Making A Giant Egg

 

Completed egg shells

Completed fibreglass shells painted in shellac ready for finishing

The first step in making a giant egg is to make a giant egg – so a mould can be made.

Depending on the size of the egg you want to make will dictate how you go about making the egg form. Since the egg we needed to make was about 60cm tall it was decided to carve it from a block of polystyrene. Since the egg shape is symmetrical it is best to turn it on a lathe.

Preparing polystyrene block for turning

Preparing polystyrene block for turning

The polystyrene has to have plywood boards glued to both ends so a lathe faceplate and tailstock centre can be attached so it can be turned on the lathe.

The corners of the block are then cut off at 45 degrees to make turning a bit easier on the polystyrene. If this is not done it is likely large chunks will break off when the lathe chisel is applied to the turning block.

It is very, very messy turning polystyrene on a lathe so ensure the work area is covered with something to collect the shavings and clean up regularly as you work. This will minimise the polystyrene getting into every nook and cranny of your workshop.

Polystyrene mounted on the lathe ready for turning

Polystyrene mounted on the lathe ready for turning

Basic shape completed on the lathe

Basic shape completed on the lathe

Completed polystyrene egg

Completed polystyrene egg

The polystyrene is removed from the lathe and the two ends trimmed. Sandpaper is used to smooth both ends until their radius makes a smooth transition around the egg shape. It is important to get the shape exactly right with no obvious flat spots or sudden changes in the radius.

To support the egg while making the mould a box was built to put the egg form into so the middle flange can be made with plasticine. Once that has been done it is given a coat of PVA mould release in preparation for fibreglassing.

Ply box for making the top half of the mould.

Ply box for making the top half of the mould.

Flange finished around egg

Flange finished around egg and mould release applied

After the top half has been fibreglassed a timber support is fibreglassed on the mould so it sits horizontal when put on its side. The egg with the first half of the mould attached is removed from the support box and turned upside down to expose the underside of the egg form. This is cleaned up, PVA mould release applied and the second half is coated with fibreglass as described in previous mould making posts.

After polishing the inside of the mould halves with wax fibreglass casts are taken and trimmed to the flange line around the mould on both halves.

The two completed fibreglass mould halves

The two completed fibreglass mould halves

Fibreglass casts for egg ready for joining

Fibreglass casts for egg ready for joining

To ensure that both halves of the egg are joined together securely they need to be fibreglassed along the inside centre seam of the egg. To do this an access panel is cut in one half that is big enough to get your hand inside the egg shell. Blocks of wood are attached to the inside of the shell around where the access panel will be cut. This allows for easy re-installation of the panel section after the work has been done.

You can see the alignment blocks in the photo below with the access panel removed.

Cutting out an access panel in one half

Cutting out an access panel in one half

Access panel removed

Access panel removed so halves can be fibreglassed together

The two halves are taped together with mylar tape to keep them aligned. They are then fibreglassed on the inside along the centre seam. Once this has been done the access panel can be glued back into position and all gaps around the panel opening and the centre egg seam can be filled with polyester filler.

After sanding smooth the fibreglass is given a primer coat of de-waxed shellac.

Halves taped in position

Halves taped in position for fibreglassing from the inside

Access panel glued back in position

Access panel glued back in position and gaps filled and sanded

The completed eggs can be seen in this post.

Oversize Tiffany Style Gift Box

Oversize Tiffany style gift box

Oversize Tiffany style gift box

A dance prop in the form of an oversize Tiffany style gift box was required for a competitive dance routine. The box was to be big enough to conceal the dancer inside and light enough so it could be carried onstage for the routine with the dancer inside. It also had to be strong enough on the top so the dancer could perform her routine on the lid.

For rigidity the dance prop frame was constructed using 12mm hollow square steel with extra braces in the base and lid sections for additional support. To keep the weight as low as possible it was clad in 7mm marine ply which was liquid nailed to the frame. Small hand cutouts were cut in the sides to enable it to be carried and a small lip attached to the front of the lid to make opening it easier.

When the dancer burst out of the oversize box by throwing open the lid it put considerable stress on the lid stays. These were custom made using 3mm flat steel to stop the lid opening too far so the dancer to get out and close it easily. Another 30cm square wooden replica of the oversize box was built to act as a step to facilitate the dancer stepping up onto the closed lid. This was incorporated into the routine to make the transition as seamless as possible.

Tiffany style box opened

Tiffany style box opened

Heavy duty hinge stays

Heavy duty hinge stays to support the lid

Making Foam Wings

Completed wing

Completed flexible wing covered in fleece fabric

The recent Wayside Chapel winged heart project had two large wings that flapped up and down under the control of a pneumatic cylinder. For safety reasons it was decided to make foam wings so they would be flexible enough to prevent someone getting their head taken off if they happened to contact a wing when it was operating.

However part of the wing had to be structural for the correct flapping motion to be achieved. This was solved by making the bottom section of the wing with a plywood core and the rest from a sandwich of 5mm closed cell foam. The steps of the construction are shown below.

Clicking on an image brings up a larger image.

Plywood and foam wing core

A 12mm foam core extension is glued to the edge of the lower plywood core

Perspex stiffener for foam wing tip

A polycarbonate stiffener is glued to the foam to hold it straight while still being flexible

Front and back foam cover sheet

A 5mm sheet of foam was glued to both sides of the plywood and foam core for strength.

Foam covered wings

Both wings have the front and back of their ply and foam cores covered in 5mm foam.

Another sheet of 5mm foam was cut out to the wing shape and the lines of the feathers were cut. Narrow strips of foam were then glued along these cuts so that when it was turned over there would be a raised feather line in the foam.

Feather line cutting

Here the foam has been cut following the line of the feathers

Raised sections on feather lines

The strips of foam glued along the feather cut lines to make raised sections

Rasied feather lines

Raised feather line foam layer glued to a wing showing the raised outline of the feathers

More raised detail added

More raised foam detail is glued to the front wing surface

Next ivory coloured cotton fleece fabric was glued over the foam wings. This gave the wings a softer look and highlighted the raised feathers and other detail.

Glueing fleece fabric to wings

Glueing cotton fleece fabric to the foam wings

Feather detail of completed wings

Completed wings fitted to the wing mechanism showing the feather detail

Making a Giant Heart

Completed giant fibreglass heart

Completed giant 3D fibreglass heart

The making of a giant 3D heart for the recent Wayside Chapel winged heart project was a great exercise in how to sculpt large objects for armatures to make large fibreglass moulds. The heart had to be made as quickly and cheaply as possible so some shortcuts were made that had both positive and negative consequences.

Instead of making a two piece mould it was decided to make a perfectly symmetrical half mould so both front and rear sections could be cast from the same mould. This was achieved by first drawing half a heart on a piece of plywood. A second piece of plywood was fastened under the first and then both pieces were cut as one on a bandsaw. After sanding the the edges smooth the plywood *sandwich* was split and fastened together, side by side, making a perfectly symmetrical heart shape.

Heart outline in ply

A symmetrical outline of the heart was made from ply and fastened to support table

making armature with ply strips

Building up the heart profile using templates and ply strips

Heart shape in ply strips

Rough heart shape defined by ply strips

Hessian covering over ply

Ply framework covered with hessian

Plaster applied over hessian

Casting plaster was applied over the hessian covering to make it rigid.

second layer of plaster and hessian applied

A second layer of casting plaster and hessian is applied over form work

To smooth the heart shape a thick layer of Gyprock top coat filler was applied using a spatula taking care to make the layer as smooth as possible.

Applying Gyprock

Applying the Gyprock top coat filler over the plaster form. It was carefully filled out to match the heart outline defined by the base ply template.

Smoothing the form

Form ready for smoothing after the Gyprock dried

In the rush to get the mould made I decided to save time by not making the heart form super smooth before applying gelcoat and matting. Instead I would apply a double thickness of gelcoat when making the mould and then sand any irregularities from the mould directly. A quick coating of wax mould release was applied before applying the gelcoat and fibreglass matting over the heart form. This was a big mistake. The wax soaked into the not quite dry Gyprock allowing the gelcoat to stick firmly to the heart form making its easy removal impossible.

Mould completion

With the fibreglassing completed the mould was ready to be removed from the form but it would not budge.

Removing the heart form

The mould was firmly stuck to the heart form. Weighing in at over 100kg the mould had to be lifted from the work table so the form could be cut out from underneath the mould

Removing formwork

Once the bottom of the mould was exposed the timber formwork could be dug out

Plaster removal

Removing the plaster and hessian reinforcement

Once the ply form work and hessian had been removed there was still a thick layer of plaster and Gyprock stuck firmly to the fibreglass. The only way to remove it was to use a hammer and chisel. The chisel had its corners rounded and the cutting edge dulled to minimise the inevitable damage that would be done to the mould interior surface.

Removing the plaster and Gyprock

After 4 hours work only half the mould had been cleaned.

More plaster removal

About 8 hours later the last of the plaster and Gyprock was removed from the fibreglass surface

Cleaning mould

Wet’n’dry was used to sand the irregularities and scratches from the mould inside surface

Waxed mould ready for use

The mould after being cleaned and waxed ready to have a cast taken

Red gelcoat in mould

First layer of gelcoat with red pigment applied to the mould. This was followed by two layers of matting.

Fibreglass casting from mould

The first fibreglass heart shell removed from the mould. It popped out very easily because the mould release was applied correctly this time.

The shell of fibreglass was very flexible and had to have bracing fitted inside to make it rigid. This was done by hot glueing pieces of cotton rope on the inside and applying fibreglass matting over the top. The front shell also had a steel framework fitted so it could be attached to the wing mechanism.

Internal bracing of heart shell

The internal bracing in the front heart shell showing the cotton rope before being fibreglassed.

Completed 3D heart

Heart shells join line covered with cloth tape and polished

52 Storey Tree House Props

We recently built a selection of hand props for the theatre production of the popular children’s book called “The 52 Storey Tree House”. Mark Thompson designed the costumes, set and props and the show was directed by Liesel Badorrek. Julian Louis was the Artistic Director. Below are photos of some of the props we made along with some construction notes.

Sporting trophies

Sporting trophies

"Vegetable Castle" sign

“Vegetable Castle” sign

The sporting trophies were sourced items found in a box at the back of a junk shop on the Central Coast. They were black but came up well with some judicious polishing and hydrochloric acid! The sign was simply a stick-on vinyl print mounted on some Alucabond. Alucabond is a strong and light substrate that is perfect for this type of application.

Cow letterbox

Cow letterbox

Giant potato masher

Giant potato masher

The cow letter box was made of empty paint tins mounted on a sculpted steel branch. The branch framework was painted with texture coating to give it a more natural look. The giant potato masher was one metre in height and made with aluminium and laser-cut polycarbonate. A turned wooden handle secured the aluminium frame together.

Pile of children's books

Pile of children’s books

"Fun with Vegetables" book

“Fun with Vegetables” book

The pile of children’s books were glued to a ply sheet so they could be quickly set/struck from the stage. The book was an old cook book dressed up as per the design.

Secret disguise bags

Secret disguise bags

Communication funnel prop

Communication funnel prop

The printing on the Secret Disguises bag was very difficult. All types of paint refused to stick to the nylon bags. After much trial and error a light spray of 3M contact adhesive on the nylon provided a stable base for the paint. A much better solution would be to avoid this type of bag altogether. The communications funnel was simply several metal shower tubes from Bunnings joined together.

Wooden tray of Ninja Snails

Wooden tray of Ninja Snails

Detail of Ninja Snails

Detail of Ninja Snails

The X12 Ninja snails on a wooden tray were made from expandable urethane foam. Details of their construction are described in another post.

Casting with Urethane Foam

Detail of a completed Ninja Snail

Detail of a completed Ninja Snail

This picture shows one of the completed Ninja Snail props made for The 52 Storey Tree House stage show. Twelve snails on a wooden tray were required for the show.

Because twelve were required their overall weight was of prime consideration. The construction technique chosen involved making a hero snail sculpture and then making a fibreglass mould. The mould was then used to cast the required snails in expandable urethane foam. The urethane foam had the advantage of a quick turnaround between castings plus being very light.

Small snail statue used as a base for sculpture

Small snail statue used as a base for sculpture

New plasticine head sculpted onto ceramic snail shell

New plasticine head sculpted onto ceramic snail shell

A small ceramic garden snail sculpture was found that had the correct sized shell. A new head was sculpted using plasticene over the existing snail head.

Fibreglass mould half

First half of fibreglass mould completed

Completed fibreglass mould halves

Completed fibreglass mould halves of the Ninja Snail

After carefully covering the snail with wax and building a flange along the centre line the first half of the fibreglass mould was made. A couple of coats of gelcoat was applied first followed by several layers of fibreglass matting. After the first half was finished the plasticene flange was removed and the other half of the snail cleaned and waxed. The second half of the mould was made in the same way as the first.

After letting cure for a day the fibreglass mould halves were removed from the snail sculpture. This step is usually glossed over in descriptions of mould making when, in reality, it can be the most difficult aspect of the whole process. It is very easy to damage the mould if it gets stuck in unexpected undercuts etc. Once released and cleaned up the mould is ready to prepare for casting.

Two mould halves bolted together

Two mould halves bolted together in timber support frame

Mould clamped and ready for urethane foam pouring

Mould clamped and ready for urethane foam pouring

The mould is first waxed and bolted together. A wooden frame is built around the mould so that it can stand flat on the bench. This makes it easy to pour in the urethane foam. A flat cover is made to clamp over the top of the mould after the foam is poured in. A few small holes are drilled in the cover to relieve the pressure buildup of the expanding foam.

It is a good idea to clamp the mould halves together as well to prevent them distorting outwards under the pressure of the expanding foam.

Mould cap clamped on after foam pour

Mould cap clamped on after foam pour

Expanding foam seeping out

Expanding foam seeping out of relief holes in mould

Urethane foam comes in a Part A and Part B which is mixed together by weight. You can also add a tint to change the colour od the foam. I chose a green base since the final colour was going to be green. Some experimentation is needed to work out the volume of mixed foam required that will expand to fill the mould (with some to spare). Once this is determined the two parts are poured into a container and thoroughly mixed with an electric drill attachment for a minute. It is then quickly poured into the mould and the top cover clamped in position. Within minutes the foam will expand filling the mould and releasing the excess out the vent holes in the cover as shown.

Casting removed from mould

Casting removed from mould before cleaning

Trimmed ninja snails

All the cast Ninja snails trimmed and ready for painting

After about an hour the clamps can be removed and, if mould release has been correctly applied, the casting should pop out from the mould. Again, this is sometimes not as easy to do as is often portrayed in “how to” videos. You will get quicker as you learn the dynamic of the materials. It is doing this part of the process that highlights how strongly you made the flanges of the mould. It often requires quite a bit of force to pop the mould halves from the casting and the mould can be damaged if it is not strong enough.

Foam inevitably seeps between the mould halves but this is easily trimmed off. The final step is painting the snails and air brushing on highlights. Small plastic eyes from Spotlight are glued in position under the ribbon masks. The ribbons themselves are folded in half and glued with some florist wire which allows them to be shaped as required.

Paint Tin Disposal

Hydraulic paint tin crusher

Hydraulic paint tin crusher

In any workshop you inevitably end up with a paint tin disposal problem. Any paint left over from projects is usually kept for possible use in the future which, over time, results in a large number of used paint tins accumulating in the paint cabinet.

I recently embarked on a paint tin disposal program which involved checking each and every paint tin in the workshop to see if their contents were still usable. I was not surprised to find many had contents that had separated, skinned over or solidified into jelly. Some could be revived with some dedicated stirring while other tins had rusted bottoms and developed leaks when stirred. In all there were about a dozen or so tins that were beyond saving while the rest, after being stirred and date marked, were put back into the paint cabinet – for possible use in the future.

Drying paint tin contents on newspapers

Drying paint tin contents on newspapers

Paint tin disposal is a messy business. Correct disposal involves emptying any leftover paint onto newspapers, letting it dry and then discarding the newspaper. Before the tins are discarded they should be left open for a few days so any remaining paint can dry out. Garbage collectors are not impressed if two or three litres of Arctic Mint acrylic is released into their load and, more importantly, when it all ends up in a landfill paint tins eventually corrode letting their contents leech into the soil and contaminate the environment.

After following the correct procedure I was left with a dozen empty tins which could not fit into the rubbish bin. Since the majority of the volume of the tins was air I decided to flatten them. Now I guess I could have done this with a big hammer but I wanted to do it with a bit more style and finesse. A steel frame was made up that bolted onto a modified 12 ton hydraulic pipe bender as shown above right. It only took ten minutes to crush all the tins into flat discs that made their disposal a breeze. It was also tons of fun.

4 litre paint tin flattened for disposal

4 litre paint tin flattened for disposal


Flattened four litre paint tin

Flattened four litre paint tin