Help request: MYOG 7×9 flat cuben dyneema tarp

It’ll be kind of short.  Rain blows in under raised edges.

You might try making something out of polyethylene tarp. maybe 3 mil.  See if that works.

3M 9460 or 9485 tape is supposed to be good for cuben.  Maybe also have a row of stitches to prevent slipping.  Just what I’ve read on other threads here.

RSBTR silpoly is almost as light as Cuben, you can sew it, it does better in the rain than silnylon.  Cuben wears out after a few years.

I don’t think it will tension well as an A frame with the hem going across the ridgeline. Also if you crank down on it in this configuration you will be pulling perpendicular to the taped/sewn cuben seam. I’d be concerned about that in heavy winds in the Sierra.

I’ve used a 5.5×9 in a half pyramid pitch and I’ve come to the conclusion that I don’t think I’d want to be above treeline with this setup. I’m not confident that the extra 18″ you are proposing would make enough difference in the swirling winds I have experienced above treeline in the Sierra.

1) Too small

2) I would use a heavier fabric

3) 1″ wide tape. Some cottage makers also put a 3-4″ wide cuben overlap over the seam.

4) Fold over twice and sew with a wide stitch

5) Heavier fabric glued on. Guy outs sewn into the hem and reinforcement. A few ways to skin a cat here.

6) Heavier fabric cut into two circles. One circle inside, one outside. Sew on webbing.

Based on these replies, I might just stick w my tarptent notch!

I have a myog polycryo tarp in this size. I really like it, it seems huge to me pitched as a 1/2 pyramid. I have only used it for fun, not when I was relying on it as my only shelter above the treeline. I’ve never used it in a storm.

Hmm.

Interesting the feedback is too small. It seems the default size from a lot of mfgs. Is that a result of the pressure to make the lightest gear possible?

My $.02 is that 7×9 is a great size in the trees but the OP mentioned being above treeline.

Makes sense. Minimum 10″ ridgeline then?

Coincidentally I have the exact tarp you designed but made from Zpacks in 2010.  Since I haven’t fab’d my own gear yet (considering that now) all I can answer are your first 2 question.

1.  I’m 5’10” and never found the size to be desperately small.  2 could fit for emergency but I would grab a different shelter on a trip for 2 if the weather wasn’t stable or on a longer trip.  But as a low A frame for one, its not hard to keep your sleeping bag out of the rain.
2. the .51 CF has held up fine for me over the years.  I’ve never been blasted by hail in it though but despite it looking and feeling delicate, can handle some serious tension when I’ve set it up in strong winds.  I bought it for bike racing the Colorado Trail and wanted the lightest and at 130g it is way lighter than a bivy and way more comfy.

I say go for it.  I wouldn’t change a thing!

I haven’t yet made a cuben tarp, but I have one in the works and from all the research I’ve done here are my answers to your first four questions. I haven’t figured out exactly how I’ll do the tieouts so I can’t answer the others.

1. Probably too small. I’d go 9’x9′ or a bit bigger, then you make the ridge line along the seam when it’s in the a-frame configuration.
2. I would use the same fabric for reinforcements, but glue on two reinforcements of different sizes (i.e. one small circle, one large one). That way the force is spread out over a larger area and you’re less likely to have a tear line along the edge of the reinforcement. This is similar to how high-end cuben sails are constructed.
3. I’ve settled on taping the seam and then sewing with a triple step zig zag stitch for this one. This technique also comes from sailmaking. Opinions vary a lot on on cuben seams, but I’ve been testing this method out with some new prototype bikepacking bags and I like it a lot. It seems like the best way to prevent tape slippage without creating a perforation line in the fabric.
4. Double fold and sew. No need to worry about the straight stitch here because it’s not stressed like a seam. And sewing is lighter than taping.

Look in the book little paperback  “Lighten Up!”.  On page 13 is the “BOMBSHELTER” 10′ x 10′ tarp drawing. That is the best tarp design I’ve ever seen. I modded my 12 x 12 tarp to set up like that and it really does give a lot of protection in a storm.