Could someone tell me the diameter of the Sullivan Tufstrand please.

I just measured it with a vernier and it is kind of oval.  It is .015"  to .020".  It says it is good to a motor up to .51 cu. in.  I never tried it yet.

I really dislike tufstrand. It tends to turn flat side into the wind. That suddenly increases the drag and unless the lead out guide is waaaaaay back that causes the plane to turn inward. With AMA making spectra fishing line legal for sport flying I dont see any reason someone would use tufstrand for anything other than reinforcing material.
Bob

Thanks for the info. Sullivan's from Brodak has gotten exee. Spyder Wire isn't cheep either but if it has less drag would be a better deal.
Any Data on what size S/Wire to use for different apps.

Is the Tuffstrand as good as C/F tow for reinforcing material?

Check the AMA site. I believe they require the same diameter as steel. That does nothing to reduce drag but gives you about 5X the strength! Of course that assumes you tie the correct knot. A bad knot reduces the line strength by 50% or more. Again all this is on the AMA website.
Bob

The yellowish color suggests its kevlar.

There was a period some years ago when people were using kevlar as parachute rigging line rather than spectra or dacron due to its superior dimensional stability, but it has largely fallen out of use main parachutes and is only found in some reserves these days.

The kevlar that was being used on main parachutes (often packed on the ground and several times a day, rather than in a clean loft like reserves that are packed only every few months that are exposed to sun only if deployed) proved to be more vulnerable to abrasion and the deteriorating effects of constant sunlight exposure than Spectra or Dacron line.

My experience with using this stuff as stooge release line mirrors that of the parachute industry. It will degrade and fray over time and constant exposure to the sun. OTOH, I have some stainless line sets that are over 30 years old that show no degradation at all.

I know several people who have tried it once none who have tried it twice! I can't believe they still sell this
stuff .. they can't have sold very many sets EVER, much less enough to justify continuing it.