Results of the wing built for static load testing..... ??

[fairchild]

Was that Chris building a test wing ??? was curious to read the details of how the load test came out......
wondering what part broke first........
Tim

[Chris In Milwaukee]

I am, but not a standard BH wing. I haven’t gotten to that stage of construction yet.

There was a Beartracks issue, I think, that had the load test results of the A wing some years ago. I’ll see if I can track it down. Might be in the old Yahoo! Group, too.

Off the top of my head, the early kit wing that was tested failed in buckling of the inner main spar cap. Don’t recall if it was the top or bottom. The earlier wings didn’t have two layers of spar cap per side that went all the way to the attach fitting. After that, all wings had two layers of spar caps per side that run all the way to the main wing attach fitting, I do believe.

[Gerhard Rieger]

10/03/2002 Wing failure occurred at 6774 lbs, 6,4 g's. No permanent wing deflection or twist after unloading was observed up to 5,7g's. The rated aircraft max allowed load is 4,5 g's at gross weight

[corefile]

has there been anything like this done on "B" wing?

[Chris In Milwaukee]

Not that I'm personally aware of, but I wouldn't sweat it. Mathematically, the B wing is stronger than the A wing. Operating at the same weights as the A model, I'm quite confident that there's nothing to worry about But that's just my personal opinion.

[fairchild]

6700 lbs to failure,..... If we just step back and think---- that's really a crapload of weight for some bent sheet metal to hold up !!! That's most of the weight of my ford f-350 (8k)
You would think if you got to 6 G in a regular aircraft---- you probably all ready have other, bigger problems...….. (discounting intentional hard aerobatics)
I wonder if there is software that can do a virtual load test ? I would think the entire structure would have to be auto-cadded in or maybe catia perhaps..... so that the software
could account for every part's strength. Maybe easier to build a wing and test it :-)

T

[PaulSA]

I know the aircraft is not certified so perhaps the "standard" rules don't apply. As I understood it, there should be no permanent distortion up to the rated load and no failure below 1.5x rated load. In that case, the G-limit should be 4.2g

[Mark Goldberg]

According to Bob Barrows - the Model B wing should be a 3,000 lb gross wing. The original 4 place wing met Bob's design criteria. Then we strengthened it after the test to failure. Mark

[Gerhard Rieger]

Yes that is how I have it too, so like my wing was build after the test and upgraded plans, its stronger , but that is just peace of mind like a savings account. we will not go past 2700 for take off or 2500 for landing. it is nice to know that the wing is stronger than tested and that you will have to plan for real abuse to mess it up. thanks Mark for your confirmation on this.

[nichzimmerman]

Mark, is there structural modification specific to the B wing that strengthens it or is this due to the modifications done on the A wing after the static test? I'm building the A wing from the most recently updated plans and would be nice to know (not that I'm setting my gross weight at 3k lbs or anything)

[Mark Goldberg]

Nic - you should set your gross at 2700 lbs for take off and 2500 lbs for landing like Bob has suggested. At least that is what I would do.

The two main differences in the Model B wing and the original BH wing are: 1) the wing ribs are closer together on the Model B wing, 2) the wing is taller from top to bottom - meaning the upper & lower cap strips on the main spar are further apart giving additional strength. Any more detail or explanation would have to come from Bob as my understanding is limited. Engineering stuff. Mark