Originally posted by guillemot:
The Buff Polysetser I mentioned above is soft and supple…Don't know about why it wouldn't be good enough. Please explain. Is it too stretch?In one word: STRETCH
Assuming English Braids Buff Polyestr is roughly the same as NE Ropes Spun Classic, it stretches under load (working elongation) maybe 12-15% or more. Ordinary double braid polyester stretches maybe 3-4 percent.
and so on.
The exotic fibers, spectra, vectran UMHW polyethelene, ec., measure stretch in the 1/2 of 1 percent neighborhood: maybe 0.4 to 0.6 percent or so.
Acceptable working loads run the same way from low to extremely high. Some of the exotic fibers stretch less and can be as strong or stronger than wire rope.
They apparently rigged the HMS Rose with it for the Master and Commander movie. Don't know if it was just for sheets, though. Way bigger than 60 feet.And that was OK, because her rig is designed for low tensions (not to mention that double braid or exotic fibers would look exceedingly out of place on a vessel like HMS Rose.
With classic/antique yachts, aside from the obvious aesthetic issues that come into play, as has been pointed out, there's also engineering issues at play: these vessels were never engineered to take the sort of stresses that can be imposed with multiple-part purchases and winches in conjunction with these exotic fibers. And that was when they were new. Most older wooden vessels have probably lost considerable structural strength over the years as fasteners degrade, stealers (short planks) are spliced in for repairs, frames sistered, etc.
For instance, consider NE Rope's Vectran V-12, a 12-strand single-braid: in 1/2 inch (12mm) construction, it has a tensile strength of 24,500 pounds — 3 times that of 1/2 inch conventional polyester double braid in the same size (~ 8,000 lbs tensile strength), and more than 6 times that of a 3-strand laid polyester like NE Rope's Spun Classic or English Braid's Buff Polyester (~ 3,800 lbs tensile strength).
As an extreme example of what can happen when the structure isn't up to the forces imposed on it, Consider the America's Cup challengers One Australia and Young America. One Australia broke in half and sank in 90 seconds off San Diego. Young America merely folded just aft of the mast and folded through 50 degrees before sinking (she took a little longer than 90 seconds).
<span style="font-family:serif;"><b style="font-family:sans-serif;">The Ballad of One Australia[/b]
Oh, they built the One Australia
To sail the ocean blue.
And they thought that they had built a yacht
The water couldn't go through.
Well, the calc's were by some bum
(Must have used a Pentium)
It was sad, when the frail yacht went down.
<blockquote>It was sad (it was sad),
It was sad (John was mad),
It was sad, when the frail yacht went down
Nobody drowned,
(Now the designer can't be found).
It was sad, when the frail yacht went down</blockquote>
Well, the skipper said: "Me buckos,
We cannot be afraid.
The wind is over fifteen knots,
But the sandwiches are made. "
Then they hit that two-foot chop
And the keel just would not stop.
It was sad, when the frail yacht went down.
<blockquote>It was sad (it was sad),
It was sad (John was mad),
It was sad when the frail yacht went down
Three million bucks
(Now it's gone, but what the f*ck;
It was sad, when the frail yacht went down.</blockquote>
They spent twenty million dollars,
To bring the Cup to Oz.
And whenever people asked them why
They could only say "because. "
Now the crew must taste defeat,
Their boat's down twelve hundred feet.
It was sad, when the frail yacht went down
<blockquote>It was sad (it was sad)
It was sad (John was mad),
It was sad, when the frail yacht went down
Filled up, and sank
(Along with three Australian banks).
It was sad when the frail yacht went down.</blockquote>
You can't blame the Race Committee,
They only did what's rlght.
A wind that only blows force five
Should not be such a fright.
If your hull is paper thin,
No-one says you have to win.
It was sad, when the frail yacht went down
<blockquote>It was sad (it was sad),
It was sad (John was mad),
It was sad, when the frail yacht went down
Broke clean in two
(All they salvaged was the crew)
It was sad, when the frail yacht went down.</blockquote>
Now, they tell this tragic story
In yacht clubs 'round the world.
'Bout how the fearless Aussie crew.
Could not sail like the girls.
While the Sheilas beat DC,
They were sinking on TV.
It was sad, when the frail yacht went down
<blockquote>It was sad (it was sad),
It was sad (John was mad),
It was sad, when the frail yacht went down
Total disgrace
(Auckland's ready for this race)
It was sad. when the frail yacht went down.</blockquote>