Charlie,
Thanks, I only read it in -- I haven't done anything yet, so whatever you got would be helpful. Hey, no problem -- have your FE guy jump in if he wants. This is the first time I've modelled something in this particular way (ortho-tropic 3D elements). I'd be happy to send him the .bdf files, as well as the PATRAN group session files, if that's what he is using. I'd be happy as a clam in mud to have someone double check it. The only one who doesn't make mistakes are those not doing anything at all!


I have 2 ideas One is to use foam as the rib material, and the other is to eliminate some of the ribs the way the Arc does.
Cheers, Kenny

--- On Wed, 4/11/12, This email address is being protected from spambots. You need JavaScript enabled to view it. <This email address is being protected from spambots. You need JavaScript enabled to view it.> wrote:


From: This email address is being protected from spambots. You need JavaScript enabled to view it. <This email address is being protected from spambots. You need JavaScript enabled to view it.>
Subject: Re: [Carbondragonbuildersandpilots] Re: rib results
To: This email address is being protected from spambots. You need JavaScript enabled to view it.
Date: Wednesday, April 11, 2012, 10:19 PM




Kenny,

I am glad you could get a baseline from the model. My FEA guy at work was asking questions today but he is not inclined to jump in. This will not be easy with the low density of wood to carbon/epoxy apx 1/5. Sandwich structure for stability strength is not a problem stability is.

I up loaded a surface model for the wing but it has some problems; the tip rib is off by 8.25 and no drag spar. I redid it today but have not uploaded it, I am not sure what you need but the model I did today has all ribs including false ribs and the drag spar surfaces. I will upload it later and you can get back to me.

Charlie Johnson, Dragonfly N-187CD
Ogden, Utah


In a message dated 4/11/2012 8:04:13 A.M. Mountain Daylight Time, This email address is being protected from spambots. You need JavaScript enabled to view it. writes:
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).
>
> 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.
>
> Then I ran a SOL 105 (buckling) to check the stability.
>
> 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
>

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