This Instructable shows the steps I took to make a durable disk seat for the bottom of a rope swing for my family to enjoy. I looked online for existing seats to purchase, however, the only ones available had a weight limit of 150 lbs. I happen to be a little over 200 lbs. (I'm working on it), and wanted to enjoy it as well. I also felt that I could make one rather cheaply as most of the materials I already had in my man cave. I thought about different methods for a while, and settled on these steps. I installed it on Easter day, 2013. I'll keep this instructable updated with any issues that may arise (hopefully none...crossing my fingers) as well as any adaptations.
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
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
The seat is composed of with two wooden disks. Take the 3/4" Plywood and, using the compass, mark the final circle dimension. I made my seat 12" wide, and am very happy with it, but I could easily see it a little larger - say 14" across. Make sure you can see where the center of the disk is, as you will be needing to drill a hole there in a future step. Use the jig saw to slowly & carefully cut out the circle. Next thing to do is use the same method to make a smaller disk that is half the width of the larger disk. This will add necessary strength and stability. I made my smaller disk 6" wide.
Step 3: Rounding Edges & Smoothing
Take the Sanding Block with the rough grit sandpaper and use it to smooth out the edges. I suggest putting a nice rounded-edge to the edges of both sides of the large wood disk, and just ONE side of the smaller wood disk. Before doing so, you may want to determine which side has the better wood grain (if you aren't going to fully paint the seat), and place the better grain on the rounded (exposed) side, as the other side is to be glued to the larger disc.
When you have it shaped the way you like, use the medium/fine sanding sponge to smooth everything really well.
Step 4: Drilling Holes
Drill a 3/32" hole straight through the center of both disks. On the SMALL disk, drill FOUR 3/32" holes in a T-pattern, about 1 to 1-1/2" from the edges. Then, on the small disk only, use the 3/8" Drill Bit to carefully drill only 1/4" deep into those 4 outer holes. This step is for countersinking the screws so we can plug the holes...Be careful as the bit will want to pull the drill bit further in. As a matter of fact, I would recommend practicing on scrap wood, or to use a drill press to help control the depth.
Step 5: Joining the Two Disks
At this point, the two disks are ready to be joined. Use the wood glue to apply a thin layer of glue to the underside of the small disk. I used a disposable brush to coat the entire surface. Take the 3/32" drill bit, or a thin nail, and use it to help align the two disks by placing it in the drilled hole in the center of the larger disk, and then threading the smaller disk on top of it. This will assure that the two centers are perfectly aligned.
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
Take the 3/8" Wood Button Plugs and generously apply glue to the bottoms of them and each of the four holes on the smaller disk. Use firm pressure or soft blows from a hammer to seat them into the screw holes. I wiped the excess glue off the surfaces and clamped everything together again for a couple more hours.
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
PLEASE READ FIRST:
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
Take the PVC Coupler and notice that there is a ridge inside at center that needs to be removed. You can see that I tried using an X-Acto knife, to no avail. That is where the Dremel tool and sanding drum came in very handy... don't put the Dremel setting up too fast, as it could heat up and melt the PVC.
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
In the mixing cup prepare a diluted 1:1 solution of Urethane and Turpentine. Mix well and brush over the entire wooden seat - especially within the center hole. Let it dry and apply another coat. The diluted solution will help the urethane to soak deeply into the pores of the wood and help to seal them from any moisture penetration. This acts as a good "sanding sealer". When the seat is good and dry give the seat a light sanding with the fine side of the sanding sponge. It is now time to add any decorations that you want to add. I simply took both a black and red Sharpie and used a quarter to trace circles randomly around the surface, and then filled them in solid with the sharpies. Simple, yet festive. By the way, on my example in the photos, I know there are some random traces of white paint left over from another project that I wasn't able to sand off the surface of the plywood. I decided not to worry too much about it as they weren't too distracting for me...OK, truth is I am impatient and didn't want to cut another circle. There, I said it.
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
Mix up a good helping of the J-B Weld Epoxy to coat the entire inside wall of the center hole of the seat. You will want to work fast as the epoxy sets fairly fast. The Popsicle sticks work well to push the epoxy into the cracks and grain of the wood. Once the inside wall of the seat is well coated, push the PVC coupler into the seat to the appropriate depth. There may be some of the epoxy that is pushed through and built up on the inserted end of the tube. Take the Popsicle stick and remove the excess and smooth it out. Take any extra epoxy and apply it to the other end of the tube - in the void between the PVC and wood. You want to make a smooth radius so that the rope won't have any points to hang up on or rub against. Now let the seat dry completely.
At this point the Seat itself is complete. Now it is time to add a rope.
Step 11: Adding the Rope
I ended up using a red & white striped, 5/8" solid braided poly rope from Home Depot. I melted the ends to prevent fraying. I also wrapped the ends with Duct Tape.
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.