Guide to Building Vacuform Models
By Walter Mertins
The purpose of this article is to present my guidelines on building a
vacuform model. These techniques are by far not set in stone, they are
simply my way.
I would have never ventured into building vacuform kits if it wasn?t
for Clinton Groves. Everything I have learned about building vacuform
kits I learned from watching Clint?s video, ?Building Vacuum
Formed Models? and by reading Russell Brown?s Airline Modeller
magazine, the Ailiner Modelling Digest (AMD) and Welsh Models instruction
sheets. If you do not own a copy of Clint?s video, keep writing
to him so that he will consider re-releasing it on CD-ROM format.
The materials that I use were all purchased at my local Hobby Lobby and
hardware store. I do not know the equivalent name for these products overseas,
but as a modeler you can decide what works best for you. I did!
I am not promising that the techniques I am introducing are the best way
for others to build vacuform models; they are simply what works best for
me. I hope they help you out as well!
Good luck and enjoy!
- flat surface (I use a 9? x 11? glass cutting board with
little plastic pegs on each corner)
- sandpaper ( I do not use water-resistant sand paper but 60 grid 3M dry
- plastic (liquid) welding cement (I prefer Ambroid Pro-Weld)
- plastic cement (again, Ambroid )
- hobby knife (X-acto) or any other modeling knife
- fine tooth hobby saw (X-Acto fine is what I use)
- epoxy (slow-curing 20 minute works best for me as it flows well)
- masking tape (I like 3M because it is not too sticky)
- A permanent marker (Sharpie medium point)
- cyanocrylate glue (I use plain old Krazy Glue)
I start by studying the plans and deciding what it is that I want to do
with the model: Am I going to modify the existing model to make a larger
or smaller variant of the subject? Or I am simply going to build it as
After deciding, I trace the outline of all the model parts while they
are still on the styrene sheet with a medium-point Sharpie. I try to mark
the parts in such a way that half of the black line is on the plastic
part and half is on the styrene sheet.
the major sections using an X-Acto knife; I prefer a slightly used blade.
Score deep but not all the way through into the styrene and then, using
a downward motion, snap the plastic apart.
Place the knife at an angle to the individual parts and score around their
contour. Again, score hard but not all the way through. Always carry all
the scoring lines all the way out of the sheet. This will facilitate snapping
on strongly to the part with your weak hand, use your dominant hand to
snap the unwanted plastic away from the part. Once the first break is
done, the plastic will almost peel off.
Only cut all the way through on the parts that are too
small to hold on to.
When cutting/snapping identical parts like engine halves, horizontal stabs,
etc., I always score a number on the inside of the part to identify the
Welsh is pretty good about placing matting parts side by side, but once
you cut them all from the styrene sheet confusion begins.
all the parts and do not worry about excess plastic since it will be sanded
away later. Do take extra care around flap tracks, etc.
Do not be afraid, snap away and show the kit who is in charge. Besides,
if you break the plastic, you can always fix it by gluing it back. Remember,
we are modelers and gluing is what we do best!
With a little patience, you will have this step mastered in no time.
I do not spend much time with the props unless I really have to. Aeroclub
makes metal replacement props for most of the Welsh kits.
Ok, here we go! So far, so good. Here is what separates the vacuform model
builders from the injection model builders.
you finish snapping all the parts from the plastic styrene sheet, you
will notice that there is a white line all the way around the parts. (White
in contrast to the black Sharpie line you drew, remember?)
Well, this is the styrene thickness, and exactly what you have to sand
away. I hope that you haven?t just finished trimming your fingernails
because when you are done with this step your fingernails will be shorter,
or tape an 8 ?? x 11? sheet of 60 grid sandpaper to the cutting board.
I leave two edges of the paper free of masking tape.
is a good time to get some strong adult refreshment!!!
Then, cut lots of 2? long or longer
strips of masking tape. Make small handles with the tape and attach to
all the parts. For the little parts,
improvise, but still make handles for them.
hope that by now the refreshment is taking effect, because I know this
is why most modelers do not like building vacuform kits: THE SANDING.
the black Sharpie line represents the outer edge of the actual part; all
the white stuff under
it is excess plastic. Not much under the fuselage, but
lots of it under engine halves, wings, and horizontal and vertical stabilizers.
coarse sandpaper will cut the plastic really fast, so try to sand applying
equal pressure on the surface of the parts. Use circular motions while
sanding and check often for proper fitting and to make sure you are not
usually start with the fuselage bulkheads. Do NOT sand them too much.
They usually turn out to be undersized if sanded to shape. Most of the
time, I dry fit them to one half of the fuselage to make sure they are
going to have the proper diameter.
I move on to the fuselage. I sand both halves a bit a time to be able
to dry fit them as I go. Again, do NOT oversand the fuselage halves. This
will create fit and shape problems. It IS possible to correct an oversanded
fuselage by adding a piece of styrene plastic, but it is best if you do
not go there at all. It is better to have a fuselage that is a bit larger
in diameter than an ugly, skinny-looking one.
Always try to apply equal pressure on all the parts as you sand.
you can see how important it was to trace the vacuform parts with a black
permanent marker before cutting them out of the sheet. As you sand the
fuselage and all the other parts down, you will notice that a tiny white
strip of styrene plastic starts to peel off the parts. I remove that excess
plastic off with my fingernail
or whatever is left of
it, then continue sanding lightly until the white
line is all gone and you end up with a nice solid black edge. At that
point, you are done sanding the fuselage. I cannot overstress the importance
of dry fitting your parts as you sand. You can always sand some more but
if you oversand you have just created more work for yourself.
So far, so good, right? Now, we move to the wings.
wings are a bit tricky. You?d probably like
just sand them down flat on the paper, but you CANNOT
trailing edge must be thinner than the leading edge. I found that the
best way to do this is to sand the
flat on the paper just for a few passes. Then I grab the wing
and sand the trailing edges on one of the straight edges of the cutting
some of the plastic off, sand the whole wing flat on the paper.
Do this to both the top and bottom halves and dry fit them as you sand.
the little white line of styrene will start curling up and separating
from the wing. This means you are almost there. Sand a little extra off
the wing tip, then the trailing edge. The reason you want to
the wing flat again is to avoid leaving a wedge-shaped trailing edge.
Dry fit the parts as often as possible.
now, if you are not completely
in plastic shavings, you have done something wrong.
this point you have fuselage and bulkheads ready. The placement of the
bulkheads is very important. I usually make extra ones for re-enforcement,
especially around the wing fairings. If you are planning to stretch or
shorten the model, make even more bulkheads; this will double the strength
of the fuselage joints. Cut a little rectangle-shaped notch at the top
and bottom of each bulkhead. This is done to allow the epoxy used to re-enforce
the fuselage joint to flow freely back and forth through the whole length
of the fuselage. Make sure you sand the points that will form as a consequence
of the cuts down a bit. These pointy ends could deform the fuselage shape
when you glue the halves together.
the bulkhead to one of the fuselage halves. Do not be shy on the use of
glue; the more the better. Just do not melt them! Make sure they are straight
and perpendicular to the fuselage. I let them dry for about four hours
before I start fitting the other half of the fuselage on.
Engine halves and nacelles are very easy to do. Just lay them flat on
the paper, apply equal pressure with your fingers, (which by now should
be nice and numb with perfectly round fingernails), and sand away. These
parts won?t need too much sanding so go easy AND DRY FIT YOUR PARTS.
Did I mention yet how important it is to dry fit your parts?
the bulkheads have dried completely, test fit the other fuselage half.
Make sure that the bulkheads have the proper shape; otherwise, they will
distort and misalign the fuselage.
the fuselage halves together. Use thin strips of masking tape to make
sure of the proper matting of the fuselage.
the fuselage has dried, it is time for Clint Groves? ?river of epoxy?
usually cut a hole on a wing fairing or on the belly where the
wing will be mated Then
I use 20-minute
epoxy because it is not so viscious and flows
I mix about 5 ml of epoxy for a small fuselage and about 10
one. Pour the
into the fuselage and then make sure
along the whole length of the fuselage. Rock the fuselage back and forth,
making sure that some
of the epoxy travels around the bulkhead as well.
that epoxy does not fuse to the plastic. It only creates a rigid bond.
It is brittle and if excess force is applied to the bond, it will break
cleanly off the plastic and rattle around inside the model.
the epoxy dries, flip the model and do the bottom/top halve.
I use cyanocrylate glue (Krazy Glue) to attach the metal parts like props
and landing gear to my models.
See, it wasn?t so bad after all. It is a long and a bit tedious of a
procedure, but once you get this far, you now have your basic injection
model kit. Use the same method/techniques that you use for building your
injection models from here on. Just remember that vacuform kits are more
delicate than injection kits, so be nice to them and you will end up with
a gorgeous-looking model. The more vacs you build, the easier they get.
Questions or comments may be sent to waltmert[at]hotmail.com.