Parachute patterns

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Handeman

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I found this thread while looking for info on using soldering irons for hot knives. Did a 25-watt iron give you plenty of heat? (I'm looking at the Weller SP25NUS on Amazon.)
What I got was more like this. It was less than $5 at a craft fair/yard sale. But yes, that should work fine.
 

Dane Ronnow

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What I got was more like this. It was less than $5 at a craft fair/yard sale. But yes, that should work fine.
The more I look at irons, I see very few that have a tip that would work well for cutting nylon. I passed on the Weller in favor of this: https://www.amazon.com/dp/B00170I1R6/

The tip shown on the iron itself, and the conical brass tip (third from left) seem like they'd work. I think the blades would lose a lot of heat by the time it gets to the point, although the curved blade seems like a good shape if you use the back of the curve.

BTW, I stumbled onto your thread here: https://www.rocketryforum.com/threads/build-thread-9-ft-24-gore-semi-elliptical-chute.122017/
I wish I'd read that before I built my parachute—a few things I'd do differently. Mine is a much smaller parachute, built for a much lighter rocket, but your info, as well as the post by @jcato on that thread gives me a better starting point for my next parachute.
 

Handeman

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The more I look at irons, I see very few that have a tip that would work well for cutting nylon. I passed on the Weller in favor of this: https://www.amazon.com/dp/B00170I1R6/

The tip shown on the iron itself, and the conical brass tip (third from left) seem like they'd work. I think the blades would lose a lot of heat by the time it gets to the point, although the curved blade seems like a good shape if you use the back of the curve.

BTW, I stumbled onto your thread here: https://www.rocketryforum.com/threads/build-thread-9-ft-24-gore-semi-elliptical-chute.122017/
I wish I'd read that before I built my parachute—a few things I'd do differently. Mine is a much smaller parachute, built for a much lighter rocket, but your info, as well as the post by @jcato on that thread gives me a better starting point for my next parachute.
I'm glad you liked the build. I used that for my L3 cert and still using it in that rocket, but I'll never build another one like that again. Running the lines over the top was a pain and really not needed. After building that and talking with my brother, a licensed parachute rigger, because of the relatively slow speed that our chutes open at all you need on a chute that size is about 5" - 6" zig-zag stitching of the shroud line to the gore seam.

For a hot knife, I use the cheap soldering iron and put the tip on the anvil part of my bench vice and pounded the tip flat and into a spade shape. The first time I used it, the thin edge of the spade rolled over when it got hot and a little pressure applied. I've been using it that way ever since. It's about 1/32" to 1/16" thick now and works pretty good. Something a little thicker and hot works much better than an actual blade because it melts through the nylon causing the edges to melt and stay together better than if it's most cut.
 

Blast it Tom!

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As I wade into this very slowly, I grabbed This hot knife/woodburning/soldering combo set from Joann Fabrics for $17.50. I was surprised on the tutorial that the instructor was using a metal straightedge to make the hot knife cut- and as I suspected, I was correct, it'll suck the heat away from a thin razor knife blade like now. With the heat all the way up, though, and keeping the blade about flat, with a wooden straightedge it did a pretty good job - I had to pull at the edges to even get a few loose strands out; as my technique improves I think that my cuts will as well, But a better blade could be made that is more suitable for curves on ripstop, to be honest. Or I'll just use one of the soldering tips!
 

Dane Ronnow

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@Blast it Tom! -- I'm making another parachute based on ideas I got from @Handeman's build, and will be using thin cardboard (poster board) for a pattern. That should give me enough resistance against the tip of the iron, without sinking much heat out. Straight cuts with a strip of the same type of cardboard.

I think the flat-blade tips act like the fins on a heat sink—bleeding off heat quickly. I haven't used my iron yet (Amazon just delivered it a couple of hours ago) but it's similar to yours, same company. And it looks to me like the Mini Fine Point would make a better cutting tip. That, or the Tapered Point (not the soldering tip). My tapered point is a little rough on the end. I'd smooth that up before dragging it across nylon.

I'll know more after I get a piece of glass tomorrow.
 

Blast it Tom!

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@Blast it Tom!
I think the flat-blade tips act like the fins on a heat sink—bleeding off heat quickly.
That's exactly it, very thin cross section for the heat to flow through versus a lot of surface area to bleed heat off. Putting it up against a metal starightedge (like folks like you & I won't...) is really shooting oneself in the foot! I liked using the razor edge but for this purpose it needs to be a short, sharp and smaller edge to allowe turns and so on.
 
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DragonRocketry

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Best thing for making your patterns is Hardboard Tempered Panel. For a hot knife blade I shape a soldering iron tip like a knife with a 1/32" cutting edge and just us a cheap soldering iron I got at Harbor Freight.
 

Dane Ronnow

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Best thing for making your patterns is Hardboard Tempered Panel.
My gores are only 11"x23". After looking at the tips I've got to cut with, I'm thinking now of using corrugated cardboard—thicker and stiffer than poster board. It's more manageable than hardboard on a small gore, but stiff enough that I can hold it flat with one hand and cut with the other. I'm cutting one pattern with 7/8" seam allowance, and one pattern for the gore itself, which I'll use for marking stitching lines.
That's exactly it, very thin cross section for the heat to flow through versus a lot of surface area to bleed heat off.
This is the iron I'm using:
If you look at the product page, top image, the two tips that I think show the most promise are the third one from the left (short conical), and the tip shown in the iron—a narrow, short, straight shaft. I think your set has the same tips. The shorter the tip is, of course, the less heat you lose between the end of the iron and the end of the tip.

I'm having a piece of glass cut tomorrow for the cutting surface, then I'll test the tips on a piece of nylon. I'll post when I know more.
 

Handeman

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Kelly

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The more I look at irons, I see very few that have a tip that would work well for cutting nylon.
I started with a Harbor Freight woodburning kit:
One of the many tips was a flat, copper blade. I sharpened the edge a bit with a file, and it worked perfectly for cutting. I think I paid $5 for the whole kit on sale.
Eventually, the iron fell apart, but I kept the tip. I turned a small adapter so that I could fit the threaded HF tips into my Weller irons, and now that combo is working great for me.
 

Dane Ronnow

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I was surprised on the tutorial that the instructor was using a metal straightedge to make the hot knife cut
I was just re-reading some of this stuff and was wondering if you were referring to my four-part tutorial. In that, I use a metal straight edge, but for drawing seam lines with an ink pen, not for hot-knife cutting. I used scissors for cutting.
 

Dane Ronnow

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@Blast it Tom! -- I did a few test cuts on glass. The Mini Flow Point worked perfectly. Neither of the blades got hot enough, and the short conical tip was too rough at the very tip.

I used a scrap piece of corrugated cardboard as a pattern edge. As long as I kept the Mini Flow Point moving, it didn't burn the cardboard. If I stopped, it burned.

The cut edges of the nylon stick to the glass and the cardboard, but peel away nicely. The edge is slightly wavy, but can be ironed flat after the gore is cut.

BTW, I've found that the nylon shrinks slightly when ironed. If you iron it—and I do, just to flatten the folds, do it before you cut your gores. After it's been ironed once, it doesn't shrink any more (that I could see, anyway).
 

Dane Ronnow

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I hate to say it, but after cutting six gores (half of what I need) with a hot knife, I can say I'd rather use scissors. By a long shot. The loose threads were not a problem for me.

The trouble wasn't with the iron or the tip. It was with using corrugated cardboard for the pattern. It was stiff enough, and held its shape, and it didn't burn. But the fabric stuck to it in the worst way, and if I wasn't very careful in removing it, I'd pull a thread three inches into the fabric. And that's not something you can iron out.

I could have used hardboard as suggested above. But then I'd have to buy a jigsaw. (I don't have carpentry tools. I'm an auto mechanic.) And it's just not worth it to me.

Anyway, yeah, I'm punting on the hot knife. Scissors work for me.
 

Handeman

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I hate to say it, but after cutting six gores (half of what I need) with a hot knife, I can say I'd rather use scissors. By a long shot. The loose threads were not a problem for me.

The trouble wasn't with the iron or the tip. It was with using corrugated cardboard for the pattern. It was stiff enough, and held its shape, and it didn't burn. But the fabric stuck to it in the worst way, and if I wasn't very careful in removing it, I'd pull a thread three inches into the fabric. And that's not something you can iron out.

I could have used hardboard as suggested above. But then I'd have to buy a jigsaw. (I don't have carpentry tools. I'm an auto mechanic.) And it's just not worth it to me.

Anyway, yeah, I'm punting on the hot knife. Scissors work for me.
I'm sure the scissor can work quite well. My advice is, use flat or french felled seams or a double lapped seam and don't try to wash the chute in a wash machine.

My very first home sewn chute was a 12" drogue I made for my scratch built DD L1 cert rocket. I used scissors to cut it out. It worked great and held up fine until it landed in a cow pasture. Cows apparently like the taste of BP residue. By the time I got there a couple of cows had been mouthing the chutes. Didn't damage them, but they were dripping cow slobber most of the walk back.

I threw the chutes in the wash machine on gentle cycle - light load. The main chute came out fine, but the drogue had unraveled so bad, the whole chute was one big ball of loose threads. YMMV
 

Dane Ronnow

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My advice is, use flat or french felled seams or a double lapped seam and don't try to wash the chute in a wash machine.
I used flat felled seams on my first parachute (below), made from a Nakka 80cm semi-ellipsoidal pattern.

01.jpg

Two things I'm doing different on this new build—two rows of stitching on all seams (flat felled and rolled hems) instead of one, and attaching the shroud lines to adjacent gores instead of crossing the chute. I think it will be easier to keep the lines from twisting before they're sewn in place.

As far as washing in a machine, I think it would be a nightmare just untangling the shroud lines. I would definitely hand wash it in a sink, then hang it up to dry.

As a last-ditch effort on this new parachute—the one I'm having problems with cutting with a hot knife—I'm going to try wrapping the cardboard pattern with a sheet of aluminum foil and see if that helps prevent the fabric from sticking to the cardboard.
 

DragonRocketry

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Easy way to wash a chute. Fold each cord up as tight as you can get it to the canopy and the use small zip ties or bread wrappers to keep them folded. I then put the chute in a pillow case and tie it shut and put in the washer. The pillow case keep the washer from beating the crap out of the chute and tangling the lines.
 

rdrown

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This is my hot knife setup. I saw this on utube and thought, I’ve got a solder gun. The knife is made from 12gauge solid copper wire, formed into a loop and the loop part beat flat on a heavy piece of iron. It works very well. I use cardboard for a backing and have very little problem with the fabric sticking.
Just my 2 cents worth. (Which is more than what it cost to make the knife)🍻😉
 

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DragonRocketry

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Not sure why I'm having so much trouble with sticking, but I'm going to figure out a solution if it kills me. (It's become a moral imperative!)
I have made a few 100 chutes over the years. I have made chutes from 9" all the way to a 28'. Here is what my setup was. My cutting table was covered in Formica. I also had a 24" x 24" granite tile for small chutes. All my template where made from Hardboard Tempered Panel and I would mark one side "this side up" and then on the back side I would sand the edges to have a small radius so the material could not stick to it when cutting. I used a cheap soldering iron and I shaped a tip like a knife with a 1/32" width for the cutting surface. I will see if I can find the drawing I did for how to shape the tip.
 

Dane Ronnow

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I would sand the edges to have a small radius so the material could not stick to it when cutting.
I think that's a large part of my problem. The bottom edge of corrugated cardboard actually sticks out slightly, and the hot knife is welding the nylon to that edge.
 

DragonRocketry

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Here is how I shaped my tip. I would mod the tip the looked like a chisel.
cutting tip.jpg
 
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