With reports of blizzard conditions in the White Mountains (finally), I spent Sunday doing some gear maintenance in preparation for the winter backpacking and mountaineering season. One of my chief outstanding tasks was seam sealing my new Scarp 1 tarptent to prevent rain from penetrating the outer silnylon shell and wetting the inner sleeping compartment. This is something I experienced on my last backpacking trip while testing the Scarp in heavy rain on the Appalachian Trail in northern New Hampshire a few weeks ago.

The purpose of seal sealing is to keep rain from leaking into your tent. When it rains, the stitching that joins two pieces of tent material can transport water from the outside skin of the tent to the inside. Seam sealing coats the stitching thread with a sealant that prevents it from getting wet and blocks up any holes in the tent fabric created by the stitching process.

The process of seam sealing the Scarp 1 is identical to any other tent. To start, you need to pitch your tent someplace where it can remain standing, or hanging in my case, for a few days so that the sealant can cure properly. Make sure the area is well ventilated and that the tent will not be disturbed as it dries.

When I seam seal tents, I use McNett's Silnet. This is a fairly viscous silicone sealer that takes some patience and care to apply but lasts forever. McNett's comes with a small brush that you can use to apply the sealant but I prefer using my wife's q-tips.These are not your normal safety swabs but tougher ones that don't fall apart easily called Johnson Safety Swabs. I find that they're good for brushing sealant on exposed thread and for pushing it into hard to reach seams. The McNett brush is good for one seam sealing session but gunks up and can't really be used after that.

After these preliminaries, it's useful to examine your tent carefully and identify the seams you want to seal. There are some seams that you don't have to seal, and others that you might want to seal on both the inside and outside of the tent if there is a lot of stitching the penetrates the tent's outer skin.

For the Scarp 1, I identified 5 different areas that I wanted to seal:

1. The side seams that run from the middle of the tent to the top of the legs
2. All of the stitching around the optional wind pole clips and attachments
3. The outside patches that hold on the pitchlocks (legs) of the tent
4. The seam between the middle pole sleeve and the outside tent body
5. The seams around the roof vents

Of these, #2 and #5 are probably the most critical for this particular tent because they are places where a lot of stitching penetrates the tent shell. For example, here are two closeups of the wind pole anchors on the outside and the inside of the tent. On close inspection, I could see daylight shining through the stitches here, which probably explains where the leaks I experienced on my last trip came from.

After my inspection, I started with sealing an easy seam, the one that runs from the middle of the tent to the top of the legs.

If you've never sealed seams before, the process is simple. With one hand, squeeze the tube of Silnet and lay a bead of sealant on top of the seam stitching. The seam I'm sealing in the photo above has two sets of stitches. Use the swab if necessary to paint the sealant onto the stitches. This is not always necessary, since the bead may settle down exactly where you want it by the force of gravity. Be patient, and only use the swab if the stitching has not been covered or you need to move some extra sealant to another location.

After sealing this seam, I sealed all of the stitching that holds the wind pole attachments on to the tent's outer skin. In this case, I did use the swabs as a paint brush, covering all of the stitching both on the outside of the tent and underneath on the inside. I also painted the stitching in the roof vents on the outside and the inside.

Next, I painted sealant on the external patches holding the pitchlocks (legs) in place. If you consider the flow of water on the tent's surface during the rain storm, this area is bound to receive a lot of water and I wanted to make sure it was properly sealed up.

Finally, I applied sealant to the seam where the middle pole sleeve connects to the outer fly fabric. This seam doesn't have any external stitching showing, but I still wanted to get some sealant into it. The trick to sealing this kind of seam is to apply a thin bead of sealant to the top half of the seam and wait. It will slowly drip into the seam by force of gravity and create a nice seal, preventing any water from getting into it. If you'd like to see another example of this, check out this post about sealing a similar seam on a Black Diamond First Light tent.

Seam sealing my Scarp 1 today, made me really understand some of the design trade-offs in this tent. For example, the use of an external wind exoskeleton reduces the weight of the tent by eliminating the need for an external fly. But in doing so, many anchors have to be stitched to the outer silnylon surface to hold the exoskeleton (wind poles) in place. These anchors require a lot of stitching that penetrates the outer shell of the tent, so that it must be seam sealed to waterproof it. On hindsight this should have been obvious looking at the tent, but it didn't really strike home until I did my preliminary seam sealing inspection and noticed daylight shining through some of the stitching.

While these trade-offs are reasonable for a 4 season tent, particularly in this weight class, they seem less optimal for 3 season use, and I find myself already lusting after Henry Shire's newest tent, The Moment (in the moment – get it?), which has far fewer seams to seal and corresponding outer skin perforations that the Scarp 1. UL tents are addicting, aren't they?

Related posts:

1. Scarp 1 Tarptent: Autumn Field Testing
2. Scarp 1 Tarptent Preview
3. Scarp 1 Tarptent: Snow Practice
4. What is a 4 Season Tent?
5. Eureka Spitfire Tent: Ultralight Goes Mainstream…