One of the less enjoyable parts of making gear from synthetic materials, such as ripstop, is cutting the material and then heating/searing the edges to prevent fraying. I have tried matches (bad idea) and candles (ok but results in uneven edges and requires considerable time and gentle care to avoid a mistake). Using a fell seam or french seam might obviate the fraying problem but again, requires more effort.
I followed several forum’s on the use of hot-knifes (including those here). Hot knifes can be obtained at fabric stores for ~$45 into the $100s. I recently came across the discussion on a forum of wood-burning knifes and soldering guns for cutting fabrics. .. and, now based on my experience, I can attest the soldering iron works well!
I purchased a $20 Weller (TB100PK) Therma-boost soldering gun in a ‘gun’ format (see pic below). The soldering gun contains 6 tips, one of which (i.e. the ‘rope cutting’ tip) is perfect for cutting ripstops.
I have used it to cut a variety of lightweight ripstops (the 1.1oz uncoated ripstop in the pic below). The cut is made by the heat alone (i.e. the tip is really not sharp) and results in a perfectly sealed edge on both sides—straight also. I have not yet tried the soldering iron on heavier fabrics (e.g. dyneema).
Remember to put scrap glass below the material to cut on and use a metal (e.g. aluminum straight edge).