Advice on a new tarp project.

I went with a flat solo cuben tarp .
Although if you plan on sharing/chilling out under it for a longer time you should make a bigger one. :) I’d personally go for hex-shaped two person tarp. Picture, for example, lawsons hex shaped tarp… Allows for a variety of pitches, even tighter with cat cut edges.

Good luck.
Daniel

I agree that a cat cut ridge is unnecessary for a well assembled cuben tarp. I firmly believe that the ubiquity of cat cuts is due entirely to the nature of previous tarp materials that have high stretch characteristics, and the persistence of such design is simply default in any new tarp design.

The classic flat tarp has much more versatility than a cat cut shape, and I really don't think it makes sense for cuben, unless the idea is to simplify a "product" from a business and support standpoint.

For your "preferred" method of pitching, instead of making a square tarp, make a trapezoid. One end being narrower than the opposite, would facilitate that pitch, without compromising your options too heavily.

As to the cat cut sides, I can't comment, the only tarp with cat cut sides I've used was a hammock tarp out of spinn. Maybe Lawson can shed some insight as to how necessary he thinks they are?

Thanks for the feedback, Danial and Javan. I am continuing to develop my idea, though slowly (any time I try to spend some time on me, the career demands I re-direct that time to it). Now if only I could find an easy source of appropriate glue. Who would think aquaseal (let alone hysol!) would be so hard to get ahold of.

Cheers

John

*ahem*.. I highly recommend the use of contact cement over any other adhesive for cuben MYOG projects.

If you can't get a hold of that, you're screwed. :p

Really….

So, you are saying that I don't need to dig up specialty glues…..hmmmm….seems to good to be true. Well, won't I look like "a tool" if that is all that is needed.

Think I will pick some up tomorrow and do a couple of test pieces. Thanks for throwing in that tip. I guess it now seems so simple, that I wish I had come up with that weeks ago.

Thanks more than you can tell

John

So, I tried your suggestion regarding bonding the cuben fibre with contact cement. Simply some "Lepage Heavy Duty Contact Cement". Didn't thin it/accelerate it with toluene.
1. Simply applied it to two 1 inch wide test strips of CT3.5K.08 Cuben, 0.5" wide coat over the two ends.
2. Let it sit for about 45 minutes until it felt completely dry.
3. Carefully lined it up, stuck the two ends together and pressed with my fingers.
4. Then compressed it for about 2 hours between wax paper and clamped slabs of oak wood.

When I took it out, I could not sheer it apart in my hands.

Now, that isn't very technically precise, I know. But, I am assuming that I can apply more than 30 lbs of sheer force. In the military I always was able to pass the point-weighted fitness test just based on hand grip alone (I only had to make the bare minimum on the run, sit ups, push ups, pull ups). Isn't 30 lbs where many of the glues were failing? Or was that 30kg?

Anyway, I still have the test piece for the thicker contact cement I found in a store (more gel like) and the "gel-contact-cement with toluene added" test piece in the wood clamps. In about an hour I will take them out.

Over the weekend I was able to finally secure some aqua-seal….but if this contact cement is working this well, I am wondering if I should bother with the aqua-seal. After all, the aqua-seal seems to be 3 times the bother and 10 times the price.

But, for those of you who are reading this and think I am missing something, PLEASE LET ME KNOW. I don't want to waste hundreds of dollars on a failed project simply because I used the wrong adhesive.

Thanks all

John

Cat cut edges really keep things tight. As far as a cat cut ridgeline goes, it depends on your hiking style and if you carry poles. I personally don't use poles much so I like to run a ridgeline between two tree's like I when I am using a hammock tarp. This is much lighter then any set of poles. So for me a flat ridgeline works the best. With that said, when I use poles (which is rare) I prefer a cat cut ridgeline since it really tightens everything up to almost drum tight. With cuben 1" per foot seems to work perfect. Since I am now longer making tarps, I was thinking of copying all my catenary curves onto tyvek and selling the templates on my site so people can use them for MYOG projects.

As far as contact cement goes. It works good but, BE CAREFUL. Once it sticks, its done. On the 1k and under varieties it gets a bit tricky to make solid bonds. I only used this stuff to bond CT5K.18 reinforcement patches to CT2K.08 material and I was very careful. It worked great for the application but after I messed up a few tarps, I stopped using the stuff, but for the price it works great. I used a 3M version for bonding plastic. With all that said I would only use it for patches. You would never be able to make a decent seam with it.

As far as seams go, just make sure you prime the material before applying adhesive or tape. It improves the bond strength by huge amounts. I am not sure if any other compaines were priming their seams because I never read anything about them doing it so my guess is they are not due to the extra time it takes and how expensive primers are. I had a lab do some third party testing and the gains were HUGE..

Well goodluck.

Just so you know Lawson, that idea of patterns sounds great. Depending on the price, I could be interested.

When you say 1 inch per foot, if you have a 6 foot ridgeline there would be a 3 inch deflection at the center?

What do you use to prime?

That's too bad you're out of the tarp business. I can see how that would be difficult to make a sucessful business.

Thanks for the input Lawson.

I do use hiking poles usually, due to a bum knee (military souvenir). But, I am thinking I will enjoy the freedom that comes from a simple flat square tarp. I will run a test first, to see if I can easily rig a taut tarp without need for cat cuts. I once chances upon a unique way of stringing up a tarp that seemed to make it near impervious to sagging, and that was when I was using silnyl. I imagine cuben has much less tendency to stretch/sag.

As for the cuben seam experiment:

I rigged a bit better way to test my seams, still not very technical.

I C-clamped one end of the cuben strips between wood and the metal side table of my table-saw. I then folded the other end of the strip between popcycle stick wood and grabbed it with pliers. Then I proceeded to pull as hard as I could.

1) gel-contact cement (comes in a tube) seam was pulled apart, leaving material undamaged
2) gel-contact cement w toluene held tight. I even had to brace the table-saw table with my foot to prevent from dragging it across the garage. Eventually the material failed and tore apart
3) the "Lepage Heavy Duty Contact Cement" (more fluid than the gel, comes in a flask-like can) also resulted in the material tearing apart, with me having to brace the table to stop the slide.

So, I think that solves it….contact cement it is.

Two caveats:

1) Lawson, I know what you mean by screwing up a seam. That stuff, once the seam is formed, has no chance for re-positioning. Over a 9 foot seam it does present a scary challenge. Before I start I plan on taping off the non-cemented area of the cuben sheet. As well, I plan on building a "jig" that holds the material tight and auto-lines it up as the two sheets are brought together. I think I will practice on the Tyvek ground sheet first.

2) I am concerned about peel forces though. I did notice that despite the strength of the cement vs sheer, there wasn't terribly strong resistance to peel. Alarmingly little resistance. Any ideas on how to prevent this without sewing? I am thinking of testing over-painting the seams with aqua-seal or maybe silnet or some other seam sealer. Just a micro-thin layer over the seam edge.

Also, Lawson, you mention priming the seam first. I am assuming that this would be the equivalent of painting toluene (I think that is all Cotol is, but I actually have a cheap replacement of toluene mixed with acetone) onto the seam area, letting it dry, then applying the cement. Am I on the right track? I get a little worried because I don't really want to dissolve the outer coating of the cuben. It seams impervious, but only a fool would jump straight forward without first asking.

Thanks everyone, this is really helping me out.

And, I second the idea of making your patterns available (of course, at a price). If this occurred soon, and I could get a view of your tarps (I know I saw them on your site quite some time ago), I might just delay my project and replace it (or improve it) based on information from your patterns.

Cheers

John

Yeah, I didn't have good results with the gel type contact cement the one time I tried it.

As far as peel strength goes, bear in mind that none of the bonding methods have good peel strength with cuben, that's the major drawback of bonding it. However, I've had strong enough peel strength with a proper 3M contact cement bond, that it delaminated the cuben, even on the varieties with the thicker mylar.

The trick of course is proper curing, and the type of pressure applied after initial bond. Clamping it doesn't seem ideal from my experience. I've had good luck using a heavy smooth sided object, like a large weight or dumbbell, and pushing it down firmly and slowly sliding it along the seam. Temperature stability within a certain range is a must during curing.

If all those things come together, you'll find contact cement has a very tenacious peel, compared to many of the other adhesives that'll just let go.

As Lawson mentioned however, and why you wont see it being used for production items. It's a PITA to work with and get consistent long bonds. Totally unsuitable for use outside of MYOG, from a business perspective.