Lightening holes??
Lightening holes??
(OP)
How do you decide where you would place the lightening holes on the ribs and spars of a wing box???
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RE: Lightening holes??
2) generally where the shear is fairly low, ie not on heavily loaded ribs.
3) that being said, you can probably design lightening hole reinforcement that minimises their effect on panel strength.
RE: Lightening holes??
RE: Lightening holes??
Ribs and spars are usually already designed for minimal weight. Further weight reduction would most likely incur a loss in strength.
TTFN
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RE: Lightening holes??
Besides the many excellent guidelines regarding lightening holes in structures provided above, I would propose one more. A carefully configured and located opening in a structural member can sometimes be beneficial in altering the stress flow in a part, such that it reduces stress concentrations at the attachment interfaces.
Good luck.
Terry
RE: Lightening holes??
Ignorance of this detail delayed a product launch by 2 years.
In general post-design lightening holes are a fairly depressing way of lightening a structure - you need to make a lot of them to make an appreciable difference, and every one is a risk or needs analysing.
Cheers
Greg Locock
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RE: Lightening holes??
When asked why the T-18 doesn't have more lightening holes, John Thorp's reply typically was "Because they weaken the stucture faster than they lighten it!!
Agree?? John Q.
RE: Lightening holes??
RE: Lightening holes??
RE: Lightening holes??
Rob Stupplebeen
RE: Lightening holes??
Mike McCann
MMC Engineering
RE: Lightening holes??
TTFN
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RE: Lightening holes??
TOP
CSWP, BSSE
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RE: Lightening holes??
RE: Lightening holes??
To my freshly electronically trained mind I was envsioning that these holes were an escape path for lightning strikes to prevent the lightning from doing serious damage elsewhere. Too overwhelmed to even consider I might be misunderstanding anything I was being told, it was several months later when another more experienced technician explained my misundstanding to me...after he had to wipe the tears from his eyes from laughing so hard at me!
RE: Lightening holes??
I thought the same thing when I was fresh out of school. Fond memories there.
Rob Stupplebeen
RE: Lightening holes??
like the 1st report i had to review ... you guy had written "asses" for "assess" ... "but spell-check didn't pick it up ..."
RE: Lightening holes??
Mike McCann
MMC Engineering
RE: Lightening holes??
That basically matches what rb1957 and other posters have said.
The remainder of the section has some further discussion on optimal arrangements, etc. You can also find more of this sort of information in the usual places (ESDUs, OEM design manuals, NACA reports, etc.).