Technique for cutting and finishing edges of tarps and rain fly’s

[Deerleg]

My wife makes flags out of nylon for our local high school band. She has mastered a technique that allows the nylon to be cut to size without the need to sew finishing seams. If nylon is cut with a scissors and the edge left unfinished it won’t be long before the wind starts to make the material run and fray.

The concept is similar to that of cutting a nylon strap or rope and putting a match or lighter to the frayed end “melting” a finished edge. This technique melts a finished edge to the nylon that will never run or fray. Never. It’s a little more trickery with nylon vs. cutting and melting a strap, but here’s what you need:
1.Standard electric wood burner available at hobby stores, Wal-marts, Target etc. $7-$12 range.
2.Metal straightedge.
3.Tempered glass (I use a recycled glass door from the front of a stereo cabinet) about 20” X 18”. If it is at least as long as your straightedge its big enough.
-Mark edge to be cut.
-Lay material flat on glass
-Align straightedge with marked edge to be cut to hold fabric in place.
-With pre-heated wood burner trace fabric along straightedge in a smooth intentional motion.
It should separate cleanly with a “cauterized” edge. Different weights of nylon and differences in how hot the wood burner are will affect how the fabric separates. With a couple of practice cuts first, it won’t be long before you get the feel for the speed needed to make a clean cut.
I have cut a tarp and other projects made of “melt-able” fabrics and once mastered saves time and holds up better than a finished seam.

[LIhikers]

You can find woodburner kits that come with different tips that can be screwed on in place of the normal wood burning one. One of the alternate tips is usually a knife blade which then gives you a hot, and sharp, tip to cut those meltable materials. Works good.

[Just Jeff]

I got one with a razorblade tip, but it didn't work too well. I think the blade was too sharp to actually let the heat melt it first. I didn't try the other tips after that, but I think they would work better than blade. Or maybe just using a duller blade.

[hikerjohnd]

What about the flammability factor? I have just received my first bundle of sil-nylon for a project, but as I understand it, it is very flammable. What kind of precautions should I consider? Thanks!

[Just Jeff]

No open flame. It doesn't immediately go up in flames, but open flames melt it quicker so your edge won't end up straight anyway. Just use a hot knife. Some people even use a propane torch to heat a butter knife for cutting silnylon.

And, um, don't burn yourself. :p

[Deerleg]

I got one with a razorblade tip, but it didn't work too well. I think the blade was too sharp to actually let the heat melt it first. I didn't try the other tips after that, but I think they would work better than blade. Or maybe just using a duller blade.

I agree.
My wife is the real expert and tells me she gets the best results using a tip shaped like a tapered cone. That way by adjusting the angle as you slide across the fabric you have better control of how much of the tip makes contact. She’s used the knife tip with similar results described in your post above.

[schda]

Not having a wood burning kit, would a soldering iron work or is that too hot? If it's too hot I could always use a propane torch to heat a knife.

[Deerleg]

Not having a wood burning kit, would a soldering iron work or is that too hot? Try it. Who knows it might work with the right touch.


If it's too hot I could always use a propane torch to heat a knife. I think the challenge would be keeping the knife at a consistent temp to achieve a clean cut over the entire length.

[Rambler]

Radio Shack is another source for hot points (solder heaters). They often have fine points, however, for computer motherboard and other parts repair. Look for burners with small screws used to interchange different points. I have always just used a candle. I do not believe it is necessary to sear the edges of silnylon.

[ben t]

Not having a wood burning kit, would a soldering iron work or is that too hot? If it's too hot I could always use a propane torch to heat a knife.

i've used a soldering iron cutting against a piece of glass for several projects, since that was all i had around the house. it worked fine to cut through ripstop nylon, silnylon, and supplex nylon. it was important to keep moving or it would overmelt the fabric - and create a thicker stiff edge that can break and create a weak spot.

just keep in mind that it seemed to take a while, and that you'll want to use adequate ventilation.

good luck and try on some scraps to get a feel for it.
_ben

[hammock engineer]

I don't think you need to do this to sil, but to DWR and uncoated it is a good idea. Thanks for sharing.

Something to consider on tarps is the extra strength and tighter pitch that an edge seam or reinforcement add. If you take the JRB tarp it has an edge seam that I think helps the strength and pitch. The McCat using 3/4" Gross gain ribbin to add strength and a tighter pitch.

Something to consider. I'll let some other tarp experts chime in. I just finished a hex tarp. I added 1" GGR to the edges. I think it makes a huge differece with only added 3+ oz. YMMV

[cwmoore]

hi Folks, I've made a lot of nylon gear. I hot cut it all, coated or not. Weller, the soldering gun folks make a pistol shaped soldering 'gun'. They have an assortment of tips available, and one is a fabric cutting tip, it has a small vertical disc on the end instead of a tip. Not easy to find, but last time I looked a few years ago, it was on their web site. A hardware store that carries Weller stuff should be able to order it for you, or it must be available somewhere on line. It works great, you can let it slide along a metal straight edge or even use it free style following a drawn line. I've cut from uncoated 1.1 to coated Cordura with it. I have one of those sewing folding cardboard measuring boards, its covered with little burn marks, but if you keep it moving its just cosmetic. I've also cut a lot of stuff on a laminate folding office table.

[LeeF]

Thanks guys. I am now officially dangerous.
I just built my first alcohol stove and now I'm waiting for material to make my first lightweight tarp. The earlier versions of tarps were up to Milspec standards and the weight proved it!

[flyfisher]

I have been cutting nylon cloth for several years with a knife heated red hot with a propane torch. It is a simple matter to heat the knife (An old steak knife with a wood handle works well) and run it along a marked edge for a yard or sometimes two. To do this, I put the cloth on my kitchen floor and run the knife with the edge up cutting upwards. It is fast and never ravels.

Also, for silnylon, this material almost never needs to be cut with heat. The silicone stabilizes the fabric so that edge fraying is uncommon. I often leave the edge of silnylon with no hem, unless it will be stressed.

[David335]

would a heated glue gun do it fi there is no glue in it.
Because my glue gun's tip get extremely hot even when there is no glue in the "chamber"