Dacron vs. polyfiber etc.

What are the relative advantages and disadvantages of "normal" modern
fabric coverings (doped and painted polyfiber) vs. the stitched,
zippered sailcloth coverings (dacron, others?) on many ultralights and
new LSA airplanes? How are the sailcloth coverings attached?

The Aventura 2-place homebuilt I saw at Oshkosh had dacron wing covering
that looked for all the world like it was held on largely by tension.

All dope and fabric systems use aluminum powder mixed with the finish to
block UV, which causes all fabric and dope to deteriorate. Dacron
"sails" as used on ultralights don't have UV protection, so they must be
changed every few years. The advantage of undoped dacron sails is
simplicity and weight savings.

Their are two main differences in dope and fabric systems: Flammability
of the finished covering system and toxicity and flammability of the
components. Polyfiber is fireproof. I've tried it, dacron fabric
finished with Polytone won't burn unless you hold a flame to it.
Polyfiber dopes and solvents are highly toxic and flammable however and
must be shipped as hazardous material at extra expense. Other covering
systems are non-toxic and non-hazardous, I don't know how flammable the
finished job is for them. The traditional butyrate and nitrate dope
systems are highly flammable, and nitrate dope as used in the early
Ceconite system is explosively flammable when cured.

Most of this information I got from the Ray Stitts polyfiber video and
manual, A&P school, and what I've tried out in the shop.

Adam Aulick wrote:
What are the relative advantages and disadvantages of "normal" modern
fabric coverings (doped and painted polyfiber) vs. the stitched,
zippered sailcloth coverings (dacron, others?) on many ultralights and
new LSA airplanes? How are the sailcloth coverings attached?

The Aventura 2-place homebuilt I saw at Oshkosh had dacron wing covering
that looked for all the world like it was held on largely by tension.


--
John Kimmel


"To announce that there must be no criticism of the President,
or that we are to stand by the President, right or wrong, is
not only unpatriotic and servile, but is morally treasonable
to the American public."

Theodore Roosevelt

guynoir wrote:

All dope and fabric systems use aluminum powder mixed with the finish to
block UV, which causes all fabric and dope to deteriorate. Dacron
"sails" as used on ultralights don't have UV protection, so they must be
changed every few years. The advantage of undoped dacron sails is
simplicity and weight savings.
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Dacron will last for twenty years or so if the plane is hangared when
not flying.

Outside, two years would be expected for sure.

There are also protectants that slow the effects of the sun on the
fibers.


--
Mark Smith
Tri-State Kite Sales
1121 N Locust St
Mt Vernon, IN 47620
1-812-838-6351
http://www.trikite.com

Mark Smith wrote:
guynoir wrote:

All dope and fabric systems use aluminum powder mixed with the finish to
block UV, which causes all fabric and dope to deteriorate. Dacron
"sails" as used on ultralights don't have UV protection, so they must be
changed every few years. The advantage of undoped dacron sails is
simplicity and weight savings.

,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,

Dacron will last for twenty years or so if the plane is hangared when
not flying.

Outside, two years would be expected for sure.

There are also protectants that slow the effects of the sun on the
fibers.


Interesting because balloon envelopes are typically guaranteed for only
500 hrs. Sun and heat cause them to become porous and a yearly annual
inspection will eventually declare your envelope unfit. It's been a few
years but there was not way to renew an envelope although several things
were tried. BTW: that's one of the things that make ballooning soooooo
expensive. Figure $30K for 500 hrs -- that's $60/hr right there!

Stubby wrote:

Interesting because balloon envelopes are typically guaranteed for only
500 hrs. Sun and heat cause them to become porous and a yearly annual
inspection will eventually declare your envelope unfit.

Perhaps the heat reduces the life of the fabric?

George Patterson
Give a person a fish and you feed him for a day; teach a person to
use the Internet and he won't bother you for weeks.

George Patterson wrote:
Stubby wrote:

Interesting because balloon envelopes are typically guaranteed for only
500 hrs. Sun and heat cause them to become porous and a yearly annual
inspection will eventually declare your envelope unfit.

Perhaps the heat reduces the life of the fabric?

George Patterson
Give a person a fish and you feed him for a day; teach a person to
use the Internet and he won't bother you for weeks.

Dacron and Stitts polyfiber are both polyester. Although plastic
formulations can differ in the filler and plasticizer, the main
differance would have to be the weave, fiber size, and fiber density.
I suspect ballons have a short life span because they must hold hot
air, and the fabric is unpainted.