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3D Wing tubes and why .037 is unacceptable

Discussion in 'Giant / Scale Scratch and Kit Build Threads' started by Dr Evil, Aug 24, 2014.

   
  1. Dr Evil

    Dr Evil 30cc

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    This should be good :smile-new:

    Ok This is my take on wing tubes and why they need to fit snug. I have seen wings 'blow apart' many times and i suspect the wing tube fit and here's why I be thinking that way. On the 55% I'm building now there is only .037 inch gap between the carbon fiber tube and wing receiver tube not much but over the large span from tip to tip it adds up a lot , and it creates a thing called (SHOCK LOAD) as well as (FLUTTER) .



    Ever heard a plane flutter ? If it survives everything is checked and all the controls are tight :confused: But you didn't think your ears were lying to you. Well it maybe time to check the tube fit :alien:



    Now the SHOCK LOAD . The shock load is when the wing tube, wing and fuselage are all going different directions at the same time and one suddenly stops the other. (not the same as finding all your debit cards blocked from hobby sites but close ):dancing-poop:



    Now here are some in field fixes i have seen and i don't like . one is to wrap tape around the tube in a couple of places the other is to run a strip of tape along the tube. here is why I dont like them they may help with the FLUTTER but do little to nothing for the SHOCK LOAD.





    10216=3687-Picture 503 (Large).jpg[​IMG] 10216=3688-Picture 504 (Large).jpg[​IMG] 10216=3690-Picture 513 (Large).jpg[​IMG] 10216=3689-Picture 516 (Large).jpg[​IMG]
     
  2. Dr Evil

    Dr Evil 30cc

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    Understanding SHOCK LOADS . In my simple mind here is the easiest way I came up with to explain shock loads . If you look at the wood spar pic with the nails in it think of it as the tube with the tape wrapped around it.works the same way just more dramatic. push the nails into your skin or flip it over and push it on your skin. your choice. :bi_polo: Now you can see how it build pressure points / hi stress areas that lead to failure :nodding-yes-by-a-ve The wing tubes and the foam cores flex and will try to fill the gap between the tape wraps. so if you need to take up the gap it needs to be smooth as you can.



    Now How to take up the gap ??????? Now remember we do not need to add any strength just take up the gap.



    Over the next couple of weekends I will be experimenting with different things :stupid:



    I did this as a separate thread as this is something that is not unique to the 55% extra and what we come up with will hopefully help others. :dancing-chicken:


    10225=3693-Picture 513 (Large).jpg[​IMG] 10225=3692-Picture 514 (Large).jpg[​IMG]
     
  3. BalsaDust

    BalsaDust Moderator

    Interesting. I will follow along to try and learn a little from a dr.
     
  4. I will also.
     
  5. Btomlinson

    Btomlinson New to GSN!

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    Dr,



    What about adding a piece of shrink tubing over the whole tube. Just a thought...



    Thanks for sharing this
     
  6. wecoyote

    wecoyote 70cc twin V2

    Maybe paint a coat of epoxy/microbaloons on the tube.
     
  7. 3daviator

    3daviator 50cc

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    I would agree that .037" is way too much. Part of the problem is, the part of the sockets you're able to measure aren't necessarily representative of the socket as a whole and is dependant on the spars where it's glued in. Most of the fiberglass sleaves are so thin they easily flex so unless the wing is assembled and line bored you have differing dia's and alignment deviation ending up with out of round holes.

    I think automotive clearcoat sprayed with a proper gun would work great. You can get a uniform coat and sneak up on the desired Dia, if you go over a little it can be sanded.
     
    stangflyer likes this.
  8. Dr Evil....did the family leave the house and forget to lock up the hammer and nails again?
     
    jtec/radiowave likes this.
  9. Sub'd



    This is a really good topic to look at Dr. E!! I'm interested to see what you come up with!
     
  10. Interesting.
     
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