Estes Prowler build

Discussion in 'Mid Power Rocketry (MPR)' started by Hugh Cronin, Jan 3, 2019.

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  1. Jan 3, 2019 #1

    Hugh Cronin

    Hugh Cronin

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    First mid power rocket. Want to know your opinion on recommended glue to attach shock cord to main tube. What I have on hand is BSI 15 min epoxy, BSI medium and thick CA glue. What would be best.
    Thanks
     
  2. Jan 3, 2019 #2

    solid_fuel

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    Of those choices I would probably use the epoxy. The CA can make the elastic brittle and that could lead to snapping off.
     
  3. Jan 3, 2019 #3

    kuririn

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    Instructions recommend epoxy.
    Double up the elastic cord and snap fit into the two part plastic shock cord anchor. There is a slot in the plastic to put a spot of epoxy. Then epoxy the back of the plastic and attach to the body tube.
     
  4. Jan 3, 2019 #4

    Hugh Cronin

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    epoxy it is...thanks
     
  5. Jan 3, 2019 #5

    GlenP

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  6. Jan 3, 2019 #6

    samb

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    Yes, epoxy is two part and yes, Estes uses the single bottle hieroglyph to represent it. I think it's used consistently in their instruction sheets.

    For the Prowler I would use whatever I had on hand.
     
  7. Jan 3, 2019 #7

    samb

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    I don't think there are too many tricks to the build. I think we already mentioned leaving out the forward thrust ring. The molded plastic loop in the nose cone can be a potential failure point over multiple flights. I usually attach the parachute to a loop in the shock cord a few inches below the nose cone.
     
  8. Jan 4, 2019 #8

    dhbarr

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    On these E2X I like to rough the fin roots & their slots; and use a file or rotary tool to hatch the inner and outer CR surfaces. The one suggestion I have that this helps w/ epoxy is those places were very hard to destroy when salvaging a motor case that spent two years in a tree. The shiny places peeled off the MMT fairly easily.
     
  9. Jan 4, 2019 #9

    GlenP

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    If one were to kitbash the Prowler and make new fins for it, what kind of material would be suitable to handle the power and speed?
    Balsa/basswood/ply, 1/8", 3/16" or 1/4"?
     
  10. Jan 5, 2019 #10

    Nytrunner

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    I'd recommend 3/32 balsa core with 1/32 basswood skins (TBII and laid between a pair of textbooks overnight)

    Crazy stiff. I just did that for the 3" BMS school rocket I plan to fly Cesaroni G's in
     
  11. Jan 5, 2019 #11

    GlenP

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    That sounds reasonable and plenty stiff. Not sure, but I think the Star Orbiter just uses 1/8" balsa, and I was thinking maybe papering 1/8" balsa might be strong enough. Depends on the hardness of the balsa if suitable for the larger engines. I would probably stick with the lower end of the power range, like D, E, maybe F, this is a 2" dia rocket. I guess I can roughly compare the bending and twisting stiffness with the stock plastic fins and just make sure the custom fins are equally or more rigid.
     
  12. Jan 5, 2019 #12

    Nytrunner

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    I just measured the Star orbiter fin sheet that lives in its bag behind my couch. They are indeed 1/8, and I read that they're balsa, but they're definitely stiffer than the school rocket balsa I just dealt with.

    When I get around to that one, I'll either skin it as well, or try my hand at papering.
     
  13. Jan 8, 2019 #13

    GlenP

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    Well, I am planning on doing a kit bash, more on that later, and had a small amount of 1/8" balsa 4" wide sheet that is just enough for one fin so I needed to get some more. I went to my local craft/hobby store, but they did not have much selection to match the leftover 1/8" balsa that I had. I did not want to get thinner stuff and laminate them myself, so I went ahead and got some 1/8" birch ply. These sheets seem plenty stiff, my fin design will be swept and extend aft so they will have to survive ground impact on landing. I probably won't paper them, just use sanding sealer and lightly round the fin edges just to take the sharp corners off. Oh, and I will have to fill two of the fin slots and make three more, going to turn this into a 4 fin model. Will have to deal with the pre-notched centering rings also.

    I also found some LOCTITE brand "instant" epoxy that comes with in a double-chamber syringe with a self-mixing funnel tip, but the tubes were in a pretty small quantity 0.14oz. I may give that a try, after I do some test parts on scrap first to see how well it works.
     
  14. Jan 12, 2019 #14

    GlenP

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    I like to look at other kits for a sanity check when I am deviating from a kit or doing a scratch build beyond what I have done myself, and I think the large swept back fins on the Pemberton Technologies 3FNC 20 oz rocket are longer and more slender than what I am planning for my 4-fin Prowler kit-bash, and they are using 1/8" ply as well, so I think I should be good for a rocket half that weight, provided the chute slows it down enough for a not-too-hard landing on a fin. My fins will be swept back, but will have a longer chord and shorter span. I may start my own thread for that kit-bash (more like an upscale clone of another OOP rocket) when I actually get around to starting it, trying to finish up a couple others first.


    https://www.apogeerockets.com/Rocket_Kits/Skill_Level_4_Kits/3FNC_Rocket_Kit
     
  15. Jan 13, 2019 at 8:59 PM #15

    Theory

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    FWIW I just completed a custom build where I used 1/8” basswood that I then “painted” with very warm laminating epoxy. Great combination!!!

    I’m planning a BT-55 build that will be designed for 24mm composite ‘F’ motors. Planning on the same technique, however with 3/32 basswood.
     
  16. Jan 13, 2019 at 11:28 PM #16

    GlenP

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    40D54AFA-9E1A-4CE6-B06F-C1A8EAE2733E.jpeg I might end up cardstock papering these with wood glue, the stickers they put on them with the price tag do not come off in one piece and leave a lot of traces of sticker paper behind. I will end up sanding them down first and not sure how much material that will remove.
     
  17. Jan 14, 2019 at 7:05 AM #17

    GlenP

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    If I were to add a Kevlar line, what weight should I use for this size rocket? I usually get the 100# for my LPR rockets, might not be strong enough. Would 200# be sufficient? I might wrap it around the engine mount and drill a hole in the front centering ring or attach it to a baffle made from the 1/8" ply scraps.
     
  18. Jan 14, 2019 at 8:03 AM #18

    dhbarr

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    I punch 1/8" 12 strand Kevlar through the top CR and around the MMT, being sure not to get in the way of the fin roots. I extend the Kevlar about to the top of the body tube where I tie on the provided elastic, then tape to make an anti-zipper wad.
     
  19. Jan 14, 2019 at 12:13 PM #19

    Scott_650

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    Four of these big brutes? Seems like a lot of fin area - is there things you can do to minimize weathercocking?

    The old-school swept style is really cool - very nice!
     
  20. Jan 14, 2019 at 2:59 PM #20

    GlenP

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    Yes they are quite large fins, and four of them, but I am trying to make them proportional/scale for a 2X clone of the Centuri Screaming Eagle. The Prowler body tube and nose are just about right. I was thinking about sizing them down a little, not sure how it would look.

    So, I will get some more beefy Kevlar and make a baffle for this one as well.

    Didn’t mean to hijack the thread, still in the planning and idea stage, I may start a new thread when I make some progress on this concept kit bash.
     
  21. Jan 14, 2019 at 7:09 PM #21

    GlenP

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    2368A9D8-5970-4911-BEA2-BB2F989C2E00.png

    Side by side comparison...

    I guess to avoid weather vaning just fly on a no-wind day, or slightly aim the rod downwind so flight path will curve back into the wind anyway.
     
    Last edited: Jan 14, 2019 at 7:21 PM
  22. Jan 14, 2019 at 7:41 PM #22

    dhbarr

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    I feel weird even saying this, but weight at the aft end and/or trimming down the nose weight can ease up if you're extremely overstable.
     
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  23. Jan 14, 2019 at 7:49 PM #23

    kuririn

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    If your 1X clone flies without windcocking, no reason to believe that a 2X upscale won't either.
     
  24. Jan 14, 2019 at 9:12 PM #24

    GlenP

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    good ideas, I will do some more detailed balance checks and swing tests, but I think I have a good vibe about the small changes I am making to the stock kit that will not eat up all the margin, but rather probably will increase it. There will be some relative weight differences in the engines A,B,C versus D,E,F that will impact the c.g. on the 1X and 2X possibly. OpenRocket has been crashing on me since I did an OS upgrade, but there's always the carboard c.p. method and good old swing testing! Most of my experience has been in the 1/2A,A,B,C,D LPR 13,18,24mm power range, from TwoBitz up to Mean Machine and Thunder ROC size. This is my first PSII kit.
     
    Last edited: Jan 14, 2019 at 9:49 PM
  25. Jan 14, 2019 at 9:31 PM #25

    Scott_650

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    Centuri Screaming Eagle was a good looking rocket, should be impressive as an upscale - nifty!
     
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  26. Jan 14, 2019 at 11:20 PM #26

    OC-Patrick

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    ...the Screaming Eagle was my very first rocket - ever (along with the Excalibur from the Big Shot combo, I still have the box).
     
  27. Jan 15, 2019 at 3:51 PM #27

    kuririn

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    Just a note for the OP. I have heard that one should never use CA on a shock cord, Kevlar or elastic. It makes the fibers hard and brittle, and weakens them so they may snap off. Haven't tested this out, and don't intend to. Just passing it on. White or yellow (wood) glue however, is OK. I have used a spot on the knots to keep them from unravelling. Cheers.
     
  28. Jan 17, 2019 at 2:34 AM #28

    GlenP

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  29. Jan 17, 2019 at 2:36 AM #29

    Nytrunner

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    Thrustcurve is your friend for quick and dirty ends
     
  30. Jan 17, 2019 at 3:09 AM #30

    GlenP

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    I guess the speed at the end of the launch rod may be the limiting factor for those that are on the max. weight lift margin. For example, a Mean Machine is a little lighter and less drag (smaller dia) so that can do fine on a D12, a 10-oz 2" dia Prowler may be a little slow at the end of a standard 3-ft rod on a D12... too close for the quick and dirty check for comfort.
     

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