The Affordaplane, a poorly executed exercise in design.

by nerobro

Pfew. So, I got the plans, and I found some time.

Several things about the plans bugged me. So I started re-engineering the plans. Lemmie tell ya, things got all pear shaped rather quickly.

So, most of the frame is 2x2x.125wall aluminum tube. This tubing has a "cyclic loading rating" of 14,000psi. The plane weighs (or should weigh) 254lbs. Loaded, it shouldn't be more than 550. Even under a 10g static loading, you could still have a 10g vibration and you'd STILL be under the rated limit for that aluminum. And that's even derated to account for aluminum's lack of fatigue limit. The actual tensile strength of 6061-t6 tubing is something like 44,000psi.

Using the square tubing more or less doubled the weight of the fuselage. Versus round tubing. But fine, I understand square tubing is easier to deal with. And heck, the bottom, engine and rear cabin frames are loaded in bending at several points, so we'll leave those alone. Swapping out the windshield, roof, and tail tubing for .. uh.. tubes. 2" diameter, 1/16" wall. Would save 25lbs. Without even coming close to having the parts "just barely adequate" for the job.

The wings have a lot of excess weight as well. The foam for the ribs is left solid. There's no real good reason for that. And the inter rib webs could also be "fixed" By cutting the webs into X shapes, and carving out half the foam on the ribs.. you could save another four pounds.

And this is on top of the whole motor fiasco.

So..... I think I'm going to look at other designs. Though, since the wings and tail are proven on this, I may just have to make my own fuselage. ... perhaps clone something like the belite.

Posted on Nov 11, 2011, 9:00 AM

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  1. As an engineer, let me tell you..... Someone, Nov 11, 2011
  2. And also. Someone, Nov 11, 2011
    1. Yup, It does.. nerobro, Nov 11, 2011
      1. I'm not saying you're wrong, I'm saying there are extremely large risks with what you plan. Someone, Nov 11, 2011
        1. Well that kills the market.... nerobro, Nov 11, 2011
  3. I had looked into it also, a while ago-. pbjosh, Nov 11, 2011
  4. What motor?. Skreemer, Nov 11, 2011
    1. Dunno yet. Looks like rotax, or rotax clone... nerobro, Nov 11, 2011
  5. Ok, another aviation guy to chime in here...... Hans, Nov 11, 2011
    1. Woo, thanks, and some answers, and challenges for you.. nerobro, Nov 11, 2011
      1. More to it than that. Hans, Nov 12, 2011
        1. So nobody's done a properly engineered DIY UL?. Bruce Bergman, Nov 12, 2011
          1. Not sure, never really looked into them. Hans, Nov 12, 2011
        2. Clark-y if you use foam ribs. Flat bottom for aluminum.. nerobro, Nov 12, 2011
          1. Ok, now you scared me with " common operation...well above the VNe". Hans, Nov 12, 2011
            1. Yup, the vne is 70mph. nerobro, Nov 12, 2011
              1. Yeah, that's always reassuring.... Hans, Nov 12, 2011
                1. Well they don't know.... nerobro, Nov 13, 2011
                  1. calculated stall speed for the affordaplane.. And "our plane". nerobro, Nov 13, 2011
  6. Out of curiosity, what's the endgoal for this?. Webwolf, Nov 12, 2011
    1. What's the point?. nerobro, Nov 13, 2011
  7. How is it a poorly exceuted design?. Jim, Nov 12, 2011
    1. If cheapest was the plan, lighter is cheaper.. nerobro, Nov 12, 2011


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