Recent content by trimtab


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    Down-Home Vibrometer

    The FFT (or DFT, in the case of digital acquisition), yields a real and imaginary part. The square root of the sum of the squares is the magnitude of each spectral line. The phase is extracted from the arctangent of the imaginary divided by the real.
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    Down-Home Vibrometer

    1. Collect data with a dummy channel indexed to an odd multiple greater than one of the rotating mass. 2. FFT the results. 3. Extract the magnitude and phase data, and relate it to the position to mass compensate. This requires very little effort, and coarse data at some sampling rate...
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    The Doak was an exercise in how to barely lift two people with 60gph of kerosene. Interesting though. I hope VTOL doesn't have to be that arduous.
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    Single seat, 325 lb useful after full fuel. Accommodate a 6'8 pilot without issues 450 mi range. 265 mph cruise. VTOL or < 100' takeoff and land at 9000' DA Cost less than $60k to scratch build. No need to be trailerable due to TO/landing performance for someone with a rural property, but...
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    Celera 500L (was: More Vaporware)

    It's a good summary using yet another approach to arrive at similar results.
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    Rectangular aluminum tube spar

    According to an Alcoa resource I used years ago but cannot find now, extrusions impart significantly different defects at the corners that impact fatigue life significantly, and the web/cap interface is often the failure initiation. Round extrusions exhibit higher cycles to failure for a given...
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    Gotta make this exhaust part

    The pie-cut-and weld method works fine. TIG is fast enough for this. You can also buy pre-bent sections and weld them together. It is pretty economical although radii of curvature are limited. CNC mandrel benders are hard to find without paying them hundreds in setup costs, and they are...
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    Strengthening & Saving EAA Chapters and Investing in the Future: Making the Case

    As a founder of the largest maker space in the Rocky mountain region, I think there is a large overlap that cod be useful for the EAB community. It has a full pro MIG/TIG/Stick/Gas area, some sheet metal, a foundry area, forge area, glass area, ceramics area, laser cutting, 3d printing...
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    Are tube spars an insult to the engineering community?

    Any strutted wing has large compression loads. It's a simple exercise to calculate the comp loads on a Cessna, for example. You won't forget about what is happening just above your head in a tight turn ever again. Hang gliders have tubular members for several good reasons. They have to sustain...
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    Bolt holes, burr and fatigue life effects

    Burrs indicate significant work hardening and/or phase transitions (especially in aluminum, titanium, and some other common alloyed materials). A discussion of why it is a problem can be found in Juvinall & Marshek. There is a list of changes and behaviors in a homogenous material that is...
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    Source of cheaper steering springs?

    Centuryspring.com Leespring.com
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    Celera 500L (was: More Vaporware)

    Prop L/D drops markedly at sonic and supersonic speeds of course.....but they still work. The TU-95 props are ultra thin section in the outer half of the diameter (look at you tubes). The engines suck down fuel like a sailor, but are still more efficient than the jet options available to them at...
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    Celera 500L (was: More Vaporware)

    No. Never ascribe to conspiracy what simple history regarding investor traps built by wide eyed true believers. Music Man v3.0.
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    Longeron orientation and strength

    Mc/I for stress. For stiffness, https://qph.fs.quoracdn.net/main-qimg-415d0e56ded5f1a40ad52b12dab9acc4 That's all. It isn't complicated or hard to calculate. As for grain direction vs strength, see attached.
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    Legal question about copyright

    Pretty great performance. This makes a 172 obsolete. There is nothing legally actionable about designing and building and selling something substantially identical to this. Copyrights are irrelevant to the plane, and if there are patents, they are long expired.