Large Scale Floats - 2012/05

www.ModelAviation.com May 2012 Model Aviation 47
Large-Scale Floats
by Lawrence Klingberg
This 54-pound, 1/3-scale Sopwith Schneider with stickbuilt
floats was on display at the Lake Havasu event.
Observations from an award-winning designer
I48 Model Aviation May 2012 www.ModelAviation.com
Photos by the author
Right: The front of the floats is shown with
spreader bars and mounting screws installed.
Hard points are epoxied into the foam.
Close-up of brace wires and 3/16-inch K & S steel fuselage
mounting rods. The crossed wires are taped to prevent
metal-to-metal interference.
Below: Strut detail and mounting arrangement.
Struts are covered with balsa and sanded, then
covered with Solartex.
In 1989, it was my good fortune
to attend the first Schneider Cup
Giant Scale Re-Enactment. The
event was held at Lake Havasu City,
Arizona, and was the brainchild of
Bob and Katie Martin. The Desert
Hawks Radio Control Club members
helped put on a spectacular waterflying
event then and in subsequent
years.
After observing this first event
and others, I thought it was time to
start building some large seaplanes
of my own. My observations of the
water-flying events led me to a few
conclusions about what kind of
seaplanes have the best chance for
competition and survival in a water
contest such as the Schneider Cup-class
of aircraft.
I felt that a biplane on floats, sitting
high off the water with clearance for
the propeller, was the best choice for
success. Most of these early airplanes
had undercambered wings, which
created substantial lift. My first choice
of an airplane to build for the Schneider
was a 1919 British Fairey IIIC biplane,
registered as G-EALQ. It was to be 1/4 scale.
It took roughly a year to draw the
plans and finish this large project for
the 1992 event. The airplane “flew right
off” the drawing board. Since then I
have built three more 1/3-scale aircraft:
a Sopwith Schneider 1919 biplane
(G-EAKI) and two 1/3-scale Sopwith
Pups, and built floats for all of them.
The purpose of this article is to show
how the floats can be constructed and
attached to large-scale airplanes. Floats
of this size must be made as strong and
as waterproof as possible.
Types of Floats
I’ll describe two methods I have used
to build large floats and what has worked
best for me. One is the built-up or stick
construction method. These floats are
constructed much like a fuselage with
1/4- x 1/4-inch balsa or spruce pieces
and some gussets at each joint to hold
everything together.
The second method of construction,
the foam float, is much less timeconsuming.
These floats are cut from
foam using the hot wire method.
Temporary templates are fastened to the
foam to guide the hot wire to conform
to the outline of the float.
Whatever type of float you choose
to build, the first thing to do is design
the side and top views. The shape of
the early floats can usually be found
in three-views or in books about the
www.ModelAviation.com May 2012 Model Aviation 49
The finished floats are installed on the airplane
with brace wires leading to the wing for increased
strength. The logo is hand painted.
particular airplane being modeled.
One thing to consider is the
location of the spreader bars and the
point on the floats where they are
to be attached. I usually make the
spreader bars using 1/4- x 11/4-inch
aluminum extrusion stock. They are
streamlined with balsa stock that
has been glued on and are sanded to
an airfoil shape.
The main struts that attach
between the fuselage and the
floats are made from 3/16-inch K
& S steel rod and the rods have
1/16-inch steel pieces brazed onto
the bottoms where the strut meets
the float. These pads (or feet) are
attached with two 8-32 pan head
screws, which go through the
spreader bars.
The wire struts that go
between the floats and the
fuselage are covered with balsa
and sanded to an airfoil shape.
They will later be covered with
Solartex and painted. With this
assembly method, everything
can be taken apart and, in case
of accidental damage, repairs are
easy to make.
Four aluminum plates with
ears on each end are made to fit
between the strut foot and the
float. These “deck plates” are
for attaching the wires for cross
bracing between the floats and
for the brace wires that extend
out to the wings.
Building the Floats
After you decide which method of
float construction to use and you have
the floats either framed up or cut from
foam, install the “hard point” in them.
This is the area where the strut feet are
attached. It must be extremely strong
because of the impact of landing on
water.
On my floats, the “pockets” where the
spreader bars slip through are made of
cedar wood pieces and are epoxied into
place. It is a good idea to put a piece of
cedar or spruce at the front and rear of
the float; this makes a strong area on
50 Model Aviation May 2012 www.ModelAviation.com
This 1/3-scale stick-built float is used on
a Sopwith Schneider seaplane. Note the
gussets and extra strength built in at the
spreader bar and strut attachment points.
The aft end of the float shows the inner sheeting
installed. After sides and bottom are sheeted, run
a bead of 30-minute epoxy along all lower seams
to keep water out.
Below: A front view
of the stick-built float
shows 1/4- x 1/4-inch
sticks throughout. Use
epoxy on all joints.
The balsa nose block
is placed after the
sheeting is done.
which to glue the sheeting. These pieces
need to be cut and shaped in their
respective locations.
When the floats are ready to apply
the thin plywood skins, I suggest sewing
approximately six sandbags of canvas
or cloth. Make them roughly 9- or
10-square inches. Use these to hold
the skins down tight during the gluing
process. The sandbags conform to the
float’s shape and ensure that all areas will
be well glued.
I cut the skins so they are
approximately 1/8 inch over size and
epoxy them on the
sides first. After the
glue sets, sand off
all excess sheeting
and then glue on
the bottom piece.
If your floats are
constructed from
sticks, run a bead of
30-minute epoxy
along the inside of
the lower longerons
or “chines” as a fillet
for strength and to
protect the seams
from water leakage.
The top skin is the last to be glued
on. Before doing this, check your work;
this is your last chance to correct any
oversights. If everything looks fine, glue
on the top skin and sand it around the
edges.
If the floats are cut from foam, put
in the usual hard points, nose, and rear
wood pieces made from spruce or cedar.
The foam floats are covered in the same
manner as the stick floats, but the thirtyminute
epoxy will have to be mixed and
applied rapidly.
Spread the epoxy on with a credit
card and then carefully place the skin
and weight it with the sandbags to hold
everything in place. After all of the sides,
bottom, and top pieces are glued on,
sand the edges and clean them for the
finishing process.
Finishing the Float
Now it is time to sand all of the float’s
surfaces and get them ready to cover. I
usually brush on two coats of Balsarite
and then iron on Solartex, making a
1/4-inch overlap seam on all corners to
ensure that there will be no water leaks.
www.ModelAviation.com May 2012 Model Aviation 51
Left: The rear float detail shows attachment and water
rudder/hinge arrangement.
Above: The Fairey
IIIC’s float shows the
deck plates and strut
attachments. The text
describes creating
the rivet detail and
seams.
Left: These stickbuilt
floats are on
the model of a 1919
Fairey IIIC Schneider
Cup airplane. Note
the odd shape of the
floats. The struts
are made from
hardwood.
The floats look nicer if you create
panel lines and rivet detail. Lay out the
float lines with a ruler, then add glue
dots 1/4 inch apart to simulate the rivets
at the seams and every 4 or 5 inches
along the length of the float.
When this is accomplished, spraypaint
the floats with Sig Butyrate dope or
Rust-Oleum. Silver or gray is usually
the best color to use. Another goodlooking
finish is to put a light stain on
the plywood sheeting and then a coat of
varnish. Factory logos are a nice touch,
such as the ones used on the Blackburnbuilt
Babies of World War I.
Along with the provided pictures and
sketches, the average modeler should
have no trouble in building a nice set of
floats for his or her big seaplane.
Good luck and many happy landings!
—Lawrence E. Klingberg
8111 Dartmoor Dr.
Huntington Beach CA 92646
SOURCE S:
Balsarite
www.coverite.com
Solartex
http://shop.balsausa.com/category_s/119.htm
Sig Butyrate Dope
(800) 247-5008
www.sigmfg.com
Rust-Oleum
www.rustoleum.com

www.ModelAviation.com May 2012 Model Aviation 47
Large-Scale Floats
by Lawrence Klingberg
This 54-pound, 1/3-scale Sopwith Schneider with stickbuilt
floats was on display at the Lake Havasu event.
Observations from an award-winning designer
I48 Model Aviation May 2012 www.ModelAviation.com
Photos by the author
Right: The front of the floats is shown with
spreader bars and mounting screws installed.
Hard points are epoxied into the foam.
Close-up of brace wires and 3/16-inch K & S steel fuselage
mounting rods. The crossed wires are taped to prevent
metal-to-metal interference.
Below: Strut detail and mounting arrangement.
Struts are covered with balsa and sanded, then
covered with Solartex.
In 1989, it was my good fortune
to attend the first Schneider Cup
Giant Scale Re-Enactment. The
event was held at Lake Havasu City,
Arizona, and was the brainchild of
Bob and Katie Martin. The Desert
Hawks Radio Control Club members
helped put on a spectacular waterflying
event then and in subsequent
years.
After observing this first event
and others, I thought it was time to
start building some large seaplanes
of my own. My observations of the
water-flying events led me to a few
conclusions about what kind of
seaplanes have the best chance for
competition and survival in a water
contest such as the Schneider Cup-class
of aircraft.
I felt that a biplane on floats, sitting
high off the water with clearance for
the propeller, was the best choice for
success. Most of these early airplanes
had undercambered wings, which
created substantial lift. My first choice
of an airplane to build for the Schneider
was a 1919 British Fairey IIIC biplane,
registered as G-EALQ. It was to be 1/4 scale.
It took roughly a year to draw the
plans and finish this large project for
the 1992 event. The airplane “flew right
off” the drawing board. Since then I
have built three more 1/3-scale aircraft:
a Sopwith Schneider 1919 biplane
(G-EAKI) and two 1/3-scale Sopwith
Pups, and built floats for all of them.
The purpose of this article is to show
how the floats can be constructed and
attached to large-scale airplanes. Floats
of this size must be made as strong and
as waterproof as possible.
Types of Floats
I’ll describe two methods I have used
to build large floats and what has worked
best for me. One is the built-up or stick
construction method. These floats are
constructed much like a fuselage with
1/4- x 1/4-inch balsa or spruce pieces
and some gussets at each joint to hold
everything together.
The second method of construction,
the foam float, is much less timeconsuming.
These floats are cut from
foam using the hot wire method.
Temporary templates are fastened to the
foam to guide the hot wire to conform
to the outline of the float.
Whatever type of float you choose
to build, the first thing to do is design
the side and top views. The shape of
the early floats can usually be found
in three-views or in books about the
www.ModelAviation.com May 2012 Model Aviation 49
The finished floats are installed on the airplane
with brace wires leading to the wing for increased
strength. The logo is hand painted.
particular airplane being modeled.
One thing to consider is the
location of the spreader bars and the
point on the floats where they are
to be attached. I usually make the
spreader bars using 1/4- x 11/4-inch
aluminum extrusion stock. They are
streamlined with balsa stock that
has been glued on and are sanded to
an airfoil shape.
The main struts that attach
between the fuselage and the
floats are made from 3/16-inch K
& S steel rod and the rods have
1/16-inch steel pieces brazed onto
the bottoms where the strut meets
the float. These pads (or feet) are
attached with two 8-32 pan head
screws, which go through the
spreader bars.
The wire struts that go
between the floats and the
fuselage are covered with balsa
and sanded to an airfoil shape.
They will later be covered with
Solartex and painted. With this
assembly method, everything
can be taken apart and, in case
of accidental damage, repairs are
easy to make.
Four aluminum plates with
ears on each end are made to fit
between the strut foot and the
float. These “deck plates” are
for attaching the wires for cross
bracing between the floats and
for the brace wires that extend
out to the wings.
Building the Floats
After you decide which method of
float construction to use and you have
the floats either framed up or cut from
foam, install the “hard point” in them.
This is the area where the strut feet are
attached. It must be extremely strong
because of the impact of landing on
water.
On my floats, the “pockets” where the
spreader bars slip through are made of
cedar wood pieces and are epoxied into
place. It is a good idea to put a piece of
cedar or spruce at the front and rear of
the float; this makes a strong area on
50 Model Aviation May 2012 www.ModelAviation.com
This 1/3-scale stick-built float is used on
a Sopwith Schneider seaplane. Note the
gussets and extra strength built in at the
spreader bar and strut attachment points.
The aft end of the float shows the inner sheeting
installed. After sides and bottom are sheeted, run
a bead of 30-minute epoxy along all lower seams
to keep water out.
Below: A front view
of the stick-built float
shows 1/4- x 1/4-inch
sticks throughout. Use
epoxy on all joints.
The balsa nose block
is placed after the
sheeting is done.
which to glue the sheeting. These pieces
need to be cut and shaped in their
respective locations.
When the floats are ready to apply
the thin plywood skins, I suggest sewing
approximately six sandbags of canvas
or cloth. Make them roughly 9- or
10-square inches. Use these to hold
the skins down tight during the gluing
process. The sandbags conform to the
float’s shape and ensure that all areas will
be well glued.
I cut the skins so they are
approximately 1/8 inch over size and
epoxy them on the
sides first. After the
glue sets, sand off
all excess sheeting
and then glue on
the bottom piece.
If your floats are
constructed from
sticks, run a bead of
30-minute epoxy
along the inside of
the lower longerons
or “chines” as a fillet
for strength and to
protect the seams
from water leakage.
The top skin is the last to be glued
on. Before doing this, check your work;
this is your last chance to correct any
oversights. If everything looks fine, glue
on the top skin and sand it around the
edges.
If the floats are cut from foam, put
in the usual hard points, nose, and rear
wood pieces made from spruce or cedar.
The foam floats are covered in the same
manner as the stick floats, but the thirtyminute
epoxy will have to be mixed and
applied rapidly.
Spread the epoxy on with a credit
card and then carefully place the skin
and weight it with the sandbags to hold
everything in place. After all of the sides,
bottom, and top pieces are glued on,
sand the edges and clean them for the
finishing process.
Finishing the Float
Now it is time to sand all of the float’s
surfaces and get them ready to cover. I
usually brush on two coats of Balsarite
and then iron on Solartex, making a
1/4-inch overlap seam on all corners to
ensure that there will be no water leaks.
www.ModelAviation.com May 2012 Model Aviation 51
Left: The rear float detail shows attachment and water
rudder/hinge arrangement.
Above: The Fairey
IIIC’s float shows the
deck plates and strut
attachments. The text
describes creating
the rivet detail and
seams.
Left: These stickbuilt
floats are on
the model of a 1919
Fairey IIIC Schneider
Cup airplane. Note
the odd shape of the
floats. The struts
are made from
hardwood.
The floats look nicer if you create
panel lines and rivet detail. Lay out the
float lines with a ruler, then add glue
dots 1/4 inch apart to simulate the rivets
at the seams and every 4 or 5 inches
along the length of the float.
When this is accomplished, spraypaint
the floats with Sig Butyrate dope or
Rust-Oleum. Silver or gray is usually
the best color to use. Another goodlooking
finish is to put a light stain on
the plywood sheeting and then a coat of
varnish. Factory logos are a nice touch,
such as the ones used on the Blackburnbuilt
Babies of World War I.
Along with the provided pictures and
sketches, the average modeler should
have no trouble in building a nice set of
floats for his or her big seaplane.
Good luck and many happy landings!
—Lawrence E. Klingberg
8111 Dartmoor Dr.
Huntington Beach CA 92646
SOURCE S:
Balsarite
www.coverite.com
Solartex
http://shop.balsausa.com/category_s/119.htm
Sig Butyrate Dope
(800) 247-5008
www.sigmfg.com
Rust-Oleum
www.rustoleum.com