Cuben Tarp Plans

[Chris M]

I was given 9m of .51oz cuben for Christmas this year, and I am trying to prep myself to start making something.

My thought is to make a 9'x7' tarp. Really, it will be like 8'10" rather than 9, I guess. This means that I will use two pieces of cuben that measure 4.5'x 7' and will take about 5 yards (including reinforcement patches).

I would like to make this tarp as strong as I can, given the fabric choice, so I am looking for the best methods for putting it all together.

My current plan is to bond the ridgeline. I have read up on some of the different seams that I could do. I was thinking of simply overlapping the material 1/2" or 1" and bonding it with Hysol. Is there a stronger seam than this?

Also, With this specific setup, I can't really add in a cat curve along the ridgeline, because the ridgeline goes across the width. Is the ridgeline being situated like this creating a weakness in the tarp? Would bonding be stronger than taping?

Since I am not doing a cat ridgeline, would it create a stronger or tighter pitch to put a cat curve on the edges? Also, would a quarter circle reinforcement patch be stronger than a triangular? Finally, (I think) would having two reinforcement layers (one on each side of the tarp) bonded down for the tieouts be significantly stronger than 1?

This turned out to be a lot of questions, but with how much cuben costs, and my lack of a job, I want to make sure I make something that is worth while. Thanks all for the help.

[Colin Krusor]

If you read through the MYOG forum threads on these topics, you'll encounter a plethora of differing opinions. Here are mine (I've made two cuben tarps):

Bonding with liquid adhesive is the strongest method for joining seams. People tape (or sew) cuben when they need the process to be fast, clean, and simple (like cottage manufacturers). Hysol is a good and often used adhesive, but others have been used successfully as well (notably high strength contact cements).

Why did you decide to use a seam perpendicular with the ridgeline? I don't think this is a weaker design, just unconventional. If you want a flat tarp (no cat), this should be fine.

I think a quarter circle reinforcement patch should be a little stronger than a triangular one. I've used the circular kind. There might have been some destructive testing of different cuben reinforcement patches by someone here (Steve Evans?).

What kind of tie-outs do you plan to use? Sewn-on grosgrain?

Catenary cut outer edges reduce coverage very little and should assist in achieving a tight pitch. I've used them on my tarps. Make sure to roll over and bond (hem) the edges.

[Chris M]

Thanks for the input. The size is based off of trying to get the most use out of as little fabric as possible.

The fabric is 54" wide, so taking two of those pieces will give a 9' length. This way, I can make a 9×7 tarp without having to use 6 yards of fabric. I believe Bryce had a tarp made for him with these dimensions that used the same tactic. I wouldn't mind having a cat tarp, but as I said, I have no constant income currently, so I would like to get as much use out of this fabric as possible (two possible tarps vs. one).

I've looked at a lot of the posts around here, and I know I don't need fast. So I decided bonding would be the best solution for me and plan to use hysol. Your posts on bonding tarps have been extremely helpful in my research so far. What type of seams did you end up using on your two tarps?

Sewn on grosgrain has been my initial thought. I haven't found a stronger way to create tieouts at least. Is using strips of cuben and bonding them on a better option?

And so did you actually bond the edges or did you sew them as well?

Thanks for all the input. I'm excited to finally use some cuben soon.

[Joe L]

You could go without the cat cuts on the outside edges until you decide that you need them.

As a fan of using a diamond/diagonal tarp rig, I don't see the need for a cat cut on the ridgeline, either.

I often tie to loose rocks instead of staking so it is easy for me to improve the angle of my tie outs after the initial set up. YMMV

At Steve Evans' website, he has an article about his testing of bonds to failure. Often the fabric failed before the bond so a couple of types of bonding were both okay. As usual, good technique was more important than expensive tool purchasing.

[Jamie Shortt]

Chris, Our projects and thoughts so often coincide. Not sure if you saw the instructions I did for my cuben tarp but they might help.

LytW8_Cuben_Cat_Tarp

LytW8_Cuben_Tarp_Design.pdf

I went through so many of the same agonizing questions because I didn't want to make a mistake with such expensive material. I am happy to say I was 100% satisfied with my tarp. Though mine is narrower using only 3 yards of material you should be able to do the same thing just making it wider with 5 yards.

I did use hysol and did a cat ridgeline. Some observations…

* I did a 1" overlap on the rideline. It is rock solid. I am guessing you could get by with less, but 1" is great.
* Hysol takes a while to setup. This means you can smooth the glued seam and adjust it for hours, don't worry it if takes 24 hours to fully stick
* Hysol is an epoxy that needs to be mixed well. I did a dry sack that is stick sticky to this day because I didn't mix it properly. The tarp is perfect though.
* Hysol did bad stuff to me. Do not let it touch your skin and make sure you use it in a ventilated area. I had bad skin and respiratory issues after using it. Read the label.
* I did not cat cut the edges of the tarp. I don't think it is needed. I honestly question is the ridgeline needs a cat cut when using cuben, but the tarp sure sets up nicely.
* I used triangular reinforcements (see instructions), I could argue for circular, but I don't think it makes much difference. BTW I used .51 oz cuben.

Hope this helps,
Jamie

EDIT < I reread your post and realize you are not using a cat ridgeline. Since my original post suggests this is likely not needed I am leaving it as it. I still don't think you need to cat the edges. The cuben material doesn't exhibit noticable stretch so having straight ridges and edges appear to work just fine with cuben. I think the bonded line is as strong or stronger than the raw material so I think you are fine to run your ridge line across the width instead of the length of the tarp. >

[Tyler H]

Jamie-

Thanks so much for the excellent instruction sheets on building a cuben tarp. Plan to follow your instructions, probably with some .74oz cuben from Lawson.

Wondering how much Hysol you used? Is a 50ml package enough?

How's your bonded seam holding up under use?

[Chris M]

I have seen your stuff on the site, Jamie. And as always, your information both here and on the site is very helpful.

Have you found that the 6" reinforcements are working well for you? Did you bartack or square stitch the grosgrain down to the reinforcement.

Does anyone know if using folded cuben strips and bonding them to the tarp would make stronger tieouts?

I think I will make it without the cat curves around the edges for now. They should be easy enough to add back in later if I want to.

Jamie, how did you go about making sure the bond along the ridgeline? I think Colin's method, but am just curious to hear how others are going about achieving the same goal.

Thanks everyone for all the help.

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