Kevlar or Nylon

[Yukon@K-9 Rocket Tech]

So it seems like everyone prefers either nylon or kevlar for their recovery lines. They both obvioulsy have advantages and disadvantages and different material propertise and stregth which I am very well aware of. I don't have any particular reasin why I should use one over the other, but probably because of my lack of experience. I want to know which one you use and why. Is there a specific reason you prefer one over the other? Thanks

 

[Speaknoevil]

There are a number of threads on this. Here is one: https://www.rocketryforum.com/threads/kevlar-vs-nylon-shock-cords.81141

 

[Yukon@K-9 Rocket Tech]

There are a number of threads on this. Here is one: https://www.rocketryforum.com/threads/kevlar-vs-nylon-shock-cords.81141

Thank you. I searched Kevlar v.s. Nylon amd nothing came out.

 

[Speaknoevil]

Yes, the search function seems to work better when you only enter specific keywords without any qualifiers.

 

[David Schwantz]

i have and do use both. I have had tubular nylon break, never kevlar. I have had the stitching break on kevlar, only due to my sewing it with nylon thread. They stretch differently. i use a lot of kevlar braided line. Mostly on smaller stuff. Fits into tight tubes. I have all the way from 100 lb stuff to 1500 lb line. nylon melts and I always use a flame proof sleeve with it.

 

[Yukon@K-9 Rocket Tech]

i have and do use both. I have had tubular nylon break, never kevlar. I have had the stitching break on kevlar, only due to my sewing it with nylon thread. They stretch differently. i use a lot of kevlar braided line. Mostly on smaller stuff. Fits into tight tubes. I have all the way from 100 lb stuff to 1500 lb line. nylon melts and I always use a flame proof sleeve with it.

Okay thank you. Also makes sense, I've always been taught to try to sew things with the same material thread

 

[Nytrunner]

I like tubular nylon for the most part. It has a little stretch to it to absorb a bit of ejection energy, and its no trouble to wrap ductape around the couple feet near the ejection charge.

If i build any small internal volume rockets, i may have to use kevlar since you can fit more in the smaller space.

 

[Yukon@K-9 Rocket Tech]

I like tubular nylon for the most part. It has a little stretch to it to absorb a bit of ejection energy, and its no trouble to wrap ductape around the couple feet near the ejection charge.

If i build any small internal volume rockets, i may have to use kevlar since you can fit more in the smaller space.

Ah I didn't think about that. Nylon would be far more dynamic and kevlar. I wonder and kevlar nylon hybrids?

 

[Devin Batten]

I use both, kevlar from the centering ring to the top of the body and nylon from then on. Kevlar absorbs the brunt of the ejection and nylon gives it a little stretch.

 

[Nytrunner]

I wonder and kevlar nylon hybrids?

You'll have to describe that

There have been folks that run a nylon and kevlar line in parallel with the nylon a bit shorter than the kevlar. That way the nylon reaches extension first and bleeds off some energy before the kevlar reaches extension.

 

[ThreeJsDad]

I use both, kevlar from the centering ring to the top of the body and nylon from then on. Kevlar absorbs the brunt of the ejection and nylon gives it a little stretch.

That is brilliant !

I am cheap and lazy so I use paracord with the center strands removed for my shock cords and make them rather long. With the core pulled out it is basically a tubular nylon cord. I also have it mounted in such a way I can remove it if need be. I have used kevlar in the past and I still use Kevlar sewing thread (60lb test) on smaller LPR's and paper rockets. On a HPR I would use either tubular nylon or tubular kevlar and have no concerns.

I would not recommend Spectra because it has no give and has a very low melting point. Dacron is nice a sit gives decently but again a bit of a lower melting point.

I will however use dacron on shroud lines with no concerns.

Keep in mind the weight of your air frame comes into play here. Keep the KE formula in mind, a lighter rockets puts less stress on the shock cord or tether.

 

[ebruce1361]

I use both, kevlar from the centering ring to the top of the body and nylon from then on. Kevlar absorbs the brunt of the ejection and nylon gives it a little stretch.

That's essentially the setup I'm going with for my current scratch build: https://www.rocketryforum.com/threads/care-for-some-scotch.157850/
The motor mount has a braided kevlar leader that extends just beyond the end of body tube, then that attaches to my deployment canister followed by a nice, long nylon paracord shock cord up to the nose cone. The kevlar takes the ejection heat while the paracord gives the whole line a bit of stretch.

 

[Kelly]

I use both, kevlar from the centering ring to the top of the body and nylon from then on. Kevlar absorbs the brunt of the ejection and nylon gives it a little stretch.

+1

 

[ep29030]

When using Kevlar, I try to do z-folds and wrap them with rubber bands to help bleed off energy when chute opens. Otherwise, you get alot of opening load force--it can be 1.5X the load of the fully stretched recovery train with round/elliptical chutes. X forms are better on opening load. Other than opening shock, Kevlar is probably superior for our normal applications. Nylon's main advantage is the 10% stretch.

 

[DaHabes]

I'm going to kevlar exclusively on bigger LPR and all MPR/HPR builds; light weight, strong, fireproof. I use at least a 5x length braided kevlar that will handle 100 G's and do a chain sinnet to absorb the shock.

https://en.wikipedia.org/wiki/Chain_sinnet

 

[heada]

I use tublar nylon in HPR since its very easy to replace once it gets singed too many times. Kevlar in MPR and LPR because I can't easily swap out the shock cord mount point. If you want the best of both, you use both. Tubular kevlar with nylon in the core. Make sure the kevlar is significantly longer than the nylon because the nylon stretches but kevlar doesn't. Kevlar provides the flame protection and the nylon takes the load.

 

[Nytrunner]

Just realized something....

Why is this thread in the propulsion section of the forum?

 

[Theory]

I use both, kevlar from the centering ring to the top of the body and nylon from then on. Kevlar absorbs the brunt of the ejection and nylon gives it a little stretch.

i use this method if im planning on motor ejection and reverse it if im not going too.

 

[Nathan]

Nylon harnesses get weak once they get a little scorched. A couple years ago a crashed a rocket when the nylon harness broke. Now I only use Kevlar. Only downside I see in Kevlar is that it seems a little less abrasion resistant than nylon.

 

[Yukon@K-9 Rocket Tech]

Just realized something....

Why is this thread in the propulsion section of the forum?

I used the app and I just noticed too, my bad. Will see if Mods can move it

 

[swatkat]

The moderator is watching!

 

[Yukon@K-9 Rocket Tech]

The moderator is watching!View attachment 409520

Yup

 

[cwbullet]

Moved to recovery.

 

[Yukon@K-9 Rocket Tech]

Moved to recovery.

Thank you