All I have ever used on even the largest airplanes is .027 , 7 strand.   Never have I ever seen any visible sign of wear anywhere even after decades of use.  A caveat though- I make my own hardware and everything including the lead out guide is made from Delrin.  It is in itself a non-wearing bearing material. It will not cut through or abraid the metal cables.   I do also double loop the cable everywhere so that there are two strands of cable running through each hole in the bell crank and at the other end where the lines are connected.   This ensures that should I ever experience a worn or broken cable there is a second backup loop there to take over.   Haven't seen any failure but old tricks my dad taught me die hard.

Dave

I finally went to using stranded leadouts after years of using solids.  There are many different types of wire configurations (1 X 7, 3 X 7, 1 X 19, etc.).  The more individual strands, the more flexible, but I wonder if the finer strands are more prone to fraying due to contact with the leadout guide.

On larger planes (i.e. 600 squares or larger), I normally use the 1 X 7, 0.031 diameter.  On smaller planes, 1 X 7, 0.027 diameter.

My concerns about strands fraying might be unfounded, but I would rather have more safety margin than not enough.  What is your experience, long term use, with the different wire configurations?

  I use the .027  1x7 brass-plated carbon steel leadouts from the Sullivan kit. I do not recommend the 19-strand - they look and feel cool, but are prone to fraying as you say, and also I have seen *many* of them fail as the individual strands are very prone to breaking when flexed.

     Brett

Thanks for the re-assurance.  I have a tendency to go overboard to prevent a failure so it is nice to be able to lighten things up a bit without concerns for strength and durability.

The rated strength is one thing, and any damage from normal handling is another.  No matter how careful I try to be, I get more dents, dings, and other scars on a plane just from getting them in and out of the car.  Snagging the leadouts on something can happen so it is nice to have some margin for that.

Another problem is spectators or other flyers who get tangled in the lines.  I can replace the lines, but not so easy to replace leadouts.

The bellcrank is 3/8 inch thick Garolite, from McMaster-Carr.  The teardrop fitting is 1/8 inch thick Delrin.