Tost Reel Cable Breakage

We've been using a Tost reel internal to the towplane (PA-25) for
several years now, and are delighted with the overall improvement in
operational efficiency and safety. However, we've also had over a
dozen breaks in the Tost-supplied rope/cable, always right where it
enters the "slug" that contains the ring that connects to the glider.
It breaks - the knot inside the "slug" is intact; we have never broken
a weak link (sized properly for the gliders we fly), and several
breaks have occurred with relatively low-time (e.g., fewer than 300
launches) cables. Any clue as to what's going on here and how to
prevent it?

When do they break? Presumably on tow, but at what point?

At 22:11 09 July 2008, Jim Kellett wrote:
We've been using a Tost reel internal to the towplane (PA-25) for
several years now, and are delighted with the overall improvement in
operational efficiency and safety. However, we've also had over a
dozen breaks in the Tost-supplied rope/cable, always right where it
enters the "slug" that contains the ring that connects to the glider.
It breaks - the knot inside the "slug" is intact; we have never broken
a weak link (sized properly for the gliders we fly), and several
breaks have occurred with relatively low-time (e.g., fewer than 300
launches) cables. Any clue as to what's going on here and how to
prevent it?

On Jul 9, 6:27*pm, Nyal Williams wrote:
When do they break? Presumably on tow, but at what point?

snip

Pretty much anytime - anywhere from initial takeoff roll to release
altitude.

this would be extremely rare....Tost tow reels are pretty common and rarely
have problems with tow ropes....I suggest you look at the installation to
see if there is some place sharp along the travel of the rope that might
cause it to fatigue early or some place where the rope is getting loose
outside the normal carry tube where it might somehow get tangled on a corner
or flat gusset in the aircraft.
I have several tow reel users that use both the TOST cable (rope) and the
Dacron I sell and have no other information from anyone on uncommon rope
breaks though the rope can fatigue normally as with almost anything so it's
not impossible, (why we train for rope breaks and other emergencies) the
TOST cable is non-stretchy purposely to prevent snapping back on release..
If you have a length of the broken cable send it to me and I'll forward it
on to TOST for their evaluation.
tim

--
Please visit the Wings & Wheels website at www.wingsandwheels.com

"Jim Kellett" wrote in message
...
On Jul 9, 6:27 pm, Nyal Williams wrote:
When do they break? Presumably on tow, but at what point?

snip

Pretty much anytime - anywhere from initial takeoff roll to release
altitude.

If I understand your problem correctly - you are experiencing rope breaks
at the point where the rope enters the weaklink piece - but the knot is
not slipping.

We use two of these systems on PA-25s and have not had that problem -
although we have had other problems. You might check inside the black
cone on the tail of the plane and see if there is some sharp edge that is
chaffing or abrading the rope there.

We use Tim's Dacron rope and we replace it frequently. Before that we had
a problem with the knot slipping. We still have a problem with the rope
snarling on the reel occasionally and not playing out competely - which is
very dangerous becuase the reel is not designed to take the towing load.

I'm not a big fan of the system - it just replaces one set of problems
with another.

Roy B.
Greater Boston Soaring Club