What I got was more like this. It was less than $5 at a craft fair/yard sale. But yes, that should work fine.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.)
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/
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.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.
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.
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.Best thing for making your patterns is Hardboard Tempered Panel.
This is the iron I'm using:That's exactly it, very thin cross section for the heat to flow through versus a lot of surface area to bleed heat off.
I started with a Harbor Freight woodburning kit:The more I look at irons, I see very few that have a tip that would work well for cutting nylon.
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.I was surprised on the tutorial that the instructor was using a metal straightedge to make the hot knife cut
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.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 used flat felled seams on my first parachute (below), made from a Nakka 80cm semi-ellipsoidal pattern.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 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.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 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.I would sand the edges to have a small radius so the material could not stick to it when cutting.