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Question? For first homemade chute

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rock2p

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I bought this ripstop nylon a while agon and started to make

some sort of chute with eugenefl. I think it might have been

an "x" shaped cute. I had trouble with hemming the edges and

put the project aside thinking I just needed to use a surger

when I got the chance.

Well, ChrisVG sent me this link

http://www.lunar.org/docs/handbook/parachutes.html

on making rip-stop nylon chutes

and so I gave it another try. It provides a simple way to hem the

edges. And that's the point where I'm at. I don't know if I want to

tie the shroud lines to the sewn on chute shroud line loops like they

suggest or sew them directly into the chute material.

That's one of my questions. What is the best way to attatch

lines.

My other question is. What should I be using for shroud lines.

I'm interested in using Kevlar but don't know what size to get.

What units do they measure kevlar in (as far as strenght or dia. goes)

I know I have seen kevlar fishing line but I don't know if that's

the same stuff or that it is more pricey than bulk kevlar.

This is a 12 inch chute. I have heard to use round and not flat

kevlar. I also have some nylon line or string but I'm thinking it

may be a bit thick but I am planning on making a 24 inch chute as

well. so what thickness should kevlar or nylon be for one that size.

A lot of questions there.

Thanks for any help. :)

Here's a pic.

And I do have to admit I went to my parents place and my mom helped me get those straight stitch lines
 

ghp3

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What should I be using for shroud lines. I'm interested in using Kevlar but don't know what size to get.
Several months ago I purchased a 3 oz spool of Kevlar thread, size 346 from The Thread Exchange, which I have mainly used for Kevlar shock cord harnesses. The thread is made from a four-strand twist. For nylon chute shroud lines, I cut the proper length of the 346 Kevlar, then separate the four strands. Each strand makes a perfect shroud line. The 3 oz spool has 225 yards for a cost of $10.25, or about 1.5c per foot. A nice dual purpose purchase.

Also, Wally World (Wal-Mart) sells a adhesive "hemming" tape that I use to seal the edges of my rip-stop chutes, much easier and quicker than sewing and seems to hold up as well.

Have fun!

George
ghp3
 

rock2p

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Heres a pic that didn't make it on the original post
 

flying_silverad

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As far as how to attach the shrouds, I have had real good luck tying them into the corner. You can sew them in but you must make sure that the sewing penetrates the shroud itself. You can use kevlar although I have found that 40-50lb dacron braid works real nice too.
If you go the kevlar route for a 12 inch chute, #207 kelar is a decent size and offers 90lb test! Make sure you get bonded as opposed to non as it keeps fraying to a min. I have been using The Thread Exchange and am now playing with Nomex thread.
 

rock2p

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Originally posted by ghp3
Several months ago I purchased a 3 oz spool of Kevlar thread, size 346 from The Thread Exchange, which I have mainly used for Kevlar shock cord harnesses. The thread is made from a four-strand twist. For nylon chute shroud lines, I cut the proper length of the 346 Kevlar, then separate the four strands. Each strand makes a perfect shroud line.
Also, Wally World (Wal-Mart) sells a adhesive "hemming" tape that I use to seal the edges of my rip-stop chutes, much easier and quicker than sewing and seems to hold up as well.

What size chutes are you going up to with 1/4 of size 346 kevlar for a shroud line?

and up to what size rocket are you using this for shock cord?

I have heard of hemming tape and hemming glue I guess I prefer the old way.

I don't know about the tape but I once saw a glued on that may have been loosened up by the heat of exhast gases, but I guess that's a wadding issue and not a hemming on.

Thanks for you help George.
 

AndyC

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Shroud lines are best sewn onto the OUTSIDE of the canopy. Take a look at a military surplus chute, and that's the way it's done. Ive tried it, and it really is stronger. For shrouds, kevlar is fine, but may be overkill (depending on your wadding/piston setup). I always use Dyneema which is very soft, compact, and very strong. It has a fairly low metling point, but this comes down to propper wadding.

cheers,

Andy
 

Micromeister

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Yeap I'm with AndyC, We alway sew the shroud lines into the outside hem of my hemi chutes, to the outside corners of the X and flat chutes. Like Geroge I purchased a number of different Kevlar line sized from the Thread Exchange. A very good source, another is McMaster Carr. I use a smaller line then George on small chutes 15 and under 50 -70lb braded kevlar fishing line is just fine. Stern still makes the line in green only. and it is kind of expensive 20 some bucks for 100yds but is it's what you can get it works very well.

Hope this helps

I'm not sure if you can see the stitching on the 36" hemi chute in this pic. Hopefully you'll be able to pick out the loop tied in the end of the shroud which is then stitched to the outside seam of the cutes.
 

rock2p

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Originally posted by Micromister
We alway sew the shroud lines into the outside hem of my hemi chutes, to the outside corners of the X and flat chutes. I use a smaller line then George on small chutes 15 and under 50 -70 braded kevlar fishing line is just fine.

Hope this helps

I'm not sure if you can see the stitching on the 36" hemi chute in this pic. Hopefully you'll be able to pick out the loop tied in the end of the shroud which is then stitched to the outside seam of the cutes.

Can you tell me what the measure ments of 50 and 70 are referring to. I'm getting a feel for the different thicknesses but I just would like to know.

With the thin diameter of some of these kevlar lines it seems that it would be difficult to make sure it is sewn securly to the chute.

I noticed what you said about the loop tied in the end of the shroud line, but could you be more specific in how you make sure the shroud lines are securly sewn in. (what kind of stitch or how much line overlap onto chute, etc.)

And do you know if there is a difference between kelar thread and fishing line? Which one usually runs cheaper?

Thanks for all you help guys.

:)
 

Micromeister

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First the easy answer: Stern kevlar fishing line is dupont kevlar. they are both the same material, however Stern is "braded" kevlar threads 50 to 70lb is the tensil strenght rating, or break strength. Most NOT all of the threads available from the thread exchange are twisted lines. you have to look hard to get to the breaded lines. Breaded is a bit more flexible than twisted but I use both either will work just fine.
If you have the time to Order for either the thread exchange or McMaster-Carr Co. you will save yourself a bunch of money over the retail price of stren fishing like. The Thread Exchange has by far the best prices on Kevlar lines I've seen in several years.

for 12" to 36" hemi chutes I tie a loop that measures about 1" long after tieing in the ends of the shrouds. by the way I DO NOT attach the ends round the outside of the canopy. We attach parallel to one axis, across the canopy. this lessens line twist when gathering the shrouds at the attachment swivel. Each loop is sewn onto the outside of the canopy using a cross stitching method all the way around the entire open loop of line, locking the loop on the canopy tips. We use 2 strand twisted 13lb kevlar thread to sew the rip-stop fabric "gores" and/or the shroud line attachments and spill hole reinforcment.
 

rocket trike

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Hello WW

We are just adding some Kevlar to our line of products. We use a soft Kevlar on our parachutes. This is not bonded so I stays soft and I feel and others in our club feels that it is easier to pack. It holds up as good as the bonded stuff. We will be offering this kevlar for .08 a foot with a min of 10 feet. We do not offer this on our web site yet but should have it on there by the end of the month. We do how ever have some on hand so send me a e-amil at rocketheadrockets@rap.midco.net if you are interested.
 

rock2p

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Originally posted by Micromister
First the easy answer: Stern kevlar fishing line is dupont kevlar. they are both the same material, however Stern is "braded" kevlar threads 50 to 70lb is the tensil strenght rating, or break strength.

for 12" to 36" hemi chutes I tie a loop that measures about 1" long after tieing in the ends of the shrouds. by the way I DO NOT attach the ends round the outside of the canopy. We attach parallel to one axis, across the canopy. this lessens line twist when gathering the shrouds at the attachment swivel. Each loop is sewn onto the outside of the canopy using a cross stitching method all the way around the entire open loop of line, locking the loop on the canopy tips. We use 2 strand twisted 13lb kevlar thread to sew the rip-stop fabric "gores" and/or the shroud line attachments and spill hole reinforcment.

Micro, Thanks for all the answers.

I wasn't recongnizing the company "Stern" or associating it with fishing. When you spelled it "Stren" the lights went on. I actually have quite a bit of experience in fishing.

That makes me think of the other fishing lines out there, like Spiderwire or Berkley's Firewire what their lines are made of and how they could be used in rocketry, but they're indeed pricey.

Now the 50 and 70 makes sense as a lb test rating.

I guess I'm referring to the other numbers I'm seeing in reference to Kevlar line, like the units on Thread exchange such as "size 346" or is this referring to lb test as well?


Thanks for the further description of the shroud line attatchment.

I guess this is one of those situations where a good picture would be worth more than a thousand words.

so if you do have a pic that shows more detail of what your describing. maybe that would help get it through my thick skull.

thanks again
 

cls

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I had zero success finding Stren kevlar fishing line, anywhere in the US. Fishermen don't like kevlar because knots don't stay tied, it's too slippery. so it's been off the market for a few years.

from what I could see all other fishing lines are monofilament so are intolerant of heat. you can tie knots in mono - obviously - but good luck gluing it or otherwise attaching it to the rocket. also mono doesn't bend so won't stow well in a really small tube.

there are some metal fishing lines but I am not ready for metal shock cords & shrouds on the rockets.


I went to my favorite sailmaker shop and got a sample of the kevlar thread they use. it is not bound together so it unravels. also it was the 35# stuff.


sounds like the Rockethead kevlar would be good. also you can order some from Apogee or Flis and maybe Thrustaero or a few other TRF places. or you can buy a huge roll of it from McMaster-Carr and send me a couple hundred feet for telling you this :)
 

ghp3

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What size chutes are you going up to with 1/4 of size 346 kevlar for a shroud line? and up to what size rocket are you using this for shock cord?
I use this 1/4 strand of 346 kevlar on 18" to 36" chutes for LPR and MPR rockets.

For the shock cord I use a single 346 kevlar line on LPR rockets (up to single "D" and 3-motor cluster "C"s), attached to the motor mount with a length of 1/4" elastic on the end, with no failures so far. For MPR rockets, I braid three strands of 346 kevlar into one 1/4" thick cord (just like I learned in summer camp!), again tied to the motor mount and use either 3/8" elastic or 1/4" tubular nylon on the end. So far no failures.

I was trying to track down the braided kevlar fishing line but wasn't able to encounter it anywhere. That's when I discovered The Thread Exchange. They make Kevlar cords as thick as size 693.

the units on Thread exchange such as "size 346" or is this referring to lb test as well?
The number refers to thread size. I don't know exactly the scale that it is based on, but in general the larger the number, the thicker the thread. Size 346 is fairly thick (about 1mm) and has a minimum tensile strength in the neighborhood of 125 to 130 lb. 1/4 strand would be about 30 to 35 lb.

George
 

Micromeister

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Cls:
As a Bass'in man for as long maybe longer than a rocketeer, I love the kevlar line! the improved clinch knot ties fast and stays put. In Rocketry related projects, two half hitches and bowlines work wonderfully with any and all Kevlar lines. Stren has discontinued the nature "yellow" kevlar line but still has Olive green, "Well they did last summers" when I picked up the last 70lb roll at my local bait and tackle "Bass pro shop".
The McMaster-Carr rolls are not huge, Actually they now have a variety of different size rolls.

Roc2p:
Do not use spiderwire, The stuff is fantastic for Bass'in but not worth 2 cents for Rocketry, it has absolutely no stretch so setting the nook can be done with the flick of your wrist, I've blasted the lure right out of the fish, water and hit myself hard in the chest by setting the hook "as normally" done with mono or even kevlar..OWWW that smarts! But it can't stand even a little heat so don't waste your money if buying Spiderwire for rocketry. Don't know the Firewire material but I'd leave it to the fisherman:D
I do not have a close up of the attachment at the moment, I'll try to snap a pic or two tomarrow evening. until then heres the best I can do for you on "thread Size to Dia. to Strength in lbs.
these numbers are fairly universal so write them down:)

# 69 .014" dia. = 30lb test McMaster #8800k41
#207 .025" dia. = 90lb test McMaster #8800k42
#346 .038" dia. = 140lb test McMaster #8800k43
#693 .045" dia. = 250lb test

Very inexpensive spools, 2 day delivery.. can't beat that with a stick. The Thread Exchange is also very competitively priced and excellent delivery.

Hope that helps a little I'll post the pics soon
 

Steve

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Originally posted by Micromister

(snip)


for 12" to 36" hemi chutes I tie a loop that measures about 1" long after tieing in the ends of the shrouds. by the way I DO NOT attach the ends round the outside of the canopy. We attach parallel to one axis, across the canopy. this lessens line twist when gathering the shrouds at the attachment swivel. Each loop is sewn onto the outside of the canopy using a cross stitching method all the way around the entire open loop of line, locking the loop on the canopy tips. We use 2 strand twisted 13lb kevlar thread to sew the rip-stop fabric "gores" and/or the shroud line attachments and spill hole reinforcment.
I don't fully understand what you are describing. Does your shroud line continue over the top of the chute from one point directly across to another?

Thanks.
 

rock2p

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Originally posted by Micromister
Cls:
As a Bass'in man for as long maybe longer than a rocketeer, I love the kevlar line! the improved clinch knot ties fast and stays put.
I too have been a bass'in man longer than a rocketeer although recently it's been more rockets. And the improved clinch knot is what I use 99.9% of the time as well. :) How is the bass fishing where you live anyways? how big do they run?



I've blasted the lure right out of the fish, water and hit myself hard in the chest by setting the hook "as normally" done with mono or even kevlar..OWWW that smarts!

LOL! I just had to laugh at this one because I can picture the times it has happened to me or one of my fishing buddies.

One time my friend got two out the three hooks on a trebble hook cranckbait stuck in his forearm in such an instance. Ouch! that one did not come out easy.

I'll stay away from the spiderwire for rocketry. I don't use it much for fishing either. Maybe I'm too cheap but I've always used mono for bass. Actuall I bough some Spiderwire Fusion once but don't remember being overly impressed with it. PowePro is another popular one here in Florida but I think it's made with spectra fibers like spiderwire as well and would not work for rocketry. I'll have to find out more about Firewire

Thanks for all the information breakdown on lines.

thanks to the others who have posted replys as well. I've taken note of all this useful information.

I will have to check out all the vendors mentioned.


It still seems like there is two systems of measurement for this kevlar or something

So let me see if I have this straight.

A size such as 346 is the lb test rating but it's real-life pound test capability is actually a bit lower, maybe? :confused:

I don't know, I just know fishing lines you just went with the rating on the box. I get the jist that higher means thicker.

I guess I'm just one of those people that cares to know (not just accept it and move on) if there is some other scale they're using out ther for this stuff. no biggie though
 

Micromeister

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Originally posted by Bushrat
I don't fully understand what you are describing. Does your shroud line continue over the top of the chute from one point directly across to another?

That is correct Bushrat, Directly across the canpoy to the same point on the other side. When all shrouds are attached invert the canopy allowing the shrouds to hang free, then gather for the swivel.
Remember it is also important to get the shroud lines the same length and attach at or very near the same point at every shroud end attachment.
I'll take a few pic, this evening, I'm sure one pic will be worth that 1000 words we're always talking about:) Humm I seem to remember having a basic dwg on one of my disks... let me look.
I found it! this simple drawing is for a 6" micro-maxx parasheet but the shroud placement works for parasheets or parachutes with 6 to 16 shrouds.
Hope this helps
 

eugenefl

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Micro, interesting arrangement of shroud lines in your drawing. It appears this setup would alleviate that one darn "pre-tangled" line that manifests once all lines are gathered for attachment. Why wouldn't everyone just do their shroud lines like this from the get-go?
 

Micromeister

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Eugene: That's a good question... which had been a mystery to me also;)

Roc2p here's a 2 pic composite of the shroud & Spill Hole stitching.
 

rock2p

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Micro thanks for the 2 pic composite.

about the drawing you posted.

You have on shroud line going from one corner to a corner opposite of it on the hexagon, but the other two shroud lines going from one corner to the next closest corner.

Do you ever arrange the lines where each line goes to its opposite corner and none attatch to a neighboring corner? If so hows the effect?

At what size chute do you incorporate a spill hole? and what may have been answered some where else here in the forum, What does the spill hole do for the chute?

Never mind that second half of the spill hole question I found the answer in a recent thread.


I've attatched a drawing of what I think is going on with attatching the shroud lines please let me know if I'm in the ball park.
 

Micromeister

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Try to get stitching in the center of the loop as well as to the outsides to lock the loop to the canopy top. you don't have to open the shroud loop up much just enough for the needle to pass between the loop legs.

I always use the diagram drawn for attaching shroud lines no matter how many there are, but you will always be using an even number of shrouds. This arrangement eliminates line twist. Any other arrangement will result in at least one twisted line. It's a little easier to see this with a 10 or 12 shroud canopy.

I use spill holes in every chute I make, flat, or hemi, only exception is a 3" mylar micro-Maxx flat canopy:) It helps to stabilize the decent removing the side to side swing of the model under the canopy. This in turn lowers the risk of hi impact landing as the canopies last swings the model to the ground.
 
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