If you roll your own engines I suggest you use Gorilla Glue (Elmer's Polyurethane). It expands and makes a beautiful tube for both engine and for Airframe. You have to put a turn of wax paper over your mandrel and then a turn of Saran wrap over the wax paper. Then squeegee the Gorilla Glue over your paper so it wets the paper. Keep it thin. Roll the paper around the mandrel tight. Then roll saran wrap over the finished product keeping it tight and wrinkle free. Then wrap it with shrink tape in a spiral like the spiral wrapped body tubes you buy. Use a heat gun to shrink the tape. Let it dry over night and you will have a very strong and beautiful tube. Sand the OD to get rid of the rough finish. If you don't have shrink tape just use packaging tape (not duct tape unless you want the tape pattern in the finished product). Wrap the packaging tape in a spiral around the rolled tube as tight as you can get it being careful not to get wrinkles in it. The glue expands and will fill in any wrinkles leaving a bump. Not using shrink wrap is ok because as I mentioned the glue expands to 4 times the original size as it cures. It will still make a good tube. These tubes are much better than the paper body tubes you buy from Estes or other hobby outfits. And it gives one much more satisfaction having made them yourself.