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  1. wsimpso1

    Wing spar sizing

    I can only point it out so many times. They don’t. Aft spars are usually there in one form or another, and they are small enough that their weights are modest, even while their structural contribution matters. And yet it must be done to have a chance of passing a sandbag test with a reasonably...
  2. wsimpso1

    Plywood Weight Comparison

    While you may be willing to use non-aircraft grade plywood in your bird, you still want to check that the stuff you are getting is as good as aircraft grade for grain, direction, and strength. I also recommend that you make sure it is marine grade, which is to say it is assembled with waterproof...
  3. wsimpso1

    Wing spar sizing

    I am getting weary of explaining why certain features are common and other ideas are not seen. Design what you feel should be adequately strong with your unconventional approach. Do the analysis for shear, bending, torsion over the span and your flight envelope, then iterate the design until...
  4. wsimpso1

    Wing spar sizing

    Every one of those Bede designed wings I have seen has a light drag spar closing out the trailing edge of the wing. You have to connect the top and bottom skins together somehow. These trailing spars are generally light, and they usually anchor the wing to the fuselage, reacting wing pitching...
  5. wsimpso1

    Inherent, quiet?

    C152, C172, PA28, C182, PA18, Champ/Citabria/Decathlon... Stay right on cruise airspeed on downwind until abeam landing numbers, then drop power and first notch of flaps, turn base 1/2 mile past threshold, pull more power and second notch on base. These airplanes slow down and come down all the...
  6. wsimpso1

    Bronze vs. sealed precision bearings for control surface hinges

    Lots of rudder pedals, elevators, and rudders on homebuilts this way. I only have this on the rudder pedals/ brake pedals. Lapped the tubes on each other and have Zerk fittings to force grease through them, etc. Surface speeds and unit loadings are really low. Also have steel on steel for the...
  7. wsimpso1

    Bronze vs. sealed precision bearings for control surface hinges

    This is a bit of thread drift, but OK. Three bearings per surface, which makes things more complicated. Five along the elevator, one big bellcrank bearing at centerline that picks up lift from both sides and the pushrod aft forces, then a spherical a little less than halfway on each side and...
  8. wsimpso1

    Bronze vs. sealed precision bearings for control surface hinges

    Bushings? Only where trim motors are moving things in my ship. No feel involved there and I have critical damping on the tabs so they can not flutter anyway. Piano hinge's in trim tabs (not a control feel issue) and rudder, where I have a stiff (low deflection) structures and my legs are moving...
  9. wsimpso1

    diffuser design info

    That scheme usually works pretty well. It might require some guide vanes. https://www.homebuiltairplanes.com/forums/threads/balsa-balsa-w-fiberglass-laminate.39971/ https://www.homebuiltairplanes.com/forums/threads/radiator-and-intercooler-design-information.21050/ There are others too. Ross...
  10. wsimpso1

    Inherent, quiet?

    GUMPS check is Gas, Undercarriage, Mixture, Pumps/Props, Switches. Prop knob is moved full forward to prepare for the go-around, and many resources teach GUMPS in pre-landing phase to make sure the airplane is configured prior to being busy with landing. So yes, prop knob will be forward on...
  11. wsimpso1

    Wing spar sizing

    If you make a one-piece wing like Paz does in Light Plane Design, you will build with a structural skin and can get away, sort of, with a single spar. Control surfaces cut from the trailing edge and closing the cut shape ends up forming a light drag spar. Break that wing into a two-piece wing...
  12. wsimpso1

    Looking for wheel fairing plans

    The wheel pants themselves are relatively straightforward. Wrap the wheel/tire/brake in plastic and tape, glue bits of foam together around it, carve to foam to a nice teardrop shape 3:1 to 3.5:1 aspect ratio is considered about perfect for min drag, glass it. Slow birds might be OK with 2 ply...
  13. wsimpso1

    Three-piece canopy on a two-seater?

    Many of the RANS designs have single flat wrap windshield that also makes the skylight and then a single piece door/window on each side, making a three-piece canopy.
  14. wsimpso1

    Sold Sonex Plans SOLD - Serial number 461

    Please edit title to include SOLD.
  15. wsimpso1

    Sold Plans: Ritz Standard A Serial #181

    Please edit title to include "Sold" once the item is sold.
  16. wsimpso1

    Cabin Heat, Water Cooled Engines - Which Way is Best and Why?

    No PhD in our household, just trying to help folks see big picture. Standard Atmosphere is taught fleetingly in a couple sophomore mechanical engineering classes called Fluids and Thermodynamics. The Standard Atmosphere and the standard lapse rate (3.56 F per 1000’) is also taught in private...
  17. wsimpso1

    Cabin Heat, Water Cooled Engines - Which Way is Best and Why?

    Standard day is 59 F at sea level. 32 F is reached at 7600 feet MSL. 75 F day at sea level means freezing at 12100 ft MSL. If you have no plans to ever fly in cooler months or cross any mountain ranges or fly over weather, you might have no worries over defog. Most of us hate the thought of only...
  18. wsimpso1

    Welded aluminium floats?

    They describe a process of anneal-straighten-precipitation hardening to -T6. This is the method for hardening 6000 series aluminum alloys. Their description of yield mechanisms is way off the mark. Metals yield by movement of dislocations in the crystal lattice of the metal. Those interested...
  19. wsimpso1

    Drilling metal tube

    Hmm. I have cut and drilled a lot of medium alloy steel (4130, 4140, 4340). Sharp tools, modest cutting speeds, and medium feed rates generally works. Please tell us alloy and temper of your material. Normalized tube (-N) is pretty straightforward. Higher tempers and/or some higher strength...
  20. wsimpso1

    Calculating Wing pitching moment/torsion using Cm?

    What is "hard" in tailess airplanes is that the tail is still there, buried in the trailing edge, but now it is in the most aerodynamically inefficient place, the place where it can least compensate for cg position, and where it contributes far less damping. CG position has to be just about...
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