This example was approximately 6 feet long, with the seat measuring roughly 16 inches and the back roughly 24 inches. Sketch out a basic design to help visualize the components. If you're unsure of how big to make the bench, find an existing one that's comfortable and simply use its dimensions.
For the materials, any sturdy 1x or 2x material will work. We opted to use 2x6 tongue-and-groove (Image 1). In this application, tongue-and-groove is an added bonus since it will increase stability. For this design, what's required includes three long pieces for the main framing members and enough to create back supports and arm rests as well (Image 2). We used kiln-dried cedar logs that were approximately 5 inches in diameter. Cedar is a good selection for many outdoor applications because it's weather- and pest-resistant.
Build the seat frame first. It's simply a large rectangle made by joining two long sections of cedar with two shorter sections (Image 1). This seat employed mortise-and-tenon joinery, created using a special system of tenon cutters and forstner bits from Lumberjack Tools. "Sharpen" the end of one log using the tenon cutter (Image 2), using a strong 1/2" electric drill. Then, using a forstner bit, cut a corresponding hole where the two pieces will join.
After all pieces are cut and drilled, assemble and secure with exterior screws. Repeat these steps for the other side of the bottom frame. Using the same method of tenon cutters and forstner bits, build the back. Set the vertical supports for the back into the rear brace of the seat. Use one log for the upper back brace mortised to fit over the vertical supports. Secure all joints with exterior screws. The armrest is essentially an "L" anchored into the outer seat frame and the vertical back supports with the same mortise-and-tenon joinery.
Four connection points are necessary to fasten the swing to the chain and two to fasten the chain to the porch. Predrill and insert large screw eyelets or hooks into the seat frame and backrest. Attach hooks or anchors to the hanging location and run chain between.