Frequently Asked Questions - 2010/07

CA cements: a suggestion
Bob Aberle | baberle@? Frequently Asked Questions optonline.net
January 2010 77
Also included in this column:
• Fuselage assembly fixtures
• Assembled A123 battery
packs sources
• Reversing brushless motors
• Removing iron-on covering
material revisited
BP Hobbies’ CA-Sucker as received, with a clear-plastic ZAP Z-End and
the yellow tip. Top: Both tips are inserted in tubing exiting the CA-Sucker.
ZAP Z-Ends were originally intended to go on the
end of CA bottles, similar to extenders. These
tips do not clog easily!
Bob used two pairs of plywood supporting triangles on the fuselage forward section
during construction. The forward area had a relatively flat bottom; the sides could
basically rest directly on the building board.
PLEASE WRITE IN with your questions,
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provide the number as a reference.
References to addresses and Web sites
are placed in a group, separate from the text,
at the end of this column under “Sources.”
Q428: “I have been using a variety of CA
type cements for years. The extremely fast
curing time certainly enables me to build
faster. But one of the things that has
bothered me for some time is the fact that
the tips of typical CA cement bottles clog
much too easily.
I seem to constantly be inserting pins
into the nozzle ends to get the cement to
flow again. Since you obviously do a lot of
building, what would you suggest to solve
this problem?”
A428: I stumbled upon an idea almost by
accident. I saw a cement dispenser a few
years ago, while attending the WRAM
(Westchester Radio AeroModelers) Show
in White Plains, New York. It was
obtained from the surgical-supply industry.
This dispenser had a plastic bulb at one
end and a thin tube at the other. The idea
was to insert the tube into a bottle of CA,
squeeze the bulb and release it, and that
would suck the cement out of the bottle.
You could adjust the flow of adhesive
coming out of the tubing by pulling on it
with pliers, to make it thinner in diameter.
This worked well, but the tubing still
became clogged easily.
01sig3.QXD_00MSTRPG.QXD 11/20/09 2:00 PM Page 77That meant you had to keep pulling on
the tubing end and cutting off the clogged
portion. Many dispensers got used up
quickly by doing that. It did dispense the
CA (especially the thin variety) at a
perfect rate, but the constant clogging was
downright annoying.
I recently purchased some plastic
dispensers from BP Hobbies that are
called “CA-Suckers,” but I noticed that
the tubing on those new dispensers was
considerably larger in diameter—so much
bigger that you couldn’t pull on them. I
thought I really had a problem.
But in my supply drawer I found two
types of CA bottle tips that I had
purchased throughout the years. I learned
that I could cut off the end of the CASucker
and place one of the bottle tips on
the end of the tubing. In both cases, the
tip fit snugly—exactly what I needed.
This works the
same way; squeeze
the bulb, with the
tip placed inside
the CA bottle, and
release it. For
some reason,
neither tips clog. I
have built an entire
aircraft and
experienced no
clogging during
the project. If you
get excess CA on
the end of the tip,
you can pull it off
with pliers.
I cannot find a
source for the tip
shown (which is
yellow) at this
time. However,
the clear tips come
from Pacer
Technology,
78 MODEL AVIATION
The sides rise considerably off the building board toward the
fuselage rear. To keep the sides aligned, Bob made a supporting
fixture to hold both in place while he added the crosspieces.
FMA Direct made this three-cell pack of A123
Li-Ion cells for Bob, for testing a then-new
Cellpro 4sa charger. The company does not
sell this type of pack.
On higher-power motor systems, the three
wires going to the ESC usually employ
separate pin-type connectors, as shown on
this E-flite 20-amp ESC. Unplugging,
swapping, and replugging any two of the
three wires will reverse a motor shaft’s
rotation.
On this smaller AXI 2204-54 brushless motor running at
approximately 35 watts input power, a Deans three-pin connector
was used. All you need do is unplug this connector, rotate it 180°,
and reconnect it to reverse rotation.
which makes the Zap brand of products.
These tips are called “Z-Ends” and are
catalog item PT-18. You can find contact
information in the source section at the end
of this column.
Q429: “I noticed in FAQ-415, the
supporting plywood triangles you used as a
fuselage assembly jig. I tried your idea but
found that it worked best on fuselages that
had a straight or flat top or bottom. What
do you recommend when the fuselage has
a sloping bottom?”
A429: I recently had a new design, and the
fuselage sides were far from being straight.
With the forward part of the fuselage
directly on the building board, I could use
two pairs of supporting triangles.
However, the aft end of the fuselage was
several inches above the building board.
I could have used a third pair of
triangles toward the rear, but there was no
way to guarantee that the sides would be
properly lined up. To make life easier for
myself, I constructed a simple support
from scrap pieces of balsa.
As you can see in the photo, both sides
rest on the same support piece, so they
have to be aligned. While held in this
position, I added my crosspieces. Then
when the cement cured, I removed both
sides from the building board. They were
aligned from the nose to the tail of the
fuselage.
These are the uncomplicated kinds of
innovative tricks you can apply to your
building process that can save a lot of time
and produce more accurate results.
Q430: “I keep hearing about the A123
Systems Li-Ion battery cells. I realize that
they have a little lower characteristic cell
01sig3.QXD_00MSTRPG.QXD 11/20/09 2:00 PM Page 7880 MODEL AVIATION
voltage and that they weigh a little more
than Li-Poly batteries, yet many are
successfully using these cells.
“So I decided to purchase a few packs
and discovered that the sources of supply
for assembled A123 packs are somewhat
hard to find. If you were buying any of
these packs for yourself, where would
you go?”
A430: I thought this would be an easy
question to answer, but it wasn’t. I looked
at several Web sites I’m familiar with and
couldn’t find anyone selling assembled
A123 packs.
I have been using a three-cell, 2300
(9.9 volts) mAh pack with a balance
connector that the people at FMA Direct
handmade for me while I was testing the
latest version of the company’s Cellpro 4s
charger. FMA Direct does not sell A123
cell battery packs.
Next I contacted Red Scholefield:
MA’s battery columnist. When these
A123 cells became available, Red and I
shared a batch of six and made our own
three-cell packs.
So it didn’t surprise me when Red
responded that he buys DeWalt 36-volt
drill motor packs from eBay, breaks them
down, and assembles them into packs for
his modeling needs. He also mentioned
Hangtimes Hobbies as a source for
assembled packs that are primarily for RC
and ignition applications.
I wanted to duplicate what I had
received from FMA Direct and found
exactly that at BP Hobbies. It has packs
assembled into two-, three-, and four-cell
configurations, with main power leads as
well as balance node connectors that mate
with E-Tec/PolyQuest balance adapters.
I’m sure there are more suppliers, but I’ve
at least given you a starting point.
Q431: “It is my understanding that when
dealing with brushless motors that have
three exiting wires, you can reverse the
motor rotation by simply swapping any
two of the three wires. Well I did that, but
to be thorough I swapped two wires, then
two more. That didn’t work. What did I
do wrong?”
A431: The true cause of your problem
might be, coincidentally, a bad connector.
Generally, you are supposed to swap
any two wires. On the higher-powered
motor systems, each of the three wires is
connected to the ESC with individual pintype
connectors. In this arrangement, it is
easy to disconnect two wires, swap them,
and plug them back in. Doing this will
change the motor-shaft rotation from one
direction to the other.
On my smaller (low powered—usually
less than 50 watts input power) motors, I
use Deans connectors. With this
arrangement, it is easy to unplug the
connector, rotate them 180°, and plug them
back together. This swaps the two outboard
pins and usually works without a hitch.
The beauty of this type of setup is that
you don’t have to unsolder and resolder a
couple of wires; simply unplug and replug.
But as I mentioned at the beginning, make
sure you don’t have a bad connector pin or
a broken wire hiding under a piece of heatshrink
tubing.
Q393 Follow-Up: That question and
answer were about techniques for removing
iron-on covering. Faye Stilley, who wrote
several books about that material, gave
some advice in the answer.
Faye recently wrote to me and indicated
that a helpful tool for removing pieces of
iron-on covering is called a “Tick
Tweezer.” This tool is approximately 21/2
inches long and has two very sharp points.
It allows you to get underneath the
covering and lift it off slightly, and then
grip it with the tweezer action and proceed
to pull it off of the airplane. This tool is
kind of like having two X-Acto No. 11
blades working for you at the same time.
You can obtain these tweezers in some
of the national drugstores, and a company
called “Tweezerman” sells sets for $5. I
couldn’t get the Web site to work for me,
but I did find this same tool on “Yahoo!
Shopping.” You might have to work at this
using one of the popular Internet search
engines.
I also received an e-mail from Peter
Arseneault, an AMA member, who told me
that he applies ordinary duct tape to the
pieces of covering stuck on his models.
Then he rubs the tape down firmly and
pulls it off, bringing up the remaining
covering with it. MA
Sources:
BP Hobbies
(732) 287-3933
www.bphobbies.com
Zap Z-Ends
www.zapglue.com/Tips.html
Hangtimes Hobbies
57 Cedar St. Ste. 6
Babylon NY 11702
www.hangtimes.com
Yahoo! Shopping
http://shopping.yahoo.com
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