drag wires

[DonJohnson]

3 questions are anti drag wires always on the top....is there a specified tension for drag -anti drag wires...what best coating to keep drag wires from rust

[Hank Jarrett]

When you twist the wing trailing edge UP at the tip the wires should move further apart. They should also be bound together where they cross to keep them from rubbing. I think the factory just wrapped the wires and where they crossed with electrical tape (the cloth type). At least that is what I have found on numerous old wings. The wires should NOT actually touch or rub.

[DonJohnson]

i found same thing,Hank, except were not tied together. Just one had cloth tape on it. Is there a specified tension for drag wires? seems like i read that somewhere but cant find it now. seems some one said 14 to15 lbs to move wire 1/2 inch at middle

[Scott]

There's no published specification as far as I've found.

The best info I found was on the Stinson forum. Apparently there are specs for stinsons and I used those numbers on both the Taylorcraft and Super Cub. 60- 90lbs I seem to recall depending on the bay.

There's also a formula to calculatetension via deflection of a rod. I believe it can be found on the same forum. So you can use a spring scale and ruler to get a ballpark tension.

The other approach is the so called "middle C" tone. Widely used, which pehaps explains why it's easy to find over tightened wires!
S

https://stinsonowners.org/forum/migrated-forums-3-technical-corner-wings/drag-wire-tensions-3/

[Hank Jarrett]

It isn't based on tension. You tighten and loosen the drag and anti-drag wires to get the spars straight. Sometimes things will "relax" over a few days and need to be adjusted again. A LASER down the top of the spar makes it pretty easy to see how far out of line the spar is, just understand a lot of times getting one bay straight will knock the next one out. You have to go down the adjustments several times before it stays straight.

[Scott]

The wings can be correctly trammeled, yet have too much or not enough tension on the wires. So both objectives need to be met.

In practice this usually means doing one bay at a time, getting the wires correctly tensioned with the spars reasonably square, then making small adjustments to get things straight.

Small adjustments involve loosening one wire, and tighting others by the same amount, so the tensions remain correct as small changes to squareness and alignment are made.
S

[Scott]

I found the formula in my notes:

Wing drag wire tension:

T= LxF / 4 x X

Where:
L length
F orce applied at mid point
X deflection

S

[Hank Jarrett]

Scott gets it. Once you get the spars straight you will have to "tweak" the wires to get tension on each. As everything settles in you will notice that wires of the same length have the same note when you pluck them. Note that wires of DIFFERENT lengths don't and SHOULD NOT have the same note!

[Jerry Miel]

I put heavy heat shrink tubing on the center of my drag lengths before I installed them and then heated them in place where they crossed.

[Scott]

The objective is both to protect the wires, and to the extent possible, eliminate relative movement between the wire. This was typically done with so called "friction tape"

Hockey tape works ok. I used koroseal.

https://2.bp.blogspot.com/-r1nuXUSgdto/WWL4xWJvrcI/AAAAAAAADmc/B4gXhyGGJ2Acj_2gI9z1LzHKSalokI9-wCLcBGAs/s1600/DSCN5659.JPG