New Cat Cut Tarp

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New Cat Cut Tarp

Postby sean_iow » Wed Feb 14, 2018 3:33 pm

I don't know if anyone is interested in yet another tarp, but just in case here's my latest version. New and improved 'lightweight' for racing :grin: Besides, I've taken the photos as I went so I could post up the process for anyone thinking of making one. My access to AutoCAD and a large format plotter at work do make it much easier though, without these marking and cutting the material would be much harder.

After drawing, measuring, making mock-ups with string etc. I finally decided on the dimension. It is 2.7m long and 2.4m wide at the front and 1.6m wide at the rear. I could of made it slightly smaller if it was just for racing but with the cost of the material and the effort of making it I thought I'd make it a generous size for all year use. After printing out the templates, which took up 5 pages of A0 paper, I joined them together to get a master for one side.

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I then cut around this, the template includes the seam allowance.

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I then assembled some plastic sheet, this is similar to corrugated card but in plastic. This was actually packing on some 8x4 sheets of aluminium I had bought some years ago. As can be seen, as I've used this for other templates in the past I had to join some bits together to get a large enough piece.

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Template overlaid

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And cut to size

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This is then laid on the fabric and cut out. I use a cutting board underneath and I use a wheeled cutter. I find with scissors the very light fabric moves too much to follow the line. I also clip the template to the fabric with bulldog/foldback clips to keep it aligned. I do have to move the cutting board along as I go which can be tricky not to disturbe the aliment of the fabric and template.

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The template has a curved ridge and sides to give a tauter pitch. The material (36g/m2 silnylon) is double sided so I could just cut out 2 the same. If using a single sided material the template would need to be flipped over to get the opposite hand. Then it's simply a matter of sewing the 2 halves together :lol: In practice this is the hardest bit, the curved ridge and very light slippery material make guiding it through the machine tricky, and it has to be guided through and held taught or it puckers and it does not feed on it's own. After sewing the ridge I had a quick check on the weight so far :geek: this also gives some enthusiasm to keep going.

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205g is not too bad considering the size. Next to add the tie-out points and hem the edges. I've used some VX21 for the reinforcements but the tie outs will be sewn to the hems so the reinforcement is mainly just at the stitching points and not to spread the load. There are also 2 little webbing loops on the underside of the ridge, set in from the ends, to hang a light from or the mesh of a bivi bag to keep it off my face.

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As I plan to use it in one set up with poles I have included eyelets to make pitching easier. I have also used Linelocs fixed to the tarp. These make the tensioning easy and also allow less line to be used. The main advantage is that a line can be shortened down to nothing. A normal runner on the guy only shortens the line by 50% before it runs out of travel. With these a 600mm line can be set anywhere from 600mm to about 10mm. The extra thread and the parts has taken the weight up to 227g

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Test pitch in the garden

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The eagle eyed will notice that the front guy is red and all the rest are yellow. When I pitch it I peg down the centre front to the ground by the pole eyelet. Then at the other end I insert the pole and peg out. As the front is fixed down this stays up. Then holding the ridge taught I un-peg the front, insert the pole and peg out. The red line will allow me to quickly find my starting point when I get it tarp out in the dark/rain/wind after hours of riding :smile: The poles are 1050mm and 700mm long and 3 and 2 sections respectively. This makes the folded length the same and does not upset my pole packing ocd.

Final thing was to make a small stuff sack, this weights 5g but some of that is the cord and mini cord-lock. 650B inner tube for size.

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The finished article weighs 249g including the guys and stuff-sack. This seems a lot but compared to say a DD Hamock 3mx3m which weights 790g without guys it's not bad. I used 6m of fabric which cost about £55 from Extremtextil + shipping. Lighter tarps are available in Cuben, and for example a commercial 3m x 2.4 cuben tarp weighs 230g without guys. This is slightly larger but would be a flat tarp and they are about £220. Is the effort of making my silnylon version worth the cost saving? Only if you like sewing with slippery material and have several evenings to spare :roll: All that is left it to seam seal the ridge, but this needs a dry and warm day to do it in the garden, so not in the foreseeable future looking at the current weather.
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Re: New Cat Cut Tarp

Postby RIP » Wed Feb 14, 2018 3:59 pm

Enjoyed that Sean thank you, one takes one's hat off to your creativity. "red line will allow me to quickly find my starting point" - good idea. I did that on my tarps, then over time added a few more lines of differing colours, and a few more tie-out markers of differing colours, so I knew which side was which etc. Now I spend half an hour in the rain trying to remember which marker/colour signifies what :lol:.
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Re: New Cat Cut Tarp

Postby whitestone » Wed Feb 14, 2018 4:06 pm

I asked Trekkertent to do something similar with the tie-outs on my tarp, red (for rear) along one of the short sides.

Is your tarp closed at the foot end Sean or are you relying on a bivy bag there?
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Re: New Cat Cut Tarp

Postby sean_iow » Wed Feb 14, 2018 4:17 pm

It's open at the foot end. I'll be in my Borah gear bivi and the length of the tarp should be enough to be clear of and splashing. I could make a little triangle of fabric to fix in the end, I'll give it a try first. I could clip it to the inner loop on the underside of the ridge which is set in 300mm from the end and then fix the bottom corners to the tie out points. I've got just enough material left for a piece this size.

As for the red guyline, I was originally going to just mark the tie out, but in what I thought of as a stoke of genius came up with the guy as it would be easier to find. Only after this did I remember some of my friend's road bike wheels (maybe zip?) have a red spoke next to the valve to make it easy to find #-O must be how I came up with it without realising.

Reg, the thought of you stood in the rain rotating your tarp to find the correct colour like a giant rubiks cube will bring a smile to my face whenever I pitch mine now :lol:
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Re: New Cat Cut Tarp

Postby RIP » Wed Feb 14, 2018 4:46 pm

:smile:. Yes it was much quicker when I didn't have all the colours and markers and things. And they don't help show which surface is which - as proved last weekend when it was upside-down with the lines in my face X_X . Hmm, sounds like I need another marker for the surfaces....
"There comes a time in your life Ponsonby, when you think: 'My God, I'm two-thirds of the way to the grave and what have I done?" - RIP

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Re: New Cat Cut Tarp

Postby Bearbonesnorm » Wed Feb 14, 2018 5:02 pm

Very nice - good work that man :-bd
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Re: New Cat Cut Tarp

Postby Teetosugars » Thu Feb 15, 2018 12:23 pm

I hate reading these MYOG threads as it just highlights how crap I am, and how much I rely on what others can make.

However, that is pretty damn fantastic so we’ll done!
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Re: New Cat Cut Tarp

Postby atk » Thu Feb 15, 2018 9:43 pm

Nicely done! I am looking forward to getting behind a sewing machine again, although I do have a pile of things to repair taking priority and terrible memories of the last time I tried sewing sil-nylon with a standard machine and foot, but anyway...

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Re: New Cat Cut Tarp

Postby sean_iow » Mon Feb 19, 2018 2:00 pm

Teetosugars wrote:I hate reading these MYOG threads as it just highlights how crap I am, and how much I rely on what others can make.


It is just practice. I would suggest you start with fabric which is easier to work with to begin with. My favourite is VX21, the stuff they make frame bags and the like out of. It's easy to work with for several reasons:-

It's a light colour on the inside so you can mark it using a biro, I use one colour for the outline and another for the seam allowance. You can then cut on one line and sew on the other colour.
It's got the consistence of say stiff paper, so it feeds nicely and is easy to guide through the machine and you wont get any puckering.
When making say a hem you can fold it over and run along it with say a plastic ruler (like you would folding stiff paper) and the crease will stay making it simple so sew.
Lot's of people start with a frame bag but I think making some simpler items first will pay off. A peg bag or pole bag are a good first project.

atk wrote:terrible memories of the last time I tried sewing sil-nylon with a standard machine and foot, but anyway...


I assume there is a better machine for these very light fabrics? I can get a walking foot for my machine so wondered if that would help? What I'd really like is a machine where I feed the two pieces of fabric in and it automatically folds and sews a flat-felled seam, I assume that such machines must exist?
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Re: New Cat Cut Tarp

Postby Bearbonesnorm » Mon Feb 19, 2018 2:17 pm

What I'd really like is a machine where I feed the two pieces of fabric in and it automatically folds and sews a flat-felled seam, I assume that such machines must exist?

Ooh that'd be super.

As for puckering with light fabrics, I find playing with the tension can make a big difference and not all materials of a similar weight like the same tension.
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Re: New Cat Cut Tarp

Postby atk » Mon Feb 19, 2018 9:41 pm

sean_iow wrote:I assume there is a better machine for these very light fabrics? I can get a walking foot for my machine so wondered if that would help? What I'd really like is a machine where I feed the two pieces of fabric in and it automatically folds and sews a flat-felled seam, I assume that such machines must exist?


Possibly but I didn't (and still don't) have the funds to bother investigating that option! A teflon foot helped a bit, different needles (i don't remember if I went finer or thicker, I just remember writing "bastard light fabric" on the box) and as Stu said, playing around with the tension on a bunch of scraps helped.

I did look briefly at the walking feet, the reviews for the addon foot compatible with the machine we had weren't great so I just left it. Partner is fairly keen to get one so we'll be looking at ex-industrial machines if/when we get back to the UK I guess.

While I wouldn't use it enough to justify it, I'd really like something like the singer about half way down here: http://terrarosagear.com/workshop/ automatic binding ahhhhh!
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Re: New Cat Cut Tarp

Postby sean_iow » Mon Mar 12, 2018 11:04 am

whitestone wrote:Is your tarp closed at the foot end Sean or are you relying on a bivy bag there?


I now have that option :smile: I had an off-cut just large enough to make a clip in end panel. It's not an exact fit but that should let some air through to help keep condensation down on the underside of the tarp. It will stop most of the breeze/rain but I'll be in a bivi bg anyway. It also adds an some privacy if I ever use it at a commercial site.

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It has added 17g to the weight though... this also shows the clips I use to fix it to the loops on the tarp. The loops were already present as they fix the linelocs to the guys are run through.

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I've also fitted my magnetic bivi bag net support

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I think I've mentioned this before. There are 2 small magnets in each half. I did some tests and I think one in each would of released too easily.

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One section will stay clipped to the underside of the tarp and the other is fixed to the mesh on the bivi bag. Once in the bag with the zip done mostly up it's just a matter of touching the two ends together and you're attached :smile: In the event of trying to move too far/tarp peg coming out and the then the magnets let go before too much strain is put on the bivi bag/tarp. This worked really well in my test in the garden yesterday morning, just need to get out and sleep under it next. All that's left to do on the tarp is the seam sealing, but there are no dry sunny days due for a while yet so that will have to wait.
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Re: New Cat Cut Tarp

Postby Charliecres » Fri Mar 16, 2018 11:34 pm

Super-impressed. Very professional job
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