Cable vs rope pulling glider from field

On Wed, 12 Oct 2011 19:38:24 +0000, Ben Watkins wrote:

At 17:43 12 October 2011, kirk.stant wrote:
On Oct 12, 10:34=A0am, Auxvache wrote:
I'd like to make a stout wire cable or rope with proper TOST ring, to
have on hand should I have to tow my 15m glider from mud/soft dirt/
guano.
Is a metal cable necessary/preferable, or would high breaking-strength
rope be sufficient?
My only experience here (Chester loam, Pegase, and stick-shift BMW)
did not end well.
Thanks in advance,
Erik

You might consider keeping a Tost ring set in your glider, as part of
your landout kit. Nice to have when you want a local to help move your
glider to a different location for derigging, etc. Rope of some sort is
almost always available, but trying to use a rope loop in a Tost release
is an exercise in futility!

Kirk


If you are putting strain on the tow rope make sure you lay something
reasonably heavy (coat, car rug etc.) over the rope more than half from
the car to the glider. That way if the rope does break the rings, weak
link etc. won't end up flying through your back window!

....and use a rope with as little stretch, which means energy storage, as
possible. A light weight cable is good too for the same reason.

Steel cable is about the worst thing you could use because of the way it
lashed round if it or a fixing breaks under load and, and is harder to
wind up and store than it needs to be. OTOH plastic rope rope,
particularly Dyneema or good quality climbing rope, both have minimal
energy storage and are easy to handle.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

On Oct 12, 2:18*pm, Martin Gregorie
wrote:
On Wed, 12 Oct 2011 19:38:24 +0000, Ben Watkins wrote:
At 17:43 12 October 2011, kirk.stant wrote:
On Oct 12, 10:34=A0am, Auxvache *wrote:
I'd like to make a stout wire cable or rope with proper TOST ring, to
have on hand should I have to tow my 15m glider from mud/soft dirt/
guano.
Is a metal cable necessary/preferable, or would high breaking-strength
rope be sufficient?
My only experience here (Chester loam, Pegase, and stick-shift BMW)
did not end well.
Thanks in advance,
Erik

You might consider keeping a Tost ring set in your glider, as part of
your landout kit. *Nice to have when you want a local to help move your
glider to a different location for derigging, etc. *Rope of some sort is
almost always available, but trying to use a rope loop in a Tost release
is an exercise in futility!

Kirk

If you are putting strain on the tow rope make sure you lay something
reasonably heavy (coat, car rug etc.) over the rope more than half from
the car to the glider. That way if the rope does break the rings, weak
link etc. won't end up flying through your back window!

...and use a rope with as little stretch, which means energy storage, as
possible. A light weight cable is good too for the same reason.

Steel cable is about the worst thing you could use because of the way it
lashed round if it or a fixing breaks under load and, and is harder to
wind up and store than it needs to be. OTOH plastic rope rope,
particularly Dyneema or good quality climbing rope, both have minimal
energy storage and are easy to handle.

--
martin@ * | Martin Gregorie
gregorie. | Essex, UK
org * * * |

Actually for the force required, 2mm Dyneema would be strong
enough. The 12V winch linked above would likely hold 2000 feet or
so. If you landed in a boggy field which wouldn't support a car and
needed to get the glider to its trailer, this would be just the
trick. Mount the winch at the front of a trailer and it could help
get the glider onto its fuselage dolly, then pull the fuselage into
the trailer.

Thanks very much for your answers--sounds like Dyneema with a weak
link and Tost ring would be a good set-up.
And, forewarned, I promise not to dehisce the nose of the glider with
Farmer Brown's tractor.
Or shatter the back window of mum's grocery-getter.

And if it gets to be a regular occurrence, I'll find another hobby.

Erik

And if it gets to be a regular occurrence, I'll find another hobby.

A landout every now and then isn't too bad. Luckily I've never gotten
into such a muddy field that I couldn't get the glider moved out.
Benefit of flying mostly in fairly dry climates I guess. There was
one time where I avoided a very muddy mucky mess by landing on a clear
unobstructed stretch of paved county road. I've only got 30ish
landouts though and a mere 6 or 7 this season.

On Thu, 13 Oct 2011 06:39:38 -0700, Auxvache wrote:

Thanks very much for your answers--sounds like Dyneema with a weak link
and Tost ring would be a good set-up.

Yes, I'd agree, but with one warning I should have mentioned: a naked
Dyneema cord is not a good idea because the slightest handling abrasion
tends to fluff it up into an unusable woolly caterpillar-like thing. I
discovered this when trying to use a thin woven Dyneema (80 lb) line to
control the VIT stop on a free flight power model - even expecting it to
handle a 90 degree bend by sliding round a 3mm brass tube was too rough
and caused it to fluff up and become unusable.

What I've found to be excellent is a core of unwoven Dyneema inside a
woven Dacron casing. I've used 100 lb kite bridle (about 0.7mm diameter)
as model glider towline. This was very easy to handle and almost totally
abrasion resistant. I believe you can get this type of line in up to at
least 3mm diameter.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

On Oct 13, 7:31*pm, Martin Gregorie
wrote:
On Thu, 13 Oct 2011 06:39:38 -0700, Auxvache wrote:
Thanks very much for your answers--sounds like Dyneema with a weak link
and Tost ring would be a good set-up.

Yes, I'd agree, but with one warning I should have mentioned: a naked
Dyneema cord is not a good idea because the slightest handling abrasion
tends to fluff it up into an unusable woolly caterpillar-like thing. I
discovered this when trying to use a thin woven Dyneema (80 lb) line to
control the VIT stop on a free flight power model - even expecting it to
handle a 90 degree bend by sliding round a 3mm brass tube was too rough
and caused it to fluff up and become unusable.

What I've found to be excellent is a core of unwoven Dyneema inside a
woven Dacron casing. I've used 100 lb kite bridle (about 0.7mm diameter)
as model glider towline. This was very easy to handle and almost totally
abrasion resistant. I believe you can get this type of line in up to at
least 3mm diameter.

--
martin@ * | Martin Gregorie
gregorie. | Essex, UK
org * * * |

Martin, you must have had some really crappy rope mislabeled as
Dyneema . The 12 strand hollow braid we use has 15x the abrasion
resistance of steel. The off road 4x4 guys use it on their bumper
winches with it going over sharp rocks and trees. I've never seen the
problems you describe.

On Oct 13, 7:18*pm, Bill D wrote:

Martin, you must have had some really crappy rope mislabeled as
Dyneema . *The 12 strand hollow braid we use has 15x the abrasion
resistance of steel. *The off road 4x4 guys use it on their bumper
winches with it going over sharp rocks and trees. *I've never seen the
problems you describe.

Yes, that sounds more like aramid (such as Kevlar (tm)) behavior.

Thanks, Bob K.

On Thu, 13 Oct 2011 19:18:12 -0700, Bill D wrote:

Martin, you must have had some really crappy rope mislabeled as Dyneema
. The 12 strand hollow braid we use has 15x the abrasion resistance of
steel.

Well, it looked and felt like Dyneema/Spectra/whatever brand you prefer,
i.e. dead slippery to handle. As I said it was naked - just a fairly
loosely woven braid with a circular cross section that was sold as 80 lb
fishing line - I've seen the same sort of line and thickness in Dacron
but then, of course, it would have been around 18-20 lb line, say
somewhere between 0.3 to 0.5mm in diameter.

Since it felt so slick I was sure it would slide round the outside of
something as relatively large and smooth as 3mm brass tube, but nooo -
the stuff had fluffed up before I even got the model out of my workshop,
so I replaced it immediately with Dacron, which worked as I'd expected
the Dyneema to do.

but The off road 4x4 guys use it on their bumper winches with it
going over sharp rocks and trees. I've never seen the problems you
describe.

But is that stuff naked or has it got a woven Dacron tube as its outer
layer? Obviously some of the stuff that was used as winch cable had such
an outer shell or the splicing method I saw described (threading one end
in and out of the casing with a big needle for 50cm or so) would never
have worked.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

On Oct 14, 2:22Â*pm, Martin Gregorie
wrote:
On Thu, 13 Oct 2011 19:18:12 -0700, Bill D wrote:
Martin, you must have had some really crappy rope mislabeled as Dyneema
. Â*The 12 strand hollow braid we use has 15x the abrasion resistance of
steel.

Well, it looked and felt like Dyneema/Spectra/whatever brand you prefer,
i.e. dead slippery to handle. As I said it was naked - just a fairly
loosely woven braid with a circular cross section that was sold as 80 lb
fishing line - I've seen the same sort of line and thickness in Dacron
but then, of course, it would have been around 18-20 lb line, say
somewhere between 0.3 to 0.5mm in diameter.

Since it felt so slick I was sure it would slide round the outside of
something as relatively large and smooth as 3mm brass tube, but nooo Â*-
the stuff had fluffed up before I even got the model out of my workshop,
so I replaced it immediately with Dacron, which worked as I'd expected
the Dyneema to do.

but Â* The off road 4x4 guys use it on their bumper winches with it
going over sharp rocks and trees. Â*I've never seen the problems you
describe.

But is that stuff naked or has it got a woven Dacron tube as its outer
layer? Obviously some of the stuff that was used as winch cable had such
an outer shell or the splicing method I saw described (threading one end
in and out of the casing with a big needle for 50cm or so) would never
have worked.

--
martin@ Â* | Martin Gregorie
gregorie. | Essex, UK
org Â* Â* Â* |

This is the stuff the 4x4 guys use - it has no sheath.
http://www.okoffroad.com/stuff-winchrope-atv.htm

Dyneema/Spectra/UHMWPE rope or whatever you call it has 15x steels
abrasion resistance, 10x steel's strength per weight and a friction
coefficient lower than Teflon plus a lot of other engineering
superlatives. It simply can't be beat as winch rope for 4x4's or
gliders. It does "fuzz up" as it wears but the fuzz actually protects
the rest of the rope.

Even this miracle material is being significantly improved.

"Abstract:
This paper reports the use of multiwalled carbon nanotubes (MWCNT) to
reinforce and toughen gel-spun ultra high molecular weight
polyethylene (UHMWPE) fibers. By adding 5 wt% MWCNT, ultra strong
fibers with tensile strengths of 4.2 GPa and strain at break of ∼5%
can be produced. In comparison with the pure UHMWPE fiber at the same
draw ratios, these values represent increases of 18.8% in tensile
strength and 15.4% in ductility. In addition, a 44.2% increase in
energy to fracture has also been observed. The mechanism of
reinforcement has been studied using a combination of high resolution
scanning electron microscopy (SEM) and micro-Raman spectroscopy.
Carbon nanotube alignment along the tensile draw direction has been
observed at high elongation ratios. Such alignment induces strong
interfacial load transfer both at small and large strains to enhance
the stiffness and tensile strength of the composite fiber.
Consequently, the mechanical properties of the composite fiber follow
closely with the rule of mixtures. Our work also reveals potential for
positive deviation from rule of mixtures if the CNT alignment can be
further optimized."