Sunday, March 23, 2008

Making a rain fly for a tent

I have an old Lake-N'-Trail tent, I am not sure what model it is but it is said to be for 2 people. I don't think it ever had a rain fly. The past several times I have had it out I have used a tarp to keep dry. This works, but it adds weight and having a fly that doesn't "fit" adds to the complexity of set-up.


Tear-down June 07' ARRL VHF contest EM89 stop, that's me by the tent.

What I have decided to do is to use Visqueen, a type of plastic sheet, to make my own custom fly. I had access to some so I didn't have to buy any materials for the project.

The first chore was to figure out the design. I want enough space between the fly and the tent that the two won't touch. The Visqueen comes on a roll and unfolds to 10' wide, so I wanted to try and use this dimension as full as I could so I would minimise waste.

I found out the real dimension of the width is not exactly 10' - it is 9'10". This wasn't too big of a deal, in fact it needed to be trimmed down anyway.

My design is basically just like the tent is - a triangular prism. Only, I decided to bring the front and back out to a point rather than a blunt edge. The theory here is less wind loading. Angles guide air up and over an object, rather than plow straight in to it. My point is supposed to be 2' out from the plane of the side.

I also added some length in front of the tent, 2.5' to be exact, for a little extra room. The tent is 6.5' so I went with 8' for the length. That way I have some space for things outside of the tent - boots, backpack, whatever I want to stick out there for more room inside.

Here you can see the front and back laid out. The big hunk folded up is the main top part.



One BIG issue with the Visqueen is it is a plastic - it doesn't breathe like fabrics do. This means some ventilation is necessary. Plastic makes a GREAT water barrier, but it blocks air too!

Joining the plastic parts together was another big issue. I tried silicon caulk first as I had some and thought it might work. Wrong. It makes a great sealer, but it doesn't adhere well - especially to plastic. So I tried some medium CA without much confidence. All it did was get the plastic wet with glue, there was nothing for it to soak in to and the chemicals wouldn't combine with the plastic.

I went to the hardware store and got two kinds of contact cement. The first kind didn't work. It was about like the caulk I tried to use. So, I didn't even bother opening the second.

One guy on the backpacker.com forums said to try and melt the pieces together with a soldering iron. I gave this a try and it works! The plastic has to tear in order for it to come apart, just like a good weld on steel. I noticed the melting makes the plastic a bit thin, though, so I am sure it weakens it to some extent. I will have to experiment with it to see how well it holds up.



This is what it looks like in 3D. I don't have the door or any ventilation holes yet, but you can get an idea of what it will look like. Once I get it done and set up it will tighten up and take shape better.

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