1/72 Scale Los Angeles Class Submarine Build, Part II

The center section of the submarines will be made from 5″ PVC pipe, but the bow and stern will be vacuformed.  Greg Prater is an old hand at this and agreed to show us how it’s done.  The first step is to laminate poplar blocks.  The center sections are glued together over a sheet of paper.  The paper allows the blocks to be split down the middle into perfect halves after they’ve been turned.
Here is the master for the stern section on the lathe.  The masters were turned to a slightly smaller diameter to allow for the thickness of the plastic sheet which will make up the finished pieces.  The flared portion on the thick (forward) end of the piece is there to help prevent the plastic sheet from wrinkling or tearing as it draws down over the master.
After the masters were split along the paper seam, the halves were placed on cardboard supports.  A strip was removed from the underside to allow the vacuum to draw the plastic tight against the lower edge of the masters through the horizontal channels in the cardboard.  This helps reduce the tendency of the plastic to drape at the bottom and keeps the plastic tight against the form.
All the masters with their cardboard spacers underneath are positioned on the vacuform table.  The suction from below draws the hot plastic sheet down over the forms, transferring their shapes to the plastic.  At least that’s the plan, we’ll see how it works!
This is the large vacuform machine we will be using.  Neither Michael nor myself have ever done this before, so Terry Hreno gave us a quick tutorial and a lot of good advice.  Terry had used this machine to pull slot car bodies before the machine was donated to the AMA.  It uses plastic sheets measuring 32 x 26 inches (81.3 x 66.0 cm).
Here Michael is positioning the plastic sheet in the frame.  We used 0.060 inch (1.5 mm) thickness for this project.  The heating element is lowered to a position just above the plastic, then the softened plastic is lowered over the forms where the vacuum draws it tight.
From below you can see the plastic as it is heated.  The sheet contorts and softens, eventually it begins to sag.  After about ninety seconds the sag is uniform and the plastic is ready.
This is the moment of forming.  The soft plastic is quickly lowered to the waiting masters and the vacuum from below draws it tight.  This is fun to watch – the shapes magically appear through the material in just a second.
There are some areas at the bottom edge of the forms where the plastic cools before it draws completely snug to the masters.  Here Michael is using a heat gun to soften any remaining areas while the vacuum is running to ensure a tight fit.
The finished product!  With the bow and stern sections formed we now have all the major hull components ready to go.

Part III here: https://inchhighguy.wordpress.com/2019/03/22/1-72-scale-los-angeles-class-submarine-build-part-iii/