued) Aerotech D10 can lift the rocket with a dead D10 next to it, and if I remember right there was plenty of margin even to lift two dead ones, but I wasn't really looking at that. I think two out of three C6s should be fine, but I'll have to confirm later when I'm home. Less than C6s may not be a good idea.
     
  28. Oct 29, 2019 #28

    neil_w

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    I had similar v-shaped transitions on the Diamond Cutter, certainly it flies fine although I haven't been able to verify the accuracy of the sim vs. actual.
     
  29. Oct 30, 2019 #29

    BABAR

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    And you can toast your successful flight with Triple Sec!
     
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  30. Oct 30, 2019 #30

    BABAR

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    You gonna glue the fins together in pairs on a jig first, to get the right angle, then sand a curve into the base of the fins pairs to match the outer diameter of the rocket? Then glue them spaced 120 degrees on the rocket?
     

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