drag wire tension

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Flyguy

Active Member
Joined
Aug 3, 2004
Messages
27
Location
SW Michigan
Can anyone give me a good "rule-of-thumb" method of tightening 3/16" drag/antidrag wires in a small acro biplane without using a real tension tester?
Thank you and Merry Christmas to all.
FlyGuy
 

Craig

Well-Known Member
Joined
Jan 30, 2003
Messages
543
Location
Jupiter, Florida
Tension

Flyguy, they are tightened enough to keep the wing square. There is no real method or madness to it, no absolute numbers. They work in tension to counteract air loads.

We laid my wings flat on the table, then used some big squares to ensure that the tension on the wires was used to achieve perfect squareness. started at the root bays, and worked outward. They do make a nice musical note whn tapped with a wrench, and mine all sound about the same - but then, I am not a musician and can't tell you what note it is!

Helps to have good straight spars, but the tension wires can take out a little bit of bowing if it is there.
 

Flyguy

Active Member
Joined
Aug 3, 2004
Messages
27
Location
SW Michigan
Hey Craig, thanks for the reply. The 3/16" dia. drag wires have a finite tinsel strength. If I overtighten I use up some of my safety margin. If I undertighten something is going to move at the bottom of a 4"G" loop at 180 MPH. I would just as soon that didn't happen. If I cannot stress each wire uniformly then some will be carrying a greater load than others. I wanted to find a way to prestress then equally without having to purchase a tension meter. Looks like I just may have to spend the bucks.
Thanks again,
Flyguy
 

Craig

Well-Known Member
Joined
Jan 30, 2003
Messages
543
Location
Jupiter, Florida
Prestressing

I would think that a simple crow-foot wrench on the end of a torque wrench would get tham all tensioned the same.
 

ZENO

Well-Known Member
Joined
Feb 22, 2006
Messages
56
Location
New England
First of all drag wires in tension are capable of pulling some mighty heavy loads...on your spar. Wood or aluminum spars are no match for the tension of drag wires. The tension should be only enough to even up the pull of the drag wire diagonally from it.

As your completing one bay after the other, take staightness checks on your spars lenghthwise. If they start looking bowed back off your drag tension otherwise you'll have a spar that looks like a snake.

ZENO
 
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