Swivels to switch out parachutes in midpower rocket advice desired

[Bill S]

I've got a question. I've always been an low powered rocket guy, but am starting to do mid-power. I've used snap swivels to attach my parachutes to the shock cord (the safety kind without protruding tabs to catch on things), on every rocket up to a Super Big Bertha, and Executioner. But now that I am going beyond that, I am thinking the snap swivels I've previously used may be inadequate.

The next rocket is around 1.5 lbs give or take a couple ounces. I want the ability to switch between an 30" and 27" parachute fairly rapidly, without adding very much weight. What would you all suggest for say 1.5 lbs up to 3 - I don't plan to get level 1 certified so I can't see building rockets much beyond 2 lbs or so (though who knows?).

I have a decently supplied fishing store nearby but am not sure what I should be looking for.
Thanks for any help.

 

[crossfire]

As you move up in rocket size and weight it would be a good idea to not use a snap swivels. Check out Top Flight Recovery for swivels. You could use their sw350 on that 1.5 lb rocket.

 

[Bill S]

It figures - I just ordered from Top Flight, and it arrived yesterday.

 

[waltr]

I do not use snaps/clips on MPR at all.
First I make a loop on the shock code, Kevlar or nylon, about 1/3 way from nose to BT. To do this, double over the cord then tie a knot to create a loop.
Then take the chute shroud lines through this loop and pass the chute through the shroud lines. This ties the chute directly onto the shock cord.
Easy to reverse to change chute.

This can be done on a Swivel WITHOUT a snap clip if you think a swivel is needed.

 

[jmasterj]

You could use 1/8" quick links for quick change outs, but that weight starts to add up quickly.

Dr Fish via Amazon has a whole range of swivels with varying load limits. Could just match your Kevlar, no point in being stronger.

 

[rharshberger]

Snap swivels CAN be used, BUT you have to do the math...yes I know math is hard. There are snap swivels rated for 200 lbs made by Owner, P-Line and many others most are designed with deep sea fishing in mind. As for the math, its just a matter of figuring out the max shock that will be imparted to the weakest part (which is probably the shroud lines not the swivel, of course if the chute opens correctly the load is spread across all the shroud lines instead of just one or two, if it doesn't open correctly most of the shock is loaded onto one or two lines possibly creating a streamer from a chute).

 

[Bill S]

I think that I am going to try Waltrs idea; it appeals to my sense of simplicity and I don't have to buy something else online. Thanks guys.

 

[jmasterj]

I suggest an alpine butterfly for that mid-line loop.

 

[Bill S]

jmasterj, thanks for that. I think that may work better than a regular old knot that might come loose. Bookmarked so I can practice it later on.

 

[jmasterj]

It's a fun one to tie!

 

[Back_at_it]

I stop using snap swivels in anything over 16oz. Just tie a loop in your shock cord and loop the parachute lines through that. Eliminates one more potential failure point.

 

[Bill S]

I stop using snap swivels in anything over 16oz. Just tie a loop in your shock cord and loop the parachute lines through that. Eliminates one more potential failure point.

That is what I decided to go with; the alpine butterfly. I practiced it a few times, but clearly I need to practice more so I can do it in the field if need be.

 

[BEC]

I second Rich. There are large coast-lock type snap swivels. They are available from stores that sell tackle for deep sea fishing.

A pair of needle-nose pliers is helpful for working with them when changing ‘chutes in the field. They are stiff…

 

[caveduck]

I have a good supply of the Dr. Fish non-snap swivels that I use for MPR to smaller HPR. They're helpful for preventing shock lines from getting twisted up if things set up so the body is spinning on descent. I usually use a larger one than I think I need and haven't had any fail to date. Someone posted some test results somewhere (not on TRF) showing the actual failure load was in the ballpark of the designation, but that means you need to de-rate by whatever safety margin you want. Some other brands had fail loads that were notably less than the claim...beware.

Snap-type swivels seem to be very vulnerable to bending open under sudden loads, but they're great for LPR.

 

[BEC]

Snap-type swivels seem to be very vulnerable to bending open under sudden loads, but they're great for LPR.

Which is why the coast lock type. For example, some that look suitable for some MPRs: https://www.amazon.com/Coastlock-Sn...=coastlock+snap+swivel&qid=1652494754&sr=8-21

I have not tried these, but I have used big ones like this in my Estes PSII builder’s models (Leviathan, Ventris, etc) and models using those parts (256% upscale Nova Payloader).

 

[rcktnut]

I use 1/8 in. quick links on MP/ HP up to 6 lbs. never had a problem in 26 years. I use good quality and appropriate width elastic also for 3lb and under rockets. No fancy knots etc. The Big Brute pictured once came in ballistic from 1500 ft. chute popped at about 500ft. no damage to rocket ,chute or shock cord.

 

[caveduck]

Which is why the coast lock type. For example, some that look suitable for some MPRs: https://www.amazon.com/Coastlock-Sn...=coastlock+snap+swivel&qid=1652494754&sr=8-21

I have not tried these, but I have used big ones like this in my Estes PSII builder’s models (Leviathan, Ventris, etc) and models using those parts (256% upscale Nova Payloader).

The mechanism there looks a bit better than the ones that use thin sheet metal as the keeper, but it will still fail with only a partial unbend of the 180 in the wire...makes me a bit nervous though I'm sure there is a load range where they will work decently. I'm also a fan of the 1/8" quick links for smaller HPR. The failure point in those is the small threads deforming and pulling out of the threaded connection under shock load, but I've never had that happen in rockets weighing only 2-3 kg. Locking climbing-style gate carabiners are the ticket for bigger HPR - they are designed for shock loads and do not have the thread vulnerability, but they are physically big.

 

[Onebadhawk]

I didn't research and source these ( because they're just perfect for rocketry )..
I don't just ship these to you home..
I actually drive these all the way to launches just in case you need them..

Try THAT Amazon,, lol..

 

[rharshberger]

I didn't research and source these ( because they're just perfect for rocketry )..
I don't just ship these to you home..
I actually drive these all the way to launches just in case you need them..

Try THAT Amazon,, lol..

View attachment 523362

Now thats customer service Teddy!

And for anyone who has never dealt with OneBadHawk, Teddy is in a class of his own, I dont fly any rocket over 10lbs that isnt using OneBadHawk recovery harnesses and hardware!