Making a torso plug.
By MikeJ

I plan to construct a mold from which I can produce an accurate one piece fiberglass torso.  Let me start by saying that this is a difficult project that might be better left to the professionals.  Fiberglass is hazardous and precautions must be taken to ensure fire and health hazards are avoided.

I made a paint & fiberglass booth to work in, note the fan in the bottom right corner, air comes into the basement through an open window, is forced into the booth by the fan and then goes outside through a window inside the booth. The booth is 10'x10'.

After hearing about long term problems of cracking, etc. with torsos constructed of wood, bondo and other materials I decided I would attempt to first create an accurate torso plug using wood, fiberglass & bondo and then use this torso to construct a fiberglass mold to allow me to make the one piece fiberglass torso.

Many thanks to all those that have answered my endless questions concerning torso dimensions.

Construction of the main torso or "plug" from which the mold will be constructed

The torso plug will be constructed from three main parts:
1.  The Conical tube
2.  The Top Dome
3.  The Bottom Dome

These three parts are separated by two .75" thick rings.

I decided to create three temporary female molds to allow production of the male fiberglass part.  The three fiberglass sections will be connected together by two .75" plywood rings.

The Tube
I cut a piece of sheet metal such that, when curled up it forms a conical tube of the correct dimensions.

Sheet Metal Template

Picture of sheet metal before it is cut out: 

Picture of sheet metal after it's cut: 

Frame to hold the sheet metal: 

Finished female tube mold, ready for fiberglass: 

Removing the mold from the fiberglass: 

The raw fiberglass tube: 

Tube with arm holes & chest panel cuts, with rings: 

Another shot of the tube section, arm sockets and chest panel trim still to come: 

The Top Dome

I make a form from waste sheet rock and plaster.  A sheet metal profile of the dome is cut and attached so that it can rotate in the form to shape the wet plaster to the correct contour.

A Picture of the dome profile and rotating assembly:

Here's a shot of the female mold for the top dome section: 

Here it is after the fiberglass has been laid: 

Here's a couple shots of the raw top section:   

The Bottom Dome

I made another form and created a new profile template to shape the female mold for the bottom section.

Here's the bottom section mold, no trim details yet:   

I decided to paint the bottom mold with a spray gloss enamel to help with the mold release.  On the top one I just greased it up with vasoline and the plaster still stuck to the fiberglass in some places.  Of course it doesn't matter that much as the plaster mold is only used once, but it was messy.

Trim added, ready for fiberglass:   

Here's the raw completed bottom dome:   

The Arm Sockets

The arm sockets are really difficult!  Here's how I plan to do it.  First cut out the hole in the tube section, then user paper to form the shape of the sides of the socket.  Use this paper template to cut a piece of sheet metal the same size.  Use the sheet metal to form a mold.  Fiberglass this mold and remove it.  Use this (inverse) mold as a master to create two fiberglass sockets.  Install them in the holes and add trim.  Simple eh?!

Here's a shot of the paper template I made: 

Here's the sheet metal mold ready to create the inverse fiberglass mold:   

Here's the inverse mold:  I will use it twice to make two arm sockets:   

Here's the two raw fiberglass sockets with the mold: 

I ended up giving away the above sockets and making two new ones.  I had sanded the mold a bit two much and had to add some bondo to regain the correct dimensions.

Here's an close up shot of one of the new sockets: 

Here's the socket with the Bondo Trim added: 

Adding the Bondo Trim

I used DaveP's technique of using foam insulation strips to make the "forms" for the chest area trim.  I then filled the forms with bondo and let cure.  After it sets up, remove the foam and sand the trim to shape.  Remember, since this must be pulled from a mold there will be some "draft", in other words the trim is wider at the base than at the crown.  The original was like this also.

The Pieces Come Together

Here's the plug with a final coat of Duratec sandable fiberglass primer.  (If the primer looks a little rough, it is.  I brush it on fairly heavy to make sure any pinholes, depressions, etc are filled.  When I'm done sanding most of the primer will have been removed.)

The primered troso plug:   

Note that I've also added the knob and microphone backplates.  Based on pictures from Michael Davis and my own research using photos and video, I finally decided not to go with the standard flat raised circle.  Instead I think I've come close to duplicating how it really was.  The knob has a ring with a slight depression, the microphone's depression is more pronounced.  Here are some pictures that I used in part to come up with this.

The Ugly Plugling

Here's the finished plug:    

It has been sanded smooth using a multi step process.  80, 120, 220, 320, 400, 600, 1000 and finally 1200 grit sandpaper was used to achieve a glossy smooth finish.  The different colors are green for fiberglass, pink for Bondo, white for glazing compond (to fill small holes) and grey for the Duratec catalyzed primer.  Weird looking, eh!?

That's it for the plug.  After about 70 hours later it's done.  Next I will make a mold from this plug.  This plug could be used for a replica as is, once the holes were cut.  But I'm not sure that the wood & bondo would hold up over time without cracks.