Winter Build - 1/3rd scale Iris

Discussion in 'Scale' started by OKTurbo, Dec 12, 2019.

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  1. Dec 12, 2019 #1

    OKTurbo

    OKTurbo

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    My first project for the winter building season is a 4” dia ARC Iris. I’m starting with the LOC kit. First thing I noticed is that the nose cone is not to scale so I asked Gordon Agnello to turn me a scale one.

    5A039439-0484-4FDE-B920-4B7D42F04EEA.jpeg 111F975E-B550-4F6B-B5CF-436D71483C12.jpeg

    The fins look good compared to the scale drawings.
    2083C4A3-0BB9-475F-83FC-709252A00757.jpeg
     
  2. Dec 12, 2019 #2

    OKTurbo

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    Nice parts in the LOC kit as usual.
    516085E5-12C4-415D-950E-0BD8F5BD0F4F.jpeg
    5DDCB60C-C189-4037-9869-5EE7CA61AF53.jpeg

    I decided to add a light wrap of fiberglass on the tubes...mostly for the finish.
    21EF4494-1E60-4CE9-A5BF-9B1B7652A89A.jpeg 93E40E3E-562D-4E10-B7C3-A40A7055135A.jpeg C8BBEEFB-6947-4693-852A-F533AFE2F194.jpeg B9331B6C-38A8-4013-8429-E8FFAA83CFE7.jpeg
     
  3. Dec 12, 2019 #3

    OKTurbo

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    Getting some primer on the tubes and dry fitting the MMT and fin can.
    97626AC8-BE4D-400F-AB7B-39EFE5BF4DE2.jpeg F1A1D321-EC27-435D-821A-D32F39B90883.jpeg 5A4BEA18-F761-434C-BDBF-B54E9F118993.jpeg
     
  4. Dec 12, 2019 #4

    OKTurbo

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    Figuring out how to add some scale details to the fins. 3mm socket head screws are perfect for the fin mount brackets. I’d like to have the gap between the body tube and fin for a scale look, but I’m afraid it will weaken the fin too much. May just have it at the bottom section where the silver nozzle section is.
    52AC9720-2FCA-440B-9E45-DA943E829ACD.jpeg 05BD16AD-15EB-4B4C-A9C2-9D3D930473C6.jpeg

    Fin tapers
    4E175D3C-3A49-4171-BB1F-B5EA5B2FD051.jpeg

    Working on a plan for the fin gaps.
    919CB9D2-FA82-415E-9060-DD1B85A73B5B.jpeg CFD7932D-B1A7-456E-A9DB-C04596AA5CA6.jpeg FD806A68-4CE9-4CCD-A9E6-3B754D0B9286.jpeg D71D0260-5581-470D-ABA3-FE9DFF2DB83F.jpeg
     
  5. Dec 12, 2019 #5

    OKTurbo

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    Something new for me. I’m using some thin epoxy to harden the balsa cone. I’ll probable add a layer of glass after this cures. Also soaked some epoxy into the eBay tubes and bulkheads.
    15823A3E-60B5-4D32-B193-4008C91C10E8.jpeg 96F693D3-0A5C-4E45-9016-966EC60D68B4.jpeg 1B5455FA-5BA4-4FB2-99C7-6753DFAD45D2.jpeg
     
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  6. Dec 13, 2019 #6

    Ez2cDave

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  7. Dec 13, 2019 #7

    OKTurbo

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    Oh yeah Dave! That’s the data / drawings that inspired me to try this. I’m going for a little more than “sport scale” since we have decent drawings and pics of the Iris.

    I got some teeny screws for some nose cone detail when I get to that point. Will be some of the finishing touches If the build goes as planned. Nice day in Oklahoma so I started to epoxy the MMT and a 54/38mm adapter.
    188F2CFA-4453-4B2D-A733-2AC5602E0A57.jpeg F3FEBE84-D3D7-4914-B19A-CA6829B9FD37.jpeg F8231100-E771-489D-9D1A-2F295B6F8EB8.jpeg
     
  8. Dec 13, 2019 #8

    Ez2cDave

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    Are you going to build the Booster for it,too, even if just for display ?

    Dave F.
     
  9. Dec 14, 2019 #9

    OKTurbo

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    Undecided if I'll build the booster too. If I do, it will probably just be for display. It does look cool with the booster though. At this scale, I'll have to check if the booster motor tubes are a common size....that will simplify my decision.
     
  10. Dec 14, 2019 #10

    mbeels

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    Looking good, the gap under the fin was a nice touch.
     
  11. Dec 14, 2019 #11

    Ez2cDave

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    On the real IRIS, each Booster motor is 4" diameter, according to Peter Alway.

    Dave F.

    booster_bandw.jpg


    booster_color.jpg


    booster1.jpg


    booster2.jpg


    IRIS -pic.jpg


    iris_&_tinytim_booster-a01-sm_red_fins_color_photo-02.jpg


    2016-0724 - 2138.18 IMG_6398.JPG


    2016-0724 - 2138.24 IMG_6399.JPG


    ROTW-2.JPG


    IRIS-booster assembly.jpg
     
  12. Dec 14, 2019 #12

    OKTurbo

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    4” full scale ... 4/3=1.3” dia for the booster motor tubes.

    So BT-55 tubes would be perfect!
     
  13. Dec 14, 2019 #13

    Ez2cDave

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    Yes, they would !

    Dave F.
     
  14. Dec 15, 2019 #14

    Nytrunner

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    With the fin gap at the rear, thats a fair amount of undupported fin area back there. Hope nothing unfortunate happens
     
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  15. Dec 15, 2019 #15

    Ez2cDave

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    Yes, THAT is a VERY VALID concern !

    Dave F.
     
  16. Dec 15, 2019 #16

    OKTurbo

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    Yes. A valid concern. I haven’t committed the fins yet...that was just a test run on some scrap. I wanted to see how the Dremel router bit would do...it did great.

    I’m still in the sanding and shaping mode.

    F4D7A616-3E04-4496-A8FE-5919DF3027C6.jpeg 8BC191CE-5BB1-437C-9D0C-A674B0D9929B.jpeg 446F14D6-7631-42FD-B5F0-2DE79129B729.jpeg
     
  17. Dec 16, 2019 #17

    OKTurbo

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    I’ve got the basic profile sanded into the fins. Decided to dry fit everything to see how it looks.

    I’d like to do the fin gap on the bottom nozzle section, but it sure looks like it would be a broken fin on a hard landing.

    C2DB5FE8-63AB-4762-9ED6-3A06B8443DDB.jpeg 5E81A284-3474-4723-8573-B41481FF5B31.jpeg C9DD90BB-4E3F-4A18-9F25-A9AFE8B5C116.jpeg B5FC4785-B6B3-487A-9A9C-142FA611A1F2.jpeg
     
  18. Dec 16, 2019 #18

    Mugs914

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    What if you were to only partially route out the gap? Maybe go /32" to 1/16" deep or so and paint it flat black to give the impression that there is actually a gap. It would be a bit weaker, but would probably hold up to most harder landings.
     
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  19. Dec 16, 2019 #19

    mbeels

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    That's a good idea, maybe it is enough of a gap impression to put a plain, flat black stripe.
     
  20. Dec 21, 2019 #20

    OKTurbo

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    Working on some of the details. Fin mount bands and the fuselage ‘bulges’.

    I’ve got some ideas on how to make the fin gap a little stronger but still look scale. Hard to describe. I’ll post pics when I get to that point.

    F294F416-4650-4355-97D9-5BAA45ACE820.jpeg A401E3FE-D2EF-4003-BD24-7D509A774AA3.jpeg D37F8C3C-84CB-44F6-A1A8-F8412BCE58C9.jpeg DFB360A5-647C-4867-9A64-0514A93F8497.jpeg AA30672F-EBE1-4D14-9194-D1B748549392.jpeg 7E013878-F611-42E0-9751-822D5E8A8791.jpeg 8531E642-A77F-4AD3-9B23-E7F09F581A87.jpeg 168A7BC4-A000-468D-94D3-3357AF51F9BA.jpeg
     
  21. Dec 21, 2019 #21

    Ez2cDave

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    Hmm . . . "Transparent Aluminum" ? LOL !
     
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  22. Dec 21, 2019 #22

    OKTurbo

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    LOL! Scotty said something about a whale tank?
     
  23. Dec 23, 2019 #23

    OKTurbo

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    Here’s my idea. It took a lot of effort to make it look this bad. The Dremell router is not easy to control. I clamped down a fence but it still looks a little crooked. The tolerances are so tight...oh well. Probably go with a couple of drilled holes and a coping saw on the other fins.
    D2C4D875-53A3-44E0-9E68-FA7A2791E0C6.jpeg 1850ABFC-D56D-4117-9815-8D6A572EF528.jpeg 67E83178-507F-4315-A9DF-12EA9EB4655B.jpeg 9AA35CA2-71C7-48F3-9053-EEC1A44334AF.jpeg
     
  24. Dec 23, 2019 #24

    Ez2cDave

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    From my perspective, I don't think that is going to add very much strength. If it were me, the Fin Roots would be solid and fully-filleted. If I still wanted the "look" of the Gap, I would just use paint to give a "visual impression" of it being there.

    Doing it any other way, would likely invite flutter or damage on landing, in my opinion.

    Dave F.
     
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  25. Dec 24, 2019 #25

    OKTurbo

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    Where’s your sense of adventure? I’m going to try it....maybe it’s my Scottish stubbornness. What’s the worse that could happen? I’m not too worried about flutter. I won’t fly it that fast. If I pick a big enough main, the landings should be good.
     
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  26. Dec 24, 2019 #26

    Ez2cDave

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    Hmm. let's see . . . The rocket sheds a fin or two and does a 180, under power, and flies straight through the front grille of your vehicle ( taking out the Grille, A/C Condenser, Radiator, Electric Cooling Fans, and wiping out that custom-turned Nose Cone ) . . . I figure about $1500 +/- ought to cover it - LOL !

    Dave F.
     
  27. Dec 24, 2019 #27

    OKTurbo

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    The second one turned out better...

    96DE70B5-DADB-458C-B763-F47D068D1D94.jpeg 740A5FC3-8593-4748-A281-974ED8B889A6.jpeg 07930ADA-A2E3-49B4-B884-BD0B085640C0.jpeg
     
  28. Dec 24, 2019 #28

    OKTurbo

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    It’s hard to gauge if you’re serious Dave...you did put a
    LOL at the end, so I’ll assume you meant it with humor.

    I wouldn’t do anything I thought was dangerous or irresponsible.

    Would you feel uncomfortable with swept back fins that looked like this?
    0A60BDB2-F42B-4B3D-B6A4-73F3B3F6B64C.jpeg

    I won’t disagree that the fins are weakened by these modifications, but I don’t think it’s a recipe for disaster. If the fin tip hits on landing, it would have the same moment and shear as the swept fin. As far as flutter goes, it would be similar to the full scale design.

    These fins are TTW and notched into the centering rings. I will fillet all the internal joints with epoxy.
     
  29. Dec 24, 2019 #29

    Ez2cDave

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    I was being humorous ( unless it actually happens - LOL ! )

    If you change the Fins, it will no longer be "Scale" . . . Leave them alone and "light that candle" !

    If all goes well, congratulations . . . If not, you can always build another one - LOL !

    Personally, as long as you don't go Transonic ( 950 ft /sec - up to Mach 1 ), I don't think you will have any issues, at all, with Flutter.

    Dave F.
     
    Last edited: Dec 25, 2019
  30. Dec 24, 2019 #30

    AfterBurners

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    I love the build so far. I had Gordon turn a nose cone for me for my Snaky kit. He did a beautiful job! Your method of soaking the balsa with thin CA is the same method I use. It really hardens the balsa and it sands like butter after it dries. I usually do 2-3 applications. I know the nose you are working is pretty big, but on most of the ones I work I make a puddle of thin CA on a plastic bag or a larger zip lock bag and I turn and roll the nose cone in the puddle working my base to the base of the cone. As I mentioned this only works with smaller sizes no bigger than 2.2 I would guess?
     

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