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Re: pressure distribution on a wing and rib loads 11 Dec 2013 01:43 #655

I took a quick look at the rib stuff, but I saw you used 40% or there abouts for the spar location. I'm not sure why, but I thought it was more like 30-33 percent. Did you use the ailerons when calculating that -- I believe you should. The aileron loads have to be reacted at the back of the fixed rib, so that load should be cumulative. If so, wouldn't that change the % location of the spar? I try to do the calculation analytically, then if it cross checks with the graphical method, you can be pretty sure that they were both done right. If it's a little different, that's not particularly surprising, but they should track well. Anyway, that's why I ask the previous couple of questions about the pressure distribution (fore/aft) on the wing, since that has potential to affect the loading of the rib. The calculation is a bit conservative anyway as the spar actually reacts some of that pressure loading. Assuming the rib reacts it all, is OK, just a bit conservative, but it's much easier to do that way, so it's worth taking the hit on the weight (which ain't much).

One thing I'd like to point out is that the loads on the ribs aren't that high, so that's why it wold likely do well to look at the 3/4 inch Home Depot foam with some wood (maybe some low-density species) or possibly composite caps. It won't take much to support that load. The only thing is accounting for the control hardware penetrations.

--- In This email address is being protected from spambots. You need JavaScript enabled to view it., "Philip Lardner" wrote:
>
> The second page/sheet of my last spreadsheet has my stab at working out the
> rib loads as la Marske. There are also a few pages of my written notes in my
> files folder.
>
> Phil.

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