Manta rays

For the past four months I’ve been working on a project: a mate of mate got a contract to refurbish a visitors’ center at a Ningaloo Reef in WA. So we’ve been building brain coral, fake rocks, manta rays and whole heap of other things. Just the two of us. A welcome change from swinging hammer in a boat yard. Today I started loading them all  into a container for the long trip to WA, and I realised that I have no record of any of that work. Frantically running around with a borrowed camera I snapped some of it.


Brain coral took three months of work. Shame that photo does not show a greater detail: all the squiggly convolutions are stippled, weeks of patient work. The whole thing is over a metre high.


First we inflated a metre diameter beach balloon and covered it in plaster. Puncturing the ball we got a clear concave surface to work on. Covering it in half an inch layer of clay, we carved the squiggly lines in, by hand, then stippled the surface of every line. Pouring in a skin of fiberglass we got the first plug, the positive original. We peeled off the clay and smashed the first plaster surface. After repairs to mangled details we covered the plug in silicone to get a mold. Encasing the mold in fiberglass jacket gave us strong base to lay the final product  – in pigmented polyester resin with several layers of reinforcing glass. Sounds like a lot of work? My word.


The square hole in the top of the coral will take a touch screen connected to other displays. To support the computer we glassed in a wooden shelf.


Another screen will fit into a rock. Looks real, doesn’t it?


In reality it’s another dirty trick. Rock surface is a skin of PVA glue mixed with latex paint, applied in several layers into a silicone mold taken from a real rock. You weld together a strong frame from square section and shape the rock with thinner steel rods. Cover the frame with chicken wire and hot-glue onto it the PVA skin of rock. This particular rock took three casts off the same mold. In the end you plaster the inside of the rock to give it strength – I can see little fingers picking at all those details sticking out of the rock surface.


Another part of display is much larger rock, a gantry about 10 feet long and 9 feet tall. Details are painted in light acrylic wash. Even this size rock is light enough for two guys to carry around, complete with welded steel frame inside. Backing is expanded polyurethane foam, to save on weight.


The final use for the rock mold was this Flintstones’ coach. The whole back and left side of the seat is a textured rock taken from the same mold. Unfortunately  I remembered the camera only after I screwed down the whole monstrosity into the container, and I wasn’t going to move it again. Rendered in solid plaster inside, it weights about 200kg, to make it sturdy enough for daily use in the reception area.


Dark timber is merbau (ipil), lighter areas structural plywood. Rock is PVA.


Finally we come to the manta rays. Client ordered three beasts, to hang from a low ceiling. 3-metre wingspan is all that the room can accommodate, so we made a 3-metre master model out of Styrofoam. Covered the shape in a thin layer of dental plaster, and for finer details a skin of wax. From this plug we cast a silicone mold, reinforced with polyester jacket.


You cast the beast in two separate sections, top and bottom, before you sandwich them together (still green) and bolt the clam-shaped mold tight. Pigment, flow- coat, muslin, and fiberglass layers, including the reinforcing for the screws to hang it from, has to be all done the same day. Two halves, then clamp it together. A long day in a hot shed.


We modified the beasts so they didn’t all look the same – shape of wing tips and and the feeding flaps around the mouth. How do you modify  fiberglass? With brute force, angle grinder, heater, lots of bog and patience.


Last thing is to attach the tail which will travel separate from the body. In this view the beast is 6 feet long.

Photos by the author

3 thoughts on “Manta rays

  1. Kris and Nat! Fantastic! I thought I was watching “The Making of the Avatar” ! And the expertise you have shown might bring the hordes to your doorstep! (or shed 🙂 More power to you both!

  2. Those are beautiful! Another place to put on my list of places to see if I ever make it out to your end of the world. I am always amazed Kris to see how your artistic self works its magic into things that are used by others. Now that I know you can do these models, I see gardens with your fantastic beasterie in my mind…

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