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I am looking at the viability of using 400# or 600# HMA on a slider up specific BASE canopy instead of 725# spectra. Spectra goes out of trim (especially from the extra heat generated on a BASE vs skydiving opening) and it sticks to velcro inside tail pockets.

I am looking to see if any DZO's have seen a higher incidence of line burn/cutting of the canopy on a line over, after switching from dacron lined tandem canopies, vs the newer HMA lined tandems. Or if anyone has seen line burn/cutting from a line over on an HMA lined sport canopy. The only issue I see with using HMA on a BASE canopy would be the possibility of a line splitting a canopy on a line over. (vectran for example would be a terrible choice for this reason)

Vectran would be a much better choice than HMA in my opinion for a whole swag of reasons. The only purpose for HMA is lower parasitic drag.

Vectran is extremely abrasive on nylon, I used vectran for a kill line once, because it was all I had, I put 1 jump on it, and it sliced the tape open all the way from the bag to the PC, and ate about halfway through the square weave on the other side.

You also need to use stainless steel grommets with vectran, they will destroy brass, which are whats standard on base canopies.

I like vectran better as a skydiving line personally, I just don't know if it would be well suited as a BASE line, as I could see it slicing a canopy clean in half on a line over.

What are your thoughts on why vectran would be better?

I'm no rigger but something sounds completely messed up with that sort of performance on 1 jumps

It took me by surprise as well. I wish I had taken photos before I rebuilt it.

Trim I don't think is too much of an issue when you are dealing with huge parachutes. I have been jumping the same spectra lineset on my storm 150 for the past 500 jumps. Inside A to outside A is def 3-4 inches at this point. Still flies just fine. Of course I am the frog in the slowly warming water so I don't really notice how much worse it has gotten.

What benefit do you see in using micro line?

I didn't see you post this on dz.com. You will get more input there I imagine. Maybe try contacting PD and NZ?

Our break setting can be deep enough that the trim change can be a issue on opening. I've had specter breaks shrink enough to stall the canopy on opening. I don't see line overs being that big a deal. Generally something like that might just result in some damage on the back corner of the tail or the back half of the end cell.

Lee

I just think that spectra is old technology, the same way we made the switch from nylon, to dacron, and dacron to spectra, we should be making the change from spectra to HMA/vectran. *that being said, dacron obviously still has its place, slider down BASE canopies, crew canopies etc)

If we are going to use a "0" stretch line on a slider up only base canopy, I see HMA/vectran as being a better option. I would actually much prefer to use vectran, I am just worried about its abrasiveness on a line over, and the need to use stainless steel grommets (not that that is a huge deal, just that you need to take out a loan to buy the tooling to set them)

The benefits I see, are lack of trim change, lower pack volume, less drag in flight (yes i know, its a base canopy, but a more efficient wing is never a bad thing) and vectran/HMA don't stick to velcro inside the tail pocket.

well yes...hence the lowers on Trangos are dacron

I think this might actually be why atair still uses 900# dacron on their spectra lined canopies.

Have you seen any damage to canopies from Vectran line overs? I hardly skydive anymore, and its not like people are getting line overs every day.

I will toss this up on DZ.com, and I'll send Jyro a message see what he thinks.

If that was the case then why aren't skydive canopies being cut in half already?


Firstly, Vectran is stronger and longer lasting all round than HMA. The only reason HMA became popular was due to its lower parasitic drag allowing for higher airspeeds. Not because it was better for general purpose.
Secondly, HMA can be very tricky to maintain. In skydiving this is not a problem. In BASE it could result in catastrophic failure.
Thirdly, I'd be interested to know what the abrasion levels of each line type are. I bet that Vectran wouldn't be a whole lot different to Dacron in the first place.

I can't think of any skydiving canopies being split in half, but I hardly skydive anymore, so I figured I'd see if anyone knew of any instances, commonplace or not.

I am particularly concerned, as the canopy I would be putting this on, would be a prototype single surface I am working on.

Honeslty, I would love to use vectran, its my line of choice for skydiving. It sounds like 500# vectran, with continuous center A's and B's would be the way to go. My kill line incident has me apprehensive, but the speed with high amount of friction of the PC ripping the kill line through the bridle is a totally different scenario than a line over.

I appreciate all the input from everyone.

Why would you decide on such a small line? Why not at least a heavier HMA? I have heard of some tandem canopies with 1000lb HMA.

Any line type will suffer from Velcro. And HMA is one of the worst.

Sure. I have seen line burn created by every line type in common use as well as some that aren't so common.

Maybe you know of a bunch of canopies that have been cut in half by line overs but I think you may be over thinking the issue.

I would be curious as to how so much damage could possibly be caused by a single jump. A number of jumps, sure. One jump I am skeptical.
Most likely the wear was due as much to pairing it with binding tape as it was the Vectran itself. For a long time Sigma drogues featured a 2 piece kill line that was 50/50 Spectra/Vectran, albeit in a Kevlar bridle. Even then, A Line over is a totally different scenario that could not possibly produce the same amount of line burn.

Trying to reduce pack volume. 400# dacron with continuous center A+B is becoming pretty commonplace. 500# vectran should be plenty adequate, I wouldn't go any less than 400#, but the 400# is holding up plenty fine for base as long as the center A+B are continuous, or 525# is used in its place.

My super scientific "let me rub some of this HMA on some hook velcro test" I did today seemed to be better than spectra. But as you pointed out, vectran is likely the better option.

And I tend to try to overthink potential issues as much as possible before trying new things on single parachute systems

I was curious if anyone had seen any totally catastrophic failures from vectran that I am not aware of, it appears that is not the case.

And my thoughts with the kill line, indeed. We seem to be arguing saying the same points back and forth meow

I dont really see why you would want to use something small on a base canopy in the first place. I have 2 UL canopies, one with 600lbs dacron, and one with spectra. The weight difference is pretty much negligible, it has some give to it on opening, and shows wear more than specta. I dont really know what people think theyre gaining in the base environment from spectra lines. I guess there is the tension knot argument, but Ive seen 3 tension knots in real life, all on spectra.

Continuous A/B lines seem like a good idea to me too. I dont understand when lines are breaking at the cascade, why a fix is to just to go to the next strength line and leave the cascade there.

If abrasion of the line against nylon is your concern, I'd be less worried about a lineover, than what it is going to do to your tailpocket, every time those lines go screaming out that little hole, i.e. every jump.

Unless, of course, your velcro is in bad shape, then the whole bottom of the tailpocket blows open, preventing damage from line burn...

Solution to the tail pocket problem would be a little protective strip of kevlar at the mouth. A kevlar tandem drogue bridle, that has a vectran kill line holds up just fine.

Or, like you said, just make sure your velcro is shit.

I have a Lightning with an open-ended tail pocket. Works well. Then you could have several sheets of ripstop nylon to put between each figure eight to reduce friction between lines on extraction.

But yeah, HMA is scary. I like dacron.

I havn't seen the posted but i may have missed it, with HMA line any wear you have on it is very hard to near impossible to see, unless it is loose fibers from a nick in the line, now with vectran the wear is much more apparent as the line ages. Now regarding the abrasiveness of vectran as other people have said and in my own experience it does not cause anymore damage to parachutes than any other line and it is very common so it would have been noted if it was.
just my 2 cents

Spectra is not fit for use on parachutes in my opinion.
The shrinkage is absurd after a couple hundred slider up jumps.