Tarp’s aren’t the most glamorous of homemade gear projects, but I’ve made a few and learned a few things along the way so here’s a few tips for the amateur. I sewed this tarp on a $50 Wal-Mart sewing machine. It’s a project anyone can do with ~$50 worth of materials if they are willing to use patience to make up for a lack of skill.
I purchased 6 yards of silnylon fabric from Quest Outfitters for $6.70/yd. 30D silnylon is the ideal choice for a lightweight tarp unless you’re able to spend ~$25/yd for 0.7oz Cuben which weighs half as much. Silnylon typically comes in a 62-65″ wide roll, so you can make a big tarp with 6 yards. I also purchased some heavier nylon (70D), 1/2″ grosgrain, drawcord, 5/16″ grommets and lineloc3 tensioners for the guy-out areas.
Small tarps (5′ x 8′) can be made from a single piece of silnylon but for a decent sized tarp you’ll need to join two panels. This is the crux move. I cut the 6 yards in half and to get two pieces of 63″ x 108″ and joined them laterally with a flat felled seam. Normally this type of seam isn’t hard, but silnylon is slippery, stretchy stuff and doesn’t crease easily to hold the seam while you sew. Plus tarps require a long seam which you really don’t want to be wonky. To make this easier, I laid the pieces on top of each other and carefully aligned and joined the edges with 1/2″ wide double sided tape. Nothing sticks that well to silnylon, so you can use pretty much any double sided tape (see your local hardware store) and it’ll stick well enough to sew yet remove easily.
I sewed the seam 1″ back from the edge (not through the 1/2″ wide tape along the edge), starting in the middle and sewing to both ends so any pernicious bunching won’t be concentrated at one spot. Then I removed the tape. Normally the next step in a flat felled seam is rolling the hem and sewing it flat to the tarp in one step. This is hard for an amateur to do well, especially with silnylon, so I did it a series of steps. I sewed the two hems together along the raw edge, then folded the hem (now 1/2″ wide) and sewed that together. Lastly I opened up the two panels and sewed the folded hem flat to the tarp. This takes a bit longer, but the skill requirements for a nice seam are lower.
I decided on 16 guy out points. This consists of one per corner (4), a robust one at the middle of each side (4) and small ones in between all of those (8). I used 70D nylon because it’s best to reinforce with a heavier version of a similar material so properties like stretch aren’t disparate. I cut out appropriately sized triangles and folded and sewed the edges that wouldn’t get rolled into the hem seam. These were sewed to the tarp with stitching around the edge, up the center and in a V as shown.
With the reinforcements sewn in place, I folded the hem twice after drawing a line on the tarp with a fine point Sharpie to ensure a consistent hem width. Like the main seam, I did this one step at a time rather than rolling and sewed it in one go. I bartacked drawcord to the 8 secondary reinforcements and added 1/8″ shockcord to buffer wind forces and so the guylines will be self tensioning. The corner and midpanel guyouts got LineLoc3 tensioners sewed on with 1/2″ grosgrain. Shockcord may be added to the stake end of the guylines.
The midpanel guyouts have grommets just behind the tensioner for a trekking pole tip. I used 5/16″ which works well. 1/4″ would also likely be fine. Weight is 470g / 16.5oz including the stuff sack (10g) and short guylines at the 4 corners. Test run is this coming weekend.