Thanks for the suggestions
. When I designed it, I was so focused on "will it work" that I forgot to estimate the cost. It has definitely gone WAY over my 15 yr old pocket money budget
. When I first thinking about it, I was happy if it ended up with a 2G or less rating, so no turns steeper than 60 degrees. As it is now, it is heaps stronger than it was going to be, and I will make very sure it flies pretty steady anyway. I won't take any risks of steep turns, dives, or anything like that with or without carbon, sheeting, or kevlar. Are there any numbers out there for balsa tension and compression strength so I can make some estimations?
Yeah . . . cost can sneak up on you, that's an expensive lesson on how a reasonable change in size expands geometrically -- twice as long becomes 8 times the volume . . . but I can think of worse ways to learn that
We do trust your intentions, but the practice of piloting often finds us on the wrong end of the envelope without any intent of ever getting there, and plans in place to never be there . . . but . . . suddenly you're there. As they say, experience is a hard teacher because she gives the test first, then the lesson afterward. At least RC piloting affords us second chances full-scale never does.
As for estimations . . . I can link you to notional material properties, but even these aren't reliable since balsa's strength varies WILDLY on it's density. This should make some sense: Low density balsa can make fantastically light structures that seem lighter than air, but crumble at the lightest touch, where heavy balsa can make large stout high-stress models that while still light, do not float through the air. Hard to say how much of what you have in your airframe unless you've kept a careful accounting, and as for taking an educated guess . . . In double-checking my answer, I stumbled on a
research paper on material properties from back in 2015. Lots of discussion -- if you want to dig into it, expect to learn a lot of good stuff (that you'd learn in a Junior level engineering "strengths of materials" course) to follow what's said -- but the interesting point is in the backmatter (it's always in the backmatter
). The charts at the end show their sample measurements between light and heavy density samples (they spec these around 70-90 and 220-280 kg/m^3), compression stress is over 5 times greater, axial is 2.5 times greater, and shear is nearly 4 times greater in the heavy than the light . . . the point is the failure loads for the wood of any single structural member in your wing depends on something we can only guess at -- it's density . . .
. . . and that's just one member of one material and all before you analyze the structure. There are some "simple" calculations (meaning can be completed on a couple of sheets of paper) of the force distribution of lift on your wing/airfoil of your length at a particular attitude/airspeed . . . but how that distributes into your wing's structure . . . in the real world, that would become a large simulation project, which we're not even prepared to fill the numbers into to run.
So, really long story short . . . no. Not really any simple ways for estimation
. . . and as for the hatch, those are good suggestions so far. I can't suggest anything simpler which would be any more effective.
