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  1. Heliano

    Composite Cowling

    May I suggest that you add a thermal insulation layer on the inside of the upper part of the cowling. A typical scenario where the inside temperatures go up significantly: after engine shutdown, or during taxi in with engine at idle. Some designs include a "venetian blind" in the upper cowling...
  2. Heliano

    bench top wind tunnel

    Cool and fun! Maybe I'll build one of those someday. However, if you are looking for meaningful results, I would suggest Burt Rutan's solution: a tunnel scale on top of a car, with adequate shock absorbing mechanism. Then you can use a model based on a much higher Reynolds number, you would not...
  3. Heliano

    The difference between winglets and higher a/r

    Interesting thread. Very knowledgeable people here. Five remarks: 1 - Winglets (or sharklets, or sabre lets, or any other name) also produce wing bending moments, very much like an extended wingspan; 2 - Commercial aircraft like the 777 have other constraints like fitting in a gate without...
  4. Heliano

    15% ethanol to be allowed in "normal" auto fuel?

    Allow me to poke my nose here: We can say we have a little experience with ethanol in my country. For the last 15 years or so my cars have run on 100% ethanol, although they can also run on gas - they are flex. Ethanol allows the use of higher compression ratio (it is equivalent of...
  5. Heliano

    Acceptable surface deviations from an ideal airfoil (Wing construction)

    Thank you, raytol. I've learned something. Very informative.
  6. Heliano

    Acceptable surface deviations from an ideal airfoil (Wing construction)

    Good thread. Let me poke my nose into this interesting discussion: Effect of surface irregularities on the airfoil depends heavily on the type of airfoil: those airfoils designed to have laminar flow along a good portion of the chord (and consequently have a "drag bucket" in the CD vs. CL curve)...
  7. Heliano

    Discussion: Echo (Ultralight Self-Launching Sailplane) design

    Peter: this is to ansewr your question about the L13 Blanik wing washout: 3 degrees geometric. See attached Pilot's Operating Handbook.
  8. Heliano

    Discussion: Echo (Ultralight Self-Launching Sailplane) design

    Another feature worth careful evaluation in such a high aspect ratio wing is the speed brake. For gliders, speed brakes are safety equipment. I remember - a loooong time ago - when designers at England's Slingsby had the idea of removing speed brakes for the sake of simplicity and weight...
  9. Heliano

    Discussion: Echo (Ultralight Self-Launching Sailplane) design

    Most interesting project, Peter. Excellent documentation. Allow me to make two comments, though: 1) About spanwise lift distribution, something you've done a perfect analysis about. The presence of the fuselage has an effect. Obviously the effect is somewhat reduced in an aircraft with such a...
  10. Heliano

    Non- Biased Engine Reviews -Viking

    A quick comment, looking at the big picture: When one rightfully says "up to the FAA standards" one has to keep in mind that certification regulations are dynamic. They change over time. Remember when all light aircraft had to be certified under FAA's CFR14 Part 23? It was a painful, time...
  11. Heliano

    The Urge to Fly

    Welcome, Mohamed! You're from a lovely country, I've been there a couple of times (to Algiers and Oran). I think that you can start by evaluating what is available in Algeria - what type of engine, what kind of materials. Here in my country buying a kit from abroad is quite expensive, so most...
  12. Heliano

    Arduino-Based Instruments?

    Impressive, Pilotgil. Well done. One question: what kind of sensor did you use? a BMP280, a MPS20, a Xgzp040 or yet something else? just curious.
  13. Heliano

    Increasing Angle of Incidence

    Congrats, Keith, for your honest efforts to learn. It does no harm to ask questions, and your questions are most welcome. As already mentioned, angle of attack and angle of incidence are totally different parameters. First and foremost: I would NOT change washout, that is, incidence change...
  14. Heliano

    Airfoil selection for an aircraft out there?

    Sorry, folks. Pressed the wrong key here and the image was repeated.
  15. Heliano

    Airfoil selection for an aircraft out there?

    One more way of getting the root to stall first: slotted ailerons like frise-type retard stall along the span of the ailerons.
  16. Heliano

    Anti-ice for experimental.

    Flying into icing conditions takes more than wing ice protection. If it is a piston engine: you have to make sure the cooling air inlet does not get blocked by ice; propellers without ice protection go unbalanced and produce a lot of vibration when ice accumulates on them; windshield needs...
  17. Heliano

    Problem with static margin and neutral point

    Good job, Scheny! As I can see you have a high tail volume and, on top of that, your horizontal tail stands high above the wing - where downwash is somehow reduced, for normal angles of attack (up to, say, 10 degrees). So I see the 84% NP as quite possible. I presume that this NP is...
  18. Heliano

    Center of drag versus center of gravity

    Let me make the subject a little more complicated (sorry): do not forget the downwash. In other terms, the airflow behind the wing is deflected downwards, and the deflection angle on the tail depends on how far and how high it is relative to the wing. This downwash reduces tail lift and is NOT...
  19. Heliano

    Center of drag versus center of gravity

    A quick cllarification: MCAS was added to the 737Max not because of controlabillity, but due to stability issues at high angles of attack.
  20. Heliano

    Center of drag versus center of gravity

    I would say that thrust height vs. CG height is far more significant than drag center height vs. CG height, because: a) drag center height, in the vast majority of cases, is not far apart from CG height; b) Thrust height can be very different from CG height, and thrust can change rapidly. Even...