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sundevil777

Dacron lines are good not just because they absorb more shock

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The relative stretchiness of dacron lines I believe is fairly well known, and important.

I think there is something about the friction between dacron lines and slider grommets that is "just right".
Ever since I've had my Pilot relined with Dacron, it has been "just right". I don't know if it is as simple as coefficient of friction or if it is a more complicated relationship with other properties, but I think dacron lines make it easy to get nice openings. I think that slippery line types, such as spectra make it more uncertain because of their different frictional or other properties. I have no experience at all with other types of lines, perhaps they also provide that just right interaction with the slider grommets.

I think more of us that jump larger canopies should consider dacron when a reline is needed. Dacron's ability to not get snagged on velcro or other such similar natural or synthetic materials is also really nice. I always felt like I was destroying my lines when they would get snagged on some velcro from my jumpsuit wrist cuffs, or some vegetation that would get snagged...

Anyway, I think early canopy designers benefited greatly from the good characteristics of dacron rubbing against grommets, and we would be grateful if other line types had that just right relationship, even if they weren't stretchy.

Just a random ramblin, what do you think?

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On 4/21/2019 at 1:37 AM, sundevil777 said:

The relative stretchiness of dacron lines I believe is fairly well known, and important.

I think there is something about the friction between dacron lines and slider grommets that is "just right".
Ever since I've had my Pilot relined with Dacron, it has been "just right"...

My 140 pilot has also been just right since I had it relined with Dacron. Love the combination.

It wasn't a fast canopy to begin with, so I don't mind the performance loss. The openings have become perfect.

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5 hours ago, Sobakin said:

Fricrion is a linear function of pressure, higher contact area = lower pressure. So if fricrion coefficient of material is the same, the total friction force will be the same on thin and thick lines.

In theory, friction is proportional to the force normal to the surface, not the pressure. However, that theory would prevent drag racing from achieving the amazing accelerations they do in fact achieve, so there is more that can go on besides the simple friction model. That is why I say that it may be a more complicated relationship that defies simple analysis of what the theoretical coefficient of friction is for the different materials.

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Do Dacron lines affect performance of the canopy in a noticeable way? Let's say I'm talking about Sabre 2 190 sqft. How different would fly Sabre 2 190 sqft with Dacron lines vs one with HMA, Vectran or Microline?

Also, can ANY canopy be relined with Dacron lines?

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(edited)
21 minutes ago, CoolBeans said:

Do Dacron lines affect performance of the canopy in a noticeable way? Let's say I'm talking about Sabre 2 190 sqft. How different would fly Sabre 2 190 sqft with Dacron lines vs one with HMA, Vectran or Microline?

Also, can ANY canopy be relined with Dacron lines?

Lines are responsible for a lot of drag which has a negative effect on how the canopy flies. This is why crossbrassed canopies use HMA 325 and such. The faster the canopy, the more it matters.

Edited by 20kN

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(edited)
9 hours ago, 20kN said:

Lines are responsible for a lot of drag which has a negative effect on how the canopy flies. This is why crossbrassed canopies use HMA 325 and such. The faster the canopy, the more it matters.

Agree, but for the example of a Sabre2 190, I think that the difference in performance is not noticeable to anyone but an experienced and attentive canopy pilot. And almost certainly it is inconsequential to the type of flying that's typically done with a Sabre2 190.

And in theory, any canopy can be relined with Dacron lines. Some manufacturers won't offer a replacement dacron lineset for some types of canopy, but if you still insist on dacron lines, any Rigger worth the title can cook one up from a stock roll of dacron. It's a lot more work than the pre-made manufacturer replacement linesets though, so likely a lot more expensive too.

Edited by IJskonijn
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23 hours ago, 20kN said:

Lines are responsible for a lot of drag which has a negative effect on how the canopy flies. This is why crossbrassed canopies use HMA 325 and such. The faster the canopy, the more it matters.

IMHO - its like the swoop mode on AADs... the image (or imagination) of the jumper is much more likely to drive their decision than any actual need.  Don't get me wrong, there are the <1% who are at the top of the game for whom it may make a difference.  But unless you are pushing the industry's envelope (not your own, but the sport's at large) you are more likely getting them because you WANT them, not because it actually makes a difference.

Just my $.02

JW

 

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Agreeing with most of the posts above PLUS, Dacron lines create more surface friction against each other and slider grommets, because they have a rougher weave.

The extra friction could abrade grooves and holes in brass grommets in as few as 400 jumps.

The worst case scenario is old, fuzzy Dacron lines that have been jumped too many times in the Southern California desert. The greater the friction, the more likely the tension knots ... more slider hang-ups ... more collapsed end cells ... more broken lines ... more hard openings ... more torn fabric ... etc.

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Another possible point is they may increase your chance of a tension knot mal. The amount of friction a line produces has an effect on the likeness of tension knots. New, slippery material is less likely to cause a knot than older, worn material.

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16 hours ago, wmw999 said:

How much do Dacron lines increase the packed size? A full size's worth?

Wendy P.

I switched from spectra to dacron on my Pilot 210 with ZPX material. I put it in an Infinity with a size 6 main tray. When I switched, I really expected it to make a big difference, but it is barely noticeable in my rig, even with the long lines of a 210.  I could easily upsize to a 230ZPX with dacron in that container.

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20 hours ago, wmw999 said:

How much do Dacron lines increase the packed size? A full size's worth?

Wendy P.

About a half size. I've had a Spectre 170 with microlines, a Safire 149 with microlines and a Spectre 150 with Dacron in an Infinity built for a 150. The Spectre 150 packs up midway between the other two.

As long as the container is not already overstuffed (like my 170 was), Dacron lines won't make a huge diffference in pack volume and should be very doable.  Personally I think it's worth a bit tighter packjob.

 

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(edited)

A couple people I know have Dacron lines on their canopies. Another benefit seems to be, even in tough environments like Perris, they last longer than the canopy. 

One guy had Dacron lines on a Pilot 96, close to 2.0 WL. Another on his Spectre (much larger). Neither seemed to have any complaint on how the canopy opened or flew (one is a camera flyer) or wear on the gear. 

When my Pilot 150 comes up for a re-line, I'm probably going to put Dacron on it. 

 

 

Edited by shadeland

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