Converted Guide Gear Tarp to Catenary Cut Tarp

[gmcpcs]

Hello,

I wanted to share my project of converting a Guide Gear nylon tarp you can get from Sportsman's Guide
http://www.sportsmansguide.com/net/c...aspx?a=1145824

into a catenary cut Black Cat Tarp like BlackBisop351's very helpful DIY guide:
https://www.hammockforums.net/index.php?page=blackcat

I also give credit to Steve D's post on creating a catenary from a blue Walmart tarp: https://www.hammockforums.net/forum/...81&postcount=1

And, also, I want to give credit to Gunner76 for reviewing these tarps:
https://www.hammockforums.net/forum/...90&postcount=1

I started with a purchase of the 11'x11' camo tarp; mainly I was looking for a cheaper way to get a silnylon tarp. These tarps are not the best quality constructed, but for the price, you are getting what you pay for. I bought two, one in the camo and one in the green. This project shows how I modified the Camo version.

I set up the unmodified tarp for an overnighter, and was impressed by the size of this thing. It hangs on a 16' diagonal, but it was just too long to hang efficiently between the normal tree spacing for my DIY hammock. I did manage a successful covering by offsetting the Diagonal by one tab, so that it hangs in between the rectangle, and the diamond.

After I got back from this trip, I had noticed that it had three different seams; one long seam which was the 16' diagonal ridgeline, and then about 58" from that on the diagonal, there was another seam. I had been trying to get a handle on BlackBishop's plans, which are very well written, but the nylon I had on hand just wasn't wide enough for me to tackle his project. I got the idea from Steve to see if I could just modify this giant tarp. (Someone else has posted in the forum how these tarps are at least 50% DIY, and I agree with that ☺)

I started the project by taking a seam ripper to the two seams that were 58" from the long diagonal seam. I ended up with a hexagonal shape that measures 9’ ¾” on the width, and about 16 ft on the diagonal. From that point, I decided I wanted to shorten the ridge line to 13 feet. (It would be lighter and more practical to go to the 12 Ft. length) I found the mid point of the ridge line, and measured 6 1/2 feet to each side, and drew a diagonal from that end point to the bottom corner of the edge. Those four cuts were made, and then it was time to measure for the catenary cuts.

Having puzzled over the spreadsheet formula's by BlackBishop and Madd777, I just chose to do the bendy stick method.
<bendy stick>
I like to use a hot soldering iron with a chisel tip blade to cut all my nylon projects, as it seals up the edge nicely.
<hot iron>
After making all the cuts, the tarp is starting to take on the catenary cut shape:
<picture>

The next step in this project involved me using an iron and the ironing board to “iron in” the half inch seam fold over. After I had done this, and finished up all the thread injecting, I would NOT do this step. What happened was the nylon stretched out after being heated, and now a couple of the side cuts are “wavy”, which doesn’t affect the tarp so much, but it doesn’t look right. I will be going back and shortening the ridgeline again, and will cut those wavy edges off.


I made my own tie out straps from material from DIY gear supply, using the Beastie Dee tougher triangle rings:
http://www.backwoodsdaydreamer.com/p...stic-hardware/

My thread injecting got a little bit better as I went through each corner tie out:



I used some triangles of extra material to add in the double layer. This nylon material is very slippery, and I used a glue stick to help hold it into place, but eventually just fudged it around, and thread injected it into place. Definitely I need to do get better skills on the next one.

[gmcpcs]

The tarp is finished!

I did a test hang in the wind, and it was tough to set up, but once it was set, it stayed put. I didn’t like the ridgeline going over the tarp, so the second time I set it up I put the line under the tarp. That held its shape better.





I made snake skins from all the extra material, just thread injecting some tubes, and having to patch some extra material on one end of the right side tube:



Snakeskins in the original stuff sack, reinforced. The stuff sack that came with the tarp was pretty flimsy on the seam, so I reinforced it with some extra thread. The snake skinned tarp fits inside just fine, with the ridgeline and S Biners.


Lessons learned:
1. Don’t iron silnylon to get your seams laid in. the material will sag and be wavy at that point from the heat.
2. Could have made it smaller, will make that adjustment to take out the wrinkles.
3. Careful construction on the tarp corner pullouts is not really necessary, but aesthetically it would look better.
4. The catenary shape pitched taut holds well in Texas winds.
5. The tarp will definitely need to have a seam sealer treatment, although it never rains here…more of that 50% DIY.
6. There is no need to rip the seams from the first step noted above, just use those as a starting point for cutting the curves.
7. Lots of extra material left over, can be used for second layers, and snakeskins. Not going to be breathable though, due to the silnylon construction. It doesn’t rain here very often anyway…

Cost: about $47.00
The tarp was $45.00 with shipping and handling from Sportsman’s Guide. I purchased two.
D-Ring Beastie ¾” $1.60 for 6
Nylon strap material ~$1.00 for about 2 feet
Weight: Before Modification: 780 Grams After Modification: 600 Grams; still not a light weight, but better than the Gigante Wal-Marto Tarp....

Thanks for taking the time to read this very long post. I will add the other photos (and the weights!) as I get some more time...

Take it easy,
gmcpcs