1996 F1d World Championships/Kibbie Dome-University of Idaho, Moscow Idaho (Photo Collage: Jim Longstreth)
How
one gets built !
Several years ago former F1d World Champion Bud Romak came to Portland, Oregon, at the request of a group of Northwest modelers and demonstrated his construction techniques for this most challenging category of competitive indoor models. The seminar was hosted by Oregonian Dave Hagen at his home over a weekend. During that time Bud Romak built a complete, flyable, F1d model. I took the following series of photographs during that symposium.
For those not familiar with this type of indoor endurance model let me give a brief description here. The term "F1d" refers to the FAI rule category. I don't have the rule book in front of me, but basically the models weigh in at minimum of 1 gram and a maximum of 2 grams. The wingspans are 65cm, or 25-1/2", long and a chord of 8" to 10". The propellors are 20" to 24" inches in diameter. The flying surfaces and the propellor are covered with "microfilm", which will be described later. The motor stick is a hollow tube of rolled balsa, and the model is braced with a superfine tungsten wire or kevlar fiber. Some competitors have developed spring mechanisms operated by the torque of the rubber band motors to effect variable pitch propellors!
World Championships are held every 2 years. Flights approaching 50 minutes are required to be competitive. The Kibbie Dome at the University of Idaho, in Moscow, Idaho, is one of the favored US flying sites and is pictured below. The balloons dotting the photo are used to steer the models at altitude in the event they are drifting into hazard. There are several models aloft in this picture, but due to their transparent covering and almost non-existent structure they are nearly invisible.
1996 F1d World Championships/Kibbie
Dome-University of Idaho, Moscow Idaho
(Photo Collage: Jim Longstreth)
2nd Place World Champion Cezar Banks
F1d in holding stand
F1d in Flight at Kibbie Dome
Jake Palmer of Salem, Oregon/Sr. World Champ
as
demonstrated by Bud Romak
Making
Microfilm
1.
Pouring Microfilm 
Building
and F1d starts with the making of the covering material called Microfilm.
A shallow tank
of water is allowed to "cure"- for 12 or more hours allowing volatile chemicals
to escape. The ideal water temp-
erature is between 68 to 74 degrees F. The microfilm based on nitrate
aircraft dope with plasticizers added. There
are commercial solutions available, and most of the competitors rely on
their favorite of the two best film manu-
facturers.
A small amount of
the solution is poured out onto the surface of the water in one
smooth,
extended linear motion.. The solution spreads out on the surface
of the water to a nearly
mono molecular thickness. It is allowed to "set" on the water's surface
for several minutes.
2.
Microfilm Onto Holding Frames 
In
the photo above, the excess film around the frame is being gathered around
the outside of the
holding frame prior to the attempt to lift the holding frame off the surface
of the tank.
This
is the point at which most would-be F1d flyers bail! One needs at
least 4 good frames
of Microfilm to build a model. And one needs at least 4 to 6 models
to compete, not to mention
1 or 2 dozen props of various diameters and pitches.
The
proper thickness of the Microfilm is judged by the colors it refracts.
"Good" film is in
the blue to gold range. The tricky part of transferring the film
to the holding frame is the
breaking of the surface tension of the water. Breaking that surface
tension without tearing the film
is a challenge. But once you have successfully lifted some frames,
you then set it aside to "cure".
There is much debate in this field as to just how long to "cure" the microfilm.
In this de-
monstration the film was allowed only a few hours before it was put on
the model. It seemed to
work fine at the time but did warp badly later on. It is always best
to have an aged supply of film
on hand. A year of "curing" is not too long.
Construction of the F1d Model
3.
Forming Curved Pieces 
Construction
of these delicate models requires thin cardboard or sheetwood patterns
and tem-
plates of the flying surface outlines. The wood for wing spars is
about .030" thick so it is quite
flexible, particularly when wetted and formed around a template, as in
the first photo. After the
wood has dried and the curve has set, the second photo above shows the
placement of the curved
elevator outline around the building template. The slots in the template
are for the placement of
the 3 ribs in the horizontal stabilizer.
The
stabilizer outline is formed in 2 pieces. Bud is adding
second outline piece. They are spliced in the middle, and then the
ribs are added. Just like any
indoor endurance model, the ribs are sliced in slender curves using a template
and glued in place
on the structure.
Note: Bud built each flying surface and then covered it. My photos show that progression, though one could build and cover in any sort of sequence your personal building habits dictate.
4.
Applying Microfilm 
In the first of the 2 photos above, Bud
is applying water to the stabilizer structure. Water is a fine
adhesive for Microfilm. As the water dries it pulls the film into
the pores of the wood. In the
second picture, he has simply placed a holding frame with
Microfilm over the stabilizer structure
right on the building board.
The
covered stabilizer is removed from under the film on
the holding frame by running a hot wire, just to the outside of the covered
structure. The
finished stabilizer is then VERY CAREFULLY set aside in a safe place.
I noticed that Bud used a
thin knife blade to lift the piece off the board and carried the finished
stabilizer in the flat of his
hand.
Once
touched the Microfilm will have a hole. Indeed it seemed impossible
that one could build
such a model without making holes, and that was the case. The model
had several patches in it by
the time it was finished.
5. Rolling Motor Tubes and Tail Booms
The
motor tube and tail booms are rolled not unlike a cigarette. The
motor boom is cylindrical
whereas the tail boom is a slender cone. Sheets of balsa about .013"
thick are used to fabricate the
motor stick. After a 10 minute soak in water the sheet of wood is
rolled onto a 1/4" round x 18" long
form or mandrel.
In
the first photo, Bud has laid the mandrel, a piece of aluminum tubing of
appropriate length on a
length of silkspan. He has rolled a little of the silkspan around
the mandrel and is wetting the
silkspan, a model tissue covering material.
In
the second photo, the sheet of wood for the motor boom has been tightly
rolled over the man-
drel, between it and the wet silkspan. There is sufficient wet silkspan
to hold all in place while
drying.
The
next 2 photos show the same process, but for the tail boom. As this
structure is a tapered
shape
it pivots, when rolled, around the thinner tip portion. Hence the
different position of Bud's
hands in these last 2 pictures from the first.
6.
Assembling the Tube and Booms 
The motor tubes and
tail booms need to have the seam edges glued together. The silkspan
has
been removed, and the balsa placed back around the mandrel. The seams
often dry off center.
Before gluing the seam must be straightened. Bud has done this and
is gluing the seam.
Here,
in these 2 pictures, the 1990
US F1d Team Manager, Andrew Tagliafico, demonstrates the use of jigs for
aligning and gluing the
seams to the rolled balsa forms used on F1d models.
7.
Building and Covering the Main Wing
The
Main Wing is built in much the same way as the stabilizer, but
with a series of short pieces of 1/16th balsa instead of a template
to provide a backstop for pin-
ning the wood forming the wing structure in place. The building
board Bud is using has the drawn
outline of the Main Wing on it. The wing is basically rectilinear
in outline, save for a slight rounding
of the forward edge of the wing tip. This was done by wetting the
wood and then bending it directly
over a hot light bulb. The heat of the lamp evaporated the moisture
and set the curve in one motion.
When the wing is
finished, it is weighed. All the parts of the model have
been weighed as construction progressed. It is critical that the
sum of the parts weigh as close to
1 gram as is humanly possible.
Once
more the finished wing frame is wetted and the Microfilm laid over the
structure. Note that
the wing is still flat. The dihedral is added to the wing and tips
after the covering, and before the
rigging.
The finished wing
is set in a holding jig prior to rigging. 
Note: The sequence of rigging was not photographed due to the fact that the wire or fibers are virtually invisible. There are drawings of the rigging of F1d models in the books listed in the bibliography.
8.
Building and covering the Propellor
The
propellor is both the source of thrust and a flying surface. It is
built in just the same man-
ner as the wing or stabilizer, but with the added complication of the pitch.
To ensure proper pitch
and alignments, the prop form is a series of protractors made of balsa.
After doing the pitch calcu-
lations for a particular diameter/pitch configurations, the protractors
are adjusted and secured. The
prop spar is laid on the protractor centerlines. The outline of the
prop blade has been formed on a
jig like the stabilizer. This outline is pinned in place on the protractor
prop form. The ribs are then
attached at each protractor station.
In the first photo,
you can see the curve of the helical pitch the protractors form.
In the second
photo you can see how each blade is covered with Microfilm. Unlike
the other flying surfaces
the prop is applied to the film in an angular, rotational, motion.
This is necessary due to the changing
surface curvature of the prop blades. The Microfilm on the holding
frame is divided into sections
with masking tape. This allows for the preservation of the rest of
the film on the frame, and thus
the covering of several blades.
Test Flights!
9. 
Note
the extra holding frames of
Microfilm resting on the fireplace. You can see something of their
refractive colors. Also, I didn't
photograph the construction of the rudder. It has no airfoil, and
is no different in construction from
the other pieces. The prop is held in place at the front of the motor
stick by a hand formed wire
thrust bearing. The rudder and elevator are glued in place and braced
with the ultra-thin tungsten
wire mentioned earlier. The main wing is removable, and fits into
paper tube sockets glued into the
motor stick.
10. Handling
an F1d
Andrew Tagliafico's
F1d in a holding stand
Lew Gitlow walks VERY SLOWLY with his F1d!
His F1d in flight
Suggested Reference Books: