On Sep 1, 8:51*am, Bob Kuykendall wrote:
On Sep 1, 6:37*am, John Smith wrote:

Lately there has been a discussion re Dyneema in this group.
Incidentally, on the DG home page there's an interesting article to this
theme (originally published by "Magazin Segelfliegen"). It's German and
I'm not aware of an English translation.http://www.dg-flugzeugbau.de/windenseil-d.html

Here's the typically-awkward-but-mostly-usable Google translation
(long link):

http://translate.google.com/translat...n&ie=UTF-8&lay...

Thanks, Bob K.

Good article as far as it goes. This is the US angle.

Essentially there are four 12-strand ropes suitable for winch
launching in the nominal 3/16" diameter commonly used on winches.

Dyneema 75, DSM, ~3500lbs BS
Spectra, Honeywell, ~3500lbs BS
Amsteel Blue, modified Dyneema 75 from Samson Ropes, ~5400lbs BS
Plasma 12, modified Spectra from Puget Sound Ropes (Cortland
Industries), ~5400lbs BS

There are sheathed options, but those add weight, expense, and larger
drum capacity for the same length.

The two brands result from two patented processes for creating the
Ultra High Molecular Weight Polyethylene (UHMWPE) fibers. Honeywell
acquired the Spectra patent when it bought Allied Signal. I don't
know about the production locations or capacities of Honeywell. DSM
is Dutch based, but has more production capacity in the US than the
Netherlands at this point.

The price of these ropes quadrupled from about 2002-2006 due to the
rise in ethane and ethylene to some extent, demand, and the rise in
natural gas used is post production. It has been stable for a least
the past two years.

Proper treatment and handling is essential with appropriate winch
modifications needed, particularly a fairlead feed, possibly a
guillotine modification and clearance to avoid any loops hitting hard
parts.

Best results are achieved with longer winch runs where heights above
1500ft are common as the reduced weight becomes a bigger factor in the
system. Rope weights and diameters are less a factor on launch runs
around 3600ft.

Some are considering looking at other ropes and hybrid solutions using
polyofelin (blended) ropes. If the launch run is 5000ft, then
perhaps 3000ft of polyofelin with 2000ft of Amsteel Blue at the glider
end. Polyofelin of sufficient strength will be larger diameter and
heavier, but still lighter than steel.

We can now get mobile 3rd party liability insurance for winching
through Costello, but the underwriter restricts us to synthetic
ropes. I've heard that one other underwriter allows steel, but that
is at a fixed base.

If interested, you are invited to join the fray at Yahoo Groups
winchdesign and winchengineering.

Some winch presentations are being considered for the SSA Conference
in Philadelphia.

Frank Whiteley