Tail Rigging
Tail Rigging
Ok guys, the next step for me is the tail installation. I didn't see anything about it in the search. So, can anybody give some instructions on rigging the tail. All I could find in the maintenance manual is to bring the wires to 350 to 450 lbs. How do I measure that amount?
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Nathan K. Hammond
- Posts: 2371
- Joined: Wed Nov 17, 2004 00:22
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Sounds like your moving right along!
Rigging the tail is fairly straight forward: to make things easy, set the tail up on a saw-horse and level the airplane left and right using the floorboards as a guide. Next, start each wire terminal end the same number of turns and don't forget the jam nuts. Now slide both horizontals on the stubs and attaching all the wires, leaving them loose. Start to tighten the wires but do them equally by counting the number of turns (I will often make a mark with a Sharpie so I know when I've made a revolution.) Right now all you want to do is take up the slack, so take 1 turns on each wire, then take another turn; always taking the same amount on each wire until majority of the slack is out.
Once the slack is out, sight down the fuselage and make sure the horizontals are perpendicular to the vertical fin. As long as the fuselage isn't twisted the vertical/tail post should be pointed straight up (because you leveled the fuselage) and the horizontals will be perpendicular to the fin. If the fin is twisted one direction or the other, resist the urge to level the horizontals by adjusting the wires, they need to be perpendicular to the fin/tail post. Your eye's are the best tool for determining if the tail is square or not; trust them. Now adjust the wires as needed to square the horizontals, and remember you may have to looses a top/bottom wire a half a turn and tighten a bottom/top wire a half turn to get things plum.
Continually check the wire tension with your finger; pluck each wire like a guitar string and listen to the note they make. Ideally you want to hear a long, low “thummmmmmmmmmm" sound; NOT a short, high "TWANG!!!" sound. When you get things square and have that nice "thummmmmm" sound, everything should be set correctly. Verify by going to the horizontal tip and shaking it up and down and make sure there is little movement (you'll have some from the tubing flexing outside the wires but no more than a 1/4".) Now lock off the wires with the jam nuts.
I know it sounds shade-tree to set the wires by thumping them with your finger but it's by far the best way to do it. They make wire tension meters but they're expensive and aren't as accurate on such a short length.
And as for the sound; if it's a high "TWANG" then the wire is stretched very tight and is under a load, let’s say for example 1000lbs of tension. If that wire has a breaking strength of 2000lbs, we've just cut its working load in half by tightening it down so much. If originally the wire broke at 6G's of pull on the airplane, now it will break at 3G's of pull, because we cut the working load in half. That's why you only want enough force on the wires to hold them in place and no more... i.e. "thummmmmmmmmmmm"
If you've got any questions don't hesitate to call.
nkh
Rigging the tail is fairly straight forward: to make things easy, set the tail up on a saw-horse and level the airplane left and right using the floorboards as a guide. Next, start each wire terminal end the same number of turns and don't forget the jam nuts. Now slide both horizontals on the stubs and attaching all the wires, leaving them loose. Start to tighten the wires but do them equally by counting the number of turns (I will often make a mark with a Sharpie so I know when I've made a revolution.) Right now all you want to do is take up the slack, so take 1 turns on each wire, then take another turn; always taking the same amount on each wire until majority of the slack is out.
Once the slack is out, sight down the fuselage and make sure the horizontals are perpendicular to the vertical fin. As long as the fuselage isn't twisted the vertical/tail post should be pointed straight up (because you leveled the fuselage) and the horizontals will be perpendicular to the fin. If the fin is twisted one direction or the other, resist the urge to level the horizontals by adjusting the wires, they need to be perpendicular to the fin/tail post. Your eye's are the best tool for determining if the tail is square or not; trust them. Now adjust the wires as needed to square the horizontals, and remember you may have to looses a top/bottom wire a half a turn and tighten a bottom/top wire a half turn to get things plum.
Continually check the wire tension with your finger; pluck each wire like a guitar string and listen to the note they make. Ideally you want to hear a long, low “thummmmmmmmmmm" sound; NOT a short, high "TWANG!!!" sound. When you get things square and have that nice "thummmmmm" sound, everything should be set correctly. Verify by going to the horizontal tip and shaking it up and down and make sure there is little movement (you'll have some from the tubing flexing outside the wires but no more than a 1/4".) Now lock off the wires with the jam nuts.
I know it sounds shade-tree to set the wires by thumping them with your finger but it's by far the best way to do it. They make wire tension meters but they're expensive and aren't as accurate on such a short length.
And as for the sound; if it's a high "TWANG" then the wire is stretched very tight and is under a load, let’s say for example 1000lbs of tension. If that wire has a breaking strength of 2000lbs, we've just cut its working load in half by tightening it down so much. If originally the wire broke at 6G's of pull on the airplane, now it will break at 3G's of pull, because we cut the working load in half. That's why you only want enough force on the wires to hold them in place and no more... i.e. "thummmmmmmmmmmm"
If you've got any questions don't hesitate to call.
nkh
7AC-5691
Super 85-12F @ DVK
Super 85-12F @ DVK
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Nathan K. Hammond
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David Johnson
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Jerry Jackson
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Tail wires
When the wire diameter is much, much smaller than its length it is easy to calculate the tension from measurement of the deflection caused by a known force. The relationship is
T=(L*F) / (4*x) where
L=length of wire between supports
F=force applied at midpoint of wire
x=deflection of wire due to the force
For example, consider a 30 inch horizontal wire that has a one pound weight suspended at the midpoint and suppose the dial indicator shows a deflection of 0.05 inches. Then the tension is
T=(30*1)/(4*.05)=150 pounds
That relationship will be accurate so long as:
(a) the force and deflection is applied and measured at right angles to the wire
(b) the ratio of length to wire diameter is so large ( say 100 or more) that the wire stiffness does not affect the amount of deflection.
(c) the force is small compared to the tension (no larger than a few percent) so that the amount of deflection is much, much smaller than the wire length.
Jerry Jackson
7ECA
8T8
T=(L*F) / (4*x) where
L=length of wire between supports
F=force applied at midpoint of wire
x=deflection of wire due to the force
For example, consider a 30 inch horizontal wire that has a one pound weight suspended at the midpoint and suppose the dial indicator shows a deflection of 0.05 inches. Then the tension is
T=(30*1)/(4*.05)=150 pounds
That relationship will be accurate so long as:
(a) the force and deflection is applied and measured at right angles to the wire
(b) the ratio of length to wire diameter is so large ( say 100 or more) that the wire stiffness does not affect the amount of deflection.
(c) the force is small compared to the tension (no larger than a few percent) so that the amount of deflection is much, much smaller than the wire length.
Jerry Jackson
7ECA
8T8