How To Make Perfect Catcuts On A Tarp

**Lost_Biker** · 07-17-2013, 12:52

Hello all. In the process of making a winter dream tarp (DIY Gear Supply template) and I wanted to share a fast and easy way to make the catcut curves.

I use a 5' long and a 10' long piece of 1/2" plastic water line to make short and long curves. Using 2 mitten hooks and some string, I make a "bow" with the pipe. I measure the depth of the curve I need from the center of the pipe to the string. Once the depth is set correctly, I lay the bow on the silnylon at the right points and carefully trace the curve with a marker. A couple of books placed on the bow will keep it stationary.

Once the depth of the curve is set on the bows, it takes very little time to make and cut the curves with a razor blade. I also save time by placing both pieces together and using tape to to hold them to a piece of 4x8 hardboard. A new razor blade cuts thru both sheets easily - just go slow and cut a few inches at a time.

Cutting both sheets at one go ensures that the catcuts are the same for both sides (mirror images). If you don't have any hardboard, a wood floor or some concrete will do - you'll need to use scissors instead of a razor blade. Cuts in the wood floor don't go over very well with the spouse and concrete dulls the blade too quickly.

**lokbot** · 07-17-2013, 13:01

that's a pretty good idea. that pipe looks like it's flexing point isn't truly parabolic, but I'm sure this will get you close enough. I'm still a sucker for plotting measurements with a ruler on a large piece of card stock.

-Loki

**Mountnman** · 07-17-2013, 13:09

I made one of these out of some 2 mil plastic from lowes as a prototype and it is a nice tarp and easy to follow directions

**richtorfla** · 07-17-2013, 13:10

Neat idea! Should make for a repeatable curve! Another item you can use to cut your fabric is a rotary cutter like an OLfa cutter. It has a round razor wheel that makes cutting on the line easier!

**Shotgunred** · 07-17-2013, 13:12

Great job Lost Biker! I think you will take a lot of the intimidation factor out of cat cuts! I know quite a few people that shy away from tarp making because of the perceived difficulty in these cuts. What depth of cut do you recommend? I went with about a half inch per foot with mine but I think one could get by with less.

**Deadphans** · 07-17-2013, 13:38

Subscribed, thank you. I was thinking of making my own cuben tarp after I research working with cuben a bit more. So this certainly helps.

**Lost_Biker** · 07-17-2013, 13:56

Originally Posted by lokbot

that's a pretty good idea. that pipe looks like it's flexing point isn't truly parabolic, but I'm sure this will get you close enough. I'm still a sucker for plotting measurements with a ruler on a large piece of card stock.

-Loki

Thanks, lokbot. No, it's not absolutely perfect - from my measuring stick, I'm not off more than 1/8" even on long cuts. I think the camera angle makes it look "off". How far I'm off when I start sewing the seams, well, that's something else!

Originally Posted by Mountnman

I made one of these out of some 2 mil plastic from lowes as a prototype and it is a nice tarp and easy to follow directions

Thanks Mountnman. It's something I've been wanting to do for a long time. It's been bugging me for a few months, so I decided to jump in the deep end and get it done before I explode.

Originally Posted by richtorfla

Neat idea! Should make for a repeatable curve! Another item you can use to cut your fabric is a rotary cutter like an OLfa cutter. It has a round razor wheel that makes cutting on the line easier!

Thanks, richtorfla. It works ok and is a fast way to crank out a tarp. I want a rotary cutter - someday. They are nice to use, but I'm old school and I was trained to use razor blades for precision work. Maybe a family member will remember this post and get me one for Xmas.

Originally Posted by Shotgunred

Great job Lost Biker! I think you will take a lot of the intimidation factor out of cat cuts! I know quite a few people that shy away from tarp making because of the perceived difficulty in these cuts. What depth of cut do you recommend? I went with about a half inch per foot with mine but I think one could get by with less.

Thanks red! I find that people think the catcuts are hard to make - this method is one I've been using for years for all kinds of things. It's easy and cheap and works well enough for beginners. Now, sewing the edges on a curve is what I hate - I can do it, just don't like it.

The depth of cut for the long center cat is 5", the short cats are 3.5". This tarp is slightly different than what Scott lists - it will be 12' long and 10' 9" wide. A little shorter, but wider.

**Whiskeyjack** · 07-17-2013, 15:54

You recommended this technique when I asked about doing this earlier in June. I ended up using a tent pole since I had several lying around, but it worked great. I wasn't looking forward to trying to hang the 12' tarp and then hang a string from the corners and trace it out. Awesome tip!

**Lost_Biker** · 07-17-2013, 16:26

Originally Posted by Deadphans

Subscribed, thank you. I was thinking of making my own cuben tarp after I research working with cuben a bit more. So this certainly helps.

Thank you, Deadphans. It really works well with the slippery syl. Using a couple paperback books really steadies the bow and once the line is drawn, most of the battle is done.

**Lost_Biker** · 07-17-2013, 16:29

Originally Posted by Whiskeyjack

You recommended this technique when I asked about doing this earlier in June. I ended up using a tent pole since I had several lying around, but it worked great. I wasn't looking forward to trying to hang the 12' tarp and then hang a string from the corners and trace it out. Awesome tip!

Glad it worked out for you, Whiskeyjack. I like this method because of my room limitations and small work area. I can slide the material around and draw the curve pretty fast now.