Adding swivels to chutes?

All this talk of swivels and snap swivels brings up an interesting question for me.

I've seen some folks attach the snap swivel / parachute to the end of the shock cord and the nose cone a few inches further down. Others attach the nosecone to the end of the shock cord and the snap swivel / parachute further down. The last group attaches both the nosecone and the snap swivel / parachute to the end of the shock cord.

What's up with that? Do any of these three methods have advantages over the others?

You need to see how everything hangs when the parachute is deployed. Some different arrangements of these items will allow the nose cone to swing around without hitting into the rocket.

Personally; I perfer to tie a butterfly knot in the shockcord a few inches to 1/3 of the way below the NC, for chute or streamer attachment. Seems to helps with Packing and reliefs a bit of stress on the chute at opening.
It is important to check the hang distance to ensure the NC isn't going to be hitting the body while they dangle below the chute on the way down

Wow, I guess I've been really lucky... I've used the same bag of cheap little swivels for all of my LPR rockets for years, and they've always worked flawlessly.

Lots of discussion about which swivel to use and that question seems to have been answered here. Being new to mid and high powered rocketry (just now completing construction of the Initiator and then will do a Loc IV), I have never used them so could some one please post a diagram or picture of exactly how and where the swivels are attached to the chute cords, shock cord etc? That would certainly help me, thank you.

The swivel goes between parachute and whatever part of the rocket the parachute connects to. It's purpose is to help tame the wild pendulum-like swinging and oscillating that the rocket does as it is suspended at the end of the shock cord and hanging below the chute during descent. It also allows the flier to easily disconnect the parachute from the rest of the rocket after flight, so that the chute can be stored separately from the rocket and so that the flier can use different chute sizes in the same rocket depending upon the flying conditions.

The swivel is permanently attached to the ends of the parachute's shroud lines, which is usually done by tying the shroud lines to one of the swivel's eyes. The other end of the swivel is attached to some part of the rocket using a temporary attachment.

In low power rocketry in the old days the standard practice was to attach the swivel to the screw eye or loop at the base of the nose cone and attach the shock cord at that same point as well. Now it is more common to attach the swivel to a loop or ring on the shock cord a short distance away from (below) the nose cone. This allows both the rocket and the nose cone to dangle freely beneath the parachute during recovery. It puts less stress on the connection at the base of the nose cone, because this connection does not have to support the entire weight of the rocket during the descent back to the ground. The swivel is attached to this loop in the rocket's shock cord via either an integral snap link that is part of the swivel in smaller rockets, or via a separate quick link in larger rockets.

To repeat: the swivel is permanently attached to the parachute's shroud lines, and then it is temporarily attached to the rocket's shock cord via either a recloseable snap link that is permanently attached to the free end of the swivel or else via a separate quick link that connects the free end of the swivel to the rocket's shock cord

MarkII.

Micromeister, I had a question about the method you posted for attaching shroud lines in parallel versus the standard "Estes" method. Do the shroud lines remain the same length in both methods? I want to give this a try.

Thanks,
Moldie

I typically attach the parachute (via a snap swivel) directly to the screw-eye simply because it's easier to pack everything in that way (I think, maybe it's just habit). I do attach the 'chute about 1/3 of the way down a much longer shock cord on my egglofter so that the egg gains some benefit from the elastic, particularly on slightly early or late deployments. The intent here is also to ease the shock to the parachute after I destroyed a perfectly good Evil Ed chute on a late deployment (never use a five second delay on an egglofter - duh).

FatBoy said:

For low power rockets I just use the same swivels used for fishing that you can get from any sporting good store in the fishing department.

Click to expand...

Same here.

I just make sure the fishing snap swivels are the kind with the locking hook on the snap and have the pointed ends instead of the round ends. The pointed ones can take more force before bending the snap open.

Handeman said:

I just make sure the fishing snap swivels are the kind with the locking hook on the snap and have the pointed ends instead of the round ends. The pointed ones can take more force before bending the snap open.

Click to expand...

There is some really good information here:

https://www.oldrocketforum.com/showthread.php?t=4507

See especially posts #3 - #6.

MarkII

Moldie said:

Micromeister, I had a question about the method you posted for attaching shroud lines in parallel versus the standard "Estes" method. Do the shroud lines remain the same length in both methods? I want to give this a try.

Thanks,
Moldie

Click to expand...

Moldie:
Yes: all shroud lines remain the same length.

luke strawwalker said:

Very nice... thanks for the pontification...

Sorry if I confused you using a "HPR" term; but I wasn't aware that the term "bonus delay" was strictly applied to HPR... Not having ever flown APCP, strictly flying BP, I was referring to the D12-3's I've launched that have sometimes been more like a D12-9... (and yes, I know there is no such thing). I've also had C6-5's end up with delays more like C6-8's... (again fictitious motor designation)... When you put a motor that is appropriate for the model in it and it does something it's NOT supposed to do, what can you do about it?? Your earlier statement came across as, "well, if you learn how to put the right motor delay in your model things like that would NEVER happen" when anybody who's flown awhile knows sooner or later you WILL come across a motor that is either a W-A-Y L-O-N-G-E-R delay than what was on the label, or shorter, but that's more rare, or you put a C motor in your model that performs like a wet "A" motor and barely gets it off the pad... Couple subpar performance with even a regular (meaning proper) delay time and that puppy's gonna be moving at a good clip when the chute pops... presuming it pops before it hits the ground. I recently lost a rocket to just such a happenstance.

Also, I've chosen motors with what I thought was the 'proper' delay only to find that the model hits a breeze on the way up or a gust weathercocks it soon after leaving the rod, and the rocket arches WAY more than you figured or intended, and the thing ejects near apogee but still carrying a LOT of horizontal velocity, especially if it's into the wind and a good stiff breeze at altitude which increases the "apparent" wind velocity. I've had a rocket or two strip or nearly shred a chute even though it looked to have little actual 'ground velocity' but was horizontal at apogee into a stiff wind aloft that was ripping past it fast enough to do nasty things.

Now perhaps you didn't mean to come across with this "well, if you knew what you were doing that wouldn't happen" attitude, but it sounded to me like it. I'll presume you didn't intend to come across that way. Perhaps you'll consider your word choice a little more carefully in the future, my friend...

Anyhow, yeah, it's still rocket science. Yes, I agree with you that one should ALWAYS endeavor to choose the right motor for the conditions, but sometimes that IS a learned skill, and from bitter experience, as I can attest. Difference between knowledge and WISDOM... (and experience).

However, the unexpected still can and DOES happen sometimes...

Have a good one! OL JR

Click to expand...

Luke:
Sorry this reply has taken this long, been quite preoccupied over the last couple months.

You are correct; I didn't intend to come across with that attitude, nor do I like to type endlessly where fewer words can and should do the trick. That MAY be the difference; Some like to beat around the bush playing lets not ruffel any feathers or perhaps state the obvious. I prefer to get the idea(s) out without all the curd, letting the chips fall where they may. Always been that way, don't see myself changing anytime soon. Some say that's being blunt or gruff; I say it's being honest and staight forward.

As to your assertion of very long BP delays...I've got to tell ya they just don't hold Up to the available data my friend.
Hundreds of thousands of BP motors have been flown, data recorded and to be sure, a very tiny fraction of a precent have a SLIGHTLY longer delay then that stated on the label. At least on ESTES motors, others manufacturers with shorter motor history may have a bit different outcome to which I can't attest but personnally having as many years and litterally thousands of recorded flights, I've yet to experience bonus BP motor delays + or - anywhere near those you posted. Even 30year old motors timed in OOP testing have performed within .5 sec of that listed on the motor. I took some time preparing for OOP testing looking back through my Log records to the early 60's. I didn't find a single motor with even that much longer timed or counted delay. Had a few Shorter then expected but very darn few long delay motors by ESTES, Centuri, MPC or Apogee. Based on those records and the massive amount of flight data from the manufacturers, I have to conlcude that there had to be some other factor involved causing such reported malfunctions. Did you send in a MESS report to S&T about such flights?

To be sure if one hasn't paid attention to which motor has been installed, we could conceivably get a C6-7 in a model that should have had a C6-3 or that D12-3 heavy model with a D12-7 would certainly "act like" it was a D12-9as one waits for that never to come ejection.

Field conditions are always a concern as well. How many of use check with the weather service for winds aloft before leaving for the field? It's just another thing to add to the Launch day check list. These Days; with all the cell phones, blackberries and other mobile communication stuff...(I don't even own a cell phone) It's even easier to have up to the minute field conditions, if your not carring your own weather station to the field.

I know most of us causal weekend flyers just go out and "shoot some off". and that my friend, is exactly what I was attempting to give food for thought on. All these things should indeed be concerns of every one of us as we to try our best to understand what we are doing taking into account as many of the variables to the very best of our abilities. Can or will stuff still go astray. Of coarse it can; but mis-matched model/motor combinations really shouldn't be one of them At least with BP motors anyway.

This is the way I do it which may already been covered. I usually use several feet of 1/8" nylon or kevlar chord instead of elastic.

What I do is run the 1/8 chord thru one end of the swivel. I sew the swivel to the chord 6-10 inches from the nose cone to keep it from sliding up or down with kevlar thread that way there are no knots in the middle of my shock chord.

For Nylon chutes I fold the shrould lines and mark the middle with a sharpie. I pull the shrould lines thru a 3/8" long piece of silicone tubing and adjust them so the three sharpie lines all line up. This keeps the chute even but will give some give on the flights with crazy delays if needed.

I attach these 3 small loops to the swivel snap. In the event of a tangle (rare) I can easily remove the chute and the silicon tubing and easily untangle the shroud lines and start over as there are no knots

It's easy to swap chutes between rockets. The chutes stay even yet can easily be undone.

With plastic chutes I wrap the pairs with a thin strip of painters tape as the lines are too thin for the silicon tubing to hold them tight.

The tape can be pulled off carefully, the chute untangled and re-assembled.

Worked for me for years up to F powered flights...haven't flown anything larger yet.

Tom

Micromeister said:

Luke:
Sorry this reply has taken this long, been quite preoccupied over the last couple months.

You are correct; I didn't intend to come across with that attitude, nor do I like to type endlessly where fewer words can and should do the trick. That MAY be the difference; Some like to beat around the bush playing lets not ruffel any feathers or perhaps state the obvious. I prefer to get the idea(s) out without all the curd, letting the chips fall where they may. Always been that way, don't see myself changing anytime soon. Some say that's being blunt or gruff; I say it's being honest and staight forward.

As to your assertion of very long BP delays...I've got to tell ya they just don't hold Up to the available data my friend.
Hundreds of thousands of BP motors have been flown, data recorded and to be sure, a very tiny fraction of a precent have a SLIGHTLY longer delay then that stated on the label. At least on ESTES motors, others manufacturers with shorter motor history may have a bit different outcome to which I can't attest but personnally having as many years and litterally thousands of recorded flights, I've yet to experience bonus BP motor delays + or - anywhere near those you posted. Even 30year old motors timed in OOP testing have performed within .5 sec of that listed on the motor. I took some time preparing for OOP testing looking back through my Log records to the early 60's. I didn't find a single motor with even that much longer timed or counted delay. Had a few Shorter then expected but very darn few long delay motors by ESTES, Centuri, MPC or Apogee. Based on those records and the massive amount of flight data from the manufacturers, I have to conlcude that there had to be some other factor involved causing such reported malfunctions. Did you send in a MESS report to S&T about such flights?

To be sure if one hasn't paid attention to which motor has been installed, we could conceivably get a C6-7 in a model that should have had a C6-3 or that D12-3 heavy model with a D12-7 would certainly "act like" it was a D12-9as one waits for that never to come ejection.

Field conditions are always a concern as well. How many of use check with the weather service for winds aloft before leaving for the field? It's just another thing to add to the Launch day check list. These Days; with all the cell phones, blackberries and other mobile communication stuff...(I don't even own a cell phone) It's even easier to have up to the minute field conditions, if your not carring your own weather station to the field.

I know most of us causal weekend flyers just go out and "shoot some off". and that my friend, is exactly what I was attempting to give food for thought on. All these things should indeed be concerns of every one of us as we to try our best to understand what we are doing taking into account as many of the variables to the very best of our abilities. Can or will stuff still go astray. Of coarse it can; but mis-matched model/motor combinations really shouldn't be one of them At least with BP motors anyway.

Click to expand...

Well, no biggie. You might just think a bit about how you come across sometimes, Micro, that's all. Sometimes you project definite "attitude".

Well, as for the 'data', yeah, I'm sure there are plenty of data available from static tests and the old motor flying program and such to verify what you're saying. I'm saying that I've experienced some delays that were really long in BP motors, far longer than what was advertised. I've had it happen, and I've seen and made the mistake from time to time of mismatched motor, wrong delay, excess weight, field conditions, etc. pop up and cause problems, which is my mistake, but I HAVE seen motors end up with longer delays than they should, and shorter as well, but usually longer. I'm not saying it's many, but I've had a few. That's just anecdotal and I'm sure you're not impressed, which is your right, but I'm sticking to my guns and saying it CAN happen. Statistically small probability, but NOT Zero!

Anyway, take it easy and I'll agree to disagree. Later! OL JR

luke strawwalker said:

However, the unexpected still can and DOES happen sometimes...

Click to expand...

About 2 months ago I had a D12-3 that was more like a 1 second delay. only one in the pack of 3. Really hard on the Big Daddy chute. :confused2:

Stuff happens even with BP.

N

If I were basing motor reliability on my own experience, I'd have to say BP is flawless. Never had much variation with Estes motors with the exception of ejection charge intensity. While I probably haven't flown thousands of BP motors like Micro, I have easily flown several hundred. My experience further supports his findings and whatever other data might be available.

HOWEVER, I have personally witnessed enough BP motor failure and variation to say that it DOES happen. The chance is very small, and I believe one could probably go their whole life without experiencing such a variance or failure (provided the motors are stored properly)- yes, Estes motors are that good! But, I know for a fact they are not foolproof and that referring to collected data does not always account for such small percentages and the unexpected.

foose4string said:

If I were basing motor reliability on my own experience, I'd have to say BP is flawless. Never had much variation with Estes motors with the exception of ejection charge intensity. While I probably haven't flown thousands of BP motors like Micro, I have easily flown several hundred. My experience further supports his findings and whatever other data might be available.

HOWEVER, I have personally witnessed enough BP motor failure and variation to say that it DOES happen. The chance is very small, and I believe one could probably go their whole life without experiencing such a variance or failure (provided the motors are stored properly)- yes, Estes motors are that good! But, I know for a fact they are not foolproof and that referring to collected data does not always account for such small percentages and the unexpected.

Click to expand...

Exactly... I agree... and Ranger's comments on the unexpected are quite correct.

I'd throw in, having read Dr. Zooch's recent experience with an "anomalous" motor, that there are more than a few ways things can go wrong. A lump in the mixture or some other contamination when the motor is pressed, or something unusual happening during shipping or storage, and of course the differences in the flight conditions at the time the motor is fired can all contribute to these differentiations from the standard norm. A lot of times a small flub in the motor can cause a minor problem when it's fired that doesn't adversely affect the flight, but sometimes it can be just enough to cause a BIG problem.

At my nephew's 4-H county fair launch in Indiana about five years ago, I was sitting on the first row of aluminum bleachers, about 20 feet or so from the launch pad, right behind the judge/advisor conducting the launch, who was standing to one side in front of me. The LPR rocket lifted off, the motor sputtering and spitting something out the back that looked like balls of metal like the 'sparky' motors spit out the back. The rocket arched into the wind away from us, and a split second later I felt an INTENSE burning under my leg :y:and LEAPT up off the aluminum bleacher seat fanning my leg, to find a neat 1/4 inch HOLE BURNED through my jeans and burned into my leg about 1/8 inch deep into the flesh. As I leapt and turned, I saw a roughly 1/4 inch white-hot ball of liquid slag kinda jumping and rolling around on the aluminum bleacher seat where I'd been sitting-- sizzling like water dropped into a hot frying pan! It cooled down to a dull cherry red within a couple seconds and then into a BB-sized ball of slag, just like the kind I've made melting soil with an oxy-acetylene torch, except instead of greenish like regular soil, this was quite dark but semi-translucent.

I deduced that the motor must have had some kind of sand or other mineral contamination in it that would not burn, but DID liquify and stick together into balls of slag that were ejected from the nozzle as the motor burned, which accounts for the sputtering and 'sparky' effect as well as one of the balls of slag being ejected in such a way that it landed on the bleacher seat and rolled under my behind and burned a hole in my pants and, well, posterior leg. The sizzling glowing ball of slag was the visible culprit.

Now, somebody tell me the odds on THAT one! I still have a little 'crater' on the back of my leg from it...

Never say never... OL JR

A BP sparky? If you can make those consistantly, you should be able to make a small pile of money.