Dual Parachute: Neat Idea Becomes Tangled Mess

[brockrwood]

One of the parachutes opened. The other was a tangled mess that did not open up very much.

I guess it worked.

The idea was to include two parachutes so that if one did not open, there was a backup parachute that might open.

But the two ‘chute approach seems to increase the likelihood of tangled shroud lines and shock cord. So maybe the cure is worse than the illness?

Hmm.

 

[David Schwantz]

use a spreader bar

 

[brockrwood]

use a spreader bar

Thanks for the tip! What is a spreader bar?

 

[ljwilley]

separate the 2 chutes in the tube by wadding and put attach the parachutes to different places to minimize them tangling with each other.

 

[brockrwood]

OK. Do I try to untangle this or just cut it?

Sigh.

 

[brockrwood]

Maybe my shroud lines are too long.

 

[rharshberger]

most dual chute systems in real life use a short shock cord (for each chute, it has a name just drawing a blank right now) back to the attachment point so that they have more length to spread apart, or you could tie them in at different points on the harness/shock cord.

 

[brockrwood]

most dual chute systems in real life use a short shock cord (for each chute, it has a name just drawing a blank right now) back to the attachment point so that they have more length to spread apart, or you could tie them in at different points on the harness/shock cord.

I think you are right. I clipped them both to a surgeon’s loop about 2/3 of the way up the shock cord. I think I will tie another surgeon’s loop about 1/3 of the way up the shock cord and tie one on there.

 

[ljwilley]

OK. Do I try to untangle this or just cut it?

Sigh.

I know how you feel.

 

[rharshberger]

I think you are right. I clipped them both to a surgeon’s loop about 2/3 of the way up the shock cord. I think I will tie another surgeon’s loop about 1/3 of the way up the shock cord and tie one on there.

the short shock cord is called a Riser iirc, and it clips between the common connection point on the shock cord and the parachutes swivel, allowing one loop to be the connection for both parachutes risers.

 

[Banzai88]

Somewhere around here I made a spreadsheet that auto calculates the length that each piece of cord should be.

I've used it on multiple LP to HP rockets and it's always worked well.

I'm on vacation on a remote island off of the NC coast right now, but I'll see if I can find it

 

[Banzai88]

Found it!

Thread 'Parachute Cluster Worksheet' https://www.rocketryforum.com/threads/parachute-cluster-worksheet.168759/

 

[David Schwantz]

A small piece of thin music wire used to spread chutes. It can be bent inside of tube and then when pulled out it spreads open. Keeps lines apart.

 

[brockrwood]

I'm on vacation on a remote island off of the NC coast right now, but I'll see if I can find it

SCUBA diving on WW2 U-Boat wrecks? Spanish galleons? Or just mackerel fishing on the back of a boat?

 

[sriegel]

I spike each canopy, stack them, and fold then together, rolling the bundle down the lines. That way, they all have to open in concert.

 

[bjphoenix]

We tend to jam everything into the airframe and hope it will work out when it comes out and the parachute deploys. I finally realized that the order was probably important so I've been putting the shock cord in first followed by the parachute. Also I needed something to restrain the shock cord while the parachute has a chance to open. I don't know how the order would relate to 2 parachutes but my point was that when they come out they are going to try to interfere with each other. Someone said they should be separated in the body tube and I was wondering how to do that. All of this is easier with high power because there bags for the parachutes and ways to tie the shock cord together. I was thinking maybe you could separate the parachutes with wadding, maybe you could wrap one parachute tighter than the other one or in some way that it would open slower.

I was wondering how multiple parachutes looked for NASA so I searched for images. I had a mental picture that our parachutes have relatively short shroud lines and that would hold the parachutes in awkward positions next to each other. It appears that NASA uses much longer shroud lines but they come together pretty close to the same point, the longer shroud lines let the parachutes have a more natural position. With our normal shroud lines you would have to tie the parachutes to different places on the shock cord or have an additional piece of shock cord to branch out from the main shock cord. Maybe experiment with a rocket you don't like.

 

[rharshberger]

We tend to jam everything into the airframe and hope it will work out when it comes out and the parachute deploys. I finally realized that the order was probably important so I've been putting the shock cord in first followed by the parachute. Also I needed something to restrain the shock cord while the parachute has a chance to open. I don't know how the order would relate to 2 parachutes but my point was that when they come out they are going to try to interfere with each other. Someone said they should be separated in the body tube and I was wondering how to do that. All of this is easier with high power because there bags for the parachutes and ways to tie the shock cord together. I was thinking maybe you could separate the parachutes with wadding, maybe you could wrap one parachute tighter than the other one or in some way that it would open slower.

I was wondering how multiple parachutes looked for NASA so I searched for images. I had a mental picture that our parachutes have relatively short shroud lines and that would hold the parachutes in awkward positions next to each other. It appears that NASA uses much longer shroud lines but they come together pretty close to the same point, the longer shroud lines let the parachutes have a more natural position. With our normal shroud lines you would have to tie the parachutes to different places on the shock cord or have an additional piece of shock cord to branch out from the main shock cord. Maybe experiment with a rocket you don't like.
View attachment 599045

NASA also uses their shroud lines to reef the chutes iirc (using cable cutters), so they can stage the rate of chute opening in two or three stages and yes their shrouds are like 3x the diameters in length possibly even 4x.

 

[brockrwood]

NASA also uses their shroud lines to reef the chutes iirc (using cable cutters), so they can stage the rate of chute opening in two or three stages and yes their shrouds are like 3x the diameters in length possibly even 4x.

Even NASA has “parawads” sometimes.



Apollo 15 splashdown.

 

[Neutronium95]

If you want more reliable recovery, I'd suggest going to better parachutes before going to more parachutes. Nylon parachutes are much less susceptible to wadding up. I really like the Top Flight Thin Mill parachutes.

 

[brockrwood]

I know how you feel.

Got impatient.

 

[Tractionengines]

Even NASA has “parawads” sometimes.

View attachment 599053

Apollo 15 splashdown.

There's a show on NASA TV which shoes the trials and tribulations of one of the programs (I can't remember which right now,may come back and edit ) where they kept having parachute deployment issues. The show has lots of wind tunnel deployments, helicopter drop tests, rigging changes, etc. Was interesting to see how much NASA still struggles with parachute deployment.

Makes me not feel so bad, when we have thread after thread of opinions, and processes, etc.

[ Edit: the show is on MARS 2020, and JPL / NASA preparing to get Perseverance to Mars. ]

 

[Banzai88]

SCUBA diving on WW2 U-Boat wrecks? Spanish galleons? Or just mackerel fishing on the back of a boat?

Ocracoke. Playing with different kinds of parachutes

 

[ep29030]

Even NASA has “parawads” sometimes.

View attachment 599053

Apollo 15 splashdown.

The Apollo program was designed for safe landing speed if two of the three ringslots deployed. So this was a “successful” recovery by their requirements.

 

[86mustang408w]

Having the chutes spread apart, or at or on different lines can work it just takes practice. One trick I found is using two spots for the chutes. One loop or quick link by the body tube exit, then another at the nosecone. It keeps them well apart, but still two. I can draw down what I mean, I don't have one like that right now but it works.

And it HAS to be packed very carefully. Probably something you wanna do the night before. And test it somehow first. You'll get this...