There are 2 major preparatory steps to laminating
outlines. First, you need a form (or template) around which to
laminate the outline, and second you need suitable strips of balsa. Preparing
the templates:  The
simplest method for creating a template is to take a photo-copy of the
plan, glue it to suitable material and then cut the template to match
the inside shape of the laminated outline. Depending on the size of
the template needed, I use either 1.6mm (1/16") balsa sheet - as
shown in the picture at left - (great for Peanut scale models) or
stiff cardboard (good for larger models). I use a glue-stick to attach
the photo-copy to the balsa or cardboard.
Depending how you will
hold the laminations onto the template while they are drying, you may
also want to have some way of holding the laminations onto the form.
The simplest method is to hold them on yourself while the glue dries
(I sometimes do this for small laminations, and using fast-drying
cellulose-based glue like C23 or Ambroid). Or you can use masking
tape, or rubber bands. For rubber bands, I sometimes drill several
holes through the template around the outline and insert some short lenghts of bamboo
skewer (around 1" long) around which rubber bands can be wrapped. Outlines
are usually symmetrical, so you only need to make one template for the
2 wingtips, one for the 2 tailplane halves and one for the fin/rudder.
Shown below are the templates I used for the Amsco putlines. I keep
all my tip templates, in case a repair is needed - I can make another
outline and splice in the damaged section.  
Preparing
the balsa strips: For Peanut scale models I use 2 or 3
laminations of 0.8mm x 1.6mm (1/32" x 1/16"). The Amsco
outlines in the pictures used 2 laminations on the wingtips and 3 for
the tailplane. For models up to around 760mm span (30"), I use 4
or 5 laminations of 0.8mm x 2.4mm (1/32" x 3/32"). Make sure
the balsa is straight-grained, as variations in the grain can lead to
cracks. Also, select balsa which is relatively soft. I generally soak the strips of balsa in warm water. Some
people use ammonia, but I don't like the smell! Ammonia may work
better (it softens the cells in the balsa), but water works fine for
me. Sometimes I even leave the strips dry (the Amsco outlines in the
photos were done without soaking), but this relies on good balsa. I
have been able to get 3 strips of 0.8mm balsa (1/32") to bend
smoothly around radiuses of 7mm (9/32") withouth cracking when
laminated dry (when done with care). When soaking the strips, I
dry them on a rag or sponge before applying any glue. Laminating
and drying: The next step is to apply the glue and let
the completed laminations dry around the form. When I use slower setting
glue like PVA (white glue) or Aliphatic Resin (yellow), I apply glue
to all the strips and form them into a "stack" before
bending them around the form. When using faster setting glues, I do
the strips one at a time. I never use Cyanoacrilate glue for
laminating... I find it hardens the balsa and makes it difficult
to sand into the correct cross section.  Once
I have the strips all glued and bent
around the form, I use rubber bands or masking tape to hold them
in place. The bands or tape are spaced carefully around the outline, so the strips
are firmly held in place and not able to flex away from the form.
Sometimes I need to re-do sections of tape, removing it and starting
fresh from the end to ensure it is right. Time spent here
ensures a good finished outline once it is dry. Masking tape has the
advantage that it does not crush the strips, as rubber bands sometimes
do. In the picture you can see 4 strips of 0.8mm x 2.4mm drying on a
form while held with rubber bands.
If I don't get it right and
a small gap between the laminations results, I squeeze C23 carefully
into the gap and this usually fixes the problem. Sometimes I have to
start over, but every time you learn a little more as you go. 
Here's another shot of the outline for the tailplane of my Amsco
monoplane peanut. This is 3 layers of 1/32" by 1/16" balsa.
You can see a slight gap in the laminations at the leading edge (on
the right hand edge of the photo). I fixed this by squeezing C23 (Ambroid)
into the gap and holding it closed with a peg while it dried.
Thoughts
from others: This is just my experience on laminating
outlines. There are many others who have used this technique and have
shared some of their wisdom. Below is an earlier posting I
discovered by doing a Google search on "laminated+outlines"... Subject: Laminating balsa outlines
From: "Robert L. Clemens" <RClemens@compuserve.com>
Date: Sat, 6 Dec 1997 09:51:13 -0500
Gentlemen,
I downloaded the following piece on laminating balsa outlines from one of the on-line free flight sites. In light of all the
discussion here in recent weeks about laminating, I thought it would be of
interest. I've not tried this technique, but it makes great sense and I will
be
using it the next time I do laminated tips, etc.
LAMINATING BALSA OUTLINES
By Steve Hales, Scale Oldtimers Squadron, FAC Following is a method I have used for several years now, but first
a little history. Before trying to laminate balsa I read everything
I could find on how to do it. The accepted method was to first soak your
strips in ammonia, then attach to the form and let it dry. After it dries,
glue each strip together. I did this and found that it was a real chore
using water based glues as the strips would open up and would have to be
reattached to the form. Also on light balsa the glue would be hard
to sand compared to the balsa. Then I started using cyanoacrolate
glues while the balsa was still on the form. Boy, did this make them hard
to
sand, added a lot of weight, and half the time I glued the darned
thing to the form even though I protected it with wax. But it was faster!
After all this experimenting I decided that what I needed was a one-step soaking/gluing process to make laminating much easier. So
I started testing all of the water-based glues for compatibility
with ammonia. Most of the glues would curdle in ammonia, but I finally
found one that would dissolve!
After more experimenting I found that it didn't destroy the glue; after the ammonia evaporated it would still bond the wood together.
This was perfect! The glue is Wilhold industrial grade woodworking glue. It is a white glue in a bottle with red lettering. It looks
very much like all of the other white glues. (Note: Elmer's Carpenter's Wood Glue mixes with ammonia too.
Sig Bond does not. B.C.)
Instructions:
- Get everything ready to laminate, cut strips etc.
- Mix a small batch of ammonia and glue to a watery consistency.
- Take a paint brush and paint the mixture onto the strips.
- Wrap and attach the strips to your form and let it dry.
- Take them off the form and install on your model.
Benefits:
- The ammonia dries faster than water.
- The finished piece has a very even texture.
- Even when using 4 lb. balsa I can't tell the finished piece is laminated.
- It sands like regular balsa.
- It adds very little weight.
(Downloaded from FREEFLIGHT on the World Wide Web http://www.ff.grci.com/index.html)
Bob Clemens
Rochester, NY
Graham Knight offered the following suggestion via the
FFML if you want to speed the process of drying the laminated
outlines:
If you are in a hurry, you can bake the parts dry in a
microwave (when using PVA or Aliphatic, has to be water soluble glue), a minute or
two at low power is usually enough, experiment on scrap to determine the
correct time and nuke in short bursts checking regularly. The template can
be scrap wood or card, you'll need to use masking tape to hold the
laminations in place, no pins in the micro!
And another thought from Niel Dennis
("Wombat" on the FFML):
I always use a "tension strip" on the
outside of any laminae when bending. This is a flat piece of ribbon or
lace (shoe lace works) that is held tightly against the outside of the
balsa as it is pulled around the curve. This compensates for the
tension/compression created by the bend. That way you can make a tight
bend with no problems (an old woodworkers trick).
In light of this comment, you could actually cut
an inside and outside template for the curve you want,
and "squeeze" the laminations between them... needing no
tension to hold them in place. Interesting thought... have to try that
some time.
|
