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New build and a rare one at that. PB.3 Praha, Vintage 1932

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  • New build and a rare one at that. PB.3 Praha, Vintage 1932

    OK guys My next build will be this. A PB.3 Praha which was a 1932 design in Czechoslovakia. It incorporates my favorite feature, a constant cord wing. I chose an airfoil for it which is a SD7062 (14%). Once again I will build a small proof of concept in 1:12 scale and than go to a 1:6 scale model. I will enlarge the flight surfaces a bit on the small scale model. I did quite a bit of research on this aircraft and found that there can be some interesting and beneficial mods made to it from the original concept and design. The original had a span of 11.5m which means that the 1:6 model will be a petite 75.5" . If I lie this one I will than scale it up to 1/4 scale at 113" wit a 12" cord (aspect ratio 9.3). That's 9-1/2 ft2 of wing area. For me that is quite big.
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    Last edited by GunnyK.; 12-24-2018, 12:23 AM.
    If it can't be done right, don't bother doing it at all.

  • #2
    Hey Gunny, the 1/4 scale will fly soooo much better than the 1:6 scale. Size wise, You'll get used to the 1/4 scale very quickly. I know... I've been there with my Aviation Concepts 2-33.

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    • #3
      Of that I have no doubt but I will not get ahead of myself. The 1:12 concept model will come first. I hope I can knock that out by the end of march and than I will start the 1/6. Most likely I will be building some components in unison. I wish I knew of a place I could fly slope here in the Chicago area. Since I am new to gliders and have no such contacts I am helpless in that matter. Any opinions on my choice of airfoil? I use the U of I airfoil plotter. I am open to suggestions.
      http://www.airfoiltools.com/search/list?page=s&no=7 I was also thinking of taking that airfoil and reducing it to 12% from the 14% or my other choice would be the SD7032 and increasing it to 12% or also the S4180 at 12% or 14%
      Last edited by GunnyK.; 12-24-2018, 12:52 AM.
      If it can't be done right, don't bother doing it at all.

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      • #4
        That is a good looking sailplane! If the foil is shown properly on the plan then just use an enlargement of that. All of my models have scale foils. On one, the scale foil on outer panels was transitioned to fully symmetrical to induce wash-out. The models fly fine as far as I'm concerned. I'm not that great of a pilot and still manage to get some decent flight times. These ain't contest ships!

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        • #5
          I doubt very much that the airfoil is represented correctly. It looks good but who knows.
          If it can't be done right, don't bother doing it at all.

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