So I really want to make a tarp 7x10 but I can't do a felled seam for the ridge line for the life of me so I'm just going to do a 5x10. I figured the 10' length should give me more usable space at the head so I can keep my stuff up there out of the rain. Also note that I will be using 1.3 silnylon from Seattle Fabrics.

My question(s):

Do I need to hem along the perimeter edges or can I leave it freshly cut?

Do I need to reinforce the tie-outs with another piece of silnylon on both sides for strength?

What thickness of grosgrain would be best for tie-outs?

Thanks!

I haven't embarked on the construction of my own tarp yet, but have done a bunch of research on here and other sites regarding the process. You definitely want to do hem along every edge. And at that, you probably want to fold/roll it over at least twice, this will add some tensile strength and prevent it from ripping/fraying. You should also plan on reinforcing the tie outs with at least one additional layer of silnylon. I'd go ahead and be safe by doing two, one on either side of the large piece. Something semi-circular is also better for these reinforcements, as it avoids any "points" receiving more pressure when you get everything tensioned. As for the grosgrain... You could use just about any size you want. I'd say that 1/4"-3/4" is the most common. This also depends on if you plan on sewing linelocs, many of which require 3/16" ribbon....

1) You definitely need to hem all the edges. Just do a rolled hem.
2) Yes, reinforce the tie outs with a single layer of silnylon cut in the shape of a triangle for the 4 corners, or a half-circle for the middles
3) I just use standard thickness 1/2 grosgrain

You will definitely need to hem the edges, otherwise, the fabric will slowly fray and unravel on you. You will need to find some way to fix. I roll the edges over twice and sew that down.

For tieouts, I cannot speak on whether or not semi-circular is better. I normally use triangular pieces. One thing that is quite important is to cut out these reinforcement pieces so that the ripstop is at a 45 degree angle to the ripstop of the tarp itself. This way, the stretch of the tarp and the stretch of the reinforcement aren't in the same direction.

Couple ideas
1. There has been some question about the waterproofness of silnylon lately. Some stuff just isn't great quality and could potentially allow some water to seap through in a really hard rain. I would order stuff from Thru-hiker which is considered better quality. You can also apply another silicon layer if you want to be safe. This is what I did after I had some doubts about the quality of one tarp's silnylon.
2. To make sewing the edges easier folded them over and glued them.
3. 5x10 is probably a good size. I've used 5x9 and its pretty good but an extra foot wouldn't hurt. The main limitation of a tarp that size is its just small. It can work but if the weather is bad you find yourself pitching it pretty low. It is a lot safer choice though. Sewing together larger peices of silnylon is really hard. I sorta made it work on one tarp (second try) and on my third try I got a straight (not catenary) seem almost perfect but it was a lot of work. Considering all the effort and wasted material I might not have saved much although it was a good learnign experience.

You don’t have to sew a ridgeline - you can glue it.

http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=51361&skip_to_post=436819#436819

I have been testing this tarp and so far it has worked flawlessly. I have yet to have a snow load test, as Mother Nature is not cooperating, but I will soon.


The only sewing was the guy-out loops.

Enjoy

Dave

Yes, hem edges, fold over twice and sew one row of stitches. You could glue it, but that would be a lot more work than sewing.

You can't figure out flat felled seam? Did you see http://thru-hiker.com/projects/basic_seams.php - good description. Except I don't bother making the seam allowance half for one of the two piece, just make them the same. I use 1/2 inch. Silnylon is thin so just fold it over twice and it's fine. You got to be able to do this seam if you're going to make your own stuff. And 5 feet is pretty narrow if it's raining and windy.

I quit reinforcing tie-outs. Sew grosgrain through the hem or flat felled seam so you're going through several layers of fabric. Do a zigzag stitch that's spaced out about 1 mm. You don't want any two needle holes closer than 2 mm. (1/16th inch) I've never had one rip out. I go out in the wind, maybe 30 MPH, not mountaineering/hurricane but that's pretty windy.

Thanks for all the replies everyone!! I guess I was looking for a really quick and dirty approach to getting into the light weight tarp club. I currently use a cheapo 8x10 blue tarp from REI but I wanted something more compact. Maybe I'll practice my seams and make a tarp I really want to use.

@Jerry: that's a real easy to read and understand example, thanks for sharing. I forgot about that site.

I won't claim to be the world's greatest sewing machine operator, but I can stumble along. I owned a factory shelter that weighed 8 ounces, and then I got another factory shelter that weighed 8 ounces, so I put together some ideas from each one and sewed my own for 8 ounces. The advantage of making your own is that you can change the standard dimensions to make it longer, shorter, taller, or whatever. I went with one of the lighter weight fabrics, but it seems to work. I've slept under it only four nights so far, but it has been rained on and it still works.

Are you asking about thickness of grosgrain, or the width? I used some pretty common stuff, maybe 1/4" wide. I did not reinforce the tie-out points, but I sewed the grosgrain into the hem in each direction.

I also added some "storm flaps" that I can attach in a hurry to the rainy side.

--B.G.--

@Bob: Yes I was inquiring about the width to use. I figured the wider it was the more surface area for a stitch I could use and thus be a stronger connection.

I use 1/2 inch grosgrain for tie-outs

Seems more than strong enough, lightweight, plenty big enough to spread load to silnylon