parachute wrapping for DD

[troj]

i understand 1.1oz fabric as a substrate can be a standard 1.1, or a 1.9oz zp if it has .8oz sqft of coating.

Regardless of how they're phrasing it, if they're calling coated fabric according to its final weight, 1.9oz "coated" is not the same as plain 1.9oz

Purosity, makes removing the air from the pack, much easier.

That's but one impact of the porosity, and a minor one.

-Kevin

[cjl]

It is very true though. It can be a rather interesting experience packing a large ZP 1.1 oz canopy. The fabric slips and slides everywhere, and it can seem impossible to get the air out.

[ClayD]

That's but one impact of the porosity, and a minor one.

-Kevin

In rocketry, I cannot think of any issues 'zero' poroasity would be needed.
Beneficial or a perk.. maybe.

I know on my hanglider the "coatings" had many uses... 1 being the infiltration of water into the fabric. very serious for hangliders, not so much for a rocket.
Keeping the airflow around the airfoil and not throgh it, again serious for hangliders, not so much for most rockets. for rockets the porosity of airflow thrtough the canopy, is easily offset by a miniscule amount of added surface area. IMO...

Form restoring value? coatings can help with nylon to restore a particilar shape. the LE on my hanglider actually had a plasitc on it to "pop" back into place. again, i dont see that as an issue on rocket parachutes.

What are the major impacts of porosity? I can only think of 1, penetration of air and moisture into the fabric.

It can be a rather interesting experience packing a large ZP 1.1 oz canopy. The fabric slips and slides everywhere, and it can seem impossible to get the air out.

yep... in the end I bolted mine to the car, flaked it out and rolled it up multiple times. finally got it to where i could fold it.

[troj]

Coated fabric for parachutes adds a tremendous amount of weight and bulk -- you can get the same benefit without all the weight, or bulk, by going with ZP.

A ZP parachute, by virtue of the dramatically reduced porosity of the fabric, created more drag than a parachute of the same size made from regular fabric. That means the parachute is smaller and lighter -- when you're going for performance, that can matter. It can also matter in rockets where space is at a premium.

The only real downside? ZP fabric is slippery as snot, which makes it a bit tougher to pack. I know a rigger who refused to pack ZP reserves, because of this. He'll pack a ZP main, but won't go near a ZP reserve, because they tend to require tighter packs to begin with.

The issue of trying to force air out when you're packing has a lot to do with packing technique.

-Kevin

[ClayD]

Coated fabric for parachutes adds a tremendous amount of weight and bulk -- you can get the same benefit without all the weight, or bulk, by going with ZP.

A ZP parachute, by virtue of the dramatically reduced porosity of the fabric, created more drag than a parachute of the same size made from regular fabric. That means the parachute is smaller and lighter -- when you're going for performance, that can matter. It can also matter in rockets where space is at a premium.

The only real downside? ZP fabric is slippery as snot, which makes it a bit tougher to pack. I know a rigger who refused to pack ZP reserves, because of this. He'll pack a ZP main, but won't go near a ZP reserve, because they tend to require tighter packs to begin with.

The issue of trying to force air out when you're packing has a lot to do with packing technique.

-Kevin

ZP is a coated fabric, it is coated with silicon.(why it is slippery) probably some teflon additive of some sort...

Zero-porosity fabric, also called "zero-p" or just "z-p," is made from the same type of nylon, but the fabric is treated with a silicone-based coating that prevents air from passing through it.

(But that is what i read on the internet???)

I have always considered ZP as a coated fabric. Since without the infused silicon, it would have a higher porosity?(more holes that arent filled with silicon-"based".)
This means that packing ZP has more bulk than standard fabric. In that theres filler within the woven cloth.

Other coatings, such as aluminzing or double-coating, teflon, i agree are bulky and nonsensicly difficult to pack. (I have folded a hanglider back into its bag...much harder than any parachute ive packed standard or ZP)

[troj]

ZP is a coated fabric, it is coated with silicon.(why it is slippery) probably some teflon additive of some sort...


(But that is what i read on the internet???)

Coated nylon and ZP are not the same thing.

Just because you read it on the Internet doesn't make it correct.

-Kevin

"On the Internet, nobody knows you're a dog."

[ClayD]

"On the Internet, nobody knows you're a dog."

yeah, but I am the nefew of a donkey!

Coated nylon and ZP are not the same thing.
"

Agreed, one is a process and one is a physical property, due to a process.

What are you calling ZP..? I think if there is discussion on what a fabric is or isnt, we need to pin down the fabric first.

1.
MO Powered Parachute cloth
1.0 ounce urethane impregnated, stabilized, zero porosity, nylon cloth
Note: the actual fabric weight is 1.2 to 1.3 ounces per square yard

2.
Soar-Coat / PN4 / Blue or equivalent 1.1 ounce silicone impregnated, nylon cloth. Zero porosity even after multiple washings
Note: the actual fabric weight is 1.2 to 1.3 ounces per square yard.

3.
¾ ounce nylon spinnaker cloth, or equivalent urethane impregnated nylon cloth. zero air permeability.
Note: the actual fabric weight is 1.2 to 1.3 ounces per square yard.

4.
1.1 ounce (F111, Exacta Chute, MIL-C-44378) nylon parachute cloth. Silicone treated. Low permeability when new (0-5 cfm)Permeability increases rapidly after 20 hours flight time.
Note: the actual fabric weight is 1.2 to 1.3 ounces per square yard

5.
1.9 ounce Nylon rip stop with polyurethane coating. (This was used in a very limited number of parachutes in the mid and late 1980’s.)
Note: the actual fabric weight is 2.1 to 2.3 ounces per square yard.

Clay
"man-rated parachute maker on the internet, is a man-rated parachute maker. Not a Dog"

[cjl]

Clay: Anything that says Zero Porosity is ZP. That means the first 3 on your list are ZP, the last two are not. F111 (your #4) is a common fabric for skydiving reserve parachutes, and it is definitely not ZP. It's still a good fabric though.