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  1. LiftDivergence

    Shaved CSK NAS1097 rivet strength allowables

    Do not do this unless there is a legitimate reason there is no alternative. Transitional joint strength not really semi-empirical, it is mostly derived from testing. Reduction in strength for microshaving is not easily calculated, and certainly not reliably. This is because the microshaving...
  2. LiftDivergence

    Best Practices - Skin Repair of Trimout Over Circumferential Splice

    Yes, and that is actually, in my opinion, another issue with the repair. Examining the photo which is an external view looking in - as you say on the (presumably) FWD skin panel there is a longitudinal splice as well. But it is not a typical lap splice, there appears to be an internal...
  3. LiftDivergence

    Best Practices - Skin Repair of Trimout Over Circumferential Splice

    Good discussion points. I agree the concept of "right" and "wrong" is only relevant insomuch as the repair needs structural substantiation which is approved by an authorized representative, which we have to assume it was. However, I do feel that there are objectively relatively better and worse...
  4. LiftDivergence

    Best Practices - Skin Repair of Trimout Over Circumferential Splice

    Hi all, A few months ago I saw an post to the "Aircraft Structures" group on LinkedIn. I'm not going to link to to the post because I don't want to link to external sites in the forum. But this is a public group on LinkedIn with ~27,000 members where various aircraft structures are discussed...
  5. LiftDivergence

    Blue Origin space tourism

    The primary purpose of New Shepard is as a sort of demonstration / knowledge building endeavor for other programs, namely New Glenn. The main cabin of the capsule is composite structure... there are a lot of composite structures on New Glenn that greatly benefited from the experience on NS...
  6. LiftDivergence

    how to calculate drag and lift coefficient at different airfoils of horizontal axis wind turbine blade

    Have a look at this site, it's part of the UIUC Applied Aerodynamics Group Site: PROPID for Horizontal Axis Wind Turbine Design https://m-selig.ae.illinois.edu/propid.html "PROPID is a computer program for the design and analysis of horizontal axis wind turbines. A key strength of the method...
  7. LiftDivergence

    Insurance Cut

    An insurance cut is an additional trim-out of material made after the removal of initially assessed damage boundaries. Usually an insurance cut is specified as 0.040". There are several reasons for insurance cuts to be specified in a repair plan: If damage such as corrosion or gouges /...
  8. LiftDivergence

    Moment of inertia using Coordinate system

    I don't think you want to look at Niu, Megson, or Bruhn for this. Instead look in any Strengths of Materials / Mechanics of Materials Textbook, look in the index, and find where they cover topics like "moment of area for composite shapes", "parallel axis theorem" etc. These methods generally...
  9. LiftDivergence

    Learning how to calculate secondary moment using Bruhn's

    Just to clarify, are you only interested in the secondary bending moment specifically? Not to be pedantic, but what Bruhn works down to is the location and magnitude of the maximum moment, or the formula for the moment at and point along the span. But these would be for the total moment due to...
  10. LiftDivergence

    Inter rivet buckling using Tangent modulus

    This is true, crippling is a failure stress, although to be crippling critical you need an L'/rho usually <20 and this is really only a term used for failure of thin-walled members of stiffened shell structures. That is one form of post-buckled strength but not the only one. Flat plates in...
  11. LiftDivergence

    Inter rivet buckling using Tangent modulus

    Alteon was a company that did structural analysis training for engineers and was acquired by Boeing. So it's a Boeing company but they have a lot of training slides/notes out there that are not proprietary material. In this case I just did it graphically. Use the stress-strain curve, draw a...
  12. LiftDivergence

    Aircraft - Fatigue Load Spectrum

    In that case the reference data I mentioned is not going to help you. It sounds like this is not really a question of how to do fatigue analysis, but rather what you're asking is effectively: "How do I develop an operational loads envelope and spectrum for this UAV?" Usually this would be...
  13. LiftDivergence

    Aircraft - Fatigue Load Spectrum

    Well there is quite a bit of data out there regarding gust and maneuver exceedance curves for commercial aircraft. Just try searching: "dot/faa statistical loads data for commercial aircraft" For example: https://apps.dtic.mil/sti/tr/pdf/ADA378308.pdf Theoretically if you have a CFD that...
  14. LiftDivergence

    Inter rivet buckling using Tangent modulus

    I went through and calculated critical interfastener buckling strengths based on the references I outlined above and the info you provided. Here are the results: 1. Peery using the Secant Modulus corresponding to Sigma_0.7 (MMPDS-2023 Figure 3.2.4.1.6(i)) on a tensile stress-strain curve to get...
  15. LiftDivergence

    Inter rivet buckling using Tangent modulus

    So there are a few things that can be a bit confusing about general interfastener buckling methods. What you'll find is that they typically rely on indexing column buckling curves from Euler-Engesser relations rather than starting from derived plate buckling formulas from Gerard or Kuhn, etc...
  16. LiftDivergence

    Backdrilling, or "match-drilling"

    In my experience, match drilling and it's counterpart match-forming are generally not specified in much detail on a repair plan / repair instruction or installation instructions. As a stress liaison / repair engineer you learn to tow a balance between being specific enough in your instructions...
  17. LiftDivergence

    aircraft passenger cabin stub beam

    I understand the caution with this data and I also would not necessarily recommend posting the SB in a thread like this. Having said that, the SB is mandatorily incorporated by FAA final rule via AD and it is standard practice for the FAA to provide all data necessary for compliance with the AD...
  18. LiftDivergence

    Steel Sleeve Around Bearing

    Respectfully, I think I understand the problem. OP said: He's saying the O/D of the bearing is set into an aluminum housing and he wants to know if there should be a steel sleeve press fit into the housing to act as a wear layer between the OML of the bearing outer race and the inner face of...
  19. LiftDivergence

    Steel Sleeve Around Bearing

    RB, the source of this graph is originally from Rabinowicz who "wrote the book" on wear, so to speak. The source of the figure from Norton is actually from the Wear Control Handbook by MB Peterson and Wo Winer. I have done some checking to make sure it is correct. I think the thing to keep in...
  20. LiftDivergence

    Steel Sleeve Around Bearing

    What makes you say none of us understand the configuration?

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