Re: 7725 BID Warp & Fill

Kevin R. Walsh

On Thu, Aug 27, 2020 at 1:44 PM Saro Marcarian via <> wrote:

To cut right to it, the Warp Breaking Strength is listed as 440 lbf/in while the Fill Breaking Strength is 360 lbf/in.  I tried to lookup references to this in our various communities and couldn't find any.  On any layup schedules specifying BID, I've never seen absolute orientation discussed.  Seems that there could / would / should be a difference.

Interesting that they use two different materials for the warp and fill.  I've never noticed a difference.  I'll have to look more closely.  

What am I missing?  Is this gonna be one of a long line of emails / threads I'll regret?  (preparing for the long list of "shut up & build" responses)

I don't think you're missing anything.  Is the question "does the orientation of BID matter for warp or fill due to the ~20% difference in breaking strength?" the answer is definitely not for our application.  In many of the layups you end up with multiple layers not because the absolute strength of the part requires it, but because you have to build up enough layers to have damage tolerance for things like climbing on the strakes, or curious onlookers poking their fingers in the surface of the canard.  But since I have never seen published loads and margins for the primary structure of our EZs, we are left to guess how much margin really is in them.  Clearly it is enough to not care about the ~20% difference in ultimate strength of BID based on orientation.  


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