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  1. 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.
  2. 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...
  3. 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...
  4. HumanPoweredDesigner

    Here is possibly a new good way to visualize low speed rotor ground effect aerodynami

    I know this is a home built forum, not an aerodynamics laboratory research forum, but I think I found a solution to a very hot topic in some aerodynamics communities, and some on here might be interested. I do apologize if this is not the right website to post this topic. Some researchers are...
  5. HumanPoweredDesigner

    Does these propeller numbers sound right? I'm studing the effects of diameter.

    I put some numbers into a computer program to see just how much better a 72 inch propeller is than a 36 inch propeller. Both have a maximum cord of 3 inches and are constant pitch. What I noticed is the 72" propeller does better, but not by a long shot. It outputs cruise thrust with 20% less...
  6. HumanPoweredDesigner

    Variable dihedral / Student Pilot and Instructor Attitudes

    You have dihedral when you want to cruise and look at your map. Then when you want to snap a turn, you change to anhedral and snap it. Then back to dihedral when you want to sip your coffee some more.
  7. HumanPoweredDesigner

    How thin can you buy/hot wire foam sheeting?

    I'm really considering aluminum structural skin for my designs. I think if foam is cut thinly enough, maybe I would not have to hot wire it to the shape of the ribs. That would save a lot of effort. I wonder if it can be bought cheaply in stacks of many thin plies. If not, straight hot wiring...
  8. HumanPoweredDesigner

    How helpful are rudders for stability on gusty days?

    I know rudders are useful for turning, and I know they provide automatic directional stabilization in calm air. But suppose your goal is to fly in a straight line, and through a gusty, turbulent area with your light wing loading. It is not gusty enough to blow you all over the place, but is just...
  9. HumanPoweredDesigner

    Foam Strength in Carbon Fiber Sandwich

    How strong does the foam have to be in a fiber carbon sandwitch in order it to do its job and not fail before the fiber carbon buckles? I'm sure this has been answered for wing skin and fuselage skin. I want to use something like this for a strut, and would like to know just how strong the...
  10. HumanPoweredDesigner

    What does 33 MSI mean, refering to carbon fiber?

    Never mind. It is just like ksi. It means million pounds per square inch. But that is only true of unidirectional. Bidirectional can be 33 MSI too and have a modulus of just over half that because almost half the fibers are going the other way. --------- Now I am trying to google the...
  11. HumanPoweredDesigner

    So how hard is it to make your own engine?

    Suppose you take 4 cylinder, cut it up into individual cylinders, and re-arrange them, say, from a V4 for to a straight 4, or you take a 4 small one cylinder engines and cut them up and wield them together to make a low vibration v4 engine for your ultralight. Just how hard would that be? How...
  12. HumanPoweredDesigner

    I think I can make a 3 hp ultralight fly well.

    I plugged some numbers into a program called PropDesigner. It gave me some nice numbers. I then did the calculations myself and got the same numbers. It and I calculated that a 3 hp engine with a 75% efficient 1 meter prop can produce 15 pounds of thrust at direct drive 4600 rpm at 40 mph, and...
  13. HumanPoweredDesigner

    How heavy is your spar?

    This question is mostly for Far 103 pilots. I'm doing a back of the envelop calculation for a truss spar for a wing 35 feet by 5 feet with a 9 inch deep spar, assuming 500 pounds gross weight and 4 G's full cantilever, with the 3D truss spar taking the torsion. The thickness of aluminum needed...
  14. HumanPoweredDesigner

    How much does wood glue weigh dry compared to wet?

    I know, I know, weigh and find out, and do the water float test if I don't have a scale, and don't forget the buoyancy of air if it is light. I'm just hoping someone on here knows. All my calculations were based on the weight of the material, but not the glue. I'm just wondering if wood glue...
  15. HumanPoweredDesigner

    How do you keep epoxy from setting on you too fast?

    I have a lot of intricate surface areas to dab epoxy on and set together. The problem is I have to mix the stuff up, and then put it on before the stuff sets. At least wood glue is good in the bottle and can be let out in any quantity as I get it. And is there anywhere I can get epoxy in bulk...
  16. HumanPoweredDesigner

    Should I set a record even if I won't win the prize?

    I've finally found some helicopter text books that have the equations I need, in the detail I need them. The equations I derived were almost right, but I multiplied by velocities from the wrong location relative to the rotors. I put the equations and my design weights into Excel, and calculated...
  17. HumanPoweredDesigner

    How many patents are ruled invalid because they don't explain it well enough?

    I read that in order to patent something, you have to explain it well enough that someone in the field could understand how it works. I've looked at many patents that don't have have pictures, or they do have pictures but it is not obvious how it works. When I read the paragraphs, they just...
  18. HumanPoweredDesigner

    How do you smoothly cut sheet aluminum?

    I've used tin snips to cut sheet metal before, though probably not aluminum 2024-t3. I don't know if it is just my bad technique, but the edges always came out bent, even if I managed to cut in a straight line. Should I be able to cut better than that? I want to cut a bunch of strips 2 feet long...
  19. HumanPoweredDesigner

    How do I cheaply thread spokes for a wheel?

    I want to cut some bicycle spokes to size and thread them and attach them to a rim I'll make. I makes for a light weight wheel. I'm sure someone else must have tried this unless they just like big wheels or heavy ones. Would it be cheaper to pay a machine shop to do it for me? The spokes are...
  20. HumanPoweredDesigner

    Is it in our best intersted to get as close to the weight limit as possible?

    I think if your plane is a pound under the weight limit, that is a pound that could have been used for a stronger engine or stronger air frame. My reasoning is that the pilot is dead weight, so you want the ratio of pilot weight to airplane weight to be as low as legally possible to get the best...
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