Aero Mail
Aero Mail continued on page 165
May 2008 7
Clearing the Air
I have been a model airplane builder and
flyer for over 65 years, every aspect of
modeling from five cent solid models up to
turbines. At this point in life, I have no interest
in turbines other than reading about them. For
the past 15 or so years most of my modeling
time is RC Scale Sailplanes.
The reason for telling you this, I have a
fairly good knowledge of building all different
kinds of model airplanes. They all have at least
one thing in common, they all require some
cutting of various materials, gluing, sanding
and finishing of same. Never giving much
thought to the dust caused, other than it is
always a pain cleaning up some times. This is
going to change starting on St. Pat’s Day.
I will stop the construction of the 1/4 scale
of the German WW II troop carrier Me 321
Gigant, and fabricate and install one of your shop filters. I read [James “Bo” Lovell’s
article “Workshop Air Pollution”] in the March issue of MA, in a Mall while my wife
was shopping.
James, your article was the best and most informative that I have read in many
years, perhaps ever. This is the first time I have responded to any article in any
publication. That is how much I appreciate your article.
Gordon Pearson
via E-mail
Keep the Air Cleaner Clean
Jim Lovell’s article on workshop air pollution is an excellent reminder of how
vulnerable we are to the materials we use in the Hobby. My personal nemesis, for
example, is latex spackle. Breathing the sanding dust will pack up my sinuses like
concrete.
Longer ago than I’d like to remember, I built a “Dust Sucker” to cut back on
workshop dust. I used an ordinary box fan, with a furnace filter duct-taped on each
side of it. When I checked the filters, I found lots of nasty stuff in them. So, I’d
usually set up my Dust Sucker, and let it run and run whilst I worked.
One day, when I was getting ready to set up my paint sprayer, I started my Dust
Sucker up and began vacuuming. When I turned off the vacuum, I heard an odd, popping
noise. Turning around, I saw the Dust Sucker fan was in flames. I quickly unplugged the
fan, opened the door, and tossed the flaming fan onto the snowy lawn (it was January, in
Anchorage, Alaska, and I was not going to run outside with the fan!).
After the fan hit the snow, the flames died away, so I got some shoes on and trotted
out to fetch it. Taking a careful, close look at the fan, I saw that the hub had been
thick with balsa dust. All of that use as a Dust Sucker had loaded dust around the hub,
where it got soaked with oil. Once it got hot enough, a spark from the fan motor was
all it took to start it burning.
When I realized what had happened, I started shaking.
Remember, I used to let the fan run whilst I painted. Another five or ten minutes,
and I’d have been spraying highly flammable epoxy paint. Had the fan waited until
then to start burning, the results would have been terminal for me and for the others in
our building.
So, I strongly suggest periodically checking any fan or other device with an
electric motor that is exposed to balsa dust for buildups. If you see dust building up
around the motor, clean it out.
Since that day, I’ve made it a policy to periodically check the motors in my shop
fans, vacuums, saws, Dremels, and so forth. Likewise, I make sure any fan I use
around spray paint is specifically made for use around flammable vapors.
Bill Bowne
Browns Mills, New Jersey
Bill has a valid point; however, only in the most extreme conditions. From the
research I did to write the article to the checking I just did on box fans, their motors,
and fire hazards, I have concluded the following.
Official Publication of the Academy of Model Aeronautics
SINCE 1936
April 2008 $4.95
Bring your model
alive with simple
airbrushing
techniques
Construct the famed
World War II Marauder
in two sizes
CoAnMveAntion 2008:
Defined by
the members
05sig1.QXD 3/25/08 11:08 AM Page 7
May 2008 165
fuselage, let the dope dry and then feathersand
the carbon where it was folded over
to the uncovered side. Carbon sands easily
until you have a number of coats of dope
on it, so go easy here and taper-blend the
edge of the carbon to the wood on the
opposite side.
Cover the second side of the fuselage in
exactly the same manner as you did the
first, letting the carbon mat fold over to the
previously covered side. When the dope
has dried, feather-sand the folded edge to
blend with the carbon on the side you
covered first.
Resist the urge to detail-sand the
carbon to be smooth at this time. If you
sand even with a little pressure on the
paper, you will quickly cut through the
carbon and leave a void.
(Editor’s note: You don’t want to
breathe in the carbon dust. Be sure to use
a mask while sanding.)
Mix some dope to a medium
consistency and brush a coat onto the
entire fuselage. When this coat has cured,
it is time to carefully sand the surface of
the carbon to be smooth using 320-grit
sandpaper. You must still pay attention
when sanding to not remove too much of
the carbon material.
After the sanding step is complete,
blend all the edges and the surface of the
carbon smooth, brush on two or three more
coats of dope, and repeat the sanding step.
At this point your fuselage should be ready
for primer.
You can go ahead and prime the
fuselage, making it ready for paint, or you
can stop here and proceed with building
the stabilizer, elevator, and wing. When
they are finished and installed, prime the
entire model (if you are planning on an allpainted
finish) or mask off the areas where
you will be using a heat-shrink covering
and prime the areas that will be painted.
I like to go the distance and apply
primer to the fuselage and sand it smooth.
What primer you use depends strictly on
what type of paint you will be applying as
a finish coat. I have found Rust-Oleum
paint to work well on this type of model,
and regular gray auto primer seems to
work fine under it.
I paint the fuselage, the tail surfaces,
and a narrow strip out onto each wing half,
and then I cover the majority of the wing
surface with a heat-shrink film. This is
hardly the recipe for a competition-quality
finish, but, then again, this model is
intended to be a trainer and will probably
get dinged during the learning process. It
makes no sense to put too much work into
the finish on this type of model!
We have our carbon-covered (and maybe
primed) fuselage in hand, and we’re ready
for some horizontal surfaces! Next time
we’ll look at how to make a light, strong
tail assembly and how to install bind-free
hinges.
Til next time, fly Stunt! MA
1) If you are generating enough wood
dust for the spark or arcing of a brushed
motor in a box fan to ignite a wood dust
cloud, you are at an industrial level of
wood dust and must be aware of its
hazards.
2) If fumes from paint or propellants
from sprays are gathering up in an
amount concentrated enough for a box fan
to ignite them, you should probably not be
in the room without a respirator, oxygen
tank, or industrial hood venting system.
3) Bill’s assumption that, like his, most
shops are closed is another sticking point.
My shop is open to the rest of my house,
and a gas pilot light has proven more
likely to ignite fumes or dust clouds than
box fans have ever thought about being.
4) I did find several government and
manufacturer-related recalls on box fans
by Lasko and other manufacturers related
to faulty motors and box-fan power cords
causing fires, but none related to
particulate matter or fumes doing so. One
article I read warned against installing a
box fan in your attic for summer
ventilation due to fire hazard, but only
because the remote location of the fan
prevents most people from cleaning it and
the high temperatures and amounts of
dust that collect in an attic would only
exacerbate the need for cleaning the fan
and motor.
I found examples of “explosion proof”
box fans and other types of explosionproof
fans. They were all for industrial
applications and venting.
In all the examples I’ve seen, the
motor is outside the fan and ducting area,
thus preventing it from direct contact with
matter being drawn through the fan.
In addition, at least in my own case,
the fan is not really gathering any more
dust or other particles than it would be if
I had placed it in the doorway pointed out
into the hall. I re-iterate: if you have
enough dust, or fumes, gathering together
in a closed environment for the electric
motor of a box fan to ignite, I would hope
that common sense would have told you
long ago that you need more than a
cardboard box and a $20 box fan.
Growing up in the South, maybe I am
more experienced with these type of fans
than people in other parts of the country.
I’ve always had to (and this is pretty
serious) make sure that the motor and
motor windings on my electric floor fans
were free of “dust bunnies,” dirt, paper,
or any other matter that might be
flammable or cause the fan motor to
overheat.
I have several fans that are over 20
years old, and I’ve had to take them apart
to clean the blades and the motor. The
factory uses a light oil in the
manufacturing process of these electric
motors. Coupled with static charges from
air movement and the electromagnetic
nature of the electric motor, the oil and
the magnetism of the motor automatically
collect dust, hair, carpet fibers, and all
sorts of things. Sometimes cleaning out
one of the older ones is pretty gross.
And if you don’t clean them out, they
run more slowly, the motors heat up, and
they either don’t keep you cool or they
quit working altogether. I’ve never had
one catch on fire or ignite anything,
although I’m sure it could happen.
Taking nothing away from Bill’s Email
and his concern for my body staying
in one piece at a reasonable 98.6°, I
think it would be an extreme case indeed
for his concerns to be realized by the
everyday modeler. And with as many
ARFs as there are out there, how much
dust and fumes do you create putting one
of those together?
James “Bo” Lovell
Birmingham, Alabama
Regarding the box-fan Shop Air Filter
in the March issue, it is important, no
matter what type of fan you use, to make
sure the motor powering your fan stays
clean and free of particle buildup. When
cleaning the box and changing the filter,
inspect and
clean the fan
(including the
motor) to
remove excess
material that
could cause the
motor to heat
up or pose a
potential fire
hazard.
The author is shown in the article
blowing the fan unit itself with an
electric leaf blower at close range to
ensure that small particles do not build
up in or around the motor area.
—MA staff
A Darn Good Helicopter
It has come to our attention that
MA’s review of the JR Vibe 90 by Ray
Stacy, which was published in the March
2008 issue, has indubitable similarities
to a review of the same product that RC
Universe published in May 2006. We
regret any confusion this incident may
have caused.
Eric Balay’s JR Vibe 90 3D research
can best be described as extensive and
among the most complete review projects
our editorial staff has observed to date.
Any enthusiast who is looking to research
his or her next helicopter project should
consider Mr. Balay’s work.
Read his RC Universe article at
www.rcuniverse.com/magazine/article_di
splay.cfm?article_id=682. MA
—MA staff
Aero Mail
Continued from page 7
05sig6.QXD 3/25/08 8:16 AM Page 165
Edition: Model Aviation - 2008/05
Page Numbers: 7,165
Edition: Model Aviation - 2008/05
Page Numbers: 7,165
Aero Mail
Aero Mail continued on page 165
May 2008 7
Clearing the Air
I have been a model airplane builder and
flyer for over 65 years, every aspect of
modeling from five cent solid models up to
turbines. At this point in life, I have no interest
in turbines other than reading about them. For
the past 15 or so years most of my modeling
time is RC Scale Sailplanes.
The reason for telling you this, I have a
fairly good knowledge of building all different
kinds of model airplanes. They all have at least
one thing in common, they all require some
cutting of various materials, gluing, sanding
and finishing of same. Never giving much
thought to the dust caused, other than it is
always a pain cleaning up some times. This is
going to change starting on St. Pat’s Day.
I will stop the construction of the 1/4 scale
of the German WW II troop carrier Me 321
Gigant, and fabricate and install one of your shop filters. I read [James “Bo” Lovell’s
article “Workshop Air Pollution”] in the March issue of MA, in a Mall while my wife
was shopping.
James, your article was the best and most informative that I have read in many
years, perhaps ever. This is the first time I have responded to any article in any
publication. That is how much I appreciate your article.
Gordon Pearson
via E-mail
Keep the Air Cleaner Clean
Jim Lovell’s article on workshop air pollution is an excellent reminder of how
vulnerable we are to the materials we use in the Hobby. My personal nemesis, for
example, is latex spackle. Breathing the sanding dust will pack up my sinuses like
concrete.
Longer ago than I’d like to remember, I built a “Dust Sucker” to cut back on
workshop dust. I used an ordinary box fan, with a furnace filter duct-taped on each
side of it. When I checked the filters, I found lots of nasty stuff in them. So, I’d
usually set up my Dust Sucker, and let it run and run whilst I worked.
One day, when I was getting ready to set up my paint sprayer, I started my Dust
Sucker up and began vacuuming. When I turned off the vacuum, I heard an odd, popping
noise. Turning around, I saw the Dust Sucker fan was in flames. I quickly unplugged the
fan, opened the door, and tossed the flaming fan onto the snowy lawn (it was January, in
Anchorage, Alaska, and I was not going to run outside with the fan!).
After the fan hit the snow, the flames died away, so I got some shoes on and trotted
out to fetch it. Taking a careful, close look at the fan, I saw that the hub had been
thick with balsa dust. All of that use as a Dust Sucker had loaded dust around the hub,
where it got soaked with oil. Once it got hot enough, a spark from the fan motor was
all it took to start it burning.
When I realized what had happened, I started shaking.
Remember, I used to let the fan run whilst I painted. Another five or ten minutes,
and I’d have been spraying highly flammable epoxy paint. Had the fan waited until
then to start burning, the results would have been terminal for me and for the others in
our building.
So, I strongly suggest periodically checking any fan or other device with an
electric motor that is exposed to balsa dust for buildups. If you see dust building up
around the motor, clean it out.
Since that day, I’ve made it a policy to periodically check the motors in my shop
fans, vacuums, saws, Dremels, and so forth. Likewise, I make sure any fan I use
around spray paint is specifically made for use around flammable vapors.
Bill Bowne
Browns Mills, New Jersey
Bill has a valid point; however, only in the most extreme conditions. From the
research I did to write the article to the checking I just did on box fans, their motors,
and fire hazards, I have concluded the following.
Official Publication of the Academy of Model Aeronautics
SINCE 1936
April 2008 $4.95
Bring your model
alive with simple
airbrushing
techniques
Construct the famed
World War II Marauder
in two sizes
CoAnMveAntion 2008:
Defined by
the members
05sig1.QXD 3/25/08 11:08 AM Page 7
May 2008 165
fuselage, let the dope dry and then feathersand
the carbon where it was folded over
to the uncovered side. Carbon sands easily
until you have a number of coats of dope
on it, so go easy here and taper-blend the
edge of the carbon to the wood on the
opposite side.
Cover the second side of the fuselage in
exactly the same manner as you did the
first, letting the carbon mat fold over to the
previously covered side. When the dope
has dried, feather-sand the folded edge to
blend with the carbon on the side you
covered first.
Resist the urge to detail-sand the
carbon to be smooth at this time. If you
sand even with a little pressure on the
paper, you will quickly cut through the
carbon and leave a void.
(Editor’s note: You don’t want to
breathe in the carbon dust. Be sure to use
a mask while sanding.)
Mix some dope to a medium
consistency and brush a coat onto the
entire fuselage. When this coat has cured,
it is time to carefully sand the surface of
the carbon to be smooth using 320-grit
sandpaper. You must still pay attention
when sanding to not remove too much of
the carbon material.
After the sanding step is complete,
blend all the edges and the surface of the
carbon smooth, brush on two or three more
coats of dope, and repeat the sanding step.
At this point your fuselage should be ready
for primer.
You can go ahead and prime the
fuselage, making it ready for paint, or you
can stop here and proceed with building
the stabilizer, elevator, and wing. When
they are finished and installed, prime the
entire model (if you are planning on an allpainted
finish) or mask off the areas where
you will be using a heat-shrink covering
and prime the areas that will be painted.
I like to go the distance and apply
primer to the fuselage and sand it smooth.
What primer you use depends strictly on
what type of paint you will be applying as
a finish coat. I have found Rust-Oleum
paint to work well on this type of model,
and regular gray auto primer seems to
work fine under it.
I paint the fuselage, the tail surfaces,
and a narrow strip out onto each wing half,
and then I cover the majority of the wing
surface with a heat-shrink film. This is
hardly the recipe for a competition-quality
finish, but, then again, this model is
intended to be a trainer and will probably
get dinged during the learning process. It
makes no sense to put too much work into
the finish on this type of model!
We have our carbon-covered (and maybe
primed) fuselage in hand, and we’re ready
for some horizontal surfaces! Next time
we’ll look at how to make a light, strong
tail assembly and how to install bind-free
hinges.
Til next time, fly Stunt! MA
1) If you are generating enough wood
dust for the spark or arcing of a brushed
motor in a box fan to ignite a wood dust
cloud, you are at an industrial level of
wood dust and must be aware of its
hazards.
2) If fumes from paint or propellants
from sprays are gathering up in an
amount concentrated enough for a box fan
to ignite them, you should probably not be
in the room without a respirator, oxygen
tank, or industrial hood venting system.
3) Bill’s assumption that, like his, most
shops are closed is another sticking point.
My shop is open to the rest of my house,
and a gas pilot light has proven more
likely to ignite fumes or dust clouds than
box fans have ever thought about being.
4) I did find several government and
manufacturer-related recalls on box fans
by Lasko and other manufacturers related
to faulty motors and box-fan power cords
causing fires, but none related to
particulate matter or fumes doing so. One
article I read warned against installing a
box fan in your attic for summer
ventilation due to fire hazard, but only
because the remote location of the fan
prevents most people from cleaning it and
the high temperatures and amounts of
dust that collect in an attic would only
exacerbate the need for cleaning the fan
and motor.
I found examples of “explosion proof”
box fans and other types of explosionproof
fans. They were all for industrial
applications and venting.
In all the examples I’ve seen, the
motor is outside the fan and ducting area,
thus preventing it from direct contact with
matter being drawn through the fan.
In addition, at least in my own case,
the fan is not really gathering any more
dust or other particles than it would be if
I had placed it in the doorway pointed out
into the hall. I re-iterate: if you have
enough dust, or fumes, gathering together
in a closed environment for the electric
motor of a box fan to ignite, I would hope
that common sense would have told you
long ago that you need more than a
cardboard box and a $20 box fan.
Growing up in the South, maybe I am
more experienced with these type of fans
than people in other parts of the country.
I’ve always had to (and this is pretty
serious) make sure that the motor and
motor windings on my electric floor fans
were free of “dust bunnies,” dirt, paper,
or any other matter that might be
flammable or cause the fan motor to
overheat.
I have several fans that are over 20
years old, and I’ve had to take them apart
to clean the blades and the motor. The
factory uses a light oil in the
manufacturing process of these electric
motors. Coupled with static charges from
air movement and the electromagnetic
nature of the electric motor, the oil and
the magnetism of the motor automatically
collect dust, hair, carpet fibers, and all
sorts of things. Sometimes cleaning out
one of the older ones is pretty gross.
And if you don’t clean them out, they
run more slowly, the motors heat up, and
they either don’t keep you cool or they
quit working altogether. I’ve never had
one catch on fire or ignite anything,
although I’m sure it could happen.
Taking nothing away from Bill’s Email
and his concern for my body staying
in one piece at a reasonable 98.6°, I
think it would be an extreme case indeed
for his concerns to be realized by the
everyday modeler. And with as many
ARFs as there are out there, how much
dust and fumes do you create putting one
of those together?
James “Bo” Lovell
Birmingham, Alabama
Regarding the box-fan Shop Air Filter
in the March issue, it is important, no
matter what type of fan you use, to make
sure the motor powering your fan stays
clean and free of particle buildup. When
cleaning the box and changing the filter,
inspect and
clean the fan
(including the
motor) to
remove excess
material that
could cause the
motor to heat
up or pose a
potential fire
hazard.
The author is shown in the article
blowing the fan unit itself with an
electric leaf blower at close range to
ensure that small particles do not build
up in or around the motor area.
—MA staff
A Darn Good Helicopter
It has come to our attention that
MA’s review of the JR Vibe 90 by Ray
Stacy, which was published in the March
2008 issue, has indubitable similarities
to a review of the same product that RC
Universe published in May 2006. We
regret any confusion this incident may
have caused.
Eric Balay’s JR Vibe 90 3D research
can best be described as extensive and
among the most complete review projects
our editorial staff has observed to date.
Any enthusiast who is looking to research
his or her next helicopter project should
consider Mr. Balay’s work.
Read his RC Universe article at
www.rcuniverse.com/magazine/article_di
splay.cfm?article_id=682. MA
—MA staff
Aero Mail
Continued from page 7
05sig6.QXD 3/25/08 8:16 AM Page 165