I like animals and I like to use them as topic for my projects. In the past few weeks I learned from Instructables that you can make many decorative items from cement, so I thought: why not try to make a dolphin from cement? I do not like to copy ideas from others, so I looked on the internet and did not see many dolphins there and the ones I saw where placed on land and not above water and they looked quite different from my idea. So I decided to continue.
In the next steps I will describe in detail what I did, but a short summary is that I made a steel frame, added chicken wire and some cloth and then applied cement. If you do not have a welding machine or if you cannot weld, it is still possible to make this dolphin by using another material like wood.
Portland cement: 10 kilograms (20 pounds)
Sand: 15- 30 kg (30 - 60 pounds)
Rebar 6 mm (1/4 inch) diameter: 7 meters (22 feet)
Rebar 16 mm (3/4 inch) diameter: 3 meters (9 feet)
Steel rod 4 mm (3/16 inch) diameter: 2 meters (6 feet)
Chicken wire: 2 square meters (18 square feet)
PVC pipe 50 mm (2 inch) diameter: 3 meters (9 feet)
End cap for PVC pipe: 3 pieces that fit on the PVC pipe
Some old cloth
Step 1: Make a Drawing
I recommend that you make a drawing of a dolphin on the actual size that you want your dolphin to be. There are many photos of dolphins available that you can use. I used a dolphin from a puzzle and drew that on a large piece of cardboard. As you can see, my drawing is not identical to the photo. But that does not matter, as long as the result looks like a dolphin it is fine. If you cannot draw very well, you could also print a dolphin and use the print as template.
My dolphin is about 1 meter (3 feet) from nose to tail and the entire thing including its tripod stand weighs roughly 40 kg (80 pounds). If you decide to make your dolphin larger, it will become heavier and more difficult to handle.
Step 2: Cut and Bend the Rebar
The rebar is quite easy to bend. I did use the DIY tool which you see at the right of the photo, but it is not really needed. Just clamp the rebar in a vise and bend it manually. Keep checking and adjusting the shape until it matches your drawing well enough. Then cut off the excess lenght.
After making the top side of the dolphin, you should make the bottom side and cut some pieces of rebar which are long enough to connect the top to the bottom at several points. I first did that on the cardboard, but I did not want to weld on the cardboard and set it on fire, so I marked all the points where the intersections of the rebar should be and then moved all the pieces to my welding table. The markings made it easy to lay all pieces on the right location.
If you cannot make this from steel, you could also make something similar in wood.
Step 3: Welding the Frame
I welded the flat shape of the dolphin first. Then I measured all the vertical connecting pieces and cut all of them once again and laid them on the table in the right order from tail to nose. After that I welded the short pieces to the vertical connecting pieces making sure they where connected in the middle forming the shape of a +.
Then I cut 2 more pieces of rebar and bend them so they could be welded to the end of each horizontal piece and form the side of the dolphin.
Step 4: Making a Support Frame
I used 3 pieces of PVC pipe and glued an end cap on one side of these pipes and let the glue dry. My idea of using PVC is that when I place the tripod in the water, the cement will stay dry, so the PVC had to be long enough so that the central vertical rebar would never touch the water. I checked the depth of the water and based the length of the PVC pipes on that depth. You might have to adjust the length of the PVC based on the water depth at the location of your dolphin. If you make the tripod somewhere inside, make sure to check if it will fit through the door.
After preparing the PVC I took the thick rebar and cut 3 pieces of 50 cm (20 inches) and welded them to one large piece of 75 cm (30 inches) to form a tripod. You could better use a piece of 100 cm (40 inches) for the vertical part as I will explain in the next step.
I welded 2 short pieces of rebar to each leg so that the rebar will stay in the middle of the PVC pipe. Then I placed the three legs of rebar in the PVC pipes and filled the PVC with cement. I used a mixing ratio of 1 part of cement and 3 parts of sand for this and make it just wet enough so the cement will flow down in the PVC pipe and completely fill it.
Safety remark: always wear gloves when working with the cement to prevent that the chemicals of the cement burn or dry out your skin.
Step 5: Make the Fins and Tail and Weld the Dolphin on Its Frame
I made the fins and the tail from the thinner steel rod, because that is easier to bend than the rebar. I welded them on the dolphin and welded the dolphin on its frame.
As you can see there is only one point where the dolphin is connected to the vertical rebar of the tripod. That might turn out to be a weak point in the future, so I advise that you make the vertical rebar longer and weld it to the top and the bottom of the dolphin for additional strenght.
Step 6: Cover the Dolphin Entirely With Chicken Wire
Cut chicken wire in parts with a width of about 30 cm (12 inches) so they are easy to handle. The size can also be larger or smaller if you prefer that. I first covered the tail and the fins by folding the chicken wire around them. It is good that you have overlapping layers of chicken wire.
When you cut the chicken wire there are many short ends of wire that you can use to bend and hook behind another part of chicken wire. I recommend to use a screw driver to pull some of the ends of the chicken wire out towards you.
It took me about 2 hours to fully cover the dolphin in chicken wire.
Step 7: Move Your Dolphin to a Point Close to Its Final Location
Since the legs of the tripod are now filled with cement and the steel part of the dolphin is welded to the tripod, the entire thing is getting large and a bit heavy, so it is easier to bring it already close to where you want it to be.
As you can see I placed some plastic under the tripod because some cement will probably fall down when you are applying it.
Step 8: Start Adding Cement to Cover the Dolphin
I can tell you from experience that the hardest part to get right is the belly of the dolphin because gravity is working against you. It could be wise to place the dolphin upside down and first cover its belly and come back the next day to do the rest. I did not think of that possibility so I did the belly at the end and struggled a bit to make the cement stick there. The good thing though is that I learned more from doing it the hard way.
I started by using a cement to sand ratio of 1:1, but later I switched to a ratio of 1 part cement and 2.5 parts sand and I think that is better.
I also started by just applying the cement directly to the chicken wire. I think that will give the strongest result, but it only worked fine for the tail and the fins. On the other parts of the dolphins body too much cement fell through the mesh, so I decided to soak some cloth in cement (only cement and water) and to wrap the cloth around the dolphins body. I used cloth which I ruptured in parts of about 10 cm (4 inches) wide. Make sure that both ends of the cloth end just over the highest point, so gravity will help to press the ends of the cloth to the dolphin body. If you have an end at the bottom side, it will probably fall down. At least that is what happened with me.
Step 9: Cover the Dolphin Completely
About one hour after covering the dolphin with cloth soaked in concrete I added a layer of concrete on top of that. I just filled the palm of my hand with cement and applied it with a vertical sliding movement. Make sure you wear the gloves here.
Make the mixture quite wet as that makes applying the concrete easier. Especially for the belly the mixture should be quite wet. If the mixture is too dry, it will not stick and fall down. When the mixture is wet, also some will fall down, but most of the concrete sticks even at the belly.
Small gaps can be filled by adding a little bit extra cement there.
Make the surface of the dolphin smooth by using a smooth piece of metal like a spoon or a knife. I just used some from the kitchen.
Step 10: Deal With Setbacks
Like I wrote before, I struggled a bit with the belly of the dolphin. It also started to rain, so I went inside and waited for the rain to stop. (They expected just a small amount of rain, so I did not cover the wet cement.) Since I had an end of the cloth at the bottom and my cement at the belly was too dry, it did not stick well enough and a part fell down. You can see on the photo that before the fin there seems to be another fin now. That was where the cement fell and the cloth came off.
I came back the next day and then finished the belly.
Step 11: Give the Cement a Few Days to Cure and Paint the Vertical Rebar
This step is easy. Just wait and give the cement some days to cure. Use the time to paint the rebar at least twice to protect it against rust.
Step 12: Place the Dolphin in the Water
I recommend that at least two people move the dolphin to place it in the water. I was standing in the water, but then the dolphin was too far above my head to be able to handle it. With two people it is much easier to handle, so we did that. My dolphin including tripod weighs about 40 kg (80 pounds).
I expect that the tripod will sink a bit more over time. If the PVC would sink too much I will place a large tile under each leg to make sure the steel does not touch the water.
Step 13: Enjoy the Result During Day and Night Time
I like the result as it is. But if you want to make something similar, you could also think about adding a pump and hose and make the dolphin spray water from its mouth or from its breating hole. Another option is to add some light. Of course you also need power at the dolphin then, so make sure you use a safe method near the water.
Runner Up in the
Stone, Concrete, Cement Challenge