Roll Wires, Lugs and Lauzon Cabanes

[Ebby]

I'm setting up the center section so I can finish roughing in the fuel lines. I chose to build the Lauzon Cabanes for my classic. I made my 2 roll wire lugs according to the Makelan plans sheet. Each roll wire has approx. 2.5 inches of thread on each end with the clevis end removed. My question has to do with the amount of unused thread showing with the roll wires installed. I tensioned the roll wires hand tight plus one turn and eyeballed the intersection where the wires cross to equalize the geometry. I cannot pass a safety wire through any of the witness holes. To me, it looks like too many threads are left exposed. For example when I snug the stop nut there is an inch and a half of exposed thread. The witness hole is 5/8" from the clevis end which means just over 5/8" of threads are engaged with the clevis. It concerns me because with a turnbuckle there is a definite guideline on the number of exposed threads according to AC43-13. Is the inch and a half a nominal amount of exposed thread on each end of the roll wires? Im thinking about making two new roll wire lugs with a longer reach.

[M Lightsey]

The rule of thumb for thread engagement is 1 1/2 times the diameter gives the maximum strength. Typically that's where your witness holes are located. More engagement won't make them any stronger.
Most flying wires have considerably longer threads on the right handed end which should be the round/lower section for roll wires.
Also keep in mind the jamb nuts will cover a portion of the threads if they're not installed for mockup.
Mark

[mtaylor]

Witness hole is the go/no go. If it's filled, you're good to go. Don't worry about anything else.

[Ebby]

Messages received and understood. Thanks fellas.