Understanding what HMA lines are for

[VTmotoMike08 0]

I want to better understand why and when HMA lines are used. It seems that you hear about HMA lines being used on certain types of canopies but not on others. I often hear about HMA lines on katanas, velocities, VXs, and other high performance canopies but you never really seem to hear about HMA being used on midrange canopies like Sabre 2's, Safires, etc.

Why not? From what I know, spectra is used on most midrange canopies and also a lot of HP canopies. But it changes dimensions due to friction heat of the slider, while HMA does not. So why is HMA not used on everything? I know it can break after X amount of jumps without showing wear, but its not that hard to keep track of how many jumps are on the current lineset and replace it when the time comes. And a broken line is not always a cutaway/ reserve ride.

It just seems to me that HMA is superior and could be used on all canopies. But I am sure that I am missing something, or else it would be that way. Can someone fill me in?

Also, what does HMA stand for? And what is the difference between HMA and vectran? Yes, I did a search and could not find the answers I am looking for. Not saying its not there, just that I did not find it and I am looking for some help.

[gearless_chris 1]

I know HMA stands for High Modulus Aramid( may be spelled wrong). Atair says they don't use HMA because they open soft enough that the lines may break during high performance maneuvers than on opening. My Nitron has HMA lines to reduce pack volume due to the no-cascade line set up. As for the rest I'm not sure.

"If it wasn't easy stupid people couldn't do it", Duane.

My momma said I could be anything I wanted when I grew up, so I became an a$$hole.

[VTmotoMike08 0]

I don't understand that. If the lines are not cascaded, wouldn't that make for overall more line length? But I do not know anything about volume per unit length of different line types.

If anyone wanted to go into a detailed conversation about all the different line types (spectra, HMA, vectran, dacron, others?) , that would be awesome.

[Blink 0]

Actually, if you look on Precision's website, many of their canopies come standard with HMA (Xaos-21, Xaos-27, Nitron, Fusion, Synergy).

The Fusion and Synergy would be comparable to the Sabre2 and Spectre (9 & 7 cell entry level canopies), but you are right, it's not as comon as Spectra lines.

The reason why you see HMA on a lot of high performance canopies, is because they don't shrink. With any canopy, when it opens, the slider slides down the lines causing friction. This friction, over time causing the lines to shrink and go out of trim. This isn't a big deal if you're on a lightly loaded rectangular canopy, but because high performance canopies are so touchy and responsive, it can be a big problem if your lines are out of trim. Can cause hard openings, line twists on opening and built in turns (anyone know of any others?).

Once you decide to go HMA, there are also different sizes, the idea here is to reduce drag (although I've read that the drag reduced from different sized HMA is negligable). The problem here is the lifetime of your lines, the smaller they are, the faster they wear out, the more often they have to be replaced.

The bad side of HMA is that they don't show wear the same way Spectra (Microline) does, they wear differently, and if you don't know what to look for, they could break "unexpectedly".

[VTmotoMike08 0]

Gotcha. I can see how line shrinkage would be a bigger problem on smaller canopies than on larger ones.

But I am still curious as to why HMA has not replaced spectra line on most canopies? Spectra (microline) basically replaced dacron lines a while ago, and it seems to me that HMA could do the same to spectra. Why is spectra (microline) still used on the majority of canopies if HMA is "better"?

EDIT: I hope my questions are making sense. I just really want to understand the different types of lines.

[diablopilot 2]

I'd say the biggest reason is the wear properties of a cascaded HMA lineset. When you make cascades/finger traps in HMA they wear between 2 to 3 times faster than continuous linesets.

As to why other manufacturer's haven't re-trimmed their canopies to be continuously lined and use HMA? I can't be sure, but based on my experience with HMA they'd probably loose out on some lineset sales, as I've had 900 to 1000 jumps on set's I've had before changing them with no more than 1/4" change in trim.

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You're not as good as you think you are. Seriously.

[lilchief 0]

If you're near a manufacture of canopies or a master/senior rigger, go and talk to them. Let them show you and explain it to you in detail. I think you'll understand more when showed then explained here, though there are a lot experienced senior/master riggers here on DZ.com.

"Once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been and there you long to return." - Da Vinci
www.lilchief.no

[riggerrob 558]

The primary reason - not all manufacturers have changed to High Modulus Aramid lines is inertia.
When any new material is introduced, it gets introduced gradually.
The first people to jump new materials are factory test pilots. Then they build a few for high-end competitors and the busiest "working" skydivers. The goal is to get a few thousand jumps on new material the first year, to identify wear patterns.
Then manufactures modify their production processes to address wear patterns and repeat the testing process.
After a few more years, they start sewing the new material into every model.
But they also face consumer resistance to new materials. For example, some POPS refuse to buy anything but Dacron lines, because Dacron lines are still the most forgiving of sloppy packing.

[riggerpaul 1]

(not really responding to riggerrob, but just posting after his post)

According to conversations I've had with PD people, there is also the problem that not all HMA is the same. There are different factories producing the stuff, and not all make their lines exactly the same way, or with exactly the same coatings etc. So finding a reliable source and second source presents a problem. Again according to PD, some of this is because the skydiving industry represents a tiny fraction of the market for lines and therefore has little sway or say in the production of the lines.

[Kolla 0]

A little bit of HMA info can be found here:

http://www.performancedesigns.com/hma.asp


edited to fix the link.... I guess it helps :)

Blue Skies Magazine

[RMURRAY 1]

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As to why other manufacturer's haven't re-trimmed their canopies to be continuously lined and use HMA?

I asked MEL this once --- continuous lines mean more drag which you do not want for a HP canopy.

rm

[diablopilot 2]

I know it means more drag, but the line is relativly low drag, and we are not talking about HP canopies.

Besides, continuous sets have been shown to work even for HP canopies. I did just fine at the 2005 Nationals on one.

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You're not as good as you think you are. Seriously.

[billvon 2,400]

>It just seems to me that HMA is superior and could be used on
>all canopies. But I am sure that I am missing something, or else it
>would be that way.

One reason is wear. Spectra wears fairly visibly, and it's pretty obvious when a lineset needs to be replaced (both from shrinkage and from visible inspection.) HMA tends to not indicate its level of wear as well, and thus is not great for jumpers who do not perform regular maintenance on their gear (i.e. most skydivers.)

[diablopilot 2]

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HMA tends to not indicate its level of wear as well

Says who. IMO the problem lies in that people don't train themselves in what to look for. HMA does show wear.

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You're not as good as you think you are. Seriously.

[Rdutch 0]

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HMA tends to not indicate its level of wear as well

Says who. IMO the problem lies in that people don't train themselves in what to look for. HMA does show wear.

I have had many, and I mean Many! line breaks on 300 lb HMA. (my nickname CutaRAY). With anywhere from 30 jumps to 300 jumps on a 300lb HMA lineset. There was no visable wear on the linesets before they failed. Most of them broke at the riser, but I did have a few at the cascade.
But the wear on HMA is quite visable if you get enough jumps on it, they definitely get fuzzy with normal wear. But 300 lb HMA will fail without visible wear (the heavier HMA is a lot more durable).
Where Vectran and Spectra usually show failure prone wear a lot better before they fail.

But then on heavier HMA I have put over 1000 jumps on a lineset. I just had my canopies changed over from HMA back to vectran, since Im not swooping and Im doing 4way now. Im sick and tired of cutaways on nice soft openings. I have never had a vectran lineset break all of a sudden.

With the 300 lb HMA its definitely a specific use lineset. I wouldn't reccomend it for normal skydive use.

I.M.O Vectran would be a lot better lineset for most canopies than HMA.
The reason why they still use spectra, is even though it shrinks with wear, canopies still remain inside spec for the lineset/canopy they are used for. Also Spectra is a lot cheaper.

As far as drag, about two years ago, some Emery Riddle students did a test in a wind tunnel, and they took lines, I think they did just the lines, not a canopy lineset, They took the amount of lines on cascaded, and the amount of lines on non cascaded lines with HMA, Vectran, Spectra and Dacron lines. The difference on the amount of drag was substantial. I remember the wind speeds were around 50 mph ( I dont know why they choose this speed). But the dacron lines created a huge amount of drag, then the Spectra, Vectran, and last HMA. I remember the difference between the cascaded and non cascaded HMA was around 12 lbs of drag. I don't remember specifics, but the non cascaded HMA was very close to the normal cascaded vectran lines when tested.

Ray
Small and fast what every girl dreams of!

[billvon 2,400]

>Says who.

Amy and I, for two.

>IMO the problem lies in that people don't train themselves in what to look for.

Agreed. Most skydivers do not. HMA can be used safely, but you have to inspect/maintain it differently than Spectra - and it takes more effort.

Think of it as the difference between a 26" x 1 3/8 clincher tire at 60psi and a sew-up at 200psi. Both can work. But if you are biking to work, the clincher is going to get you there without failure far more often, and for far longer without replacement, than the sew-up.

[mjosparky 3]

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For example, some POPS refuse to buy anything but Dacron lines, because Dacron lines are still the most forgiving of sloppy packing.

And your point is?

Sparky

My idea of a fair fight is clubbing baby seals

[riggerrob 558]

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For example, some POPS refuse to buy anything but Dacron lines, because Dacron lines are still the most forgiving of sloppy packing.

And your point is?

Sparky

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Some POPS had life all figured out 30 years ago and please don't waste your time telling them anything new.
Thirty years ago,the best rig on the market was a Racer with a pull-out, Pegasus main, Featherlite reserve, blast handle, etc.
Only sissies wore mechancial FXC 8000 mechanical ADDs, but what was the point because mechanical ADDs were "unreliable" because they frequently "misfired" at 1800 feet, so there was no point to wearing a "dangerous" AAD.
All the cool kids wore Kreuger Balloon Suits and let ther hair blow in the breeze. Altimeters were only worn by sissies. And if you wanted to be a real skydiver, you went to Casa Grande to jump from the Lodestar, etc.

Oh! And since they learned the "best" packing method 30 years ago, please don't waste your time trying to tell then that this new-fangled PRO-packing will save wear and tear on their knees.

[crazydiver 0]

I haven't seen anything mentioned thus far about the differences in line types as far as "forgiveness" of hard openings. I definitely think that the wear factor has lead to a slow adoption of HMA on "midrange" canopies. I would also argue that the ability of dacron and microline (spectra) to stretch on opening thus taking up a bit of the opening forces rather than your body could be another factor. HMA does not stretch nearly as much, if hardly at all, when loaded. Spectra and dacron do. I suppose this could be a similar reason that many of the midrange canopies (excluding icarus) do not use vectran since it also does not stretch much on opening.

Just so I'm clear, don't confuse stretching on opening with stretching over time. Dacron stretches on opening and stretches permanently over time. Spectra stretches on opening, but tends to shrink from friction over time. HMA stretches very little on opening and only shrinks marginally over time.

My 2 cents.

Cheers,
Travis

[davelepka 4]

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I would also argue that the ability of microline (spectra) to stretch on opening thus taking up a bit of the opening


HMA does not stretch nearly as much, if hardly at all, when loaded. Spectra and dacron do.


Spectra stretches on opening

I'm not so sure about Spectra stretching.

[RMURRAY 1]

good information!

"300 HMA" from PD, "350 HMA" from NZ Aerosports and the blue "340 HMA" from Skyworks are all really the same size - is that true? does your Velo break lines because there are less of them to carry the load compared to a JVX or VX?

rm

[Rdutch 0]

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good information!

"300 HMA" from PD, "350 HMA" from NZ Aerosports and the blue "340 HMA" from Skyworks are all really the same size - is that true? does your Velo break lines because there are less of them to carry the load compared to a JVX or VX?

rm

I dont beleive the 300lb from pd is actually 300 I think its a little more. Its not the number of lines that caused the breakage. There are many kinds of HMA, and even more weaves. I have had a few different type of HMA on my Velocity.

My point wasn't to make the HMA on the velocities look bad, I was trying to point out that HMA can break without any show of wear. I know Shannon Pilcher has put hundreds of jumps on a lineset of 300lb Hma. Im sure other people have also.

Ray
Small and fast what every girl dreams of!

[mjosparky 3]

I ask again, you point is?
Sparky

My idea of a fair fight is clubbing baby seals