Monday, 18 July 2011

Mini Cat Cut Tarp

After having a night on the moors a couple of weekends ago under a tarp I got to wondering... Do standard size solo tarps really need to be as big as they are?  I always tend to use a bivi under a tarp to keep wind blown rain off the sleeping bag/quilt.  So if I use a bivi why don't use a smaller tarp to keep direct rain off and save a bit of weight in the process.

I've also been looking into making stuff with Cuben Fibre, mainly tarps and stuff sacks.  It's not cheap stuff.  In fact it's very expensive and you also need bonding tape and different techniques to manufacture than the sewing of conventional fabrics.  The material comes in 54" wide rolls and therefore any conventional sized tarp will need twice the length of the tarp in raw material to make.  This means that unless you can get Cuben cheap (if you can, I'll be your best friend) you can't buy the material for less than a finished tarp in many cases.  But if you could make a tarp by cutting the two sides from a single piece of cuben you half the cost of a finished tarp, albeit a much smaller one.

After having a trawl around the internet it would seem that Mountain Laurel Designs make exactly such a tarp.  I want one, but I didn't want to spend a lot of money getting a tarp that would end up being too small to practically use.  So I thought I's make one just to get to grips with the size and to see if I liked it.  So I set to work...

As always when making new things, the measuring and making the pattern takes up the majority of the time.  The whole "Development" part of the process took one evening.  The dimensions were worked out on paper then some cheap material was tacked to an 8' X 4' sheet of ply and this was taken into the garden.  Using a spirit level I levelled up the edge I was working on strung a piece of heavy string between each end and when I got the curve I wanted I went over with a spray can and hey presto... A nice cat curve was transfered to the material.  All edges of the tarp have a cat curve.  Then the usual cutting with the soldering iron, sewing the ridge line, then the 10 tie out points, the exterior hem and finally the grosgrain pull outs.  The finished product looks like so

The pitch was restricted by the rabbit hutch.  But first impressions were favourable.  My first tarp was an 8' x 5' flat tarp, so I'm used to squeezing into a corner to avoid wind blown rain.  You would definitely need to use a good bivi under this tarp if the wind was up.  But for a summer overnighter or weekend trip a tarp of this size is more than adequate.  The fabric used in this one is pretty heavy and I wanted a prototype to play with rather than to try and make the finished article.  The re-enforcement patches are spinnaker as it resists holes being pulled in the fabric, which this black stuff is prone to do.  I will hopefully get a bit of use from it this summer, the seam will need to be sealed first though.

I think a higher flatter pitch is needed for non windy days to maximise coverage.  I see no reason why one edge can't be pitched down to ground, making a mini lean to if conditions dictate.  I will be putting a couple of pull out points, mid panel on each side which will result in a very stable little shelter.  Even with 0.75oz cuben I reckon it would come out around about the 100g mark (sorry for the imperial/metric mash up).  A true mentalist lightweight bit of kit.  If this summers outings go well with the prototype I hope to build a cuben one over the winter.

I also think that to be a truly useful bit of kit a beak would need to be employed as it's only 8' long.  More stuff to play with!


Mac E said...

That looks pretty good, I'm sure it would be fine pitched to the ground on 1 side if required.

Assuming you're using a bivvy bag could you make a head end pyramid type tarp from the standard width cuben?

Shed Dweller said...

Hi Mac

I reckon you could make quite a good beak with standard width cuben. The rain skirt that I've got is about 54" long and that works.

Tomas said...

Really nice workmanship, looks very professional!

A nice idea for a bivy-friendly tarp might be this kind of "microtarp",

peterson said...


Did you ever make your beak for the tarp? I have a cuben tarp and would like to make a modular one for it- need not be too big not go to the ground, say halfway down the front guy; but would certainly add tons of extra protection.



Shed Dweller said...

I've got a prototype one that never got finished. The beak itself isn't really a problem, the way you fasten it onto the tarp is the main issue. A good fitting can by draped over the top and fixed with guy lines. I want something that clips on. The front pole of the tarp is a problem too. If I ever finish it than I'll write about it.