This project could possibly be finished in a long weekend. The time-consuming tasks would be waiting for the wood glue and the different coats of Urethane to dry.
My main concern for this instructable is that it would hold up to the weather. I had concerns regarding water infiltration and keeping it waterproof. I believe the following steps provide great weather resistance...
Step 1: Materials & Tools
Compass with Pencil
Exterior-Grade Wood Glue
1" Chip Brush
1/2" PVC Coupling
x4 1" Wood Screws
3/8" Hardwood Button Plugs
Sanding Block with Rough-Grit Sandpaper
(I like to take a 2x4 scrap and glue the Sandpaper to it)
Medium-Fine Sanding Sponge
Jig Saw with wood blades
Rotary Tool (Dremel) with small Drum Sander attachment
3/32" Drill Bit
3/8" Drill Bit
J-B Weld 2-Piece Cold Weld Epoxy
Applicator/Stir Sticks (I prefer Popsicle sticks)
5/8" Solid Braided Poly Rope
Duct Tape (duh)
Double Swivel Round Eye - with one opening end
Step 2: Cutting the Seat Disks
Step 3: Rounding Edges & Smoothing
When you have it shaped the way you like, use the medium/fine sanding sponge to smooth everything really well.
Step 4: Drilling Holes
Step 5: Joining The Two Disks
Insert the screws into each of the four holes - one at a time, applying firm pressure while screwing it in. Then, firmly clamp the two disks together for a couple of hours to assure there are no gaps between the two disks. You will probably need to sandwich the smaller disk between the large disk and another board as I did in the photo.
Step 6: Plug the Holes
When dry, take the hand saw to cut the heads off the button plugs. Then use your sanding block, and sanding sponges, to sand the surface flush.
Step 7: Drill, or Cut, the Center Hole
Use the compass to mark the center of both sides of the seat with a 1-1/8" circle (Outer dimension of the PVC Coupler). I used a large drill bit, and then used the jig saw - cutting in small cuts around the perimeter of the circle. It didn't need to be a smooth cut circle. As a matter of fact roughness helps in the gluing of the inserted PVC coupler (next step).
After using the saw, use the Dremel and sanding attachment to round-over the edges of the hole on both sides of the disk.
NOTE: I used a 1/2" PVC Coupler to line the center hole as I wanted to seal up the wood as much as possible to prevent water damage to the wood. I had planned to use a 3/4" twisted nylon rope, so the coupler's 13/16" hole made sense. However, after inserting the 1/2" coupler, I then found a softer/smoother 5/8" rope that I liked better and ended up using, which caused there to be a bit more play between the rope and seat - not a problem, but I am very particular...thus it bothered me. You could also use 1/2" PVC pipe which has a 5/8" hole... tight tolerances - which may not be preferred... difficulty in threading rope, entrapment of moisture, etc.
Step 8: Prepare PVC Insert
You will also need to dry-fit the coupler into the seat hole to determine where you need to cut it. The PVC coupler is NOT to support any weight when the seat is sat upon...You don't want it to be flush with the either side as you don't want undue pressure on the epoxy that will be holding it into the seat. This is simply a barrier between the wood of the seat and the rope. Insert the coupler in the seat so that it is still roughly 1/4", or a little more, from the surface of the seat and mark the other side of the coupler to be the same distance from the other side of the seat when it it centered within the hole. (sounds confusing, but I hope you understand... y'all let me know if you want me to draw a diagram of this) Use the handsaw, or other method, to cut the PVC to the appropriate length.
Use the Dremel tool and sanding drum to round over the inner edges of both sides of the PVC tube. Also use the Dremel to roughen up the outside of the PVC Coupler so that the epoxy will have something more to grip to. I used the wire brush attachment to smooth the inner surface & edges a little...I don't think it did too much good. I just didn't want any surface to wear on the rope while in use.
DO NOT GLUE IN YET.
Step 9: Seal the Wood
When you finish adding any additional graphics to your seat, you want to now brush on a couple of coats of pure, non-diluted exterior-grade Urethane to protect it.
Step 10: Insert the PVC Tube
At this point the Seat itself is complete. Now it is time to add a rope.
Step 11: Adding the Rope
Please... I am no expert on hanging a rope from a tree branch, so you must research elsewhere as to the most appropriate/safest way to install your rope line. Hang rope at your own risk. I can only state the method that I chose with which to install MY rope (which may or may not be proper):
I tied a loop into the end of the 5/8" rope. I then took some nylon twine, tied a weight to the end of it, and threw the weight over the branch where I wanted the rope to be located. I then tied the twine to the loop of the 5/8" rope, pulling it over the branch. I inserted the other end of the 5/8" rope through the loop and pulled the loop all the way up to the supporting branch (I call this the slip-knot method, for obvious reasons).
Determine how high you want to position the seat from the ground. Insert the rope through the seat and twist two knots into the rope where you want the seat to be positioned. I said TWO knots because I wanted the knot to be large enough so that the seat's wood surface rests on the knot -- not the PVC resting on the knot. You will find that after swinging for a while the rope stretches, causing the seat to get lower, and it will require you to re-knot the rope again. I advise that you let everyone swing for at least a month before you tie a new knot.
I also installed a Double Swivel Round Eye high up on the hanging rope, to allow for the twisting that people do while swinging. I like how the lower section of the hardware can be opened to allow easy changing/removing of the swing.
After thinking about this for a while, I believe I will add thimbles to the loops in my rope to help protect the rope from wear & tear. You can see a photo of one below. I recommend buying galvanized ones.