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A Faster Method For Stick Fuselages
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by Marcel Lavoie
Jan 26, 2007
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Over
the last several years I have devised a method of building box
fuselages from stick balsa by lifting up the longerons when
building a side frame, then placing a strip of balsa under them
for marking and cutting the uprights, together with some tools
to do the job.
The typical way people build is to place the upright strip over
the longerons, and by sighting down or eyeballing, try to obtain
the correct angles and length. That requires quite a bit of
skill and time. My approach is far easier and faster. It works
great for diagonal spacers and Warren truss type of structures
with all the angled cuts, as well as for cross pieces.
The method described here deals with 3/32" and 1/8" square balsa
strip, with some changes when using smaller and larger sizes
of balsa(more on this later). A favorite model, the Miss
Canada Sr., is used to illustrate the system. As a
side note, the method has been found to be a great help to a
fellow modeler handicapped by a stroke.
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Getting ready:
The tools for cutting spacers are very simple to make. There
are two types of cutters, but at this point the discussion centers
on what I call a MARKER/CUTTER because it is a double-ended
tool in which one end is used to mark where the cut goes, and
the other end of the tool, the cutter, finishes the job. The
tool is made by sandwiching a short (3/8") length of razor blade
between two popsicle sticks having both ends squared off. Cut
a 5/32" deep x 1/4" wide U-shaped opening in one end and square
off the inside corners, then glue a piece of blade to the other
end to serve as a marker. The blade should project from both
ends no more than 1/32". I use popsicle sticks because they
are readily available and are a convenient size (1/16"
x 3/8" x 4-1/2").
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Use epoxy for gluing the sticks together and contact cement
for the marker blade. This arrangement gives a very rigid support
for the blade, even the narrowest ones I use which are 1/4"
wide. The long "handle" helps a lot in keeping the tool close
to the vertical for nice square cuts. I use blades from our
local Dollar Store and some double edged blades. I will leave
it to the reader to work with what he has available. Better
quality blades should give better results but the tool works
beautifully to ensure accurate cuts on the first try, thus speeding
the work along greatly. A second item that is required is a
set of jig/building blocks as can be seen in the photos . These
are made from a strip of hard 1/4"(16 lb.) square balsa cut
into blocks 1/2" long with one end sanded to 90 degrees and
the other end cut to about 30 degrees. They could be made of
pine or some similar wood.
Drill pilot holes about one third of the way from the square
end to receive the pins which should be a tight fit in the hole.
Make about 30-40 of these blocks which will be used mainly on
the outside edges of the longerons. The pins remain in the blocks
permanently. This size block can be used for both the 3/32"
and 1/8" strips. A Pin Driver is next, make this from a 4-5
inch length of 1/4" diameter hardwood dowel with a 1/8" diameter
hole drilled into each end. The depth of the holes is such that
the straight pins do not penetrate my gypsum wallboard building
board and ruin the kitchen table(ouch!). A last item that is
needed is an end-grain chopping block, again hard balsa or pine,
onto which the strip is placed for cutting after it has been
marked. The two faces of the block have to be parallel of course
and sanded smooth. Always use the end-grain block as this
will give a cleaner cut as well as prolong the life of the blades.
Paint/colour all these tools (though not the faces of the
block) with a bright colour so that they will be easy to spot
among the clutter. This may seem like a long preamble but the
tools just described will be available for future building jobs.
It would be useful, nay, necessary, to provide for some type
of container to hold the knives and blocks (mine were purchased
at the same $ Store).
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And
now, for the fun part:
Compared to the standard way of placing the upright strip
over the longerons, this new way is actually fun. Protect the
plan in your usual way to prevent the structure from sticking
to it. Lay down the longerons by placing the blocks for the
top longeron in line with the upright positions. For the bottom
longeron, place the blocks about 1/4" off to the side of the
upright positions so as to allow free passage of the upright
strip under the longeron and to leave room for the marker. Glue
up the several pieces of the top longeron if it is made up of
more than one piece such as for a cabin model. For the inside
edges of the longerons a pin at every second station might suffice.
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A word here on how to hold the tool... I find that holding
it at a point about one third up from the bottom end gives a
good control in keeping the tool vertical as well as making
it easier to apply a slicing motion when needed for harder strips.
OK, so we are ready to start. Insert a strip of balsa under
the bottom longeron, then under the upper one. Line it up on
the upright position and gently push blade side of the marker
up against the top longeron to mark the angle at that end. At
this point it would be a good idea to put a mark of some sort
on the piece to ensure its proper orientation later - a "<"
pointing towards the front is what I do.
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Remove the strip and place it on the block for cutting with
the other end of the tool. Re-insert the strip under the bottom
longeron and slide it up against the top longeron which by this
time has been lowered back down onto the plan. Push the strip
up fairly tight against the top longeron and proceed to mark
the lower end of that upright. Experience will tell you how
much pressure is right. Remove, cut, and, voilą, one very neat
fitting upright.
The angles and length are perfect! You really have to work
hard to get a reject. The speed of this method and the high
degree of accuracy is miles ahead of the old ways. After one
side is built, remove it from the building board, but leave
the blocks in place to build the second side. With the jig blocks
in place it should not at all be difficult getting the two sides
the same. A little care is necessary, but then again, we always
do use a little care, don't we?
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The business of cutting diagonal cross pieces is handled in
the same manner. Since we need the top view of the plan to cut
the cross pieces, I draw a basic copy of that onto a strip of
paper and staple it a few inches above the top view of the actual
plan. The assembly of the side frames is done over this drawing
using poster board triangles about 5" high x 3" at the base
to keep the frames in line and square. An extension at the base
is bent over to a 90 degree angle to allow stapling the triangles
to the building board. For a typical model of, say, 36" span,
eight to ten of these triangles are needed. As each pair of
cross pieces is cut mark them with an arrow as before. When
gluing in place put the arrow marks towards the in- side of
the fuselage.
For smaller models using 1/16" square such as Peanuts, life
is even simpler:
The tool, if one can dare call it that, is simply a short length
of razor blade glued onto the side of a popsicle stick. Narrow
the end of this tool to 1/4" wide to accommodate tighter inside
curves on small models. Leave no more than 5/64" projecting
from the end and glue it on using contact cement. A neat way
to measure this is to push the cutting edge of the blade through
a scrap of the chosen longeron material with about 1/64" projecting.
This simple device will be used to cut the uprights and cross-pieces
while the strip is still under the longerons. For 3/16"
and 1/4" wood on larger model the type of marker/cutter described
at the outset is made bigger, eg, two strips of 1/16" ply or
pine, 3/4" x 5" long, with a 1/2" wide opening, just over 1/4"
deep. Jig blocks 1/2" square could do for these two sizes of
strip.
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So, there it is. It is not an automatic thing, but after you
get the feel of using these tools - and this will come quickly
- you will be surprised at the beauty of it. Anyone having questions
or suggestions can reach me at harrier@nb.sympatico.ca, or at, Marcel
Lavoie, 111Victoria Street, Campbellton, N.B. Canada, E3N 1J6
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