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Thread: Latest Scratch Design/Build

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  1. Latest Scratch Design/Build 
    #1
    Join Date
    03-01-2002
    Location
    Houston, TX
    Posts
    132
    Here is a picture of my latest scratch design/build. One design goal was to try to get the build time to approach that of a flat foamie. I have aesthetic problems with the flat foamies, but have to admit they build fast and fly well. All of the plane is sturdy board, with the exception of a balsa wing leading edge. The body is essentially a foam monocoque box with another small box in front to, hopefully, make it look a little better and to give something to butt the wing against. The cowl is another box. The wing is also monocoque, with no spars and no trailing edge - just top and bottom pieces of sturdy board bent over 6 foam ribs and joined at the front by a balsa strip leading edge. The tail surfaces are flat foam. Wing span is 30" and chord is 6". Weight, without battery is 8 oz, a little more than I had hoped for. I think the body, and maybe even the wing, could be made with 2 mm depron and still be strong enough, which would help the weight a little. I painted it with Krylon Short cut paints, which are pretty foam-friendly.

    Another design goal was for the plane to be able to take off and land on the grass field I usually fly from. So big wheels are placed well forward.
    Attached Images
     

  2. Latest Scratch Design/Build - Performance 
    #2
    Join Date
    03-01-2002
    Location
    Houston, TX
    Posts
    132
    The pictures are of the third version of the series. The first version had a symmetrical airfoil (I don't remember which one off hand) and a J250 motor. It was a real dud. It always appeared to be struggling just to stay in the air and would barely make it over the top of a loop. It also would stall and fall off on a wing given half a chance. I decided to try a new wing using the WASP airfoil from Profili, keeping the same wing plan form and wing construction. The WASP airfoil made a WORLD of difference - it would now do everything I am capable of, and it had a much wider useful speed range then Version 1 - a little faster and a LOT slower. In version 3, I replaced the J250 with a BP 21 brushless. I have not been able to fly the brushless version yet because of the wind - maybe tomorrow.
    Attached Images
     

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