# Help? Harness twisting?

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#### Rob702Martinez

##### Zip-Tie Oversight Committee
TRF Supporter
Hi looking for pics of setups that have the bigger bolt swivels to stop the airframe from twisting the harness. Had 3 instances of failure in one day due to twisted harness'. Is it possible to cut the kevlar a few feet from airframe opening, to install a swivel? Best way to do so?

Had this problem on a 4" diameter 6 foot in rocket, 2.2" diameter 47in rocket. and. 4" diameter 30in rocket. Even with a drouge attached mid harness, same result. It actually rolled the drouge shroud lines around the harness. All harneses are permanetly attached to the MMT. :bangpan:

Thoughts?

#### Bat-mite

##### Rocketeer in MD
Hmm, I had posted, but deleted because I misunderstood. The problem is with the harness being permanently attached to the booster, so that even if you have a swivel at the coupler, the drogue would still spin around the booster harness.

I am at work with no pictures, but here is an idea. Get a short harness with two loops. Attach the short harness to the coupler. At the other end of the short harness, put a quick-link, swivel, quick-link, and link that to the booster harness. Then, make sure the drogue is coming off of the quick-link that is forward of the booster.

Here's the idea:

The booster is what spins, because of the fins. So this way you keep the drogue free from the spinning end.

#### rcktnut

##### Well-Known Member
I use the appropriate sized swivels needed for the size of the rocket and attach to the chute. The harnesses can twist all they want and not effect the chute.

#### timbucktoo

##### Well-Known Member
Staff member
TRF Supporter
Global Mod
I did this.

Nope,,,

Some boosters spin,, some do not,, even different builds of the same rocket...
If the booster is spinning you have to put a swivel one the boosters harness...
The lower you can put this swivel,, the closer to the object that's spinning the more effective it will be...
The harness is soft,, if you put this swivel up high near the av bay it will not help,,
the harness begins it's twist down low,, at the spinning booster,, this is where the soft harness twisting will put the most torque on the swivel,,
so you will have the best chance of the swivel spinning instead of the harness twisting...

Make absolutely certain that you use a swivel that is appropriately sized and rated to handle the load of the booster...
A fishing type swivel is good if you have a drogue spinning and it won't take any more load then the drogue chute can apply...
This is not the type of swivel that will handle the load of the booster...
Be certain to understand the difference between a "Failure Rating" ( that's what fishing type swivels are listed with ),,
And a "WLL" or "Working Load Limit" ( This is what heavy swivels are listed with ),,
the point being, a swivel can sustain it's WLL without deforming in any way,, the swivel will sustain it's WLL indefinitely....

Teddy

This is exactly what I mean,,,
This is a good set up,, this should work,,,
Have you flown this set up Tim,,
Did this booster spin before you did this ??
Does it spin since you did this ??

Teddy

#### timbucktoo

##### Well-Known Member
Staff member
TRF Supporter
Global Mod
This is exactly what I mean,,,
This is a good set up,, this should work,,,
Have you flown this set up Tim,,
Did this booster spin before you did this ??
Does it spin since you did this ??

Teddy
Had a few rockets that would spin and booster harnesses would get extremely twisted so I have been using this technique more & more (after you sold me a harness with same set-up). Booster still spins but harnesses have very little if any twist!

#### Rocket86

##### Well-Known Member
I do this as well. Prior to installing a free spinning swivel low in the booster harness it would twist all the way down to the ground. With this setup the harness is not twisted at all. I use a swivel at each chute attach point to keep them from twisting.

Tim,
That's great,, that you still see the booster spinning while falling from apogee
but now when you recover the rocket the harness isn't twisted anymore..
This is exactly what your trying to accomplish, but on some rockets it can be easier said then done..

John,,
That's exactly why I sell the ball bearing fishing swivels as well as the heavy ones..
Just because the drogue may spin if it is slightly off,, one side a bit higher on the shroud lines then the other....

I have the really heavy material,, 3/4" Tubular Kevlar..
I call it tug boat material,, you should see how heavy it is,, it's nut's,, lol...
Because of this material I got the next size up in swivels-- 3/8"...
You just wouldn't believe how heavy and physically big these things are,, it's pretty funny...

Great set up guy's....

Teddy

#### Rob702Martinez

##### Zip-Tie Oversight Committee
TRF Supporter
Sent an email to Teddy for some ideas but my question now, would be, can i cut my OBH 11/32 harness bout a foot up from the airframe and install the SS 1/4" swivel. Certain knot i can use or just put one at the end of the harness, then run a short extension to the nose/main section. Of course all parachutes on swivels. Drouge included.

#### soopirV

##### Well-Known Member
I haven't started using swivels yet (only getting started in DD), and am hoping someone can help me understand how you determine how much load will be borne by the swivel? Do you just simulate it, and determine the velocity of the rocket when the chutes deploy (drogue and then main)? From there, is there an easy way to get to the Gs imparted to the harness? Or do you simply say, "10 lb rocket x a safety rating = y lb WLL"?

#### blackjack2564

##### Crazy Jim's Gone Banana's
TRF Supporter
Had 3 instances of failure in one day due to twisted harness'.
Even with a drouge attached mid harness, same result. It actually rolled the drouge shroud lines around the harness.
Thoughts?
Every time I had issues like this, changing the drogue size eliminated them.

Drogue must be JUST large enough to "brake" decent & allow the fincan to fall vertical.

Problem usually arises when drogue is too small and fincan spins [while falling horizontally] underneath the drogue. Upsizing drogue will "usually" solve. There may be other underlying issues, but this one seems most common. [from my experience]

Have you been able to see the spinning under decent?
What are you seeing happen?

#### Handeman

##### Well-Known Member
TRF Supporter
Jim is right, a larger drogue to get the fin can dropping vertical will eliminate the spinning to a great extent. With that said, the larger drogue will probably add to the drift of the rocket.

I try to find a happy medium. The fin can stays below the payload section the whole way, but if it spins a little, I use ball bearing swivels. I've tried the non-ball bearing "barrel" swivel on one flight. It deformed and was useless after that one flight. I have a 4" 10lb rocket with an anti-zipper fin can. i.e. the fincan separates from the lower tube, not the lower tube from the av-bay. I've used the same ball bearing swivel for 7 years. It is a #8, 500 lb swivel like THIS with welded rings.

I had a very severly twisted shock cord that twisted up the drogue my L3 rocket the last time I flew it. I bought a climbing swivel rated at 30Kg similar to THIS I haven't had a chance to fly that one yet.

The good thing when using swivels on the drogue side of DD is that you don't need a large charge to separate the rocket. You only need enough to get the drogue into the air stream and the drag on the drogue will do the rest. That way the shock loads are not very large on the swivel. If you use a swivel while flying drogueless, the shock loads could be much higher if the payload gets way below the spinning fin can when the main opens and the fin can falls the length of the two shock cords before hitting the end with an open main holding the other end up. That's not too bad for smaller rockets, it's easy to over size things to hold up, but with heavier L2 and L3, I've seen 3/4" aircraft plywood bulkheads fail when the fin can hit the end of a long shock cord. A swivel doesn't have a chance.

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I am an advocate of getting every component sized correctly and working together correctly..
This means if you have a rocket zipper you don't use a wider harness and an anti zipper design,,
you find out why it was moving so fast on deployment and correct that problem..

I completely agree that drogue sizing is super important...
You're looking for the shape of an inverted "V" falling from apogee..
I like altitude,, I like descents as fast as I can get from apogee but still be controlled...
The further out the legs of the "V" are indicates a very fast decent and a very small drogue...
Good,, as long as the 2 halves aren't flailing around uncontrolled..
The further in or closed the legs of the "V" are the slower the descent and the larger the drogue..
Not good if the payload section is pointed down,, you want the payload section pointed out into clear air when it fires the main...
You don't want the payload section pointed down and fire the main directly into the path of falling rocket parts...

There's a link in your post Rich,, to a swivel,, Spro's ball bearing swivels of that type are --
#8 is a 400 lb failure rated swivel...
#10 is a 500 lb failure rated swivel...
There is a mistake in the way those are listed,, I know because I sell them,, I carry the #10 - 500 lb swivel for $5 ea,, always have.. I also carry these type of swivels,, They are much stronger and much more expensive.. I have these in size #10-- that's listed as a 1500 lb failure rating and they're$7 ea...

I would never recommend or advocate using any of these types of swivels to carry any more load then a drogue chute can apply...
If you want to carry the rocket a heavy swivel like these are in order as they'll take the load without deforming...

This is the reason I sell swivels like these...
And again, I don't mind saying it,, the best prices around...

Teddy

Oh,,
That really heavy man rated rock climbing swivel you linked to Rich,,
I think it's a viable piece,, but cost prohibitive...

Teddy

#### K'Tesh

##### OpenRocket Chuck Norris
TRF Supporter
Your question brought this idea back to me... Attaching a drogue to the top of a main parachute (perhaps with a dedicated shroud line going to it), then reef the main so that the the whole bundle is unrolled, and ready to deploy when the JLCR releases. Would this work? Why, or why not?

I realize that there would have to be something done to make ensure that the JLCR isn't lost when it releases. Perhaps a tether attaching it to the attachment point with the drogue.

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#### rharshberger

##### Well-Known Member
Your question brought this idea back to me... Attaching a drogue to the top of a main parachute (perhaps with a dedicated shroud line going to it), then reef the main so that the the whole bundle is unrolled, and ready to deploy when the JLCR releases. Would this work? Why, or why not?

View attachment 302453

I realize that there would have to be something done to make ensure that the JLCR isn't lost when it releases. Perhaps a tether attaching it to the attachment point with the drogue.
Appearances are that it would work, the issue is whether the band on the JLCR is strong enough to keep the main reefed during the descent and keeping the JLCR in place.

Appearances are that it would work, the issue is whether the band on the JLCR is strong enough to keep the main reefed during the descent and keeping the JLCR in place.
+1...

( If I'm understanding the pic correctly... )

Teddy

#### Rob702Martinez

##### Zip-Tie Oversight Committee
TRF Supporter
Every time I had issues like this, changing the drogue size eliminated them.

Drogue must be JUST large enough to "brake" decent & allow the fincan to fall vertical

Have you been able to see the spinning under decent?
What are you seeing happen?
I have a 36'' crossfire chute on the 4'' drago, 6 foot, 11 lbs wet, about 10 feet from the fin can, then the rest about 6 feet, to the nose with the main bundled with CR or CC. The main is 64'' crossfire. All chutes have swivels, but one continuous shock cord, on all of them actually. It never dawned on me to permanently attach a short harness about 2 feet longer then the fin section, attach a bolt eye x eye swivel and go from there.

on the dink, it rolled up the drouge along the shock cord and came in spinning in an inverted ''V'', wide, and the fin section was spinning like a hamster wheel, as it was spinning. Not cool, at all. The main plactered it self to the shock cord from spinning.

on the drago, a very very slow spin inverted "V", looked about the right distance apart, however the fin section, spinning like a hamster wheel. Main deploy malfunction. Also not cool.

on the punisher, it was just a mess. partial deploy on main. Also not cool. Twisted mess.

#### Rob702Martinez

##### Zip-Tie Oversight Committee
TRF Supporter
Jim is right, a larger drogue to get the fin can dropping vertical will eliminate the spinning to a great extent. With that said, the larger drogue will probably add to the drift of the rocket.

I had a very severly twisted shock cord that twisted up the drogue my L3 rocket the last time I flew it. I bought a climbing swivel rated at 30Kg similar to THIS I haven't had a chance to fly that one yet.
I was looking at those climbing ones, do they rotate smooth?

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#### Rob702Martinez

##### Zip-Tie Oversight Committee
TRF Supporter
If you want to carry the rocket a heavy swivel like these are in order as they'll take the load without deforming...
View attachment 302452
This is the reason I sell swivels like these...
And again, I don't mind saying it,, the best prices around...

Teddy

Teddy

#### Rob702Martinez

##### Zip-Tie Oversight Committee
TRF Supporter
I just had a type conversation with and shipped to Rob...
He really is a nice man...
CJ this is right up your alley....
Would somebody please ask Rob if there are any good lookin women around where he lives ?????

Teddy
Ha ha. Thanks for your help Teddy! I really appreciate it, amazing customer support. Let me know when you come to Vegas