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07-24-2011, 07:56 AM
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Join Date: Apr 2007
Location: Memphis
Posts: 159
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Re: problem fuel tanks/leakers
My aluminum-skinned, fiber glass innards tanks are 3 years+ installed; no problems.
See: New fuel tanks with fiberglass innards
Barney, in Memphis
RV-3 & 4 flying
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07-24-2011, 08:23 AM
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Join Date: Mar 2010
Location: Raleigh, NC
Posts: 863
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A better solution?
IMHO, a molded polyethelyne fuel tank "a la Sonex" would be a better solution to the fuel tank issues.
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07-24-2011, 08:26 AM
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Join Date: Jul 2011
Location: Indianapolis, IN
Posts: 77
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Quote:
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a molded polyethelyne fuel tank "a la Sonex" would be a better solution to the fuel tank issues.
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You still get the same issue of hydraulic rupture (although somewhat lessened dependent upon how it's molded) not to mention if you have a fire start from a source other than spilt fuel the tank will melt. It's also more prone to abrasive failure if the aircraft impacts and skids along a hard surface, such as a runway.
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Aviation Safety/Crash Survivability Researcher
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07-24-2011, 08:34 AM
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Join Date: May 2008
Location: central oregon
Posts: 1,089
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Quote:
Originally Posted by SteveinIndy
You still get the same issue of hydraulic rupture (although somewhat lessened dependent upon how it's molded) not to mention if you have a fire start from a source other than spilt fuel the tank will melt. It's also more prone to abrasive failure if the aircraft impacts and skids along a hard surface, such as a runway.
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if you have a fire that melts the fuel tank i think the airplane is already totaled and you are either totaled as well or have un-assed the fire zone.
aluminum if it skids down the runway will get worn through probably as fast as a plastic tank, some plastics actually resist abrasion wear fairly well. i didn't think the tank really was that exposed to the exterior to be a skid plate anyway...
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07-24-2011, 08:50 AM
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Join Date: Jul 2011
Location: Indianapolis, IN
Posts: 77
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if you have a fire that melts the fuel tank i think the airplane is already totaled and you are either totaled as well or have un-assed the fire zone.
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...or you've been knocked out and are unable to escape but could otherwise survive. It's not a "you either survive to evacuate or you're dead on impact" sort of dichotomy. The use of non-protected fuel lines and single wall (or fiberglass lined metal) tanks likely explains in part why there is such a high rate of post crash fire in EAB crashes. The number of folks running their engines on mogas probably contributes to this as well, but that's a topic for another discussion.
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aluminum if it skids down the runway will get worn through probably as fast as a plastic tank, some plastics actually resist abrasion wear fairly well. i didn't think the tank really was that exposed to the exterior to be a skid plate anyway...
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You'd be surprised. That's one of the major drawbacks of a lot of EABs is that they tend to crack up rather easily and expose things that aren't overtly exposed to begin with. Then again, I'd still rather fly in almost any homebuilt over a Cirrus for that very reason. There's a reason why some of my friends who work for the NTSB and FAA not so jokingly refer to Cirrus aircraft as 'Ronsons' after lighter brand whose slogan was (is?) "It lights the first time, every time".
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Aviation Safety/Crash Survivability Researcher
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07-24-2011, 10:05 AM
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Join Date: May 2008
Location: central oregon
Posts: 1,089
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so anyway, you mention parts get exposed to runway surfaces, ok. but you don't mention the difference in abrasion resistance from al to whatever plastic would be used.
and in a fire, say you are knocked out. Do you really think a fire directly behind your seat that is hot enough to melt plastic isn't going to kill you by poisonous gases or heat? the scenario where you are in the plane with a hot enough fire to melt the tank just doesn't seem very livable to me, even before the tank melts
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07-24-2011, 10:14 AM
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Join Date: Jul 2011
Location: Indianapolis, IN
Posts: 77
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but you don't mention the difference in abrasion resistance from al to whatever plastic would be used
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Are you a materials engineer because I can get pretty technical on this and was trying to refrain from pointing out that polyethylene doesn't have better abrasion resistance than aircraft grade aluminum and making you look rather foolish. You can take most industrial grade polyethylene containers, put a weight in them such as water and drag them behind you at a walking pace on concrete and have a visibly appreciable loss of thickness.
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Do you really think a fire directly behind your seat that is hot enough to melt plastic isn't going to kill you by poisonous gases or heat?
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Probably not (assuming that the aircraft stays intact enough for the fuel tank to actually remain in its original position) but then again a crash hard enough to knock a person unconscious is going to make it pretty **** likely that the fuel lines are going to separate and that fuel directly behind your seat is going to wind up in the cockpit with you. The point that fuel systems can and should be improved stands. That is my point, nothing more and nothing less. For starters, having a fuel tank behind the seat is questionable from an engineering standpoint but I digress.
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Aviation Safety/Crash Survivability Researcher
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07-24-2011, 10:29 AM
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Join Date: May 2008
Location: central oregon
Posts: 1,089
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Quote:
Originally Posted by SteveinIndy
Are you a materials engineer because I can get pretty technical on this and was trying to refrain from pointing out that polyethylene doesn't have better abrasion resistance than aircraft grade aluminum and making you look rather foolish. You can take most industrial grade polyethylene containers, put a weight in them such as water and drag them behind you at a walking pace on concrete and have a visibly appreciable loss of thickness.
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I am certainly not a materials engineer. i hearby give you permission to make me look foolish, i would like to see an examination of the difference in abrasion resistance between the two materials at the thicknesses that would be used.
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07-24-2011, 10:51 AM
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Join Date: Mar 2005
Location: SE Florida
Posts: 1,499
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I love to learn
Quote:
Originally Posted by Mel
Although 6061 is somewhat weldable, I think that 5052 would be a better choice.
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Mel,
Thanks for the education. How does 5052 compare to both 2024-T3 and 6061-T6 for strength?
Charlie
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07-24-2011, 11:06 AM
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Join Date: Mar 2005
Location: SE Florida
Posts: 1,499
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2 concerns
Quote:
Originally Posted by WingedFrog
IMHO, a molded polyethelyne fuel tank "a la Sonex" would be a better solution to the fuel tank issues.
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I'm not familiar with the fuel tank location in a Sonex. For wing mounted tanks, the material would need to have UV protection. I think that the effects of the fuel on the plastic would mean that sort of fuel tank would have a shorter life expectancy, compared to aluminum/ProSeal.
Charlie
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