From the Lab December 1996 [Archive]

skranish

Dec 01, 1996, 01:00 AM

<h3>Some Directions for 'From the Lab' </h3>

Welcome to 'From the Lab', a monthly column on the technical side of  electric
flight. This column will discuss electrical and electronic topics, and even some
aerodynamics. My intent is to cover technical issues in a not-too-technical manner. 

This month I am introducing the 'Beginner's Corner', in which I will attempt to teach
some of the basics of electric flight systems. 

<hr>

<h2>Beginner's Corner: Volts, Amps, and Ohms - Watts it all about? </h2>

In the last edition of 'From the Lab', I included a reader survey that posed the
following question: 

Do you know what amperes and volts are? Can you explain the difference? (yes or no
will do, I KNOW the difference) 

The responses ranged from yes to no, and those of you in the 'no' category NEED to
learn this. You don't need to understand all of the physics involved, or all of the
battery chemistry, but you need to understand volts and amperes. 

<h3>Electrons </h3>

Electricity is basically the flow of electrons. Electrons are little round things that
look like ping pong balls, except that they are really really really tiny. They typically
have a big black '-' (that's a minus sign) painted on them, so you can tell them apart
from all of the other really really really tiny particles that you occasionally read about
in the newspaper (you know, leptons and shleptons and putons and the like). The '-' sign
means that they have a negative charge, and they have a negative charge, because,
well, Benjamin Franklin (the guy who didn't have enough sense to get out of the rain)
guessed wrong. Really. Oh, and electrons are much easier to get hold of than the really
really really tiny particles that you occasionally read about in the newspaper. Cheaper,
too. 

<h3>Amperes </h3>

Electrons need something to flow through. Usually they flow through a wire, but it is
really hard to push ping pong balls through a wire, so we will use a pipe instead. Without
the pipe, we would look a lot like the famous ping pong ball scene on Captain
Kangaroo. Consider a stream of identical looking ping pong balls flowing through a pipe.
There are two obvious characteristics to the flow of ping pong balls: the quantity of ping
pong balls, and the speed with which they are moving. The speed is actually a function of
how hard they have been pushed. If they are pushed hard, they will move fast, but if they
are pushed gently they will move slowly. 

Current, measured in Amperes, is the quantity of
ping pong balls that pass a given point in a second. If you want to get technical about
it, an Ampere is 6.2422E+18 ping pong balls per second, but it is hard to pay attention
long enough to count that high, and it is very hard to count them all anyway, because
they all look the same. A lot of ping pong balls are a lot of current, and very few ping
pong balls are very little current, and that is accurate enough for right now. The ping
pong balls all pass through the pipe, and none can sneak out through the sides, so you
will see the same quantity of ping pong balls passing at any point along the
pipe.  This is important if you want to learn how circuits work. 

Current up to about 10 Amperes may be measured with a standard analog or digital
multimeter. Most multimeters have a 10 Amp fuse in the current input. 

<h3>Volts </h3>

If you have ever lifted and then dropped a fragile object, such as an egg or a Ming
Dynasty vase, you have probably noticed that the results of dropping it are closely
related to how high you lifted it before you clumsily dropped it. As you lift the
object, you are adding potential energy to the object. If you lift it a little, you add
only a little potential energy. If you lift it a lot, you add a lot of potential
energy. When you let go of the object (oops!), the potential energy is released. If
there was very little potential energy to release, the results may be minimal, but if
there is a lot of potential energy, well, watch out. The potential energy has go
somewhere, and if it cannot be transferred into whatever you are dropping the object onto,
it goes into reducing the object bits and pieces. (You may recall this from learning how
to fly your airplanes.....) 

If you really lift it a lot, like to, say, low earth orbit, you are adding a lot of
unnecessary complexity to the example, so please don't. 

Volts are a measure of potential energy. It is really the same thing as lifting
the egg or vase. If you have a lot of volts, you can push the ping pong balls really
really hard. If you have very few volts, you can only push the ping pong balls gently. 

Potential, measured in Volts, is  the amount of push
required to move a particular number of ping pong balls a particular distance down the
pipe. If you want to get technical about it, a volt is 1 newton-meter per 6.2422E+18 ping
pong balls. A newton is the push that will accelerate 1Kg at 1 meter per second per
second, and a meter is a meter, so if you want a lot of push, you need a lot of
volts. 

Voltage may be measured with a standard analog or digital multimeter. 

<h3>Resistance </h3>

Since we are pushing ping pong balls through a pipe, lets consider the what effect the size
of the pipe has on the way the electrons flow. If the pipe is really small, the ping pong
balls bump into each other a lot, and slow down, and have a hard time getting through
the pipe. If the pipe is too small, the ping pong balls get jammed in the pipe and don't
move at all. But if we use a really big pipe, the ping pong balls can move very
freely, and the pipe does not slow them down at all. 

The same is true of electrons flowing through a wire: if the wire is too small, the
electrons bump into each other, slow down, and get confused. Then they do what electrons
always do when they get confused about what they are supposed to do: they turn the
energy they were supposed to do something useful with into heat, which is largely
useless, unless that is what you were after in the first place. 

Resistance, measured in Ohms, is the tendency of any
conduit for electrons to resist or restrain their flow. It  is essentially
a push back against the ping pong balls, and to overcome it, we need to either use a
bigger pipe or a bigger push (more volts). If you want to get technical about it, ohms are
the ratio of volts to amperes in a particular circuit element, which results in really
complicated units that are not worth explaining. Just consider resistance to be a push
back. 

This, by the way, is why everyone tells you to use really big, heavy wiring in your
electric planes. Anybody who tells you otherwise is just trying to make sure that their
planes fly better than yours. The wiring provided in the Great Planes Spectra and
PT-Electric is grossly inadequate (too thin). You should really use 12 or 13 gauge wire. 

Resistance of a passive device, such as a resistor, may be measured with a
standard analog or digital multimeter. The multimeter actually produces a current, and
measures the resulting voltage, and displays the result as resistance. A multimeter cannot
be used to measure the impedance of an active device, such as a battery, or the resistance
of an active device, such as the MOSFETs in a motor controller. These measurements
will be discussed in future columns. Also please note that it is very difficult to measure
small resistances, such as the resistance in a piece of wire, a connector, or a motor
armature, because the measurement may be below the resolution of the meter, or of about
the same value as the contact resistance in the probes. This will also be discussed in
future columns. 

<h3>Some Perspective </h3>

To give you some perspective about the currents and voltages that we deal with in
electric flight applications, consider the following examples:

<ul>
<li>A Speed 600 class motor (05 can motor) draws about 18 to 20 amps at 8 volts, and is
considered a low power motor </li>
<li>When stalled, the same motor can draw over 70 amps (really!) </li>
<li>A 100 Watt light bulb draws less than 1 amp, but at a much higher voltage (120 Volts) </li>
<li>A washing machine motor draws a few amps, but also at a much higher voltage (120 Volts) </li>
<li>Most of the circuit breakers in your house will trip at about 15 amps. A high current
household circuit is 20 amps. </li>
<li>50 thousandths of an amp (50mA) through your heart will probably kill you. Fortunately,
this is hard to do. </li>
<li>Most of the motors we work with have a resistance of a fraction of 1 ohm, which is
not much. If you do not use a fuse, this is the ONLY thing that limits the stall current
of your motor. </li>
<li>The connectors we use have a resistance of only a few thousandths of 1 ohm (hopefully) </li>
<li>The resistors used in most electric circuits (the little multicolored cylindrical
things) have resistances ranging from a few hundred to a few hundred thousand ohms. </li>
</ul>

In the world of electrical things, the voltages we deal with are pretty low, but the
currents we deal with are very, very high. Much higher than most people realize. Most
multimeters, both analog and digital, have a 10 amp fuse in the current measuring circuit,
so they cannot be used directly to measure motor operating current. 

<h3>Additional Reading </h3>

More on this next month. In the meantime, you may want to consider some additional
reading. Dover Publications, Inc of New York publishes Basic Electricity, Prepared by
the Bureau of Naval Personnel. This is a basic textbook on electricity, and covers batteries,
motors, basic circuits, and some underlying physics. I think it was intended for
teaching Navy technicians, who could be assumed to have only a high school education, so
pretty much anyone who is reading this should be able to understand it, if they are
willing to try. It is available at Barnes & Noble, and at $11 (which of course is just
the cost of manufacturing and distribution, because the cost of writing the book was paid
for by you tax dollars) it is far cheaper than most physics or engineering texts. I am not
recommending that everyone add this to their personal library, but if you are trying to
learn the basics, it is a good and economical place to start. 

The Beginner's Corner will be a regular feature of this column. Next month's
column will discuss Watts and milliampHours, and why it is hard to measure Watts and next
to impossible to measure milliAmpHours with a simple meter. 

<hr>

<h2>Covering Material Weights </h2>

Once upon a time, we covered our models with tissue paper and dope. It weighed almost
nothing, added a lot of stiffness to a model, and the fumes were, well let's just say an
interesting experience. (I only recall falling over once) If you really wanted to lavish
money on a model, you could cover it in silk, which was heavier, stiffer, and more
expensive. Silkspan offered a middle ground, though it was generally cheaper than tissue. 

Then along came the plastic coverings. If you haven't been in modeling all that long,
you may not realize that what we now know as 'MonoKote' was once called 'Super MonoKote',
to differentiate it from the original 'MonoKote', which was a sticky-back material similar
to the current 'MonoKote Trim'. Way back when, we called it 'MoneyKote', because it seemed
to be so expensive. 

Now we have an enormous variety of plastic covering materials available. There is
MonoKote, Oracover, UltraCote, Supercoat, Coverite, and a zillion others. Actually, some
of these are the same product sold under many different brand names. Oracover and
UltraCote appear to be the same German product. Sig, Hobby Lobby, Coverite, and probably
others all sell a low temperature covering made in England. If you read the UK magazines
and look at the advertisements, you probably know that there just are not that many
different coverings sold in the UK - so some of these must be the same thing. 

What I really want to discuss here is the weight of these coverings. Sadly,
almost none of the manufacturers supply this information in their advertising. Those that
do, make rather vague claims. 

 There are at least two weight tabulations that I know of:

<ul>
<li>Model Aviation, 'Heat Shrinkable Coverings', February 1988, pages 40-43, 134-139 </li>
<li>Don Edberg's spreadsheet, which he was kind enough to send to me. Perhaps we can get him
to keep it posted on a web site somewhere. </li>
</ul>

Both of these tables use as a unit of measure oz/1000 sq in, which is a bit less than
oz/sq yard (A square yard is 1296 sq in). 

Neither of these tables is entirely up to date, and neither covers a all of the
available coverings. The weight of covering material is of significant importance to
electric modelers, because the correct choice of  covering is an easy place to shave
an ounce or two off of a typical model. To make things even more complicated, there
is not a single weight number to associate with each type of covering. The weight of a
particular brand may vary with the color of the covering, with transparents
generally the lightest, and fluorescents generally the heaviest. (Edberg's table does list
some coverings by color) To add even more complexity to this, it is entirely possible that
some of the vendors selling 'house brand' covering have changed manufacturers from time to
time, without changing the name of the product, so the numbers may be meaningless. 

According to Edberg, MonoKote opaques are about 1.7oz/1K sq in, and transparents are
about 1.3oz/1K sq in. Opaque Oracover/Ultracote is from 1.75 oz/1K sq in to 2.3 oz/1K sq
in, depending on which numbers you want to believe, and Oracover Fluorescents and Pearls
are probably over 2oz/1K sq in. Oracover Lite is probably closer to 1oz/1K sq in (I do not
have measurements on these newer versions of Oracover/Ultracote). According to Tom Hunt,
Ultracote Lite is NOT the same product as Oracover Lite, and is actually about 50%
heavier. 

After using Pearl Oracover on my GP Spirit, and being horrified by the weight gain, I
decided it was time to start paying attention to the weight of the covering materials I
use. The choice of materials for the Neon was based largely on catalog claims, but for the
Griggs Rocket that is almost finished, I adopted a new approach. Each time I open a new
roll of covering, I cut a 1" wide strip off the end of the roll, remove the backing,
and weigh it on a balance that can resolve 0.1grams (actually it is marked to 0.1g, and
can probably resolve 0.05 grams). I then put the sample in an envelope, marked with the
weight, brand, color, and size of the sample. Remember that the width of the roll varies a
bit from brand to brand. It would probably be more accurate to simply strip the backing
off of an entire roll, and weigh the entire roll of covering, but it would also be kind of
wasteful unless you have an immediate use for it. (Without the backing, most covering
attracts dust and lint via static electricity, making it pretty useless if you are picky
about how your models look). 

I then went through some simple calculations to find out what a 1" x 26"
strip of 1 oz/1K sq in material would weigh, so I could use the value as a sort of
benchmark. The value is 0.74g/26 sq in = 1 oz/1K sq in. (By the way, this is the same as
0.55g/26 sq in = 1 oz/sq yd) 

By way of example, my Neon 400 gained exactly 1 ounce when I covered the wing using
Yellow Oracover Lite, with Fluorescent Orange Oracover top tips and a 6" wide Dark
Blue Oracover stripe on the bottom. The Neon has 390sq in of wing area, so this works out
to 1.28 oz/1K sq in, which is pretty low, given that I used some Oracover opaque and
Fluorescent. 

For the Griggs Rocket, I am using Sig Supercoat with some Oracover Fluorescent trim.
The sample strips from these covering weighed:

<ul>
<li>Sig Supercoat Dark Blue, 0.8g for 1" x 27", which translates to about
1.04oz/1K sq in.  (probably should be rounded to 1.0) </li>
<li>Sig Supercoat White, 0.85g for 1" x 27", which translates to about 1.1oz/1K sq
in. </li>
<li>Oracover Fluorescent Red, 1.25g for 1" x 24", which translates to about
1.8 oz/1K sq in. </li>
</ul>

I am using the Supercoat specifically to reduce the finished weight of the
airframe, and the above numbers show why this change of covering materials is a good idea.


If you would like to make some similar measurements, please feel free to email me your
results. But PLEASE, tell me how big a piece you are weighing, and what you are
using to weigh it. Digital scales, such as the Pelouze unit described below, are useless
for this sort of application because of their limited resolution, unless you are willing
to weigh an entire roll. I am using a rather old Pelouze balance, complete with a
set of sub-gram weights. I don't know where you would find one of these today, but Edmund
Scientific would be a good first try, unless there is still a head shop in your
neighborhood. 

<hr>

Dihedral: How Much, and Single vs. Poly 

E-Zone reader The Fords (unusual first name) noticed my mention of planning to build a
Great Planes Spectra, using the Spirit wing I already have built. He (or is it she?)
wanted to build a straight V-dihedral wing, because it would easier to build and cover
(his/her opinion, not mine). So he/she wanted to know how the V dihedral would affect the
flying of the finished plane. 

My Graupner Hi-Fly (circa 1974) showed both straight dihedral and polyhedral options in
the plans for its two piece wing. My decision to build it with straight V
dihedral was based solely on storage and transportation considerations, although I do
not remember having any complaints about its flying characteristics. 

The V dihedral is 7 to 8 degrees under each tip, 140mm under each tip with a half-span
of 1136mm. The polyhedral version shows 2 degrees or 25mm each side for the 655mm center
panel, and a total of 130mm under each tip, again with a half span of 1136mm. (no angle
was given for the outer panels) 

I tried looking up dihedral in some of my reference books, and was disappointed by how
little I found on the topic. Howard Chevalier's book Model Airplane Design and
Performance for the Modeler (available from New Creations) says the following (yes I
know I am violating someone's copyright, but this is effectively a review, so stow
it): 

"For airplanes using rudder only control, the dihedral angle  should not
exceed 6 degrees. The lower limit depends on the pilot's experience and type of
flying." There is a little more about dihedral for aileron controls, and for free
flight, but that is about it. 

Andy Lennon's new book from Airage Publishing (Model Airplane News), R/C Model
Aircraft Design is a really a collection of articles, rather than a book, and
lacks both references and an index. The best I could find was a suggestion that
sailplane dihedral should be 6 degrees per side for a rudder only sailplane. No mention is
made of V vs polyhedral. 

Martin Simon's classic book Model Aircraft Aerodynamics (Argus Books, available
from Zenith Books 800-826-6600; I bought mine at Barnes & Noble) has some discussion
of how dihedral works,  and some comments on the different forms, but no real
suggestions on design criteria. 

Having failed to find anything meaningful in the books, I asked my not-quite-local
expert: Bob Parks, an MIT Aerospace Engineer, who designed the Phoenix R/C Rocket Glider,
competed on the US Space Modeling World Championship team a number of times (and
I think he won a number of times), and worked all of the successful MIT man-powered
airplanes. The following is extracted from several emails back and forth with Bob: 

<blockquote>
Blaine Beron-Rawdon did a very good series on that in Model Aviation mag about 9
years ago. 
Basically, polyhedral is more effective than V.. the higher angle at the tips has a
larger moment arm to the CG, so you don't need as many inches rise at the tip. The style
of dihedral is really not that critical however (given the same EFFECTIVE dihedral). I
would decide it based more on structure and esthetics. 
The efficiency loss of dihedral is usually overestimated... dihedral actually acts
somewhat like a winglet, and the induced drag is pretty much just a function of the
PROJECTED span. 
>Did you mean POLYHEDRAL here? 
Any type of dihedral.. It really does not hurt efficiency that much. 
Unless you are an awesome rudder/aileron pilot, you get better "real
world" performance with a bit more dihedral than most planes have. (MOST pilots I
have seen cannot turn efficiently with flat wing aileron/rudder gliders). Blaine now
suggests 15 degrees per side for sailplanes, this gives a loss in projected span of 3.4%,
induced drag goes up by about 6%, and for most models, this would be a loss of 3% in L/d
when floating and less when cruising. Personally, I have not tried this much, but
generally use more like 12 to 13 deg.. and This was based on what Blaine USED to use. (His
1978 Mirage design is one of my all time favorites, and convinced me of the merits of a
lot of dihedral) 
Blaine has a nice set of Excel templates for doing airplane stability that covers a
lot of this. It is called Plane Geometry and costs about $20. Highly recommended. email to
<a href="http://rcgroups.com/shared/nospam.php?u=evd&d=netcom.com">evd(at)netcom.com</a>  for info. 
>OK: how do we calculate EFFECTIVE dihedral for straight vs poly applications?

See Blaine's article, or better yet, get his program. Suffice to say that a
reasonable polyhedral scheme has the same effect as roughly 20% more V dihedral (ie
measured in inches at the tip) 
</blockquote>

I hope the above at least partially answers the question about dihedral. I will contact
Blaine and try to get copies of his articles, and perhaps a copy of his spreadsheet
templates. 

<hr>

<h2>The Reader's Survey </h2>

Last month's column included a Reader's Survey. I got a surprising number of
responses (more than 30!), which means there are actually people out there with nothing
better to do with their time than to read what I write. Please keep it up. 

If you did not respond to the survey yet, please feel free to do so. 

The following summarizes some of the more interesting answers: 

How long have you been flying model airplanes? This ranged from real soon now to
over 62 years. Dick Gibbs wins this one. 

How long have you been flying electric airplanes? This ranged from real soon now
to about 10 years. Most seemed to be a few years, and most obviously did not start with
electrics. So much for the idea that we cannot convert slimer flyers. 

What size airplanes are you flying? (Speed 400, Astro 05, Astro 60, converted
washing machine motor?) This pretty well covered the whole range, although it appears
than no one is using washing machine motors. I think most respondents are using Speed 400,
Speed 600, and Astro O5s. A few people are using larger Astros and Aveoxes. 

What DON'T you like about electric airplanes? The most common response, if any,
was short flight times. Some folks also mentioned the heavy batteries and fragile nature
of the planes, the (perceived) cost of drive trains compared to slimers, and the
difficulty of determining an appropriate drive train for a particular model. Outright lack
of tolerance from slimer flyers was also mentioned. 

How many flyable planes do you currently have? Answers ranged from none to about
5, with a high of 12. This made me feel good about my 3 (should be 4 later this week)
flyable planes. Many people have slimers and/or sailplanes in addition to electrics. (I
have 2 flyable sailplanes, and several close to flyable). 

Are there any planes you particularly like/liked? The Graupner UHU and
derivatives probably got the most mentions here (yeah!). Great Planes kits, except the
Electri-Cub, generally got high marks. The Goldberg Electra is also well liked. Several
people liked the Astro Mini Challenger, but thought that no one else liked it. 

Any you particularly disliked? I did not see any consistent pattern here, and
many people did not mention any dislikes. 

How many NIB kits do you have? How old is the oldest one? (my answers are
embarrassingly large!) Some people did not know what 'NIB' means. It stands for
'New-in-box', meaning that you are essentially collecting, rather than building the kits.
I am VERY guilty of this, with something like 30 NIB kits, some of which are at least 25
years old. The number is not going to go down if I spend my time writing columns, rather
than building airplanes. Responses ranged from none, which means you are not supporting
the industry as you are obligated to do, to about 20. If this was a contest, I won,
or possibly tied with Jordan Kaplan. 

Do you want to see any math in this column? Would you prefer that I avoid math
entirely? The answers were a mixed bag. You will see math when I have set up
something on my computer that allows me to capture equations into a GIF file.  I
don't like representing anything but the simplest equations in ASCII. 

What sort of math tools do you prefer: sliderule, calculator, spreadsheet, MathCAD,
canned program, finger counting? Some people actually know what a slide rule is, and a
few confessed to actually having one. Calculators or spreadsheets were pretty popular. Few
people have MathCAD, which is unfortunate, because it is a good tool. Some people wanted
canned programs, which I really don't like, because you never really know how a
calculation is being done. (Eflight sees a lot of traffic discussing how ElectriCalc
does or does not do calculations) No one wanted to use finger counting. One person
mentioned Mathematica, which is like MathCAD on steroids. I think I will try to present
complex math in both MathCAD and spreadsheet form. 

Do you know what amperes and volts are? Can you explain the difference? (yes or no
will do, I KNOW the difference) Enough people answered NO that I have started the
'Beginner's Corner' section. 

Do you want to see software code as part of this column? Schematics? This was a
mixed bag; when I get set up to include graphics you will probably see schematics or
diagrams. 

<hr>

Winter Flying 

"Hey, let's go flying!" 

"It's too cold outside, my hands will freeze!" 

"So wear gloves!" 

"How can I fly with gloves on my hands? I can't even feel the sticks or
trims." 

"Well, put a glove on your transmitter instead of your hands!" 

Sounds silly? It's not. B.C. Inc of Payson, Utah sells the 'Radio Glove', a fleece
lined transmitter cover that makes winter flying downright comfortable (assuming you have
warm boots and socks on). I have been out flying recently with the temperature in the high
20s to low 30s (F), and the Radio Glove made it really pretty comfortable. 

The Radio Glove completely encloses your transmitter, with shaped openings on either
side for your hands, and a clear plastic faceplate (actually a window) on the front so you
can see the meter, display, and trims. The Glove closes with velcro, and includes an
elastic strap to hold the transmitter in place inside. The overall design is pretty
sophisticated, with stiffeners where required. The material used on the outside has enough
'body' (I think the fabric folks call this 'hand') that the hand openings retain their
shape even after you remove your hand from the glove. 

The Radio Glove comes in two sizes, regular and large. Contrary to what you might
think, the sizing is for your transmitter, not your hands. If you have a typical small
transmitter, such as the Futaba Conquest 4 channel, the regular size will do just fine. A
somewhat larger transmitter, such as the JR XF622 will fit in the regular size glove, but
with less room to spare. A porcupine style transmitter with a zillion switches on top
requires a large glove, which has about 2" more space from about the middle of the
window to the top of the glove. Some of the newer 4 channel and 6 channel transmitters are
large enough that they may also require a large glove. You may want to check with the
manufacturer of the Radio Glove to determine which size is recommended for your particular
transmitter. 

The Radio Glove is designed to be held, rather than hung from a neck strap. The
manufacturer suggests that you can just drill a hole in the plastic faceplate to attach a
next strap, but a rather large hole would be required. I would suggest making a standoff
attached to the transmitter neck strap fitting on one end, and the plastic faceplate on
the other. The attachment to the faceplate should include a fitting that allows attaching
the neckstrap entirely external to the Radio Glove. 

I have made one slight modification to my Radio Glove. I added a plastic post to
the neck strap attachment point on my transmitter, about 1.25" inches long, to hold
the faceplate away from the sticks. I use stick extensions from Guidari RC International,
so my sticks are longer than the normal ones. 

I will soon make an additional modification by adding two buttonholes to the back
of the Glove. This will simplify attachment to the Petal Elite 6
transmitter tray that I use to hold my transmitter while flying. This is MUCH more
stable than a simple neck strap. I have always preferred flying with a tray, and highly
recommend it. 

The Radio Glove is highly recommended if you want to go flying in cold weather
without freezing your extremities. 

Some other things you should have to go flying in the winter:

<ul>
<li>warm boots - make sure they are actually insulated, not just padded. Sorel boots are
probably the best for just staying warm - they come from Canada, and lets face it  -
the Canadians KNOW about cold! </li>
<li>warm socks - get WOOL socks, not some silly plastic stuff. I have always found that
socks with a terrycloth-like (looped pile) inside are far warmer than a simple knit
fabric. It is best to wear two pairs of socks, a thin liner sock and a heavy outer sock </li>
<li>flannel lined pants. I had a pair when I was little, and never forgot them. About a
decade ago they reappeared in the LL Bean catalog, and they are now the only pants I wear
in cool or cold weather. They are much comfortable to wear indoors than jeans with
thermal underwear, which can be rather stifling. Beans sells jeans, chinos, and several
other styles. Not cheap, but worth every penny. </li>
<li>fingerless gloves. Yes, they look weird, but they really do keep your hands warm while
still allowing good dexterity with your fingertips. They should be available anywhere that
outdoor sporting goods are sold. </li>
<li>a good parka and hat. If you don't already have these, you probably don't have any
business being outside in the winter. If it is below about 25F, I usually wear a heavy
sweater under my parka. </li>
<li>some common sense. You do need to know when to come in from the cold. </li>
</ul>

Battery capacity is adversely affected by cold weather, so you should make an effort to
keep charged batteries warm. I keep them in an inside pocket in my parka (NOT the same
pocket as my car keys!). 

As an electric flyer, you should be glad that you don't have to fight with fuel and
starters and flooded engines and glow plugs and all that stuff in the cold. 

Yes, I know that it is almost Summer in Australia, but you can just save this
information for next June. 

Addresses: 

Radio Glove, 1077 So. 930 W, Payson Utah 84651  801-465-4228    US$34.95
plus US$5 shipping. R. Brent Billings 

Guidari R/C International 170 University Ave W, Suite 12-103, Waterloo, Ontario N2L 3E9
CANADA   US$17.95  plus US$5 shipping 

Petal Saber 6 Transmitter Tray, available from Hobby Hangar, 1862 Petersburg Road,
Hebron KY 41048   800-611-3860  US $18.95 plus shipping. 

<hr>

<h2>Useful Tools </h2>

This section will become 'Tool of the Month' in the next column, but I would like to
start out by discussing several tools I have found to be useful. 

<h3>Coverite 21st Century Iron </h3>

Most likely, you already have an adjustable iron for applying heat-shrink covering
material. Most of these irons use a bimetal strip thermostat (a weird little coil that
expands and contracts with temperature changes), and the knob on the top is simply
adjusting the trip point of the thermostat. These thermostats typically have a temperature
hysteresis (swing) of 10 to 20 degrees. I have not tried to measure the actual temperature
swing of the 21st Century Iron, but it is obviously very small. It is also
calibrated by temperature (F), rather than some arbitrary number scale. If you look
at the instructions for most plastic coverings, you will find recommended temperatures for
most applications. The 21st Century Iron makes it easy to set the temperature as
appropriate for your application, which is typically quite different for application over
foam, sheeted foam, tacking down over an open structure, and final shrink. I frequently
adjust the temperature while I am working, and at some point in the future will purchase a
second iron so that I can keep one at tacking temperature and another at shrinking
temperature. Highly recommended, even if you already have a cheap iron. 

<h3>Pelouze Postal Scale </h3>

Let's face it: weight is the worst enemy of electric powered flight. If you want to
defeat the enemy, you have to know where it is. So the best thing to do is weigh
EVERYTHING that goes into a model. I frequently make up a simple spreadsheet listing all
of the components and subassemblies in a model as I am building it, so I can estimate
the finished weight, and if necessary, do something about it before the model is finished.
If there is an instruction booklet, I write the weights of subassemblies in the booklet as
I build them, so I have the weights available for future reference. Lightness
can be added by adding lightening holes,  leaving out doublers, or using a lighter
covering material. The Pelouze PE5 scale has a resolution of 2 grams or 0.1 oz, and sells
for about $65 from New Creations R/C or Staples. 

<h3>X-Acto X2000 Knife </h3>

Ergonomic design has started to arrive in modeling tools. The X2000 knife handle is
wrapped in a cover of slightly resilient rubber-like plastic, with a nicely tapered shape.
It is MUCH more comfortable to hold than the standard straight aluminum handle, and very
well balanced. I don't know if it will show up in hobby shops; I bought mine for $3.99 at
Staples. Tower does list it in their catalog, but like most things not sold
under one of their captive brand names, it is just buried in the back. If you are an
aging baby-boomer like me, and have a hard time holding a pencil, this knife is well worth
the money. 

If you would like to recommend a 'Tool of the Month', please feel free to contact me at
<a href="http://rcgroups.com/shared/nospam.php?u=skranish&d=world.std.com">skranish(at)world.std.com</a> 

<hr>

<h2>Source of the Month </h2>

New Creations R/C, PO Box 496, Willis TX 77378 (409)-856-4630 is mentioned several
times in this column. Tell Kirk I sent you. 

Please see the above section on Winter Flying for additional sources. 

If you would like to recommend a 'Source of the Month', please feel free to contact me
at <a href="http://rcgroups.com/shared/nospam.php?u=skranish&d=world.std.com">skranish(at)world.std.com</a> 

<hr>

<h2>COPYRIGHT </h2>

The document is copyrighted (c) 1996 by Steven Kranish, and may not be copied or used
in other forms of publication (electronic or paper) without written permission from the
author. I will probably grant permission, but I would like to know about it, so go ahead
and ask. 

<hr>

<h2>CONTACTS </h2>

If you have any questions, please feel free to contact me at <a href="#skranish(at)world.std.com">skranish(at)world.std.com</a>