Thursday, 15 July 2010

New Tarp - Catenary cut solo tarp.

I've always liked the look of the catenary cut tarp. You see them a lot over in the states more so that over here. I used to assume this was because the states suffered less with heavy winds and rain than we do, which may be the case. So logically, in my mind anyway, I thought that they weren’t all that much cop for use over here.

I’ve mentioned before that I’ve assumed a lot of things about lightweight gear before actually getting to use it. More often than not my assumptions proved baseless and the gear has performed beyond my initial expectations. Maybe so in this case too? I’ve never owned a cat cut tarp or even seen one being used. Also Colin Ibbotson has used one it seems in most conditions in this country and gets on well with it. So why not make one? Why not indeed…

I’ve done this project in proper low tech DIY mode. The material used was some cheapish stuff I found on the internet which looked and felt like 1.1oz Sil Nylon or 1.4oz when it’s been coated – around 40g m2. It turns out that after making a tarp for a friend which you can see in the previous pictures in the Lakes SUL trip, the material is actually coated and delaminates if treated harshly. The pattern was made by pinning the material to a flat wall and then plotting out where the corners of each side would end up. Then using further pins and heavy nylon cord the catenary curves were created and carefully transferred to the material. Obviously the material had to readjusted to plot each edge. Not only has the main seam got a cat cut also all the edges also have a slight cat cut so as to keep the fabric taught.

The tarps been put together pretty quickly as I want to use it this weekend on a trip to the lakes with Steven and Phil. I still need to attach the guy lines which won’t take long. I also need to seal the seam. This I do with two parts white spirit and one part silicone bath sealant. Most people use a paintbrush to paint in on but this takes ages. I use a glitter pen, the sort that squeeze out a glue with glitter in. Empty the glitter out and replace with the silicone solution and hey presto – a sealant pen. Much quicker and the solution doesn’t go off in the air like it does when you’re using a brush.

The re-enforcement panels are made from 35g m2 spinnaker fabric. I use this as it doesn’t stretch like nylon. I think the combination of the non stretch of spinnaker (but the catastrophic nature of which it can rip) and the stretchy nylon (and ability to withstand shearing) makes a good strong partnership. There may be a reason why other manufacturers don’t use this combination, if anyone knows please let enlighten me.

I’ll do another post after the trip and let you know how it gets on. We are forecast for 35mph winds, gusts up to 50mph and heavy, sustained showers (surely that means rain?)


Phil said...

I've seen silnylon reinforced with cuben, and that didn't work. The silnylon stretched, the stitching went with it and the cuben didn't. This results in the cuben pulling away from the stitching.

However - I'm keen to see if this was an isolated incident and whether the spinnaker works differently. I reckon it'll get a decent test tomorrow night!!

Shed Dweller said...

Hmmm, after having pitched in the garden last night, there are slight pull holes in the nylon, this happened with the back pack I made with the same material but they never got bigger. You're right, tonight is going to push this tarp to its limits. The design is good the materials are average.

Maz said...

My brother-in-law works as a sail designer and cuben fibre was developed by a company in the US owned, now, by the company he works for. We have access to off-cuts at low cost so he and I are going to build ourselves tarps - probably based on the Spinntwinn - from spinnaker, silnylon and from cuben. He's as experienced as anyone in stress on fabric (making sails as he does) so it should be a really interesting experiment to see what we get from it.

Anonymous said...

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Shed Dweller said...

Hello Anon

Your comment landed in my spam inbox, how rude of me! I'm glad you found it helpful. In time when I get the manufacturer of these down to a tee I'll do a comprehensive step by step guide.