Lightning and the i3

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MarkN

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Being in a car during a lightning storm is fairly safe because if lightning strikes the car the electric charge will travel on the surface of the metal car body (the skin effect). What about the i3 with its carbon fiber reinforced plastic body? Does the carbon fiber conduct electricity?
 
No, carbon fiber conducts electricity very poorly. When composite airplanes are tested they do not fare well without additional LSP (lightning strike protection) measures with either metal mesh systems or conductive paints. The FAA demands additional testing before approving a composite airliners (ie the Dreamliner) for use.

I also wonder if BMW has addressed this issue! Does Tom have any more info on this?
 
i3me said:
No, carbon fiber conducts electricity very poorly. When composite airplanes are tested they do not fare well without additional LSP (lightning strike protection) measures with either metal mesh systems or conductive paints. The FAA demands additional testing before approving a composite airliners (ie the Dreamliner) for use.

I also wonder if BMW has addressed this issue! Does Tom have any more info on this?
Click to expand...

I doubt it's any more dangerous than a cloth top convertible with the roof up. As it will be overwhelmingly used in cities with a preponderance of tall buildings I doubt that this is a significant cause for anxiety. Most i3s will be second or third cars. So take the tin top when lightning is likely.
 
Dear Chris, that sounds preposterous to me. You have to deal with limited range already. But not driving the car I like to use as a first car, because there might be ligthning at the end of a warm summer day, isn't what a lot of people are inclined to think of.
 
robster1979 said:
Dear Chris, that sounds preposterous to me. You have to deal with limited range already. But not driving the car I like to use as a first car, because there might be ligthning at the end of a warm summer day, isn't what a lot of people are inclined to think of.
Click to expand...

Sorry, should've put a suitable hint. :^) <--Tongue in cheek smiley. OK?
 
Good points about metal faraday cages but the real issue with composites is they get heavier with age due to moisture ingress.

When water inside the CFC is super heated by a lightning strike it will literally explode.

Some of the German Grob training aircraft are made of carbon fibre composite and have a metal mesh but like many CFC and GRP airframes is has absorbed water. It is not cleared for flight in known icing - metal mesh and no airborne de-icing.

There was an accident a few years ago where 2 glider pilots landed on top of a Shell garage near Dunstable UK after their glider was struck by lightning - they found themselves in mid air with no glider around them:

http://www.aaib.gov.uk/cms_resources/dft_avsafety_pdf_500699.pdf
 
ecoangel said:
Good points about metal faraday cages but the real issue with composites is they get heavier with age due to moisture ingress.

When water inside the CFC is super heated by a lightning strike it will literally explode.

Some of the German Grob training aircraft are made of carbon fibre composite and have a metal mesh but like many CFC and GRP airframes is has absorbed water. It is not cleared for flight in known icing - metal mesh and no airborne de-icing.

There was an accident a few years ago where 2 glider pilots landed on top of a Shell garage near Dunstable UK after their glider was struck by lightning - they found themselves in mid air with no glider around them:

http://www.aaib.gov.uk/cms_resources/dft_avsafety_pdf_500699.pdf
Click to expand...

Coo! Very entertaining. Non-fatal AAIB reports can be such fun. So I think the i3 should be limited to a ceiling of 2-3 ft above ground level. Certainly not to be flown into electrical storms. :)
 
so is there no real research done by bwm about this

i have seen 3 lighting strikes
2 on cars in front of me and 1 just in front of me or something, only thing i knew i was walking the oposide direction suddenly and dont no wy.

so the risk is real you just may have bad luck.

is the water ingress also a problem over time and wil it undue the weight savings of the carbon?
 
I'm pretty certain I was struck in a 3 series a few years back. I say pretty certain as it's not the sort of thing you can know unless somebody sees it from afar. I was driving in torrential rain when the flash occurred and it sounded like something very large had hit the windscreen.

Later investigation showed a central crack in the glass and numerous small "stone chip" type marks on the edge of the windscreen near the surrounding metal body panels. There was nothing overhead that could have fallen at the time. Very weird experience.

But would I be worried about being struck in my i3? Nope, its way too fast to be caught by a lightning strike :mrgreen:
 
FWIW, CFRP is conductive. The roof is CFRP and there's CFRP between the front of the car and the passenger's compartment. I'm not about to test it, but if I had to guess, BMW thought about this and the car is as safe as any car in an electrical storm. Now, how much damage, if any, to the actual car if hit, I do not know and hope never to find out!
 

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