1.1oz SilPoly tarp marking and cutting approach

[Emvious]

First off, thanks to all the amazing people in the forums and in the community as a whole. In the span of about 6 months I’ve made a DIY gathered end with an integrated bugnet, a 30ish degree underquilt that attaches via Kam snaps, and a 0ish degree top quilt. Along with a new pack from ULA I have shaved about 10lbs off my base weight. The amount of experience and info in these forums is astounding and has been invaluable.

That brings me to my next project, a Thunderfly clone tarp from 1.1oz silpoly a-la Kitsapcowboy’s badlander. In his posts he talks about superimposing both halves and cutting as one. I’m torn with going a step further and folding the superimposed sides in half as a mirror image and cutting once, resulting in all 4 quadrants getting cut at the same time. I’m also considering just marking and cutting each part individually.

If everything lines up then folding and cutting is great, if any part of it slips then the whole deal is off kilter at best. I had also toyed with doing the ridgeline seam first to make sure it lines up and then mark and cut after that. I’m not worried about time and energy, but mostly about doing it right and as close to perfect as I can get for someone who barely knows what he’s doing.

Anyone have any good or bad experience with any of the above?

[IRONFISH45]

Have you worked with your cosen fabric on a lsrge project?

Do you have a large space without any cats, kids, dogs irritated spouse?

If you have the space and feel confident, give it a try.

I fold in half once, clip or pin very carefully. I personally would never cut both sides together, using a four layer cut. Cutting four slippery chunks of long fabric at the same time would be asking for problems because my work space is just not appropriate.

Be sure to mark the right side of each piece.

If you are not careful your ridge line seam will bunch up a bit on one side, so even if the top tarp halves are the cut exactly, one piece will be slightly gathered if you are not careful. Lots of threads in regard to shrinkage and solutions.

I cut each side double, then use clips and pins carefully along the edge to hold everything in place. Lots of appropriate space is very helpful.

[kitsapcowboy]

I cut once through four layers of fabric on most two-panel tarp builds, and I generally make my large cat-cut templates as a half-curve for exactly that reason. It's a little trickier but it saves a lot of time and guarantees perfect symmetry. (NB: I have a large (20x22) flat wooden floor to work on, and a 56"x34" mat on which to cut.) That said, if it goes wrong, it's probably likely to go horribly wrong. However, to date it has never gone wrong for me. Also, I often sew the ridge line first pass before doing the trimming and cutting, both so I can keep the tarp panels aligned and also so I leave myself the option to salvage the unaltered material if I make a critical error along the long top edge. Align, measure, and re-check everything before you make your cuts, and make sure your disc in your rotary cutter is sharp. Good luck...

[Cruiser51]

I just completed the KSC BatWing, in 1.1 Silpoly, did exactly as you are thinking and it was quite successful.

The silpoly is really slippery (especialy large pieces) and I didn't trust it to stay lined up and in place .... so I pinned the perimeter before and after each fold to force the alignment. I would strongly suggest you use some method of keeping it aligned (clips, pins whatever you use) to keep it all on the right place.

Just a thought.

Brian

[slugbait]

Most people will manage this method just fine-but- the first silnylon tarp I made I folded twice and proceeded to cut the bottom edge in a cat cut. This worked well until I unfolded it and discovered I had inadvertently cat-cut the top edge as well. I had not intended to make a cat-cut ridgeline and have had time to regret this mistake every time I have to bend over when under the tarp (I'm 5'3"). My next tarp had a straight cut ridgeline.

[jellyfish]

Use a lot of clips to hold it together. (don't use pins in the ridgeline area or you will just be punching holes in it that could leak later on).

I have a few videos that show different ridgeline techniques. They are in this playlist: https://www.youtube.com/playlist?lis...Y8vqloZivnP0IX

Sew slow. If you feel like your fabric is slipping on the feed dogs, adjust the foot tension. If it is still slipping, use tissue paper under the fabric to help the feed dogs along. A walking foot is nice here, but it is not necessary.

[Emvious]

Thanks everyone for the responses. The support in this community is amazing.

I ended up sewing the ridgeline seam first and folding it in half along the seam, then cut the left and right sides together. Hope that makes sense. I thought trying to fold it again might be too problematic to keep it all aligned. In the end it worked out great. The only issue was my poor sewing ability on the felled seam but it is passable and is now sealed and should work fine.

Headed out st the end of August to the North Cascades for a 5 night back country trip and can’t wait. I have this nagging fear that everything I have made will fall apart on the trip but I’ve tested it all and t seems to be holding fine.

Marginal pictures but the best I have currently

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