April 2003 147
AS FLYING SEASON approaches, and is probably well underway in
parts of the country, I hope we have all decided to build that .15 Rat.
You may recall that in the last column I included the rules for the
event. I hope you have decided to join us in the Rat circle.
The debate on airplane type and configuration has filled most
conversations in the past few months. Which wing will be the best?
Upright, inverted, or the F2C type? Right now the answer is unknown.
What is known is that each airplane has its benefits and drawbacks.
While easier to build, the uprights have the design problem of
getting a filling mechanism around a minipipe. Most uprights tend to
be slightly slower, and they tend to require a little down on takeoff
because of the angle at which these sit because of the long landing
gear. If the upright is built using a side-exhaust engine, the problem
with the fuel filler is a nonissue. The upright will probably not draw in
as much dirt as an invert.
Although it’s probably faster, the inverted type has the potential for
starting problems since most engines are of the front-intake variety.
And will the air coming off the propeller combined with the open
venturi act as a big vacuum cleaner and draw dirt and other items into
the venturi, causing potential engine damage? A filter or screen over
the venturi opening might be necessary if you are going to run the
inverted design.
It’s clean in design, but the F2C wing type will probably suffer
from poor shutdown characteristics. This design will need a full-length,
or double, elevator because the traditional elevator may not provide
adequate maneuverability during shutdown; this will require at least a
full lap to bring the airplane safely into the pits.
What will the speeds be? I think a good .15 Rat should run roughly
13 seconds for seven laps, but that is only speculation at this time; the
development of the airplanes is not that far along.
What propeller will be the best? Length? Pitch? I think 6.100 x
6.000 inches would be a good starting point; an upright may not work
as well on the same propeller as an invert, and the invert may not work
as well as the F2C wing type. Propeller selection will require many test
sessions to see what the engines like and what they dislike.
Will heat be a problem? For some it will be, and for others it
probably won’t. Attention to cooling and the ability to control cooling
may become more important in this event than most might think.
How much fuel should a .15 Rat carry? I think 2.5 ounces is the
magic number; that should provide more than
adequate range, yet be small enough to get into
each design airplane.
Since .15 Rat will put the minipipe back in
Control Line (CL) Racing, I am working on
some carbon-fiber minipipes. Will these work
any better than aluminum ones? I don’t know,
but I do know that I will be able to work with
various sizes by turning out different-size
plugs. By the time this column is in your
hands, I hope to have tested various sizes and
lengths of minipipes on different propellers to
achieve a performance baseline. Will different
weather conditions affect minipipe selection? I
don’t believe so, but a selection of sizes may
become useful.
Leadout Guides: A useful and much
overlooked piece of equipment on any CL
Racer is the leadout guide. I put a small,
efficient adjustable leadout guide in all my
new airplanes. This guide was Stoo
Willoughby’s concept. I changed the design’s
construction method and dimensions, and now
CONTROL LINE RACING
Dave McDonald, Box 384, Daleville IN 47334; E-mail: [email protected]
Author’s small fuel filters made from 5⁄16 hex aluminum.
Lightweight adjustable leadout guide weighs roughly a gram.
Details of the adjustable leadout guide. Author expains construction in text.
04sig5.QXD 1.24.03 9:19 am Page 147
I can use it in any racer I build. I have
included a sketch of the part and a picture for
your convenience. If you can’t make one, I
have a supply. Drop me a note about ordering
one.
The adjustable leadout guide is simple to
build, but the way I do it does require a mill
and some patience. I start by gluing with
cyanoacrylate two pieces of aluminum that
have been milled flat. Clamping them in the
mill, I find center and drill holes for the spring
grouper; these are #50-size holes, which is the
tap size for 2-56. After these holes are drilled,
I tap them in the mill to ensure that they are
tapped straight. Make sure you do not tap
them all the way through; you need a shoulder
in the hole to keep the spring from threading
out the other side.
Then I mill the material to get the part’s
desired thickness. The part in the picture is
milled to .095 inch in thickness. The holes are
drilled .070 inch, so you need to double-check
your dimensions before you mill because you
have very little wall thickness left as you get
to the finished size.
After the part is milled to the desired
thickness, I remove it from the vice and drill
and tap for the 1-72 or 2-56 flat-head screws.
Either size will work; if you’re more
comfortable using the 2-56, feel free. After the
holes are drilled and tapped, I cut the material
to width. The part’s width is noncritical. After
the part is cut, I split the halves open and mill
the slot between the holes. This slot should
not go past the outer wall of the two outside
holes.
The guide in the picture and in the drawing
148 MODEL AVIATION
will take .014-inch wires; therefore, it has
.0075 inch milled off the center of each part.
This gives me the .015-inch slot and allows
the wire to be slid from hole location to hole
location.
Stoo Willoughby’s original part did not
require milling because he used a third piece
of material in the center and removed the
small pieces between the holes after he drilled
and tapped the holes. I opted not to do this
because I could not find the right size of shim
material for the center. The method I use
allows me to make the part the same way
every time, and by simply milling the center,
different thickness works for different wire.
If I was using this on an airplane that took
.018-inch wires, I would mill the slot .0095
inch on each side so the wire would slide
through. If the application were for F2C I
would mill .0065 inch, allowing the .012-inch
wires to be moved. The design is simple, and
most dimensions are noncritical.
The hardest part of this project, which is
not that hard but does take practice and
patience, is winding the spring grouper.
Grouper springs are wound in closed coils
from .018-inch wire, on a .037-inch mandrel.
This produces a spring with 551⁄2 coils per
inch and the correct diameter to thread into a
2-56 tapped hole. You will need a reversing
electric drill, or preferably a lathe, a #63 drill
bit, a leather glove, and a little practice.
Put the drill bit in the chuck with the shank
sticking out. Bend 1⁄2 inch of the end of the
wire at a right angle, and poke this between
the jaws of the chuck. Pinch the wire firmly
over the mandrel between your thumb and
finger, and start winding at the slowest speed.
Use the glove; it gets hot! The drill has to be
run in reverse to produce a spring to screw into
a right-hand thread.
After grinding the ends of the spring flat
and deburring, test it in the threaded hole. You
may need to use a #62 or #64 drill as the
mandrel to get the fit right. However, the #63
should work fine if you are careful with your
drilling and tapping.
If you want to be able to take the lines off
the model, make sure you wrap your lines with
thin copper wire, such as from stripped
electrical cord. The maximum diameter of the
finished lines must be .070 inch or less. Double
loops can be used, provided they are made
with one loop just outside the other so they
will lay flat as you pass them through the slot.
Make sure you don’t forget the grouper spring
on the lines before you make up the ends!
Fuel Filters: How many times have you
wanted to put a small filter on an airplane, only
to learn that the filter no longer exists? I was
looking for some recently and could not find
adequate quality or size filters, so I decided to
make some. They are small and made from
(5⁄16 hex) aluminum. The filters are
approximately the length of a penny and have
a hidden O-ring design. They work well in
small places such as a cowling, inside a Rat
model, a B Team Race model, or almost
anywhere.
I have a supply of these and other items,
such as check valves, shutoffs, and 1⁄2A heads.
If I can help you locate parts used in CL
Racing, please let me know; I am happy to
assist.
As always, your contributions are solicited and
appreciated. MA
Only
$29.95
Plugs between your charger and wall socket.
Provides constant, safe, trickle for radio or
glo-starter chargers.
Can also be used on most any small charger rated 4 to 7 watts.
(cordless drill, screwdriver, cellular phone, flashlight, etc).
You get home and the weather
is great, but you can’t fly
‘cause your batteries are dead!
If you had Lil’ Trickler ®,
your batteries would be ready
to go when you are!
ORDER ONLINE or send check /
money order for $29.95 (plus $5.50 s&h;
outside U.S. add $7.50 s&h)
RK PRODUCTS
Dept A • P.O. Box 4145 • Enterprise, FL 32725-0145
Tel: (386) 574-2750 • Fax: (386) 574-2304
visit our website: www.liltrickler.com
Trademark Registered; Patent Pending RK PRODUCTS
04sig5.QXD 1.23.03 3:22 pm Page 148
Edition: Model Aviation - 2003/04
Page Numbers: 147,148
Edition: Model Aviation - 2003/04
Page Numbers: 147,148
April 2003 147
AS FLYING SEASON approaches, and is probably well underway in
parts of the country, I hope we have all decided to build that .15 Rat.
You may recall that in the last column I included the rules for the
event. I hope you have decided to join us in the Rat circle.
The debate on airplane type and configuration has filled most
conversations in the past few months. Which wing will be the best?
Upright, inverted, or the F2C type? Right now the answer is unknown.
What is known is that each airplane has its benefits and drawbacks.
While easier to build, the uprights have the design problem of
getting a filling mechanism around a minipipe. Most uprights tend to
be slightly slower, and they tend to require a little down on takeoff
because of the angle at which these sit because of the long landing
gear. If the upright is built using a side-exhaust engine, the problem
with the fuel filler is a nonissue. The upright will probably not draw in
as much dirt as an invert.
Although it’s probably faster, the inverted type has the potential for
starting problems since most engines are of the front-intake variety.
And will the air coming off the propeller combined with the open
venturi act as a big vacuum cleaner and draw dirt and other items into
the venturi, causing potential engine damage? A filter or screen over
the venturi opening might be necessary if you are going to run the
inverted design.
It’s clean in design, but the F2C wing type will probably suffer
from poor shutdown characteristics. This design will need a full-length,
or double, elevator because the traditional elevator may not provide
adequate maneuverability during shutdown; this will require at least a
full lap to bring the airplane safely into the pits.
What will the speeds be? I think a good .15 Rat should run roughly
13 seconds for seven laps, but that is only speculation at this time; the
development of the airplanes is not that far along.
What propeller will be the best? Length? Pitch? I think 6.100 x
6.000 inches would be a good starting point; an upright may not work
as well on the same propeller as an invert, and the invert may not work
as well as the F2C wing type. Propeller selection will require many test
sessions to see what the engines like and what they dislike.
Will heat be a problem? For some it will be, and for others it
probably won’t. Attention to cooling and the ability to control cooling
may become more important in this event than most might think.
How much fuel should a .15 Rat carry? I think 2.5 ounces is the
magic number; that should provide more than
adequate range, yet be small enough to get into
each design airplane.
Since .15 Rat will put the minipipe back in
Control Line (CL) Racing, I am working on
some carbon-fiber minipipes. Will these work
any better than aluminum ones? I don’t know,
but I do know that I will be able to work with
various sizes by turning out different-size
plugs. By the time this column is in your
hands, I hope to have tested various sizes and
lengths of minipipes on different propellers to
achieve a performance baseline. Will different
weather conditions affect minipipe selection? I
don’t believe so, but a selection of sizes may
become useful.
Leadout Guides: A useful and much
overlooked piece of equipment on any CL
Racer is the leadout guide. I put a small,
efficient adjustable leadout guide in all my
new airplanes. This guide was Stoo
Willoughby’s concept. I changed the design’s
construction method and dimensions, and now
CONTROL LINE RACING
Dave McDonald, Box 384, Daleville IN 47334; E-mail: [email protected]
Author’s small fuel filters made from 5⁄16 hex aluminum.
Lightweight adjustable leadout guide weighs roughly a gram.
Details of the adjustable leadout guide. Author expains construction in text.
04sig5.QXD 1.24.03 9:19 am Page 147
I can use it in any racer I build. I have
included a sketch of the part and a picture for
your convenience. If you can’t make one, I
have a supply. Drop me a note about ordering
one.
The adjustable leadout guide is simple to
build, but the way I do it does require a mill
and some patience. I start by gluing with
cyanoacrylate two pieces of aluminum that
have been milled flat. Clamping them in the
mill, I find center and drill holes for the spring
grouper; these are #50-size holes, which is the
tap size for 2-56. After these holes are drilled,
I tap them in the mill to ensure that they are
tapped straight. Make sure you do not tap
them all the way through; you need a shoulder
in the hole to keep the spring from threading
out the other side.
Then I mill the material to get the part’s
desired thickness. The part in the picture is
milled to .095 inch in thickness. The holes are
drilled .070 inch, so you need to double-check
your dimensions before you mill because you
have very little wall thickness left as you get
to the finished size.
After the part is milled to the desired
thickness, I remove it from the vice and drill
and tap for the 1-72 or 2-56 flat-head screws.
Either size will work; if you’re more
comfortable using the 2-56, feel free. After the
holes are drilled and tapped, I cut the material
to width. The part’s width is noncritical. After
the part is cut, I split the halves open and mill
the slot between the holes. This slot should
not go past the outer wall of the two outside
holes.
The guide in the picture and in the drawing
148 MODEL AVIATION
will take .014-inch wires; therefore, it has
.0075 inch milled off the center of each part.
This gives me the .015-inch slot and allows
the wire to be slid from hole location to hole
location.
Stoo Willoughby’s original part did not
require milling because he used a third piece
of material in the center and removed the
small pieces between the holes after he drilled
and tapped the holes. I opted not to do this
because I could not find the right size of shim
material for the center. The method I use
allows me to make the part the same way
every time, and by simply milling the center,
different thickness works for different wire.
If I was using this on an airplane that took
.018-inch wires, I would mill the slot .0095
inch on each side so the wire would slide
through. If the application were for F2C I
would mill .0065 inch, allowing the .012-inch
wires to be moved. The design is simple, and
most dimensions are noncritical.
The hardest part of this project, which is
not that hard but does take practice and
patience, is winding the spring grouper.
Grouper springs are wound in closed coils
from .018-inch wire, on a .037-inch mandrel.
This produces a spring with 551⁄2 coils per
inch and the correct diameter to thread into a
2-56 tapped hole. You will need a reversing
electric drill, or preferably a lathe, a #63 drill
bit, a leather glove, and a little practice.
Put the drill bit in the chuck with the shank
sticking out. Bend 1⁄2 inch of the end of the
wire at a right angle, and poke this between
the jaws of the chuck. Pinch the wire firmly
over the mandrel between your thumb and
finger, and start winding at the slowest speed.
Use the glove; it gets hot! The drill has to be
run in reverse to produce a spring to screw into
a right-hand thread.
After grinding the ends of the spring flat
and deburring, test it in the threaded hole. You
may need to use a #62 or #64 drill as the
mandrel to get the fit right. However, the #63
should work fine if you are careful with your
drilling and tapping.
If you want to be able to take the lines off
the model, make sure you wrap your lines with
thin copper wire, such as from stripped
electrical cord. The maximum diameter of the
finished lines must be .070 inch or less. Double
loops can be used, provided they are made
with one loop just outside the other so they
will lay flat as you pass them through the slot.
Make sure you don’t forget the grouper spring
on the lines before you make up the ends!
Fuel Filters: How many times have you
wanted to put a small filter on an airplane, only
to learn that the filter no longer exists? I was
looking for some recently and could not find
adequate quality or size filters, so I decided to
make some. They are small and made from
(5⁄16 hex) aluminum. The filters are
approximately the length of a penny and have
a hidden O-ring design. They work well in
small places such as a cowling, inside a Rat
model, a B Team Race model, or almost
anywhere.
I have a supply of these and other items,
such as check valves, shutoffs, and 1⁄2A heads.
If I can help you locate parts used in CL
Racing, please let me know; I am happy to
assist.
As always, your contributions are solicited and
appreciated. MA
Only
$29.95
Plugs between your charger and wall socket.
Provides constant, safe, trickle for radio or
glo-starter chargers.
Can also be used on most any small charger rated 4 to 7 watts.
(cordless drill, screwdriver, cellular phone, flashlight, etc).
You get home and the weather
is great, but you can’t fly
‘cause your batteries are dead!
If you had Lil’ Trickler ®,
your batteries would be ready
to go when you are!
ORDER ONLINE or send check /
money order for $29.95 (plus $5.50 s&h;
outside U.S. add $7.50 s&h)
RK PRODUCTS
Dept A • P.O. Box 4145 • Enterprise, FL 32725-0145
Tel: (386) 574-2750 • Fax: (386) 574-2304
visit our website: www.liltrickler.com
Trademark Registered; Patent Pending RK PRODUCTS
04sig5.QXD 1.23.03 3:22 pm Page 148
