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Bruce

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Any suggestions on what to use to connect the parachute and shock cord to the screw eye in the nosecone on low and mid power rockets?

We swap payload sections and parachutes often enough that tying them on is not desirable. Looking for a link that can be opened and closed.

Tried fishing snap clips, but they seem weak and some of the stronger ones have bits that stick out and snag on things...

For larger rockets, screw links work well, but the smallest are 1/8" which are too heavy for C-F powered rockets.

So we currently use split rings, but they are hard to open and not super strong.

IMG_9872.JPG

(The pink covering over the loose ends of the Kevlar is adhesive heat shrink)

Any suggestions?
 
cut a loop off one of your kevlar cords..run it through the screw eye, then through the loop of the other kevlar cord..then join them all with a knot like a bowline and maybe a "stopper knot" at the end.

Tony
 
Thanks, that sounds reasonable, but I was hoping to minimize the number of bulky knots while still having both the shock cord and parachute attached to the screw eye independently...
 
I second quick links. Cheap, fast and easy to use. The only drawbacks are they may be a little heavier than you like and can take up too much space if everything is a tight fit.

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Thought about these the other day. Chain master link. One cord over each pin. Anyone tried them. Small size lighter that quick links. ... "loosing the keeper" is a problem, but the are cheep, and can get very small.
Thoughts?
20210301_231033.jpg
 
I wish they made tiny quick links, but I'm afraid that 1/8" is the smallest and those are too heavy and bulky for lightweight C thru F powered rockets.

I think the chain master link is an excellent idea! I'll give it a try.
 
I found a chain master link from a single speed bike. It weighs about 3.8 grams,

IMG_9879.JPG

By comparison, the split ring we were using before weighs about seven tenths of a gram,

IMG_9880.JPG

And the smallest screw link weighs about 8-1/4 grams,

IMG_9881.JPG

So I put the chain link on the rocket and it worked fine

IMG_9882.JPG

Not the easiest to open, but that's probably not so bad. I'll bet it's stronger than the split ring by quite a bit...
 
I like snaps and spring links.
1614848383883.png1614848741724.jpeg
 
I like the look of that !
Not easy to open "IS" a good thing. With the size of your cord and knots, it looks like the sliding plate can't move in too far. Also a good thing, so keeper does not get exposed to snag on something.
If you have smaller cord: Then a smaller link. And vice versa. (IF you go bigger, then get links with cotter-pins. No spring to fight with, and NOT going to open by accedent. At the moment not sure how small you can get this style.)
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I wonder if the shock cord or shroud lines could potentially catch on the exposed sharp end of a folded cotter pin?

Here's some more options I found,

Number 35 roller chain master link. This looks a lot like the single speed bicycle chain link:

IMG_9894.JPG



Number 41 roller chain master link:

IMG_9896.JPG



Number 40 roller chain master link. Why is it bigger than the number 41 even though it has a smaller number?

IMG_9893.JPG

And in the boating section of the hardware store I found this tiny D shackle. Stainless even:

IMG_9892.JPG
 
For low power rockets, this should be more than adequate.
It is all I use on all of my high power kites for exchanging lines, kites and they hold every time. Some of my kites have no problem lifting me off the ground at 230 lbs. They will hold.
A simple Kevlar loop with the knot working as the backer, the parachute, tie on with the larks head.
https://www.canadiankitecompany.com/pages/how-to-tie-a-larks-head-knot-for-kite-flying
 
That knot works great when always under some tension. Even a minimum amount if tension. BUT If it gets slack, and the "loop" side is a rope with "memory" that tries to untwist; it can open and allow the "knotted" end to slip out.
 
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I wonder if the shock cord or shroud lines could potentially catch on the exposed sharp end of a folded cotter pin?
One thing I would be careful of if using chain links is to make sure the Kevlar stays on the round pins. That is where the strength of the links are, not across the plates. Maybe a little tape or heatshrink might work in that situation.
 
Thought about these the other day. Chain master link. One cord over each pin. Anyone tried them. Small size lighter that quick links. ... "loosing the keeper" is a problem, but the are cheep, and can get very small.
Thoughts?
View attachment 453157

Put it all together, wrap with electrical tape. Should not come apart, or lose keeper. Easy to remove tape, and if done carefully, tape can be re-applied.
 
I've been using fishing snaps with swivels. There are many different styles & sizes. I get the ones that don't have anything protruding to snag on things. And since they come in different sizes you can select one that fits.

I have been using these for LPRs with great success and no failures. And I like the fact that I can easily unfasten my parachutes and store them not folded. For example, in the below pic , top row, I would use the safety snap, crosslock snap, or coastlock snap but not the others since they all have something sticking out that will snag on something. And I buy them with either rolling swivels or barrel swivels so my parachutes don't wind themselves up.


Snaps-and-Swivels.png
 
I also use various fishing swivels for for low power and ball bearing swivels for mid. No problem finding ones that are the right size with no sharps. I never store chutes attached. They hang on a line.
 
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