Well, there is always duct tape! You may have to replace it occasionally, but for a cheap, quick fix, that would work as well as anything. For something a little more exotic, try s Tenacious Tape ($5/roll). Its a durable, super-sticky tape that is designed for fabric repair. Available in clear or colored versions, each role is 20 inches, so youll need two. Lay the tent on a flat surface, pull the torn seams together as closely as you can, then tape the tear together. Put the tape on the outside of the tent.
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Otherwise, Id send it to a repair center where it can be patched properly with sewn-on fabric similar to the original stuff. in Seattle can do this for you.
One question: Is it time for a new tent? Ive never had a tent last more than nine or ten years at the most. After all, it doesnt take a lot of exposure to sun and UV for the tent fabric to start degrading. It may look fine, but likely only retains half of its original strength, if not less. s big nine-person, three-room Tetragon ($160) is quite nice. Might be time for an upgrade.