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10-23-2011, 08:54 AM
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Join Date: Dec 2009
Location: Boulder, CO
Posts: 4,435
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Larry,
Good job!
And my sympathies to the pilot, and please thank him for letting the technical issue come to the community.
Dave
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10-23-2011, 10:01 AM
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Join Date: Apr 2008
Location: Riley TWP MI
Posts: 3,070
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Quote:
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I'm not sure if the modified tank is fastened to the center section. but it looked pretty tightly fitted around the spars and that entire area. I suspect that the modified design would have failed also, perhaps even more so.
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If you are talking about my tank, yes it is fastened to the main center channel. And yes, it too will fail in the event of a crash. But it can not be any worse than the original. Being sprayed from head to foot with gasoline can not get much worse. I still have not decided what to do about my tank: modify it, design a new tank, or put the original back in with modified fasteners.
As for fastening the original tank, I like John Bender's idea of the greased pins extending only halfway into the F-1204 main center channel so that they will not bind.
Instead of using nylon straps, I thought about metal straps that will bend along with the aircraft structure during a crash.
https://docs.google.com/viewer?a=v&p...mMzJh&hl=en_US
In the event of an off airport landing, my check list includes shutting off the master switch, closing the fuel valve, and unlatching the canopy. The accident mentioned above happened on takeoff and there was no time to shut off anything. After an accident with fuel spill, I think the best thing to do is to walk away (if able) and leave the master switch on. The fans will be moving gasoline vapors inside of the instrument panel. You would not want the master switch to make a spark.
Joe Gores
Last edited by Mich48041 : 10-23-2011 at 10:33 AM.
Reason: Corrected typo
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10-23-2011, 10:31 AM
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Join Date: Apr 2008
Location: Riley TWP MI
Posts: 3,070
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Quote:
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perhaps an L angle to secure the tank to the baggage floor rather than a strap.
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The baggage floor is going to be bent and will not remain flat. Any fasteners on the forward end of the tank need to give a little to allow for some movement. The fasteners need to be the weak link, not the tank.
How about a nylon strap held to the floor with a square washer and screw? It would be simple and light weight.
Another consideration is the filler neck. With the tank moving during a crash, a longer fuel hose coupling will bend easier.
Ralph Clark posted about a longer hose:
http://www.vansairforce.com/communit...2&postcount=13
Joe Gores
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10-23-2011, 10:56 AM
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Join Date: Nov 2007
Location: Jesup, Iowa
Posts: 1,657
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Hey Joe - -
That is why I used a pull-hand-tight only type nylon strap. Can't get it very tight, and that is what I wanted. It will 'give' some, but keep the tank in general position. My temp fix was to make it safer to -ME- for now, and hopefully will be able to throw away if a good fix is offered. The floor seems to stay fairly flat, but a little give I feel is needed. I used two of the current tunnel screw to hold the alum angle in place on the inside center bracket. Take the two screws out, and the 2 new NO-HEAD pins, and the tank will come out about as fast as it did before. Also, I found out it is best to use one of the original front mounting bolts on the inside hole to get the tank in position, then put the pin in the outside hole, and it was lined up then. Then take the inside one out, and install the 2nd pin. My small bit reaches in just fine to remove the special pins.
John Bender
322.7 hours.
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10-23-2011, 11:01 AM
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Join Date: Apr 2008
Location: Riley TWP MI
Posts: 3,070
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John,
You have lots of good ideas.
Joe Gores
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10-23-2011, 11:16 AM
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Join Date: Sep 2006
Location: Douglas Flat, CA
Posts: 589
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I'm not an engineer, but I am a bit skeptical about substituting headless pins for those bolts.
Without a head on the bolt, there's no clamping force, so the bolt shaft is more subject to bending forces. Those forces will try to pry the anchor nut off of the rivets that hold it onto the back side of the strip on the tank. The anchor nuts are secured with AD3 rivets intended to see only shear from tightening torque, not the combination of tension and bending they'd get from the pin.
My reasoning is that the joint is similar to that of the rod ends used for tail surface hinges on most RVs. By now, we know that the torque on the jam nuts on the shanks of those rod ends is critical. If the jam nuts are loose, all of the bending in the rod end shank is reacted by the puny little AD3 rivets that secure the anchor nuts. The rivets would loosen pretty quickly, allow bending play in the rod end, and then become a flutter liability.
Thanks, Bob K.
__________________
Bob Kuykendall
HP-24 kit sailplane
EAA Technical Counselor
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10-23-2011, 01:05 PM
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Join Date: Nov 2007
Location: Jesup, Iowa
Posts: 1,657
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Hey Bob - -
Appreciate your comments. Remember, this we hope, is temporary ! If the rivets loosen, or break, the tank falls about 1/4". The strap still holds it in general place. Easy enough to re-do the rivets if needed later. Easy to visually check from time to time.
John Bender
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10-23-2011, 02:24 PM
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Join Date: Feb 2008
Location: Hartlepool, England
Posts: 183
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A UK very slow build for many reason (084). I do not intend to ever remove the wings when built. The biggest change I would like to see with the RV12 is the tank(s) put in the wings. Safer and better as far as I'm concerned.
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10-23-2011, 02:35 PM
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Join Date: May 2008
Location: Marietta, Ga.
Posts: 220
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Plastic gas tanks
I just gave Ebay a quick look and there's a number of plastic tanks that might fit; I forget what the width of the area is, but Jeep makes a number of tanks that might fit. There's a 21 gallon tank that fits a CJ 78-86 that's 23x16x15, and there are some flat boat tanks that might work, with some modifications.
Meade
1/2 N612RV
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10-23-2011, 03:17 PM
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Join Date: Jan 2011
Location: Clearwater, Florida
Posts: 398
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Since this last incident and the overall interest in alternative tank design, I would like to see an E-LSA approved, removable (for inspection purposes) plastic tank offering.
Such a tank would be suited for our specific fuel types, molded for a secure but easy installation and provide improved leak resistance in the event of an impact which distorts the platform which supports it.
Presently, Van's offers a prefabricated aluminum tank, at an additional cost.
A molded, plastic tank, if purchased in bulk, may be a safer and more reasonable alternative to what is presently offered, not to mention the ease of construction/installation of the present tank.
I hope Van's is interested in investigating alternatives to the present installation/design of the fuel tank. It appears that it could be a serious problem.
The RV-12 is talking to us.
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