Trident build

Discussion in 'Low Power Rocketry (LPR)' started by sjh1, Aug 11, 2019.

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Use Thicker fin stock

  1. Yes

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  2. No

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  1. Aug 11, 2019 #1

    sjh1

    sjh1

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    Just starting a trident build. Just sanding and sealing all those nosecones takes awhile. I got a question for all of you. The fins on this model are only 3/32 thick and seem awful flimsy. I am thinking of tracing them out on some thicker stock. What do you guys think?
    20190811_trident.jpg
     
  2. Aug 11, 2019 #2

    neil_w

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    You could just paper them for some extra stiffness...
     
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  3. Aug 12, 2019 #3

    Oldschool77

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    I used 3/32 when I cloned mine. But balsa varies, if not comfortable with the quality, paper them like neil suggests.
     
  4. Aug 12, 2019 #4

    BABAR

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    Papering with glue will give you more strength than papering with adhesive backed paper
     
  5. Aug 12, 2019 #5

    BABAR

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    Scan your fin templates before the build with a ruler, just in case you encounter fecal turbine interaction
     
  6. Aug 12, 2019 #6

    neil_w

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    Another thought.

    As @Oldschool77 says, balsa density can vary enormously. The difference between a very hard piece of 3/32" balsa and a soft piece is night and day. It is always possible that you got a soft piece. Or maybe not, and your senses are fooling you.

    Here's how to check:

    1) Weigh the full set of fins.
    2) Measure the dimensions of the fins. Ignore the bit at the rear that curves to match the tail cone.

    This will be enough to calculate the density of the balsa in your fins, and it will confirm if you really got a soft set, or if you're worrying about nothing.

    If they really are soft, then I would repeat that simply papering them is probably the easiest solution. As @BABAR says, gluing paper onto each sided affords the most strength. Or you could cut a new set from a harder piece of 3/32" balsa.
     
  7. Aug 12, 2019 #7

    heada

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    swap 3/32" balsa for 3/32 lite-ply. The lite-ply should be much stronger and more forgiving than the balsa at nearly the same weight.
     
  8. Aug 12, 2019 #8

    Cl(VII)

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    I papered mine with label paper, then went over that with thin CA. The fins have survived about 10 flights almost completely undamaged, and that method only added a few grams per fin.
     
  9. Aug 12, 2019 #9

    RocketGeekInFL

    RocketGeekInFL

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    Be careful with the thinner tubes, they are easy to tweak when putting together. As for the fins, I used label paper and then CA on the edges and they are as solid as ply.
     
  10. Aug 13, 2019 #10

    sjh1

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    Thank you all
     
  11. Aug 13, 2019 #11

    GlenP

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    Thicker stock will add a little weight and drag on an already heavy draggy model. I would avoid A engines then, barely enough altitude to pop a chute. But the thicker fins will survive the landings better.
     
  12. Aug 16, 2019 #12

    sjh1

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    While sanding the fins I broke a corner off and had to glue back, so it looks like I do need to do something. I traced the fine on to a heavy stock paper just in case but I decided to go the papering route. Notice the left fin.

    20190816_140058[1].jpg
     
  13. Aug 16, 2019 #13

    sjh1

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    One side papered with shot of the adhesive used.

    20190816_150956[1].jpg
     
  14. Aug 17, 2019 #14

    sjh1

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    Motor mount complete. Since 4 rings are exposed, I may paint it from there down.

    20190816_210055[1].jpg
     
  15. Aug 17, 2019 #15

    sjh1

    sjh1

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    I was concerned that the lower tube's nosecone was only 3" from the top of the motor. I thought that this might eventually burn the base of the nosecone, so I glued a bit of aluminum foil to the base. Don't know it will help anything, but what the heck.

    20190817_120055[1].jpg
     
  16. Aug 17, 2019 #16

    sjh1

    sjh1

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    Instead of tying the shock cord to the lower nosecone of the upper tube. I used some kevlar cord and tied the shock cord to a snap swivel on the other end.

    20190817_125142[1].jpg
     

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