After a little figuring, I decided to constrain the aft of the rib in the inboard/outboard direction (like the aft spar would). The Eigen vector is now 1.05, so that means the 50 Lb load is about it for the original rib. It could take a bit more stress, but is not stable. The negative eigen vector (reverse loading) is .72, which mean it's good for 36 Lb in the down direction.
So, any new rib would only have to be good for a little better than this. It's a pretty spindly little rib
--- In This email address is being protected from spambots. You need JavaScript enabled to view it., "Kenny" wrote:
>
> OK,
> I got the model of the rib up and running. It consists of the trusses and the gussets, but not the plywood that is on the aft member of the truss (or so that's what I think it is). I applied a load of 50 Lb with a linear SOL 101 run (up at the bottom aft tip) as an initial starting point. I'll get some plots up in a couple of days (having a little issue with that -- might have to resort to some screenshots).
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> The max deflection is about a tenth of an inch, and the max stress is around 4600 psi in the spruce and 5300 in the spruce plywood.
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> Then I ran a SOL 105 (buckling) to check the stability.
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> unfortunately the Eigen vector was only .21 (buckles at .21 times the load). So, I need to look an see how the aft edge is constrained (aft spar?). Anyway, making some progress, so it should only be a few days before I can show some results on the current capacity, which will give an idea of what any alternative rib would have to meet.
>
> Kenny
