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#31
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Aeronca 11AC Chief Project FS
On 2008-06-24, Victor Bravo wrote:
The stabilizer mounting system on the 601 and possibly the 701 is in my opinion not rigid enough. I will point out, however, that you slammed the 601's accident record based on inflight wing structural failures, and in none of them has the horizontal stabilizer done anything but remain firmly attached. Whatever the cause of the accidents is (and I believe it's going to turn out to be pilot or builder related), it's not that. -- Jay Maynard, K5ZC http://www.conmicro.com http://jmaynard.livejournal.com http://www.tronguy.net Fairmont, MN (FRM) (Yes, that's me!) AMD Zodiac CH601XLi N55ZC (got it!) |
#32
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Aeronca 11AC Chief Project FS
On Tue, 24 Jun 2008 14:16:34 -0700 (PDT), Victor Bravo
wrote: On Jun 24, 6:32 am, Gig 601Xl Builder wrote: Jay, he's full of crap. The Horz Stab has four attach points. It doesn't move at all unless you count the fact that the entire airplane moves when you move it. I am indeed full of crap sometimes, but not this time. The four attach points that Dr. Einstein here was referring to are the exact parts that moved slightly when I pulled on the stabilizer tip. Here's a graphic visual example for the mechanically challenged: Imagine that the four stabilizer mounting tabs on top of the fuselage were all 12 inches tall, instead of the one or two inches tall that they actually are... So the horizontal tail would be mounted a foot above the top of the fuselage. Under this example, when you tried to move one stabilizer tip forward and the other one aft, it would move easily, and the four foot-long imaginary mounting tabs would all move back and forth a little as you twist the tail left and right (looking from above). In order to prevent this type of movement, you would have to rivet sheets of aluminum between these tall stabilizer supports to make the system "torsionally stable". You would be riveting "shear webs" between the stab supports, to oppose the shearing (and then twisting) relative motion. Now of course the mounting tabs are not a foot tall, so you cannot swing the stabilizer tip fore and aft with one finger like you could if it was a foot tall. But the stabilizer mounting tabs ARE an inch or two above the fuselage, and this distance is NOT braced in shear or twisting. So you CAN move it fore and aft a little, and when you do this you CAN see the mounting tabs move relative to each other a little. Ladies and Gentlemen, you CANNOT move the stabilizer back and forth this way on an undamaged Cessna, Taylorcraft, Champ, or Beech. You cannot do it on a Luscombe, you cannot do it on an undamaged Piper Cherokee, and you cannot do it on a Maule and you cannot do it on a Grumman Yankee. I can go on if I have not made the point clearly enough. The stabilizer mounting system on the 601 and possibly the 701 is in my opinion not rigid enough. The tabs are not braced against shearing or twisting. There is no reason you should be able to move the stabilizer back and forth on a standard configuration light aircraft like that. When you move it like this, you are slightly bending the stabilizer mounting tabs (and the attach structure on the fuselage) back and forth a little bit each time. Build a 2000 lb 601. ** Posted from http://www.teranews.com ** |
#33
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Aeronca 11AC Chief Project FS
Victor Bravo wrote:
On Jun 24, 6:32 am, Gig 601Xl Builder wrote: Jay, he's full of crap. The Horz Stab has four attach points. It doesn't move at all unless you count the fact that the entire airplane moves when you move it. I am indeed full of crap sometimes, but not this time. The four attach points that Dr. Einstein here was referring to are the exact parts that moved slightly when I pulled on the stabilizer tip. You said 3 inches. I went out to the airport last night and checked this just to be sure. On my unfinished 601XL (but the tail is attached per specs) I was able to get 1/2 inch. of total movement. So either you got you were dealing with a broken 601XL or as I said before you are full of crap. But let's say you were correct, and I am most certainly not saying that you are, what possible in-flight stress could take advantage of such a condition to cause damage or failure of the plane? I can't think of any force acting on the airframe in flight that would do what you are doing with your hand. Now I'm not saying you couldn't bend the attach points enough to make it move 3" but you'd only get to do that once on my plane before I hit you with a baseball bat. |
#34
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Aeronca 11AC Chief Project FS
On Wed, 25 Jun 2008 09:01:34 -0500, Gig 601Xl Builder
wrote: Now I'm not saying you couldn't bend the attach points enough to make it move 3" but you'd only get to do that once on my plane before I hit you with a baseball bat. Here's a Piper with a bit too much play in the vertical stabilizer: http://www.wanttaja.com/avlinks/wire1.JPG :-) Ron Wanttaja |
#35
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Aeronca 11AC Chief Project FS
with a baseball bat.
Here's a Piper with a bit too much play in the vertical stabilizer: http://www.wanttaja.com/avlinks/wire1.JPG :-) That's the one that the Auburn Power Company uses to turn off the power when they work on a line isn't it?? Cheers: Paul N1431A KPLU |
#36
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Aeronca 11AC Chief Project FS
On Jun 25, 7:01 am, Gig 601Xl Builder
wrote: So either you were dealing with a broken 601XL or as I said before you are full of crap. Sorry to ruin your day, I'm not full or crap this time. The aircraft was inspected by myself and two other people from our EAA chapter. I did not measure the movement, and I rough guessed three inches total movement, which would be 1.5 each way. I could be wrong and it may have only been 1 inch... but it was more than a half inch I assure you. Now Gig, why do you think that anyone who says they found XYZ on another airplane is automatically full of crap because it's not that way on your airplane? I can't think of any force acting on the airframe in flight that would do what you are doing with your hand. A combination of any-all of: vibration, asymmetrical loads from slipstream swirling back on the fuselage, sideslip angle, gusts, rudder input slightly moving the fuselage, etc. etc. If you ever did "slow flight" in a Piper Tomahawk, and the instructor told you to turn around and look at the tail, you would damn well know how much a tail can shake back and forth from just air loads! Now I'm not saying you couldn't bend the attach points enough to make it move 3" but you'd only get to do that once on my plane before I hit you with a baseball bat. You can come out and try to move the stab tips of my T-craft back and forth all you want... and it won't move... and I won' even threaten to whack you with a bat much less actually do it. Your comment shows me that you know your stabilizer can be moved, and you know it's not good for the airplane. |
#37
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Aeronca 11AC Chief Project FS
On Jun 24, 2:22 pm, Jay Maynard
wrote: I will point out, however, that you slammed the 601's accident record based on inflight wing structural failures, and in none of them has the horizontal stabilizer done anything but remain firmly attached. You are correct, my comment about the tail has nothing to do with my comments about the wing problems. My reasoning for discussing the tail flexibility was (believe it or not) not meant to inflame or upset anyone, it was meant to point out that the 601 appears to me to be built a little too lightly in many areas, in an attempt to make the LSA weight class. Regardless of what any of you mugs think, I'm old enough to be more concerned about flight safety than most anything else, and my motives were as pure as Captain Zoom's ego. My intent was to make people take notice of a POSSIBLE flexibility issue in the 601 and 701 tail and simply be an informed owner. Once again I invite any real live engineers to look at the issue I raised and let all of us know how much of a big deal (if any) it was. |
#38
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Aeronca 11AC Chief Project FS
On Jun 24, 7:27 pm, clare at snyder dot ontario dot canada wrote:
Build a 2000 lb 601. Do you have any idea of how much strength, stiffness, redundancy, and flight safety can be gained from an additional ONE POUND of aluminum designed into the right places on a light aircraft? My friend, you need to spend some quality time building balsa wood free flight models and learning how aircraft structure works. |
#39
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Aeronca 11AC Chief Project FS
Victor Bravo wrote:
On Jun 24, 7:27 pm, clare at snyder dot ontario dot canada wrote: Build a 2000 lb 601. Do you have any idea of how much strength, stiffness, redundancy, and flight safety can be gained from an additional ONE POUND of aluminum designed into the right places on a light aircraft? My friend, you need to spend some quality time building balsa wood free flight models and learning how aircraft structure works. You are coming off pretty snotty, VB. Show and tell time. Let's see the airplanes you have designed and built... |
#40
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Aeronca 11AC Chief Project FS
Victor Bravo wrote:
On Jun 25, 7:01 am, Gig 601Xl Builder wrote: So either you were dealing with a broken 601XL or as I said before you are full of crap. Sorry to ruin your day, I'm not full or crap this time. The aircraft was inspected by myself and two other people from our EAA chapter. I did not measure the movement, and I rough guessed three inches total movement, which would be 1.5 each way. I could be wrong and it may have only been 1 inch... but it was more than a half inch I assure you. Now Gig, why do you think that anyone who says they found XYZ on another airplane is automatically full of crap because it's not that way on your airplane? Well my plane is being built according to the plans. And you can rest assured there that the Horz Stab can't be moved 3 inches without bending the attach points past the point where they have been damaged. |
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