Today's Message Index:
----------------------
1. 04:49 AM - Source for Bakelite - 1/32" thick (Alfio)
2. 05:41 AM - Re: Source for Bakelite - 1/32" thick (Ed Anderson)
3. 05:43 AM - Re: Source for Bakelite - 1/32" thick (Robert Borger)
4. 06:32 AM - Re: Source for Bakelite - 1/32" thick (Vern Little)
5. 07:19 AM - Re: Poor Wiring Practice for VHF Noise? (stearman456)
6. 08:50 AM - Re: Source for Bakelite - 1/32" thick (Robert L. Nuckolls, III)
7. 04:43 PM - Re: Source for Bakelite - 1/32" thick (Robert L. Nuckolls, III)
8. 09:10 PM - Re: Source for Bakelite - 1/32" thick (Don)
Message 1
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Subject: | Source for Bakelite - 1/32" thick |
I am building a Wingtip VOR Antenna, and am in need of 1/32" thick bakelite (3.25"
x .8"). Any body have a source (mail order as reside in Canada) for this bakelite?
Thanks.
Alfio
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=368760#368760
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Subject: | Re: Source for Bakelite - 1/32" thick |
Here is some material that may serve as a stand-in for bakelite - appears to
be used as an arc insulator among other things.
http://www.mcmaster.com/#garolite/=gp981g
Ed
--------------------------------------------------
From: "Alfio" <longeron@gmail.com>
Sent: Saturday, March 17, 2012 7:48 AM
Subject: AeroElectric-List: Source for Bakelite - 1/32" thick
>
> I am building a Wingtip VOR Antenna, and am in need of 1/32" thick
> bakelite (3.25" x .8"). Any body have a source (mail order as reside in
> Canada) for this bakelite? Thanks.
>
> Alfio
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=368760#368760
>
>
>
Message 3
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Subject: | Re: Source for Bakelite - 1/32" thick |
Alfio,
Why bakelite? There are lots of much better (stronger, more durable, more easily
worked) plastics available today.
I don't know about bakelite in particular, but McMaster-Carr has a large selection
of plastics of various types and sizes.
http://www.Mcmaster.com/ > Raw Materials > Plastics
There is probably something suitable for your purpose.
Blue skies & tailwinds,
Bob Borger
Europa XS Tri, Rotax 914, Airmaster C/S Prop.
Little Toot Sport Biplane, Lycoming Thunderbolt AEIO-320 EXP
3705 Lynchburg Dr.
Corinth, TX 76208-5331
Cel: 817-992-1117
rlborger@mac.com
On Mar 17, 2012, at 6:48 AM, Alfio wrote:
I am building a Wingtip VOR Antenna, and am in need of 1/32" thick bakelite (3.25"
x .8"). Any body have a source (mail order as reside in Canada) for this bakelite?
Thanks.
Alfio
Message 4
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Subject: | Re: Source for Bakelite - 1/32" thick |
When all else fails, Aircraft Spruce. They only offer down to 1/16"
material, however. Search for Phenolic.
Beware: This stuff is toxic so be careful when machining it.
Also know as Micarta in some places.
V
-----Original Message-----
From: Alfio
Sent: Saturday, March 17, 2012 4:48 AM
Subject: AeroElectric-List: Source for Bakelite - 1/32" thick
I am building a Wingtip VOR Antenna, and am in need of 1/32" thick bakelite
(3.25" x .8"). Any body have a source (mail order as reside in Canada) for
this bakelite? Thanks.
Alfio
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=368760#368760
-----
No virus found in this message.
Checked by AVG - www.avg.com
Message 5
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Subject: | Re: Poor Wiring Practice for VHF Noise? |
nuckolls.bob(at)aeroelect wrote:
>
> When every systems guy has to fight for and then
> jealously guard space on the airplane allotted to
> his efforts, it would be a disaster of some discovery
> were made where separation of certain wires from certain
> other wires was necessary or useful.
>
Of course! I never stopped to look at it from that angle. That makes perfect
sense. Thanks very much for the help.
Dan
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=368766#368766
Message 6
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Subject: | Re: Source for Bakelite - 1/32" thick |
At 06:48 AM 3/17/2012, you wrote:
I am building a Wingtip VOR Antenna, and am in need of 1/32" thick
bakelite (3.25" x .8"). Any body have a source (mail order as reside
in Canada) for this bakelite? Thanks.
Alfio
Bakelite is is the world's first synthetic plastic. It was the
material of choice for millions of molded shapes in the crafting
of consumer products back about 1933.
http://en.wikipedia.org/wiki/Bakelite
The stuff is still made but it's position in the marketplace is
more for historical authenticity or decorative purposes as opposed
to new product design. The stuff is brittle and in 1/32" thickness
would be VERY fragile. In fact, I sort of doubt that Bob's design
uses real Bakelite. I think he may have used the term to describe
the piece of plastic more as a historical recognition of its function
than for it's material. Bob is of my generation . . . many terms applied to
ideas common to our experience took on names that were more generic
than specific. I.e., all copy machines are 'xerox' machines, all
tissues are 'kleenex' etc.
The purist craftsman would recognize that this insulator
serves TWO purposes. First, it's a structural material that
maintains the position (.31" gap) between the two lower
pieces of aluminum. It's second function is to serve as
the dielectric in the capacitor formed between the lower
left and upper aluminum strips.
The exact value of that capacitor is a function of separation,
surface area and the dielectric constant of the insulating
material in the gap. This capacitor was no doubt 'tuned'
on the bench. Substitution of some plastic other than the
material used in the original design will change the value
of that capacitor.
Emacs!
This particular technique for attaching a feedline to the
antenna is called a 'gamma match'. It is characterized by
a gamma rod that taps up from ground onto the radiating
element of the antenna. If the rod tapped onto the radiator
at the base, the impedance presented to the feedline is
zero ohms; if connected at the tip, it is thousands
of ohms.
Somewhere between the base and the tip, we find 50
ohms. Problem is, the gamma rod is not itself a
confined transmission line . . . it has an inductive
reactance that degrades the transfer of power between
the antenna and feedline.
We can put a capacitor in series with that inductance
to resonant it at the frequency of interest thus
creating a series-resonant circuit. This has the
net effect of putting a 'dead short' between the
end of the feedline and the tap on the antenna
in spite of the fact that they are separated from
each other by some distance.
Back in my much younger days, adjustment of a
gamma match involved moving the tap in search of
the impedance Nirvana followed by a re-tuning
a variable capacitor . . .
Emacs!
to wash out the new value of inductive reactance
in the gamma rod. In fact, the last antenna I built
with this technology used a capacitor very much like
this one.
In the case before us, Bob Archer has deduced the
right place to tap the antenna for 50 ohms. He also
crafted the DIMENSIONS and MATERIALS for a
capacitor that most nearly cancels out the reactance
of the gamma-rod. In the capacitor above, the
dielectric (insulator) is air. In Bob's design,
the dielectric is 'Bakelite' . . . or something
he called by name.
The short answers come with two options:
(1) use any durable dielectric material of the
same thickness to craft a similar device
knowing that the 'match' will not be optimized.
I suspect that the resulting antenna will not
suffer so badly that degradation of performance
will be observable by a pilot in the cockpit.
Epoxy/Fiberglas (like etched circuit boards)
would be good.
(2) craft a new capacitor design that is
adjustable. You could use a small variable
capacitor like this . . .
Emacs!
With an adjustable capacitor, the new match can be
optimized with the application of suitable test
equipment.
Even better, I might craft a new, optimized
but fixed capacitor as a double sided etched circuit
board and even add an SMA right angle connetor
to the assembly to make a more elegant termination
of the coax.
To make a reasonable approximation of Bob's original
design, look for any plastic material of the right
thickness. 1/32 is not going to be easy, thicker
material will be much easier but demand large changes
to other dimensions.
Bob . . .
Message 7
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Subject: | Re: Source for Bakelite - 1/32" thick |
At 07:40 AM 3/17/2012, you wrote:
><eanderson@carolina.rr.com>
>
>Here is some material that may serve as a stand-in for bakelite -
>appears to be used as an arc insulator among other things.
>
>http://www.mcmaster.com/#garolite/=gp981g
Looks like this comes in lots of flavors none
of which are named 'Bakelite' and include
some of the legacy g-type insulations that
were once popular for etch circuit boards.
These were in fact epoxy glass formulations.
There are a bunch of plastic materials that
could be substituted for the Bakelite. I
was just walking down the isles at Lowes
and found a number of plastic products or
containers for product that were fabricated
from 1/32" (or thereabouts) material. Some of
the bottles for stuff like liquid dishwasher
detergents looked like they could supply a
piece of pretty durable plastic of that
thickiness.
I thought about this on the way home from
Wichita and concluded that one handy solution
would be to craft the capacitor/insulator
assembly from a piece of single sided copper
clad. The copper would replace the top aluminum
plate. It would also provide nice 'solder pads'
for direct connection of the coaxial feedline.
The two nylon screws would be replaced by
bonding the under side of the ECB material
to the matching stub.
I've got some plans for some experiments on the
Medicine Lodge OBAM aircraft antenna range (my
back yard) to see if I can measure any performance
difference between a VOR antenna with versus one
without a BALUN. I can also craft the Archer
style VOR antenna and do the experiment to deduce
the proper change in dimensions to us 1/16" FR-4
ECB material in place of the Bakelite. I've got
probably 100 square feet of the ECB material and
a shear. I could provide .8" wide strips of the stuff
along with modified dimensions optimized to the
change of dielectric constant for the insulating
materials.
Does anyone have a B-A wing tip antenna kit that
they've not yet installed? It would be handy to
borrow it for the experiment . . . to be returned
in as-new condition.
Bob . . .
Bob . . .
Message 8
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Subject: | Source for Bakelite - 1/32" thick |
Bob,
I have one that has the wrong cap on it. I talked to Bob Archer and he told
me thet the cap belongs on one of his dipole ant rather than on the
monopole that it is installed on. He sent me a replacement cap that I have
not installed yet. I can ship the entire thing to you for the experiment.
You will also notice that the "Bakelite is different on each cap" Send me an
address via the email address that shows with my name.
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Robert L.
Nuckolls, III
Sent: Saturday, March 17, 2012 4:42 PM
Subject: Re: AeroElectric-List: Source for Bakelite - 1/32" thick
<nuckolls.bob@aeroelectric.com>
At 07:40 AM 3/17/2012, you wrote:
><eanderson@carolina.rr.com>
>
>Here is some material that may serve as a stand-in for bakelite -
>appears to be used as an arc insulator among other things.
>
>http://www.mcmaster.com/#garolite/=gp981g
Looks like this comes in lots of flavors none
of which are named 'Bakelite' and include
some of the legacy g-type insulations that
were once popular for etch circuit boards.
These were in fact epoxy glass formulations.
There are a bunch of plastic materials that
could be substituted for the Bakelite. I
was just walking down the isles at Lowes
and found a number of plastic products or
containers for product that were fabricated
from 1/32" (or thereabouts) material. Some of
the bottles for stuff like liquid dishwasher
detergents looked like they could supply a
piece of pretty durable plastic of that
thickiness.
I thought about this on the way home from
Wichita and concluded that one handy solution
would be to craft the capacitor/insulator
assembly from a piece of single sided copper
clad. The copper would replace the top aluminum
plate. It would also provide nice 'solder pads'
for direct connection of the coaxial feedline.
The two nylon screws would be replaced by
bonding the under side of the ECB material
to the matching stub.
I've got some plans for some experiments on the
Medicine Lodge OBAM aircraft antenna range (my
back yard) to see if I can measure any performance
difference between a VOR antenna with versus one
without a BALUN. I can also craft the Archer
style VOR antenna and do the experiment to deduce
the proper change in dimensions to us 1/16" FR-4
ECB material in place of the Bakelite. I've got
probably 100 square feet of the ECB material and
a shear. I could provide .8" wide strips of the stuff
along with modified dimensions optimized to the
change of dielectric constant for the insulating
materials.
Does anyone have a B-A wing tip antenna kit that
they've not yet installed? It would be handy to
borrow it for the experiment . . . to be returned
in as-new condition.
Bob . . .
Bob . . .
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