Elevator CA Hinge Problem
06-28-2004 | 10:12 PM
#1
Elevator CA Hinge Problem
Have a SIG LT-40 that has sheered off the inboard CA hinges two times now. Not sure why this is happening. I guess I'm going to replace them with hinge points by Robart since I don't have much wood left. I have many questions:
1. What size hinge points should I use?
2. Obviously I have a Manufacturing Problem, What could it be? The hinges didn't bind, the gap was not sealed, I didn't notice any flutter, but not sure I could recognize it.
3. How can I fix this design problem? Are the hinge points more robust?
4. I did notice that at full elevator motion I have a little torque in the stabilizer could there be a slight alignment problem? I would think the outside would shear off first if this is the problem.
5. Also is there a potential for overspeeding the aircraft such as powering though a loop instead of letting off power at the top of the loop? I'm just a beginner and not doing too much to the airframe.
6. Not much slop in the control surface from what I can tell, so don't think that is a problem.
7. The design has a fairly long distance from the last support to the horn, potential issue?
Any inputs would help. Thanks
1. What size hinge points should I use?
2. Obviously I have a Manufacturing Problem, What could it be? The hinges didn't bind, the gap was not sealed, I didn't notice any flutter, but not sure I could recognize it.
3. How can I fix this design problem? Are the hinge points more robust?
4. I did notice that at full elevator motion I have a little torque in the stabilizer could there be a slight alignment problem? I would think the outside would shear off first if this is the problem.
5. Also is there a potential for overspeeding the aircraft such as powering though a loop instead of letting off power at the top of the loop? I'm just a beginner and not doing too much to the airframe.
6. Not much slop in the control surface from what I can tell, so don't think that is a problem.
7. The design has a fairly long distance from the last support to the horn, potential issue?
Any inputs would help. Thanks
06-28-2004 | 10:54 PM
#2
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From: Vancouver,
BC, CANADA
RE: Elevator CA Hinge Problem
Hmm... the inboard two on mine failed as well... unfortunately I flew the plane into the ground, so I can't really tell if I had the same recurrent problem you do.
06-29-2004 | 08:49 AM
#3
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RE: Elevator CA Hinge Problem
ORIGINAL: fstevenj
1. What size hinge points should I use?
1. What size hinge points should I use?
2. Obviously I have a Manufacturing Problem, What could it be? The hinges didn't bind, the gap was not sealed, I didn't notice any flutter, but not sure I could recognize it.
3. How can I fix this design problem? Are the hinge points more robust?
4. I did notice that at full elevator motion I have a little torque in the stabilizer could there be a slight alignment problem? I would think the outside would shear off first if this is the problem.
5. Also is there a potential for overspeeding the aircraft such as powering though a loop instead of letting off power at the top of the loop? I'm just a beginner and not doing too much to the airframe.
7. The design has a fairly long distance from the last support to the horn, potential issue?
06-29-2004 | 09:09 AM
#4
Senior Member
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RE: Elevator CA Hinge Problem
ORIGINAL: fstevenj
Have a SIG LT-40 that has sheered off the inboard CA hinges two times now. Not sure why this is happening. I guess I'm going to replace them with hinge points by Robart since I don't have much wood left. I have many questions:
1. What size hinge points should I use?
2. Obviously I have a Manufacturing Problem, What could it be?
>I do not believe it is a design/manufacturing problem. This
>plane has been around for a long time and I am certain that
>if this were a common problem, not only would others have
>commented on it, but it would have been noted and corrected.
The hinges didn't bind, the gap was not sealed, I didn't notice any flutter, but not sure I could recognize it.
3. How can I fix this design problem? Are the hinge points more robust?
4. I did notice that at full elevator motion I have a little torque in the stabilizer could there be a slight alignment problem?
>It sounds like you MAY have a warp in the fixed or moveable part
>of the elevator. This will cause little if any binding at low movement
>but will cause some binding as you go to full movement. Other
>possibilities for the "torque" include wood that is cracked under the
>covering (try moving the offending part), the horizontal stab (elevator)
>is not completely glued and/or the fuselage in that area may have
>a crack under the covering.
I would think the outside would shear off first if this is the problem.
>Have you ever tried to tear a CA hinge ? I doubt you can do it.
>If they are CAed in place PROPERLY, the wood will tear BEFORE the
>CA hinge does. The best way to install a CA hinge is to drill a
>small hole in the center of the slot FIRST. Then when you apply
>the THIN CA it will wick into the hinge and wood (2 or 3 drops per
>side).
5. Also is there a potential for overspeeding the aircraft such as powering though a loop instead of letting off power at the top of the loop? I'm just a beginner and not doing too much to the airframe.
>There is always a potential for overspeeding a plane. Personally I
>wouldn't be overly concerned about it.
6. Not much slop in the control surface from what I can tell, so don't think that is a problem.
7. The design has a fairly long distance from the last support to the horn, potential issue?
>While it MAY be a POTENTIAL issue, I wouldn't worry about it. This
>plane is a trainer, and won't be flown at high speeds or doing precision
>aerobatics where it would be noticeable.
Any inputs would help. Thanks
Have a SIG LT-40 that has sheered off the inboard CA hinges two times now. Not sure why this is happening. I guess I'm going to replace them with hinge points by Robart since I don't have much wood left. I have many questions:
1. What size hinge points should I use?
2. Obviously I have a Manufacturing Problem, What could it be?
>I do not believe it is a design/manufacturing problem. This
>plane has been around for a long time and I am certain that
>if this were a common problem, not only would others have
>commented on it, but it would have been noted and corrected.
The hinges didn't bind, the gap was not sealed, I didn't notice any flutter, but not sure I could recognize it.
3. How can I fix this design problem? Are the hinge points more robust?
4. I did notice that at full elevator motion I have a little torque in the stabilizer could there be a slight alignment problem?
>It sounds like you MAY have a warp in the fixed or moveable part
>of the elevator. This will cause little if any binding at low movement
>but will cause some binding as you go to full movement. Other
>possibilities for the "torque" include wood that is cracked under the
>covering (try moving the offending part), the horizontal stab (elevator)
>is not completely glued and/or the fuselage in that area may have
>a crack under the covering.
I would think the outside would shear off first if this is the problem.
>Have you ever tried to tear a CA hinge ? I doubt you can do it.
>If they are CAed in place PROPERLY, the wood will tear BEFORE the
>CA hinge does. The best way to install a CA hinge is to drill a
>small hole in the center of the slot FIRST. Then when you apply
>the THIN CA it will wick into the hinge and wood (2 or 3 drops per
>side).
5. Also is there a potential for overspeeding the aircraft such as powering though a loop instead of letting off power at the top of the loop? I'm just a beginner and not doing too much to the airframe.
>There is always a potential for overspeeding a plane. Personally I
>wouldn't be overly concerned about it.
6. Not much slop in the control surface from what I can tell, so don't think that is a problem.
7. The design has a fairly long distance from the last support to the horn, potential issue?
>While it MAY be a POTENTIAL issue, I wouldn't worry about it. This
>plane is a trainer, and won't be flown at high speeds or doing precision
>aerobatics where it would be noticeable.
Any inputs would help. Thanks
CA hinges are VERY strong IF INSTALLED PROPERLY. I have a Gee Bee Y with an OS 1.60 in it that uses CA hinges and I have never had any problems. I also have CA hinges on other planes that I fly at speeds in excess of 120 mph and have had no problems.
If you want to change hinges, I would use nylon "pin" hinges. They have a brass pin connecting the two halves together and are installed using epoxy and possibly also toothpick "pins" through the wood AND the hinge. DuBro (among others) make them.
I would suggest relocating the hinges and, after checking for a warp, install new CA hinges.
06-29-2004 | 09:44 AM
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From: Peanut Gallery
RE: Elevator CA Hinge Problem
ORIGINAL: fstevenj
Any inputs would help. Thanks
Any inputs would help. Thanks
06-29-2004 | 11:39 AM
#6
RE: Elevator CA Hinge Problem
By manufacturing problem, I meant build/installation problem. One thing pointed out to me by some aeronatical buddies is that maybe the stabilizer needs to be stiffer. They said if the stabilizer is not as stiff as the elevator and when loaded it is flexing more than the elevator hence causing the hinge to fail.
One question on the hinge points is that since it is a stick build up stabilizer the hinge point is longer than the the stick is wide so some of it won't be glued in. Is that a problem?
I was going to install the hinge point at the very end since there is wood there. Is that a problem? MINN you said put it in 3/4".
Another question is how many hinge point do you recommend I install. The are a total of 4 CA hinges holding the elevator on, but was going to install 6 hinge points. What do you think?
Last comment, Campy you say that the wood will tear before the CA hinge, well this is not what happened. Twice I have had the CA hinges tear at the gap an no structural damage has occured to the wood that they are in.
Thanks again for your help
One question on the hinge points is that since it is a stick build up stabilizer the hinge point is longer than the the stick is wide so some of it won't be glued in. Is that a problem?
I was going to install the hinge point at the very end since there is wood there. Is that a problem? MINN you said put it in 3/4".
Another question is how many hinge point do you recommend I install. The are a total of 4 CA hinges holding the elevator on, but was going to install 6 hinge points. What do you think?
Last comment, Campy you say that the wood will tear before the CA hinge, well this is not what happened. Twice I have had the CA hinges tear at the gap an no structural damage has occured to the wood that they are in.
Thanks again for your help
06-29-2004 | 11:51 AM
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From: Locust Grove,
GA
RE: Elevator CA Hinge Problem
While I don't have a lot of experence with building, I will tell you that if your control is not stiff, then your surface will flutter and this will wear out your hinge. Make sure that the rod connection both sides is stiff and that the control cannot flex. If it is one complete control surface, make sure the control is stiff and will not flex.
