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TomAiello

Micro Lines v. Dacron

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Microlines have less pack volume, its easy to tell wear on them, has a sight elastic to them, less drag, etc.

Dacron more elasticity and it returns to its original length wich allows for softer openings. Less likely to suddenly snap, best for CRW.

Is there some specific application you are wondering which would be better for?
Yesterday is history
And tomorrow is a mystery

Parachutemanuals.com

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Is there some specific application you are wondering which would be better for?



Yes. But I already know the textbook answer. I like to question the conventional wisdom.

My application is, of course, BASE. BASE canopies all (the exception is the Pooster, which isn't even worth talking about) use Dacron lines. I can think of all the stock "reasons" but I'm trying to think about other ways to do things.
-- Tom Aiello

[email protected]
SnakeRiverBASE.com

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I think that some skydiving companies are ahead of the curve on the thinking here...

Reserves used to be all Dacron but now you can get microline (Spectra). I sill would'nt use HMA as reserve lines... and same with Vectran. Spectra 1000 should be able to be used on a Base canopy but you need to watch the trim on it since it will shrink just like a skydiving canopy.

That might be the only thing I'd worry about is that dacron rarely goes out of Trim and Spectra rapidly does.. how will that affect the canopy?
Yesterday is history
And tomorrow is a mystery

Parachutemanuals.com

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That might be the only thing I'd worry about is that dacron rarely goes out of Trim and Spectra rapidly does.. how will that affect the canopy?



That's the major concern with BASE lines. An out of trim canopy will have inconsistent (i.e. off heading) openings. Having a 90 degree off heading may be no big deal sometimes. Other times...
-- Tom Aiello

[email protected]
SnakeRiverBASE.com

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the other thing to work about is snapping your neck.

dacron functions as a shock absorber in a base canopy. (much more so than would spectra, vectran, etc.)

sincerely,

dan<><>
atair aerodynamics
Daniel Preston <><>
atairaerodynamics.com (sport)
atairaerospace.com (military)

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the other thing to work about is snapping your neck.

dacron functions as a shock absorber in a base canopy. (much more so than would spectra, vectran, etc.)



This is the specific piece of the conventional wisdom that started me questioning it. I've never had a BASE canopy that I thought opened too fast (even with ZP topskin and secondary inlets). I'm interested in seeing what else we could re-examine to create snappier openings.

I'm not sure that changing the lines would create faster openings (they might just be harder). But it's my lack of certainty (and basic lack of knowledge about micro lines in general) that have led me to start this discussion.
-- Tom Aiello

[email protected]
SnakeRiverBASE.com

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I don't see how changing line type would change the speed of the opening. Personally, to me it seems like Dacron is the best available for BASE applications. The reason I say that is because the wingloadings are usually lower (ie parasitic drag isn't as big a concern) and the shock absorbing effect of the dacron would be a plus. I would think switching to a different line type would give the benefit of lower pack volume, but would contribute to harder opening shock and may contribute to broken lines.


"Holy s*** that was f***in' cold!"

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Spectra - wears well, thin, shrinks quickly.

Dacron - does not shrink, wears well, shock absorber, thicker.

Vectran - wears quickly, thin, does not shrink.

As an aside, I talked to Beezy at Precision about my frayed vectran brake lines and he recommended replacing them with dacron. Brake lines are higher wear than other lines, so that makes sense.

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Ok, but I'm placing an order to PD and they're asking me if I want 535 lb Dacron, 550 lb Microline or 825 lb Microline. I want the same kind of line I have now on my Spectre, but of course I don't know what kind of line I have. Does anyone know which one I want?


"Five days? But I'm angry now!"

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Dacron = big-assed lines. Commonly used on student gear. Larger pack volume, increased drag, lasts longer.

Microline = thin stuff. Commonly used on high performance canopies. Small pack volume, needs to be replaced every 300-500 jumps.

550 or 825 microline? Simple. Are you a fatass like me? If you're over... I dunno. 180lb naked, you probably want the 825. If you're heavier and
go with the 550, it'll need replacing sooner.

_Am
__

You put the fun in "funnel" - craichead.

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Oh, ok, but one other question then (and it seems pretty obvious but I thought I would ask anyway) is there a packing volume difference between the 550 and the 825?

And if I could get your opinion - I'm 160-165. Should I play it safe and go with the 825?


"Five days? But I'm angry now!"

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...bill, if your frayed Vectran lines are on an FX or VX, I would urge you to consider the X-Mod from Precision. It will cost more, but you will get HMA lines and greatly improved performance, at least in my opinion. Also, in the long run, the rest of the Vectran will need relpacing more often, so the X-Mod actually ends up being less expensive over 800 to 900 jumps. Just a thought. I seem to recall that you have or have had a Safire as well. I don't think that PA is doing an HMA conversion on that canopy though.
alan

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I remember reading a very very detailed article regarding the "opening shock/stretch factor" of dacron vs. spectra. Basically it took that theory and threw that in the toilet. Very detailed explanation using physics formulas and real world experimentation. Basically, the jist of it was that the very slight amount of stretch that dacron has will have no observable impact on the reduction of opening force vs. anything else. Wish I could remember where it was, but I believe is was on dz.com somewhere.

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Chuck,
For the record here are the real facts:

Dacron- It has resistance to wear but does stretch.
It usually goes out of trim (gets longer in dimensions)at the center cell and brake lines first. It does not shrink at all. Comes standard in 525lb, 600lb, and 900lb.

Spectra - This shrinks and will not stretch(relative to the loaded dimensions). Usually shrinks most at the outer most lines and also the brake lines. It wears well, thus giving the user a "false" sense of being in good shape, when actually the lines are out of trim.The 500lb goes out of trim really fast compared to the other sizes.
It comes in 500lb, 725lb, and 1000lb. There is no such animal as 825lb. This is a number used by PD to differentiate between their unsized (uncoated)725lb that they use on their reserves.CSR, the line manufactuer, sells them the line labeled as 725lb.

Vectran-Does not stretch,is dimensionally stable, but wears the fastest of the line types. This line usually last 400-600 jumps on the average canopy. Vectran comes in 580lb, 725lb, 1050lb, and 1600lb.

HMA-Has vectran-like characteristics except that it has a better wear componet. But here is the scary part- the polymer can stress crack in areas that are sewn. In other words, you never know if and when the line may break.
This is one of the reasons that they do not cascade the lines. It also is hard to fingertrap.
Hope this help answer some questions,

"MEL"
Mark E. Lancaster
The Icarus Service Center
2222 Buffalo-West Springs Hwy.
Buffalo, SC 29321
Skyworks Parachute Service, LLC
www.Skyworksparachuteservice.com

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If we're just tossing ideas around, here's one:

Lines that combine dacron & spectra --

Most round emergency canopies for hang glider pilots use dacron lines, because of tradition and for the supposed shock absorbing effect. The canopies are built very light compared to round skydiving reserves.

One US company's top-of-the-line hang glider reserve uses spectra lines for minimum bulk, except for sections of line, a couple feet long, which are dacron. I think the dacron sections are at the canopy end of the lines.

Whether the short sections of dacron provide useful shock absorption, I don't know.

Peter Chapman
Toronto, Canada

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we have experimented with (and are still experimenting with) spectra over braided aramids. but there are many issues with designing such a hybrid line. i.e. load distribution between core and cladding, fill or braided core, mismatches in coefficients of thermal expansion, mismatches in elasticity, abraision between core and cladding, termination method, etc...

sincerely,

dan<><>
Daniel Preston <><>
atairaerodynamics.com (sport)
atairaerospace.com (military)

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