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  1. HumanPoweredDesigner

    All Moving tail question

    It is starting to sound to me like the higher the percentage of the tail surface that is fixed (vertical or horizontal stabilizer), the more stick free automatic recovery is provided. But the higher the percentage of the tail surface that is moving (rudder, elevator), the smaller, less draggy...
  2. HumanPoweredDesigner

    All Moving tail question

    I don't know how you could fillet an all moving tail to avoid interference drag. Flap junctions have drag too, but they can be smaller. I read the FAA guidelines for estimating drag, and they said multiply the smooth wing area by 0.01, and the control surface and flap area by 0.015. So I...
  3. HumanPoweredDesigner

    All Moving tail question

    I read that a U-tail has more horizontal stabilizer authority for its size during normal flight, but that during a spin, the rudders can blanket the horizontal stabilizer, making it less effective. The T tail escapes this. Did I read that book right? I can also understand why an all moving tail...
  4. HumanPoweredDesigner

    Beautiful airfoils !

    Yes, the GOE is much better for slow gliders, not your speedster. What cruise Cl are you planning to use? As for the naca 65: Airfoil Investigation Database - Showing NACA 65(2)-215 Maybe the low Re data is not showing any good laminar flow effects that would appear at higher Re. But compared...
  5. HumanPoweredDesigner

    Wing-tip losses and fences

    The equation I've seen on the net a lot is 3D CL = 2D Cl * AR / (AR + 2). One site even had a derivation of it. I don't know how accurate it is, though I have heard there are other variables at play. I don't know how much winglets would affect CL. I would assume you would add their height to...
  6. HumanPoweredDesigner

    Downwash Angle

    Wow! Thanks! That is just the paper I needed. It is now saved on my hard drive.
  7. HumanPoweredDesigner

    How much drag do king posts cause?

    Drag coefficient - Wikipedia, the free encyclopedia Are those drag coefficients based on frontal area or total surface area?
  8. HumanPoweredDesigner

    Airfoil data

    Javafoil... That would explain why they have the clark Y and the clark Y smoothed, and some graphs are smooth and others very jagged. It depends how many coordinates they used. But that means the airfoils are compared head to head as long as they have enough points and smooth graphs. All the...
  9. HumanPoweredDesigner

    Airfoil data

    I downloaded Profili. It is VERY user friendly and robust. Well, robust compared to what I plan to use it for. Who knows what you need it for. The free download does not let me check the airfoils that I want, but does demos on the first airfoils in the alphabet. I can scroll through the full...
  10. HumanPoweredDesigner

    Folding wing designs?

    Are you using a fabric wing or structural skin? For my hpa, the wings will come completely off, with beefed up ribs at the junction. I'm going to use tape over the crack but you could use a cuff. I think you need an access port to get in there and unbolt stuff. For the aileron link, you need one...
  11. HumanPoweredDesigner

    candidate for magic airfoil section?

    That is at Re = 100,000. It is probably much better above 500,000. The clark Y smoothed has a 2D Cl of 54 in the naca wind tunnel at Re = 100,000.
  12. HumanPoweredDesigner

    candidate for magic airfoil section?

    If you want a thick airfoil with good L/D, how about this one: Airfoil Investigation Database - Showing SIKORSKY DBLN-526 It is 26% thick with L/D = 53 at a high Cl. Only problem is I don't know how you'd attach ailerons or flaps. The Cl max is over 2. The lack of a low drag bucket is probably...
  13. HumanPoweredDesigner

    candidate for magic airfoil section?

    http://www.worldofkrauss.com/foils/show_compare/?id[]=1103&id[]=483&chord=6.5 That is the difference that smoothing the coordinates can make. Most of the airfoils in the data base are jagged and have polars accordingly. What I've learned from the polars posted in this thread is that the Cl...
  14. HumanPoweredDesigner

    Here are some spreadsheet graphs I generated from an woldofkrauss database:

    How can this blunt ended airfoil have such decent L/D? Airfoil Investigation Database - Showing SIKORSKY DBLN-526 I like the thickness, and the L/D max is at the Cl I want to use for the cord I could have with that thickness. I'm afraid to use that foil even if it is that good, because I...
  15. HumanPoweredDesigner

    Here are some spreadsheet graphs I generated from an woldofkrauss database:

    You can make an RC flying law mower, and the aerodynamics do not scale either. My plan is to fly it with XPlane, and then have an RC robot pilot fly the full sized plane with sand bags in the seat. If it crashes, it was cheap anyway. I'll use a propeller that will shatter on impact and leave...
  16. HumanPoweredDesigner

    Here is an interesting animation series of the airfoil:

    FLOW AROUND AN AIRFOIL Seeing those streamlines return to horizontal boggled my mind at first, but it makes sense now. Seeing those vertical columns get transposed still boggles my mind.
  17. HumanPoweredDesigner

    Has anyone here ever made a model glider out of just glue and notebook paper?

    I mean cut out airfoil shaped ribs, and glue three 1/8 inch strips of paper on top of each other to make spar caps, and have paper skin around it. Make a tail and place a few paper clips in front to get the CG right. Build it with a 3 foot span and 6 inch chord. Use only notebook paper and wood...
  18. HumanPoweredDesigner

    Tandem wing design discussion

    Does anyone know how to calculate the angle of incidence of air hitting the rear wing? By angle of incidence, I mean if the rear wing is directly behind the front wing in level flight and the angle is measured relative to the line connecting the wings. I'm not building a tandem and in no way...
  19. HumanPoweredDesigner

    Here are some spreadsheet graphs I generated from an woldofkrauss database:

    I should have posted this in the Light Stuff forum. The reason I did this was to try and figure out a way to make a thick airfoil with good L/D. Slow ultralights are blown around by the wind. I want one that takes off slow, flies slow, and glides very well, so I can feather the prop and glide...
  20. HumanPoweredDesigner

    Here are some spreadsheet graphs I generated from an woldofkrauss database:

    Interpret these how you like. Half of the outliers either have typos or really jagged polars. These are at Re = 100,000, and include 1200 airfoils. The database copies very well into spread sheets. I only did thicknesses above 8% and L/D above 30 and camber above 1%, and I cut off some of the...
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