I guess there's really only one way to find out - to build a number of test ribs in different configurations and see how they perform verses their weight. I already have a small stock of 5mm foam board and 248 twill cloth (enough for 3 or 4 test ribs) and have just ordered a quantity of Aeropoxy, though it will be a couple of weeks before I get my hands on it.
Any thoughts on calculating the loadings along the horozontal stabaliser? I'd love to get that done and dusted so I can start putting together a bill of materials for ordering. How do you calculate the max load the H-Stab is subject to?
Phil.
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Sent: 09 October 2011 13:32
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Subject: [Carbondragonbuildersandpilots] Re: pressure distribution on a wing and rib loads
The flexibility of the wood or composite comes from the thinness. Try bending 1/16 or 3/32 by .75 wood, and you'll see that it's pretty easy. I guess you are talking about the vertical portion in the front and aft of the rear. I'm still not keen on them for that. Hmmm, how about just using the fiberglass and wrap the front and back the same as the top and bottom so you end up with a C-channel around the foam rib. Even in the case of the spar pultrusions, they are wrapped (that's the recommendation for the manufacturer), so you should wrap them anyway, and now it's heavy and over-strength (I think). What you want is just enough, maybe a wee bit extra, and that's it.
You want some flexibility in the upper and lower caps or you will get some pull-off pre-stress between the rib and the cap, and it will want to separate. So, the wood is flexible, and the wet lay-up fabric is flexible so they would be much better in this app. If you do use something I think you should be looking for an actual layup verses a pultrusion.
I do like your plan for the ribs - I think that should work out OK
I'm thinking right now that that leading-edge stringer can go, IF, the GR/EP skins are used for the LE. I'll have to do some modeling to confirm.
