Seam Sealing FAQ

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An important step in keeping dry in your Six Moon Designs shelter is to ensure your seams are adequately sealed. Choosing the best sealer for the job and the best method of application depends upon the fabric used to construct the shelters canopy.


At Six Moon Designs, our shelters canopies are made using one of three different fabrics. Each fabric has different characteristics and different requirements for seam sealing.

Silicone Nylon

We use Silicone Nylon or its common name "silnylon" in the majority of shelters we build. Over the last decade its proven its worth in ultralight shelters. Because its fibers are infused in a coating of silicone, this fabric is both stronger and lighter than traditional tent fabrics. Since silicone is inert, it has the added benefit that it will never mold or mildew. The tight bond between the coating and fabric yarn insures that unlike traditional polyurethane coated fabrics, it will never delaminate.

The downside is that seam tapes designed to work on polyurethane coated fabrics will not stick to silicone nylon. This requires you hand seal the seams. In order to seam seal silicone nylon, you need a silicone based sealer. The silicone in the sealer will form a permanent bond with the silicone in the fabric. Once seam sealed, your tent will last for years.

For Silicone Fabrics, we recommend using McNett's SilNetTM. It is also possible for you to easily make your own sealer. This is handy if you have a number of items to seam seal or wish to save some money. Instructions for making your own seam sealer can be found below.

Polyester Fabric

We have a new lower cost ultralight tent with a canopy constructed from more traditional polyester fabrics. While not as light as silnylon, polyester fabrics do have a number of attractive properties. Polyester is hydrophobic so it repels water.  Unlike silnylon it doesn't tend to stretch when it gets cold. So it stays more rigid once setup. Polyester is more resistant to UV light. So it receives less damage when setup for longer periods of time. Finally the Polyester fabric is fire rated but we still recommend you keep it away from any flame source.

For Polyester Fabric, we recommend either McNett's Seam GripTM or McNett's Seam SureTM.

Cuben Fiber

Cuben Fiber is not a fabric in the traditional sense. In stead it's two layers of thin Dyneema tread layered at cross angles (vertically and horizontally) sandwiched between to layers of a Mylar like substrate. The four layers are then heat bonded together to form an incredibly strong and light material. Our Cuben Fiber is about half the weight of the silynylon we typically use.

For the most part all of the critical seams on the Cuben Fiber tents are bound with a special Cuben Fiber tape that will render the seam water tight. Some of less critical sewn seams do need to be seam sealed. This can be done with either McNett's SilNetTM, silicone seam seal or McNett's Seam GripTM seam sealer.

Seam Technology

Typical seams found on most shelter are composed of two panels of fabric joined together with a lap seam. This is a pretty simple seam and when made on standard fabrics, it's also easy to seal with seam tape.

In contrast, our tents are designed differently in order minimize tent weight. We combine elements of both the inner tent and the outer canopy into a single tent. This results in compound seams that are composed of three or more panels of material.  The multiple layers of material makes it impossible to use seam tape to seal these seams. Thus requiring manual seam sealing. This technique also makes it impossible to seal the canopy from the underside.

Contray to some seam sealing products, we recommend seam sealing the seams from the outside on all of our shelters.  Attempting to seam seal compound seams from the underside will not yield acceptable results.

In the case of the Skyscape - Scout tent, the canopy is polyester fabric. As you examine the underside of the seams, you'll note that the some seams are seam taped. You can skip seam sealing these seams. To achieve a good seal, you'll need to seam seal all of the seams not taped.

Sealing Your Shelter

  1. Setup and Inspect your Shelter - Setup your tent before sealing it. Get inside and lay down to make sure it fits your needs. Make a through inspection to insure it's properly sewn and all the seams are in good condition. Make sure you are happy with the shelter before proceeding. Tents that are seam sealed by customers are not eligable to return it for a refund.
  2. Seal the Seams - Most of seams on Six Moon Designs shelters are designed using butt seams. These seams keep the the threads on the inside where they are less exposed to dirt and grim. Butt seams must be sealed from the outside of the canopy. Applying sealer to the underside of the seam will not seal them.

    Work in a well ventilated area, pour a small amount into a paper cup, and close the jar to keep rest of sealer from thickening. Use a small brush to apply a thin coat of sealer to all exterior seams. For butt seams, hold them open to allow the sealer to soak into the seam and coat the threads. If sealer thickens while applying, add some more mineral spirits.
  3. Stripe the Floor - For shelters with floors, adding a series of strips sealer to the floor of the tent. This will reduce the tendency of your sleeping pad from sliding around on the silicone nylon floor.
  4. Drying your Shelter - Allow your shelter to cure for at least 8 to 12 hours after sealing. Once cured, the sealer dries to a clear matte finish that is nearly invisible, and will be both durable and flexible. You may find your seams to feel tacky. This will dissipate with shelter usage. You prefer, it can be eliminated by sprinkling on a light coat of unscented talcum powder.

Making your own Seam Sealer

seamseal If you wish, you can save some money when seam sealing SilNylon shelters. You can easily make your own sealer that'll work as well as the commercial stuff. It'll also give you a better looking seal.

  1. Purchase the following items. They should be are available from most local hardware stores.
    • GE Silicone II clear tub and sink caulk - The small tube will make enough to seal several tents. The large tube will make enough to seal everything you own and then some.
    • Mineral Spirits - Commonly used for cleaning paint brushes. Preferably the odorless kind. Your nose will be thankful.
    • Small brush to apply the sealer - A 3/4" foam brush works well.
    • Paint stirrer attachment for an electric drill.
  2. Dilute Silicone In a glass jar, mix one part mineral spirits with one part silicone caulk (1 ounce of mineral spirits and 1 ounce of silicone should be enough). When mixture is the right consistency, it will be smooth and milky, and flow evenly when applied. If it's too thick or lumpy, the waterproofing won't flow well into the seams, or be absorbed by the exposed threads.
    • Hint #1: You can mix by hand with a regular paint stirrer, but caulk is stiff, so will take much longer to mix. Using an paint stirrer in an electric drill will give your sealer a smooth silky appearance. It will dry faster and clearer.

    Last Updated on Friday, 25 March 2016 10:03



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