Also included in this column:
• Propeller suppliers
I HAVE WRITTEN about the benefits of
having a well-thought-out model, fuel
system, and approach to flying a Speed
model. Jerry Rocha of Napa, California,
demonstrated the benefits of this systematic
approach in 2006 with his .21 Sport Speed
model.
He placed first in every contest in which
he entered in the summer, including a win at
the Nats and setting a record at a contest in
Merced, California, with a speed of 159.65
mph. In December 1998 the team of Fogg
and Brown set the record of 158.39 mph that stood for eight years.
If you look closely at the picture of Jerry’s engine installation,
you can see many good ideas. The pressure-feed system used for
the fuel tank departs from the layout many other Speed fliers use.
The needle valve is placed in the venturi instead of on a remote
block at the rear of the engine; this eliminates many fittings and
pieces of fuel tubing that offer places for leaks to occur.
Jerry made the valve assembly, but FFer Doug Galbreath sells
a similar unit. The needle valve has a hex cut on the short stub. A
wrench made from a small Allen bolt is used to adjust the valve
when needed. The pressure line is soldered high on the side of the
tank, thus helping to keep fuel from draining into the engine
through the pressure fitting’s .022-diameter hole.
The lines used to fill the tank are not overlooked in this wellplaced
installation. The vent line is located on the front of the tank
and is used for the vent as the tank is filled.
Notice that none of the brass tubes are simply soldered in a
hole. The long runs of tubing along the sides of the tank increase
surface area and lessen the chance of a leak developing where the
tube penetrates the tank material. This is the best method I have
Much can be learned from this view of Jerry Rocha’s .21 Sport Speed engine setup.
seen for pressure-tank construction.
A common method for installing tubing is to make a hole in the
tinplate and solder the tubing into the hole. A leak often develops at
this solder joint.
I had so much trouble with pressure tanks that I would carry a 1-
quart bottle of water to test tanks for leaks at contests. Jerry’s clean
system is far superior to the “poke a hole and solder” method.
Pressure tanks are often just bedded in silicone to hold the tank.
Vibration during flying will cause the tank to touch the pan. This will
often cause a leak that will require removing the tank from the silicone
and repairing the leak—a messy job at best.
Examine the cowl shape Jerry used. The reason for the change is
explained in the text.
Steve Wilk of Eliminator Props shows the extensive inventory of
propellers he offers for use in many events.
Jerry’s method eliminates the chances of
that happening. He glues a piece of balsa
wood to the bottom of the tank with silicone
glue. After that sets, he trims the wood to
match the tank. Then he glues the tank into
position using silicone.
He ensures that the tank does not touch
the pan by using a volt ohmmeter to make
sure no contact occurs between the tank and
the pan. The filler pipes are isolated from the
pan and model with short pieces of fuel
tubing, as can be seen in the pictures.
Jerry is quick to give credit to his friends
who helped him with parts and ideas for his
record holder. He said Luke Roy machined
the wing for him on a three-axis CNC mill.
The wing uses a lifting airfoil in the center
and transitions to a symmetrical shape at the
tips. Luke also machined the pan from a
casting supplied by Bill Husted.
Do those names look familiar? I think the
team of Husted and Roy held the record in
every piston-powered Speed event at one
time or another. They developed the recordholding
Rattler 29.
Jerry’s model is not peculiarly light. No
cooling vents were used since Jerry said he
felt that the NovaRossi .21 ran quite cold on
10%-nitromethane fuel used in Speed events
now.
The engine cowling departs from the
conventional shape in that it is a large radius
on the front, as shown. Jerry said that shape is
used to stop the cowl from producing drag if
the model is not flying tangent to the circle.
Another feature that is difficult to see in
the pictures is the method used to hold the
minipipe. At the rear of the pipe is a band
made from aluminum that is attached to the
model. The band is isolated from the model
by a Teflon insert that insulates the heat from
the minipipe from the model.
The pipe is installed after the model is
assembled by gently sliding it through the
rear support and onto the exhaust stub of the
engine. Light pressure is required to do this.
The rear guide and support stops engine
vibration from shaking the pipe off the
engine.
As for engine rework, Jerry said he
adhered to all the items spelled out in an
article by noted engine tuner Tim Gillott that
was printed in the North American Speed
Society’s newsletter Speed Times.
The cylinder timing was set at exhaust
port at 170° and transfers at 130°. The head is
shaped after the form that Tim Gillott
developed.
The glow plug is the Nelson two-piece
with the element pulled down to just below
the steel. The head was set at .006 after the
engine was fully broken in. Jerry said it took
more than a gallon of fuel to get the engine
loosened up.
Jerry tested several different propellers on
his way to a record. He ended up using a
propeller that Steve Wilk made and sold; it
was a model M3 finished to a diameter of 61/8
inches with a pitch of 61/2 inches. Jerry’s
engine will turn this propeller at 33,700 rpm
in the air.
Jerry will machine custom heads for the
NovaRossi .21 and the GZ .049.
Speed fliers rely on many home-based
businesses to supply equipment. One of the
most important items purchased are
propellers since the main line suppliers have
stopped producing items for our branch of the
hobby. Fortunately we have two propeller
suppliers that are examples of well-run home
businesses: Eliminator Props run by Steve
Wilk and ZZ Prop run by Mike Hazel.
Steve attended the Nats this past July. In
the pit area he set up a display of the many
propellers and items he has available. Steve
said that he has close to 2,000 propellers in
stock. This large inventory allows him to fill
an order in just a few days.
Mike Hazel has been supplying
propellers and Speed equipment for many
years. He also fills orders quickly. If an
item is out of stock because of high
demand, Mike is quick to notify a person
with a ship date. He produces propellers in
carbon and fiberglass to satisfy whatever
requirement you have. MA
Sources:
Jerry Rocha
(707) 255-0651
Eliminator Props (Steve Wilk)
(763) 531-0604
[email protected]
ZZ Prop (Mike Hazel)
(503) 859-2905
[email protected]
Edition: Model Aviation - 2007/03
Page Numbers: 141,142
Edition: Model Aviation - 2007/03
Page Numbers: 141,142
Also included in this column:
• Propeller suppliers
I HAVE WRITTEN about the benefits of
having a well-thought-out model, fuel
system, and approach to flying a Speed
model. Jerry Rocha of Napa, California,
demonstrated the benefits of this systematic
approach in 2006 with his .21 Sport Speed
model.
He placed first in every contest in which
he entered in the summer, including a win at
the Nats and setting a record at a contest in
Merced, California, with a speed of 159.65
mph. In December 1998 the team of Fogg
and Brown set the record of 158.39 mph that stood for eight years.
If you look closely at the picture of Jerry’s engine installation,
you can see many good ideas. The pressure-feed system used for
the fuel tank departs from the layout many other Speed fliers use.
The needle valve is placed in the venturi instead of on a remote
block at the rear of the engine; this eliminates many fittings and
pieces of fuel tubing that offer places for leaks to occur.
Jerry made the valve assembly, but FFer Doug Galbreath sells
a similar unit. The needle valve has a hex cut on the short stub. A
wrench made from a small Allen bolt is used to adjust the valve
when needed. The pressure line is soldered high on the side of the
tank, thus helping to keep fuel from draining into the engine
through the pressure fitting’s .022-diameter hole.
The lines used to fill the tank are not overlooked in this wellplaced
installation. The vent line is located on the front of the tank
and is used for the vent as the tank is filled.
Notice that none of the brass tubes are simply soldered in a
hole. The long runs of tubing along the sides of the tank increase
surface area and lessen the chance of a leak developing where the
tube penetrates the tank material. This is the best method I have
Much can be learned from this view of Jerry Rocha’s .21 Sport Speed engine setup.
seen for pressure-tank construction.
A common method for installing tubing is to make a hole in the
tinplate and solder the tubing into the hole. A leak often develops at
this solder joint.
I had so much trouble with pressure tanks that I would carry a 1-
quart bottle of water to test tanks for leaks at contests. Jerry’s clean
system is far superior to the “poke a hole and solder” method.
Pressure tanks are often just bedded in silicone to hold the tank.
Vibration during flying will cause the tank to touch the pan. This will
often cause a leak that will require removing the tank from the silicone
and repairing the leak—a messy job at best.
Examine the cowl shape Jerry used. The reason for the change is
explained in the text.
Steve Wilk of Eliminator Props shows the extensive inventory of
propellers he offers for use in many events.
Jerry’s method eliminates the chances of
that happening. He glues a piece of balsa
wood to the bottom of the tank with silicone
glue. After that sets, he trims the wood to
match the tank. Then he glues the tank into
position using silicone.
He ensures that the tank does not touch
the pan by using a volt ohmmeter to make
sure no contact occurs between the tank and
the pan. The filler pipes are isolated from the
pan and model with short pieces of fuel
tubing, as can be seen in the pictures.
Jerry is quick to give credit to his friends
who helped him with parts and ideas for his
record holder. He said Luke Roy machined
the wing for him on a three-axis CNC mill.
The wing uses a lifting airfoil in the center
and transitions to a symmetrical shape at the
tips. Luke also machined the pan from a
casting supplied by Bill Husted.
Do those names look familiar? I think the
team of Husted and Roy held the record in
every piston-powered Speed event at one
time or another. They developed the recordholding
Rattler 29.
Jerry’s model is not peculiarly light. No
cooling vents were used since Jerry said he
felt that the NovaRossi .21 ran quite cold on
10%-nitromethane fuel used in Speed events
now.
The engine cowling departs from the
conventional shape in that it is a large radius
on the front, as shown. Jerry said that shape is
used to stop the cowl from producing drag if
the model is not flying tangent to the circle.
Another feature that is difficult to see in
the pictures is the method used to hold the
minipipe. At the rear of the pipe is a band
made from aluminum that is attached to the
model. The band is isolated from the model
by a Teflon insert that insulates the heat from
the minipipe from the model.
The pipe is installed after the model is
assembled by gently sliding it through the
rear support and onto the exhaust stub of the
engine. Light pressure is required to do this.
The rear guide and support stops engine
vibration from shaking the pipe off the
engine.
As for engine rework, Jerry said he
adhered to all the items spelled out in an
article by noted engine tuner Tim Gillott that
was printed in the North American Speed
Society’s newsletter Speed Times.
The cylinder timing was set at exhaust
port at 170° and transfers at 130°. The head is
shaped after the form that Tim Gillott
developed.
The glow plug is the Nelson two-piece
with the element pulled down to just below
the steel. The head was set at .006 after the
engine was fully broken in. Jerry said it took
more than a gallon of fuel to get the engine
loosened up.
Jerry tested several different propellers on
his way to a record. He ended up using a
propeller that Steve Wilk made and sold; it
was a model M3 finished to a diameter of 61/8
inches with a pitch of 61/2 inches. Jerry’s
engine will turn this propeller at 33,700 rpm
in the air.
Jerry will machine custom heads for the
NovaRossi .21 and the GZ .049.
Speed fliers rely on many home-based
businesses to supply equipment. One of the
most important items purchased are
propellers since the main line suppliers have
stopped producing items for our branch of the
hobby. Fortunately we have two propeller
suppliers that are examples of well-run home
businesses: Eliminator Props run by Steve
Wilk and ZZ Prop run by Mike Hazel.
Steve attended the Nats this past July. In
the pit area he set up a display of the many
propellers and items he has available. Steve
said that he has close to 2,000 propellers in
stock. This large inventory allows him to fill
an order in just a few days.
Mike Hazel has been supplying
propellers and Speed equipment for many
years. He also fills orders quickly. If an
item is out of stock because of high
demand, Mike is quick to notify a person
with a ship date. He produces propellers in
carbon and fiberglass to satisfy whatever
requirement you have. MA
Sources:
Jerry Rocha
(707) 255-0651
Eliminator Props (Steve Wilk)
(763) 531-0604
[email protected]
ZZ Prop (Mike Hazel)
(503) 859-2905
[email protected]