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 Post subject: Re: Stalker in accident
PostPosted: July 22, 2015, 10:13 pm 
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> foam

It's worth noting that your butt doesn't have an even pressure pattern when you're sitting down. You don't sit on your hips; your weight rests on what looks like some triangulated bracketry hanging off the bottom of the pelvic bone. Depending on how the seat is shaped, substantial pressure may be on the tailbone as well. (you can find pictures online with all the proper medical terminology)

Once those two (or three) points bottom out, your pelvis is now a solid connector from the seat pan to the base of your spine, no matter how much fluffy padding is supporting the rest of your bottom.


Given the uneven pressure pattern, you might be better off putting your foam between the seat pan and the floor instead of up top...

I'm betting there have been studies done about this sort of thing; I know the USAF did extensive testing on ejection seats. [clickety] dtic.mil has a paper on B-52 ejection seat cushions, http://www.google.com/url?q=http://www. ... Iq2UHGevHg ; some of it looks directly applicable to the subject at hand.

edit: this one talks more about the accelerations involved; it's about F-111 ejection systems. http://www.google.com/url?q=http://www. ... ocVSBk-Bkw "indicated vertebral fracture rate among survivors was 40.3% (25 of 62)" Um...


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 Post subject: Re: Stalker in accident
PostPosted: July 25, 2015, 8:19 pm 
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Joined: October 18, 2010, 9:49 pm
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Location: NASHVILLE
I purchased 1 sheet each of all 3 densities of 1 inch thick Confor foam to see what it's characteristics are. I purchased it from seatfoam.com. I have tried these densities in various configurations using a Kirkey aluminum seat as a starting point.
First of all Confor appears to be nothing more than 3 different densities of memory foam. If you have ever slept on a Memory Foam bed you will recognize the same characteristics. When it is cold all three samples get as hard as a rock, so the way your seat feels will change with temperature, especially if you place the foam under an existing Kirkey formed seat cover which will insulate the Confor foam from your body heat. If the Confor is bent repeatedly while cold it will crack, therefor it should be attached to an inflexible surface. Using it over Springs or steel straps will cause it to fail. The softest sheet tears easily and came in with a 3 inch tear on one side. The soft sheet is not very useful for me. You can pinch it down to 1/16" with your index finger and thumb. The medium and firm sheets worked best for a seat cushion . Confor foam cuts easily with out tearing using a sharp fillet knife. The hot wire cutter does not work well. The foam is too dense and cools the nichrome ribbon quickly even with the heat setting at max on the cutter. There was a harder wavy melted layer on some of the edges that looked like they had been cut with a very hot knife. It looked like the tough melted edge could help prevent tearing during rough handling and shipping. I tried setting a piece on fire with a propane torch. It would start to burn but would self extinguish when the torch was removed. A heat gun would not melt it or deform it in any way....very hot setting.
If I had known what this stuff was before purchasing it, I would not have used it. It may work best when used as the entire seat but so far, under a Kirkey seat cover, Sorry, I am not impressed.
I have a practically new Memory Foam bed that I should have cut up for this project.
I am in Oshkosh today and talked to the people at seatfoam.com. They confirmed that Confor is just different densities of memory foam.

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 Post subject: Re: Stalker in accident
PostPosted: July 26, 2015, 12:41 am 
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veightseven,

Thanks for the report on the Confor Foam. Your description of the different densities pretty much confirmed what Janice suggested I use; one layer each of medium and firm. If you’re still in Oshkosh tomorrow, look for this airplane (see photo). It belongs to a friend of mine. In the front cockpit, it’ll have a plaque with a poem I wrote titled Eagles.


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 Post subject: Re: Stalker in accident
PostPosted: July 28, 2015, 10:17 am 
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XCARGUY
I didn't see the plane, but as you know there were thousands of planes there. It was zoo....but in a great way. There is no way to see and do it all in a week.

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 Post subject: Re: Stalker in accident
PostPosted: July 28, 2015, 10:54 am 
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Joined: November 15, 2009, 9:58 pm
Posts: 394
Location: Port Angeles. Wa
Late to the discussion but have questions I have not seen asked. What injuries did the passenger have and why was there a difference between passenger and driver?

JMR

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 Post subject: Re: Stalker in accident
PostPosted: July 28, 2015, 11:49 pm 
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Kartracer47 wrote:
Late to the discussion but have questions I have not seen asked. What injuries did the passenger have and why was there a difference between passenger and driver?

JMR


JMR,

I incurred a slight fracture T2, a pretty nasty fracture in T10, a compression fracture in T11 and a burst fracture in T12.
My theory as to why I was hurt and the passenger wasn’t is this; the front and rear suspension were intact and fully functional on the right side of the car, thus cushioning the impact somewhat on that side of the car. After going airborne, the car impacted the ground slightly nose down. With the LF suspension torn away, there was nothing in that corner of the car to cushion the impact. As the car made contact with the ground, the energy transfer from the front of the car to the rear was extremely aggressive and literally slammed the rear of the car into the ground.
In determining why I was hurt vs. my passenger, other factors should also be considered. I was wearing a HANS, my passenger wasn’t. The HANS allowed my neck and head to move forward only so far where as my passenger’s head and neck were thrust forward and downward (this is evident in the video) which allowed his spine to bend and absorb the initial shock much more so than mine. Being that the impact with the ground was both horizontal and vertical, the HANS did what it was designed to do for the horizontal impact (the car striking the ground nose first—this happened at 47mph). However, during the vertical portion of the impact (the rear of the car being slammed aggressively to the ground), the HANs may have worked against me. Having said that, I still advocate the use of a HANS while on track.


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 Post subject: Re: Stalker in accident
PostPosted: July 29, 2015, 1:59 am 
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Wow, something that is supposed to aid in injury prevention may have contributed to your injury. I am very sorry for what you are going thru.

JMR

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 Post subject: Re: Stalker in accident
PostPosted: July 30, 2015, 12:10 pm 
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Xcarguy,

I was reading an article on gear-up landings today on Avweb (there's always something new to learn) and it contains some info relative to your situation. Looks like you'd have been much better off if the same impact had been on concrete rather than in the dirt...sort of counter-intuitive, as landing in on a "softer" surface would seem to lead to less impact and less damage, but it turns out not to be the case. A portion of the article is pasted below.

I hope that your recovery is progessing well. Bill

"Avweb, "Yikes I've Got A Gear Up...", July 26, 15 ........Put it on the pavement. The real risk you are facing in a gear up landing is a quick stop or loss of control after touchdown, not fire. If you hit with some vertical velocity—perhaps after stalling the airplane at 10 feet—a paved runway will translate that vector into a horizontal vector and let the airplane slide. An unpaved surface may give under the vertical vector, forming a crater, and stop the airplane quickly. An unpaved surface may also give uneven resistance to the parts of the airplane in contact with it during the slide out (or even dislodge chunks) and make it impossible for you to control the direction the airplane is sliding.

In the 1970s NASA did full scale crash tests of general aviation airplanes at its Langley facility. Two of the tests using Cessna 172s were significant in that the parameters in terms of speed and impact angle (shallow) were nearly identical except that one airplane was crashed on concrete and one on dirt. The airplane that impacted on concrete had significant damage to the forward, lower fuselage as it hit, however, the hard surface did not give so the forward and down impact vector was translated into a purely horizontal vector. The airplane slid well over 100 yards before coming to a stop. If the occupants were wearing shoulder harnesses, the crash would probably have been survivable.

The crash onto dirt was a different story. On impact, the dirt compressed, forming a shallow crater, and stopped the airplane before it traveled more than two feet. The airplane was destroyed and the deceleration loads, as well as cabin deformation, were such that the crash was not survivable.

Films of pilots performing gear up landings show that a certain percentage stall the airplane more than five feet above the ground—high enough for a significant vertical vector to develop by the time the airplane hits the ground. Because turf can compress on impact, form a crater and rapidly decelerate the airplane, the risk of getting hurt in a gear up landing is higher on a grass runway."

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 Post subject: Re: Stalker in accident
PostPosted: July 30, 2015, 11:13 pm 
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Bill,

Thanks for sharing the gear up info.....very interesting outcomes.


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 Post subject: Re: Stalker in accident
PostPosted: July 31, 2015, 2:31 pm 
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Quite obvious in this clip. It might have skidded on a hard surface.

http://www.marketwatch.com/story/video- ... 2015-07-30

Kind of like Mythbusters, NASA style. :shock:

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 Post subject: Re: Stalker in accident
PostPosted: July 31, 2015, 4:39 pm 
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Location: Louisville KY
And in auto racing, one of the many reasons why a car into the fence is a bad, bad thing -- the fence "Gives" ("craters" is the term I believe), stops the car suddenly, Of course, then usually tosses the thing back out into traffic. Oh, and it acts like a cheese grater. Not to mention the hazards of the fence posts.

But yes, the thing craters like a dirt landing.

The problem w/ the concrete barrier is when you hit the thing at the bad-magic angle, and it neither slides down the track nor starts spinning. And I assume the same would be true of a bad airplane landing, that there is a really bad angle beyond which no/little horizontal slide happens?

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 Post subject: Re: Stalker in accident
PostPosted: July 31, 2015, 11:19 pm 
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Thanks for the link Martin, although watching the video and seeing the plane destroyed made me cringe. I was cheering for the 172 as it looked like it was going to pull out of the dive (Yes! Look at that thing start to fly! Level out! Level Out!) then I saw the wires that it was suspended on... Didn't look like there was much in that airframe that didn't bend during the impact. Reading the article and seeing the video and learning about "cratering" in dirt has made me rethink my emergency landings. I'd always been somewhat predisposed to landing on a road instead of a soggy farmer's field or a field full of cows or crops previously, now the feeling is even stronger although the soft areas had some attraction so that the airframe props and engine didn't suffer too bad. No more....avoid craters, land on the road! I guess in your neck of the woods you'd be happy to have a field to land in, a flat field that is rather than one that is 45 degrees from horizontal. :D

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 Post subject: Re: Stalker in accident
PostPosted: August 1, 2015, 12:42 am 
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mgkluft wrote:
Quite obvious in this clip. It might have skidded on a hard surface.

http://www.marketwatch.com/story/video- ... 2015-07-30

Kind of like Mythbusters, NASA style. :shock:



Hard surface testing: https://www.youtube.com/watch?v=Bi7kF2RkN5c


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 Post subject: Re: Stalker in accident
PostPosted: November 4, 2015, 5:13 pm 
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Location: Louisville KY
To dust off this topic...

I saw yesterday that the sprint / midget guys are using a "crash pad" -- basically 1-2-3" of "802SAM Shock Absorbing Material Bottom" in the bottom of the seat -- in an effort to prevent the kind of injury discussed here.

HOWEVER...

The manufacturer's web page only briefly mentions testing, but not any specifics about who did the testing, what the material is, etc.

And it does NOTHING for the fact that many compression injuries are from the body crashing into the belts above, not just / only crashing into the seat below.

This sounds like voodoo safety to me. Sorry. Kinda like those "horse collars" that were supposed to prevent Basilar skull injuries before the HANS people figured it out?



http://www.802solutions.com/content/Analysis1.htm

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 Post subject: Re: Stalker in accident
PostPosted: November 4, 2015, 7:07 pm 
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geek49203 wrote:
To dust off this topic...


Plus we need to ask xcarguy how his recovery is progressing.

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