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  1. saksmito

    787 Hi-Lok installation

    We did manufacturing and repairment. The comment about the maintenance manual was just a way of talking. About the second question no, not any fastener manual allow to cut hilocks. Anyway I was just kidding. We didn´t cut any hilock. Anyway the problem is not a joke. You can break the matrix...
  2. saksmito

    bifilar vibrations 3P

    Thanks a lot for your response. It´s been very useful. Anyway I still have a question not answered in that forum (better said answered but not understood). As it seems when the blade makes it´s way through the air it passes from bearing more to less weight in one roll. Multiplied by the number...
  3. saksmito

    787 Hi-Lok installation

    First we applied the torque, and when it didn´t break we cut the collar. Maybe working with aluminium is not a problem, but as you may know when working with composites you can break the matrix because of a very high pressure load. I´m talking about defective rivets, not about forgetting the...
  4. saksmito

    787 Hi-Lok installation

    Sometimes we had problems in the factory when using hilocks. We used to cut a little bit the collar when applying a very high torque and it didn´t break. I think that happens because of bad quality controls of the manufacturer of the rivets.
  5. saksmito

    How would I make a tube with multiple bend from carbon fiber?

    We have been making air ducts for the A380. First we tried Aquapour and it was useless. It didn´t dry and had it to dry for weeks (works very well for small parts with high surface exposed to water). For big parts it doesn´t dry. The inflating bag is the best idea we have found. There´s a...
  6. saksmito

    Honeycomb Core

    Where is your company? I can give you a couple of addresses in Spain. Haven´t been working for them in years, but we used to work with HRH. Maybe they have some HTP.
  7. saksmito

    Why do flags flutter?

    Madprof. I´m talking about the flag fluttering, not the nature of turbulences (I thought this was the question). On the other side. If you want to demonstrate that viscosity is the responsible for turbulences I think that you are late (unless you are Prandtl or Glauert by night). Congrats for...
  8. saksmito

    bifilar vibrations 3P

    Hi. I´ve began to work on the Sikorsky S76 just a couple of months ago and have a question. Where could I find info about bifilar vibrations and the way the S76 dampens them. I´ve seen in the configuration that it has a damper consisting of four masses with an excentrical movement. The problem...
  9. saksmito

    air flow past a flat plate at some inclined angle

    I agree with cpsenior. For high angles (this has just passed through my mind now) in first I would suppose a detached current around the edges. Study it assuming the current impacts the plate, the flow runs through the plate and then goes straight ahead following the original current path. For...
  10. saksmito

    Fatigue damage due to compressive load

    In my career, in the subject "resistance of materials" we were taught about the "core" of the beam (sorry. I studied in Spain and don´t know the name in english). It´s the part of the beam where you apply your load and have only compressive stress. It used to be a geometrical closed curve within...
  11. saksmito

    Contraction of holes in composite post-drilling?

    I´ve been working with laminates of carbon-epoxi for a long time and never seen something like that, and less that amount. From my own experience... have you checked the drills? maybe they are badly marked. Other solution is that the worker has mistaken and didn´t tell you. To me this is...
  12. saksmito

    Birdstrike calculation

    If you need a force you could try using the size of the bird/2 (length/2) as a mean value (from head to the center of mass). Anyway I agree with the previous answers. If you have an impact you are studying a dynamic load. You have a very high energy in a short time (dirac delta). Materials don´t...
  13. saksmito

    Why do flags flutter?

    Would like to apologize for the bad temper of the answer before. Of course the material matters. Air has viscosity, and any surface will produce a vortex. The question is that regardless of the material this vortex is created within the leading edge of the flag. If you had a wooden mast and a...
  14. saksmito

    Why do flags flutter?

    I´m an engineer. I´ve never seen that.
  15. saksmito

    Blade element model

    Everything depends on the accuracy of the model you need. For a simple one I would reduce it to a first year degree problem. Sum the forces and moments acting on the blade and transport them to the hub. I think it should be enough as a first aproximation, and if you don´t want to take into...
  16. saksmito

    Fatigue damage due to compressive load

    I´ve never worked with NASTRAN, but regarding the fundamentals of your question I can tell you that you are right. Compressive loads can create fatigue stress. I can tell you for the fatigue cracks created in engine pistons. I think it should be more important in pieces which support side...
  17. saksmito

    Why do flags flutter?

    By the way, to madprof, your mistake is to assume that the flag is the creator of the oscillations. The vortex are there even with no flag (assuming there is a mast). Look at the experiences with wind tunnels and cylinders. The vortex are the same as the flag fluctuations.
  18. saksmito

    Why do flags flutter?

    Many interesting guesses, but the truth is that this phenomenon is called Von Kármán vortex street. It´s not tue to the flag, but to the mast. nveneno and rb1957 are right. Answering to madprof, the frequency of the oscillations depends on the thickness of the mast. Of course the pmaterial of...
  19. saksmito

    Tangential Tension

    As you say I think the solution could be to put a mechanism similar to the one in the bicicles to keep tension in the chain. How much tension should you use? You can make triple integrals, but I think that the ultimate solution will be a manual adjustment according to your feeling. On the other...

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