How one gets built !
By Jim Longstreth and edited by Andrew Tagliafico/Portland, Oregon
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.
An album of photographs from the 1996 F1d World Championships in Moscow, Idaho at the University of Idaho in the Kibbie Dome.
1996 F1d World
Championships/Kibbie Dome-University of
Idaho, Moscow Idaho (Photo Collage: Jim Longstreth)
F1d competitors and Models at the 1996 World Championships
2nd Place World Champion Cezar
Banks
F1d in holding stand
F1d in Flight at Kibbie
Dome
Jake Palmer of Salem, Oregon/Sr. World Champ
Building an F1d
as demonstrated by Bud Romak
Making
Microfilm 2. Microfilm Onto Holding Frames
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". Construction of the
F1d Model
3. Forming Curved
Pieces 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 5.
Rolling Motor Tubes and Tail Booms
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 mandrel,
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
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 temperature 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 manufacturers.
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.
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.
There is much
debate in this field as to just how long to "cure" the microfilm. In this
demonstration 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 these delicate models requires thin
cardboard or sheetwood patterns and templates 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.
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.
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.
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
pinning 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 manner 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
calculations 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:
- Building and Flying Indoor Model Airplanes by Ron Williams. This book is unfortunately out of print.
- Indoor Model Aircraft by Lew Gitlow. This book may be ordered from Indoor Model Supply. Happily, it contains much of the information in the Williams book. The Address for IMS is: Box 2020, Florence, Oregon 97439
