From: bartley@spss.com (Dennis Bartley)
Newsgroups: rec.boats
Subject: Polyesther leisure chutes
Date: 6 Oct 92 20:28:18 GMT
Article-I.D.: spssig.bartley.718403298
Organization: SPSS Inc.

Way back last winter I asked if anyone on the net had experience with
polyesther spinnakers. Nobody really did. In an unusual leap of faith
(for me), I went out and bought one anyway. Now that sailing in the
midwest is coming to a close, here's what I've learned so far.

Polyester comes in 2 forms, film or spun into thread. The film is
usually called mylar, as a thread, it's called Dacron (or Terrylene?).
I'm dealing with the thread version.

The theory is that because dacron is less stretchy than nylon,
spinnakers made from it would hold their shape better, and be made of
a lighter cloth than equivalent nylon chutes. Also, when nylon gets
wet it becomes much stretchier, and more apt to tear.

Maintaining shape in a spinnaker is important. Unless you're sailing
almost dead downwind, there is airflow over the chute which generates
lift. This becomes especially important when reaching. The
stretchiness of nylon is not a desirable feature for holding shape
through waves or gusts.

The potential problems with polyester are it's cost, it
doesn't handle shock loading as well as nylon (this is where stretch
is a good feature), and may be more difficult to fly. 

The cost wasn't that much of a
problem. For a J30 a nylon .75 oz chute would have cost around $1400.
For $200 more I had a .6 oz. poly chute. Amortized over it's expected
life of at least 4 years, that's not much at all. Last year the only
manufacturer of lightweight spinnaker cloth was in Japan. Dimension in
the US is now making the material, so material costs should drop a little.

Theoretically shock loading may be a problem, but here's an anecdote
from my sailmaker: down at Key West race week he was on a Taylor 40.
It was a pretty windy series, and they were doing windward/leeward
courses. In one race where it was blowing 25 or 30 true, after the
first run they threw there 3/4 oz chute below expecting to use the 1.5
oz. the next time. When they went to set it, the bag somehow jumped
into the water and they had a real mess. After dragging the 1.5
onboard, the only chute available was the new .6 oz poly. Without
telling the back of the boat what was going on, they hooked it up. Of
course sheets got screwed up in the earlier mess, the sail didn't
fill right away, and it was flogging quite a bit. When it did finally
fill, it was quite abrupt, shock loading. Nothing happened to the
sail. After the race the sailmaker inspected it carefully, and
couldn't find anything wrong. 


My experience has been pretty positive. A .6 oz. poly chute can
probably easily replace a .75 oz. nylon. This chute seems to work
pretty well downwind. It's not particularly difficult to trim. Earlier
attempts at using dacron in chutes didn't deal well with it's lack of
stretch. Newer designs seem better. 

It worked great on a reach in a reasonable breeze (20 kts apparent). When
going from a run to a reach in a breeze, I didn't have to worry about
doing a spinnaker peel. The cloth seems to come in most colors
including hot pink, luminous green, etc (though mine is pretty plain
red and white). So far I haven't gotten to test it's ability
to handle shock loads :-)



Anyone else have a poly chute yet?
Newsgroups: rec.boats