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lw_hughes
24th November 2009, 01:00 AM
Its been a while and im getting back into rockets. I need to fix up some old chutes. I imagine there are better quality ones out there but i kinda like the look of the old estes chutes. I remember those terrible white stickers used to attach the shroud lines to parachute. Im wondering what is the best kind of string and mean of attaching them? I was thinking small dabs of epoxy with a sticker on top?

gpoehlein
24th November 2009, 02:15 AM
For my competition chutes, I bought some light cotton carpet thread from a local craft store. I attach it with small squares of Scotch Magic Tape. I just tie a small knot in the end of the shroud line and loop it under the tape. Personally, I think epoxy is overkill on a low power model.

luke strawwalker
24th November 2009, 02:19 AM
Hmmm... that's a good question...

I don't think you'll have particularly good luck with epoxy on the typical plastic chute material... but it's worth a try and report your findings...

I've used small squares of duct tape for attaching shroud lines, because the stuff WILL NOT turn loose of the parachute material-- it will rip the entire corner off the chute before it lets go.

AFAIK, nobody really uses the 'tape dots' method anymore, at least not with the string coiled under the dot to attach it... I've been using bits of duct tape or even electrical tape, and either punching a hole through it with a holepunch or making a small slit crosswise (parallel with the chute edge, not perpedicular) and then threading the shroud line through the hole and simply tieing it back to itself into a 'loop'... pretty much guaranteed that the thing can't PULL APART; the loop will have to rip through the tape and chute material or the shroud line break before the shroud can let go.

The real cat's meow is nylon chutes-- I picked up a bunch in several different sizes from Top Flite Recovery at NSL2007 and I'm well pleased with them... they're excellent quality. As far as regular plastic chutes go, Evil Ed here on the forum sells some terrific chutes (Ed Hartle Engineering). They're tough and flexible, really nice chutes.

Other than that, it's pretty much the way it was back in the day, except for the use of kevlar, which some folks are really in love with. It's TERRIFIC for shock cord leaders coming up from the motor mount, but I don't think it's really necessary for shroud lines, though some folks use it and swear by it.
I just use heavy 'carpet thread' and have good luck...

Later and hope this helps! OL JR :)

MarkII
24th November 2009, 03:05 AM
The classic method of applying paper reinforcement rings on both sides, then punching a hole through the center of each one, and finally tying the shroud line to the canopy via each hole works for me. Estes' plastic parachutes, which are all pre-assembled now, have their shroud lines attached that way and they hold on really well. For smaller diameter parachutes, though, those holes can be rather large. You can instead use self-adhesive mailing labels. Cut them up into little squares and apply a pair on either side of the canopy at each attachment point. Then thread your shroud line material through a suitably-sized needle, punch it through the double-layer at the attachment point, and tie it on.

MarkII

lw_hughes
24th November 2009, 06:06 AM
I wonder how far you can take scale parachutes. The look of those apollo era chutes is spectacular. Is anyone selling something to replicate that look? Operation -20 year old saturn V overhaul - is about to begin here

powderburner
24th November 2009, 08:23 AM
If by scale parachutes you mean the ones that actually curve around the edges without strings pulling down and extra edge material poking out, that is an actual parachute (compared to the flat-pattern "parasheet" design that Estes uses) with a 3D shape and cut from gores and stitched together. Yeah, they look cool, but are you ready to spend more on parachutes than the rest of your kit cost?

strawwalker and these other guys are right, there are some NICE nylon parachutes out there, quite a few vendors have good stuff. Some vendors will custom build the parachutes with colors for separate gores that you can specify. It just costs a little more. IMO, they take a bit more volume for packing inside a model rocket.

I don't think most model rockets (as in 99%) need anything as sturdy as a sewn nylon parachute for any functional reason. They are very nice, they are definitely cool, I think you would like them, but they are probably not necessary unless you have a very heavy model rocket.

You can also build your own mylar chutes pretty cheaply by finding a hunter's "space blanket" at a sporting goods store. This is a sheet of thin aluminized mylar, silver color, that unfolds to something like 5 feet by 6 feet. This will give you lots of parachute (dang, I meant parasheet) or streamer material to play with. For shroud line I have used anything from cheapo kite string (dollar store kite kits) to spools of heavy thread for stitching canvas (hardware store) to spools of carpet thread (fabric store, but relatively expensive stuff). IMO kevlar is nice but completely unnecessary. I mean, you're going to protect the entire recovery system anyway (you are not going to protect just the plastic chute and leave the shroud lines hanging out?) so if it's protected, you don't have to use kevlar. Knots tied on the ends of the shroud lines and taped down with short pieces of scotch tape has worked well for me too (some other guys mentioned this previously).

Before you worry about using 1,000 pound "test" shroud line material or how to make permanent anchors to the chute, remember that most of these model rockets only weigh like a pound, and with 8 or 10 or 12 shroud lines (more lines makes the chute look rounder and prettier!) that suspension load is divvied up N ways. And if one shroud tears out, there are plenty more that will still make the chute work until you can get home and repair it.

One of our TRF guys (micromeister) likes to use very fine stainless steel braided fishing leaders as the recovery system anchor at the "rocket" end, and this can be a good idea for protecting from hot ejection gas. If you are building with intentions of launching the same rocket 50 times it might be worth it. (Most of mine end up in trees or given away well before 50 flights.)

You could use a length of kevlar cord tied to the motor mount and extending out the front of the rocket, then tie on your shock cord and the rest of the recovery system. I have had OK luck with heavy nylon cord (surveyor line) for a main tether line attached to the rocket, and it is handy because it is locally and readily available, but I work some Elmers white glue into the nylon to help make it a little more resistant to heat damage.

Hope some of that helps-

Edit: I don't happen to be a big fan of those paper tape tabs, they seem to be hit-or-miss on the quality of adhesive on the back. Sometimes they stick great. Sometimes I pull out an old rocket and they have fallen off the chute. Try 'em if you want, but be prepared to go back to scotch tape.....

hcmbanjo
24th November 2009, 05:37 PM
A couple things to consider about the tape disks:

Don't use paper disks. They will tear! Be sure to use the plastic, permanant disks. That's the Avery label package # 05729.

I found the shroud line threads at JoAnn fabrics in Orlando. It's Coats and Clark brand, Button and Carpet - Catalog # CA00011. Even though it's a 74% polyester / 26% cotton blend, it looks to be the same thing some of the larger vendors carry. 50 yards = 50 (+ or -), 12" parachutes

The 7" long tweezer is the best "third hand" for tieing off the knots. It's hard to tie a thin string knot without leaving a 1" loose end. The tweezer will help with feeding the line through when tieing a knot. I started using them when rigging model ships. You can find similar at Harbor Freight or www.modelexpo-online.com

To any first-timer, learn to tie a square "reef" knot for shroud line attachment to the parachute.
http://www.proknot.com/html/square_knot.html
A "Granny" knot (tieing a second overhand without reversing it) can slip and pull loose.

Micromeister
25th November 2009, 04:53 PM
While I agree with just about everything everyone else has posted I do have to say Many of us still use the "coiled Knotted shroud" over punching holes in the matieral which tend to tear out or off particularly in mylar chutes.

That said: I personally use mylar tape or Silver adhesive backed Trim monokote to make my tape strips. Around this time of year I look for mylar chrismas wrapping tapes in 1/2" or 3/4" wide. A.S.P. also sells a good size roll of 1/2" Silver mylar tape that works well.
3/8" x 1/2" pieces are generally more then large enough for most 2" to 30" Chutes. What i've found over years of competition chute making is a simple overhand knot about 1/4" from the end of the shroud and a half bend around the rectangular tape strip keeps my 2 strand kevlar should lines on the chute permanently. I generally destroy the chute from old age or rarely with to little wadding burn Holes long before a shroud line parts.

I believe the Kevlar line i'm using is for Shrouds is somewhere between 13 & 27lb test. I buy it from Edmund Scientific in 600yd rolls for about 20 bucks. This stuff is just perfect for Chutes NO more worry about burning off the should lines as with cotton or other threads, this stuff takes the heat and keeps on holding. it's a bit stiffer then cotton requiring a bit more breakin folding, but it's proven it's worth time and again in chutes from 2" to 48". I hope the product number is on the photo as i can't put my finger on it this morning. Highly recommended stuff:D Found the product Number #3034863 hope it helps.

Silver Mylar tapes seem to be the thinnest, lightest materal i've found so that's what I recommend. Doubling up on both sides of the chute material is fine for sport flying, but it adds a lot of bulk unnecessary and unwanted for competition flying. Under normal loads (everything except Eggloft models) single sided taping is all that's needed. Very heavy models and egglofters really require "over the top" should lines anyway.

Burnishing down the mylar tape is another trick that ensures the tape stays put. I use a leather working burnishing tool but a wide smooth ball point pen top or other rounded smooth object works just fine. The trick is getting inside the half bend and all around the knot, locking the kevlar string in place in the adhesive.

Talc Baby powder is a very important addition if you want to be sure your mylar and plastic for that matter chutes open smoothly and fully blossom. Especially on cold or high humidity days. rubbing talc into the creases as PatB mentioned is critical to having your well krinkle crush broken in chutes to open consistantly. Required to open no, not always, but a very helpful additional step of repeated consistancy and smooth operation;)

Heres a couple Quicky Competition chute pictorials that may help.

rocketsmith
25th November 2009, 10:51 PM
To make a very strong plastic chute try running the shroud line up over the top of the chute. Add a tape dot to the point in the middle of the chute where they all cross and at the edge of the chute. Then tie all the shroud lines together. I have done this with big 36" plastic chutes like the ones from Apogee and it works well. Just take care when folding and packing to prevent fouling the lines that run up over the top.

MarkII
26th November 2009, 07:30 AM
Odd, but I can't recall a single time when I had a parachute strip any of its shroud lines. They have always stayed on.

MarkII

Micromeister
28th November 2009, 03:48 PM
To make a very strong plastic chute try running the shroud line up over the top of the chute. Add a tape dot to the point in the middle of the chute where they all cross and at the edge of the chute. Then tie all the shroud lines together. I have done this with big 36" plastic chutes like the ones from Apogee and it works well. Just take care when folding and packing to prevent fouling the lines that run up over the top.


Adding a few very small 1/4" x 1/8" strips of silver myar tape to those over-the-top shrouds helps keep them in place rather then at the apex, can be a big help in keeping the chute as small as possible after folding. By Moving that center "dot" of tape down about 1" on each side of the apex, using only a tiny strip of tape on each shroud keeps the lines in place and untangled. on larger chutes 30-48" adding a second piece midway between the eged disc and near apex strips helps maintain order with these over-the-top shroud chutes;)

powderburner
28th November 2009, 06:39 PM
Odd, but I can't recall a single time when I had a parachute strip any of its shroud lines.

Mostly when I made "competition" chutes out of dry cleaner bag material, and the actual failure mode wasn't really the shroud line detaching but the chute material right above it tearing.

With Estes-type chutes I have only had a very few failures. From what I remember, this usually happened when I pulled out an old rocket without doing any refurb, and a dried-out tape tab came loose. Still, it seems pretty rare even for that to happen.

shrox
28th November 2009, 07:28 PM
I learned something new...but the center shroud line would be a different length than the other two.

http://www.rocketryforum.com/attachment.php?attachmentid=13767&d=1259164083

Handeman
28th November 2009, 07:52 PM
I learned something new...but the center shroud line would be a different length than the other two.

http://www.rocketryforum.com/attachment.php?attachmentid=13767&d=1259164083

Actually they wouldn't be. Once they are pulled together, the distance from the common point on the shrouds to the edge of the chute should be the same on any shroud.

tbzep
28th November 2009, 08:23 PM
That's the way the Estes Chinese pre-made chute shrouds are done. I don't like the thin fuzzy shroud lines, but otherwise, it's ok.

Micromeister
30th November 2009, 06:33 PM
I learned something new...but the center shroud line would be a different length than the other two.

http://www.rocketryforum.com/attachment.php?attachmentid=13767&d=1259164083

No Shrox:
All shroudlines are exactly the same length. When they are put under load they draw the same. I use this method with 3 to 8 lines (6 to 16 attachment points.) The shrould lines for each chute all remain the same length and this attachment method greatly reduces shroud line twist.

WillyK
2nd December 2009, 11:41 PM
Micromeister,

Great diagram on "reduces cross shroudlines" for 6 point (3 line attachment). I've learned something as well!!!

Could you or someone detail how the "reduces cross shroudlines" would tie-off with 4 lines and 8 lines.

Thanks.

... Bill

luke strawwalker
3rd December 2009, 12:35 AM
Micromeister,

Great diagram on "reduces cross shroudlines" for 6 point (3 line attachment). I've learned something as well!!!

Could you or someone detail how the "reduces cross shroudlines" would tie-off with 4 lines and 8 lines.

Thanks.

... Bill

Should basically keep 'em all parallel would do the trick-- for four lines (octagonal chutes) simply lay the chute like a stop sign and have one line to the left two points, one to the right two points, and one line from the left center top to bottom points, and one line from the right center top and bottom points. Simple... basically two 'center lines' in the hexagonal diagram above.

For round chutes using say 16 lines, you'd do it the same way... start at one side with the two closest points, then attach the next line to the the two points next to them above and below, working your way around like that until the chute is completed. Complicated but it would achieve the "non-tangling" pattern.

BTW, I've started doing my chutes like this since Micromeister posted it (THANKS! GREAT idea!) and the shrouds ARE all the same length when you're done...

Later! OL JR :)

Micromeister
3rd December 2009, 10:17 PM
Exactly LS:
As long as you keep the attachment points parallel it's almost automatic:)

Bill:
I'll try to attach a couple pfd layouts that might help show one of the main problems with 8line-16point chutes. They really take up a lot of space regardless of how well they are folded and packed.
I've now replaced all my canopy cutting patterns with 12point rather then 16. I can easily skip every other point for 3 shroud- 6point sport flying chutes.
Here are both.

powderburner
4th December 2009, 07:29 AM
I think Micromeister's comment about 12-point chutes being a little better than 16- is very true. I experimented (way back in the olden days) with what it would be like to make competition chutes with 24, 30, and even 36 shroud lines and it got to be way more headache than it was worth. You definitely have problems with packing to get a clean deployment, and even with really big diameters the corner attachment tabs start turning the whole outer edge of the chute into one big wad of tape. And it is hard to discern any significant improvement in "roundness" (leading to better performance, theoretically) in a model rocket chute for all the extra added shroud lines. I think the sweet spot is around 10 to 12 shroud lines, but using only 8 still makes a good-looking chute.

dragon_rider10
13th December 2009, 07:12 PM
I have had good luck with Rocketchutes.com chutes and their Nomex protectors. The shroud lines are really thick, though, for some of the smaller Estes models. Hard to get through the nose-cone eye or even through a snap-swivel. I wouldn't use them on anything with a body tube smaller than at BT-55.

RimfireJim
23rd January 2010, 06:12 AM
I think Micromeister's comment about 12-point chutes being a little better than 16- is very true. I experimented (way back in the olden days) with what it would be like to make competition chutes with 24, 30, and even 36 shroud lines and it got to be way more headache than it was worth. You definitely have problems with packing to get a clean deployment, and even with really big diameters the corner attachment tabs start turning the whole outer edge of the chute into one big wad of tape. And it is hard to discern any significant improvement in "roundness" (leading to better performance, theoretically) in a model rocket chute for all the extra added shroud lines. I think the sweet spot is around 10 to 12 shroud lines, but using only 8 still makes a good-looking chute.
This old (1974) NAR report http://www.nar.org/pdf/TCR2.pdf referenced by KeithTX in a post about spill holes (Spill hole size affect on descent rate) (http://www.rocketryforum.com/showthread.php?t=8736) also evaluates the effect of number of shroud lines on the drag coefficient of a chute, and concludes that there isn't any appreciable increase in Cd above 12 lines.

bobkrech
24th January 2010, 01:38 AM
This is one of the most informative threads I've seen in quite a while. Such a simple fix for the age old problem of twisted shroud lines.

Just want to say thanks for the useful info.

Bob

shrox
24th January 2010, 01:56 AM
No Shrox:
All shroudlines are exactly the same length. When they are put under load they draw the same. I use this method with 3 to 8 lines (6 to 16 attachment points.) The shrould lines for each chute all remain the same length and this attachment method greatly reduces shroud line twist.

Yes, I realized that later.

dave carver
24th January 2010, 04:28 AM
I've been doing my 'chutes like this for a long time and never understood why the parachutes still have the old way of stringing things up printed right on the 'chute:rolleyes:. I've cut and re-sewn the lines on nylon chutes, too.

Maybe some day the attachment point thing will be straightened out, so to speak.

luke strawwalker
24th January 2010, 05:11 AM
I've seen the same thing from the 'tape dots' and tape disks-- they tear, turn loose, the glue dries out, whatever... very unreliable.

I needed some material for making dots for a chute, and didn't have anything handy but duct tape. I cut some small 1/2 inch squares from the duct tape and attached it to the chute, and punched a small hole for the shroud.

What's good about duct tape is, the adhesive is VERY strong, and it's pretty long-lived too (won't dry out and turn loose after six months or a year) and duct tape is reinforced with a grid of strings, which greatly strengthens the attach point and spreads the loads. Once attached to a typical plastic parachute, the adhesive on the duct tape is SO strong it'll tear the whole corner off the parachute before it turns loose.

I advise using talcum powder to dust the chute, to make sure the adhesive doesn't stick the chute together-- the talcum 'seals' the edges of the tape...

I like it... :) OL JR :)

evil ed
1st February 2010, 06:13 PM
I've seen the same thing from the 'tape dots' and tape disks-- they tear, turn loose, the glue dries out, whatever... very unreliable.

I needed some material for making dots for a chute, and didn't have anything handy but duct tape. I cut some small 1/2 inch squares from the duct tape and attached it to the chute, and punched a small hole for the shroud.

What's good about duct tape is, the adhesive is VERY strong, and it's pretty long-lived too (won't dry out and turn loose after six months or a year) and duct tape is reinforced with a grid of strings, which greatly strengthens the attach point and spreads the loads. Once attached to a typical plastic parachute, the adhesive on the duct tape is SO strong it'll tear the whole corner off the parachute before it turns loose.

I advise using talcum powder to dust the chute, to make sure the adhesive doesn't stick the chute together-- the talcum 'seals' the edges of the tape...

I like it... :) OL JR :)

Another real goodie is the vinyl electrical tape ( 3M, avaliable at wallyworld). I think it has 5 different colors in the same package. Put a strip of the tape on a piece of glass, then cut the size and shape y'all want.