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Source for Bakelite - 1/32" thick

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Ed Anderson

Joined: 10 Jan 2006
Posts: 475

Posted: Sat Mar 17, 2012 4:41 am Post subject: 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(at)gmail.com>

Sent: Saturday, March 17, 2012 7:48 AM

To: <aeroelectric-list(at)matronics.com>

Subject: Source for Bakelite - 1/32" thick



 	  Quote: 	
		   



 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

_________________
Ed Anderson
Rv-6A N494BW Rotary Powered
Matthews, NC
eanderson@carolina.rr.com

rlborger(at)mac.com
Guest

Posted: Sat Mar 17, 2012 4:43 am Post subject: 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(at)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

sprocket(at)vx-aviation.c
Guest

Posted: Sat Mar 17, 2012 5:32 am Post subject: 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



--

nuckolls.bob(at)aeroelect
Guest

Posted: Sat Mar 17, 2012 7:50 am Post subject: Source for Bakelite - 1/32" thick

At 06:48 AM 3/17/2012, you wrote:

 --> AeroElectric-List message posted by: "Alfio" <longeron(at)gmail.com>



 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.



 



 [img]cid:.0[/img]



   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 . . .



 [img]cid:.1[/img]

   

   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 . . .



 [img]cid:.2[/img]



   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 . . .

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nuckolls.bob(at)aeroelect
Guest

Posted: Sat Mar 17, 2012 3:43 pm Post subject: Source for Bakelite - 1/32" thick

At 07:40 AM 3/17/2012, you wrote:

 	  Quote: 	
		  

<eanderson(at)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 . . .

dsvs(at)ca.rr.com
Guest

Posted: Sat Mar 17, 2012 8:10 pm Post 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.



--

nuckolls.bob(at)aeroelect
Guest

Posted: Sun Mar 18, 2012 7:24 am Post subject: Source for Bakelite - 1/32" thick

At 11:09 PM 3/17/2012, you wrote:

 	  Quote: 	
		  



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.


	


    Interesting! You can send the stuff to me at

    P.O. Box 130, Medicine Lodge, KS  67104-0130

    or if you need to go UPS, then 209 Curry Lane

   Bob . . .

harrismarkr(at)hotmail.co
Guest

Posted: Sun Mar 18, 2012 10:02 am Post subject: Source for Bakelite - 1/32" thick

Hi Alfio



I am planning on doing the same do you have a drawing with the required dimensions on.The drawing I have dose not have the dimensions.



Thanks



Mark

Rent our beautiful 3 bedroom luxury villa in Orlando, Florida.

View our virtual tour but book direct with us. See the link below:-

http://www.florida1strentals.com/property.php?id=21

Contact Emma and Mark Harris 01582 529820

harrisfloridavilla(at)hotmail.com

On 17 Mar 2012, at 11:48, "Alfio" <longeron(at)gmail.com> wrote:



 	  Quote: 	
		   

 

 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

dsvs(at)ca.rr.com
Guest

Posted: Wed Mar 21, 2012 4:14 pm Post subject: Source for Bakelite - 1/32" thick

Package is on the way via Fedex.  Open from the bottom marked open this

side.



--

Alfio

Joined: 05 May 2008
Posts: 6

Posted: Tue Mar 27, 2012 3:48 am Post subject: Re: Source for Bakelite - 1/32

 	  harrismarkr(at)hotmail.co wrote: 	
		  Hi Alfio



I am planning on doing the same do you have a drawing with the required dimensions on.The drawing I have dose not have the dimensions.



Thanks



Mark

	




Here are some dimensions (enclosed jpg), though some dimension information is still missing for the gamma match. I will probably just borrow an SWR meter and 'play'.



Thanks for all that responded. I'll be looking for paper phenolic xxx since it has low dielectric loss at high frequencies.

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nuckolls.bob(at)aeroelect
Guest

Posted: Tue Mar 27, 2012 6:25 am Post subject: Source for Bakelite - 1/32" thick

 	  Quote: 	
		  Here are some dimensions (enclosed jpg), though some dimension 

information is still missing for the gamma match. I will probably 

just borrow an SWR meter and 'play'.



Thanks for all that responded. I'll be looking for paper phenolic 

xxx since it has low dielectric loss at high frequencies.


	


   Here's a little clearer image that I think is

   adequately dimensioned.



http://www.matronics.com/forums/viewtopic.php?t=89235

        Bob . . .

Alfio

Joined: 05 May 2008
Posts: 6

Posted: Tue Mar 27, 2012 8:09 am Post subject: Re: Source for Bakelite - 1/32

Thanks Bob. I have that one as well. I am still looking for some dimensions on the gamma match though. The gap is identified, but not how far it is from the wingtip support for instance.

nuckolls.bob(at)aeroelect
Guest

Posted: Tue Mar 27, 2012 6:05 pm Post subject: Source for Bakelite - 1/32" thick

At 11:09 AM 3/27/2012, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "Alfio" <longeron(at)gmail.com>



 Thanks Bob. I have that one as well. I am still looking for some dimensions on the gamma match though. The gap is identified, but not how far it is from the wingtip support for instance.



 

 	


   Did a little autocad layout and found that the top

   capacitor plate doesn't come all the way to the end

   of the capacitor di-electric. Given that it's

   a 60-60-60 triangle with an inside dim of 5.00

   inches, the details come out something like this:



  http://tinyurl.com/7jatp88 



 

   Bob . . .    [quote][b]

nuckolls.bob(at)aeroelect
Guest

Posted: Tue Mar 27, 2012 8:54 pm Post subject: Source for Bakelite - 1/32" thick

At 11:09 AM 3/27/2012, you wrote:

 --> AeroElectric-List message posted by: "Alfio" <longeron(at)gmail.com>



 Thanks Bob. I have that one as well. I am still looking for some dimensions on the gamma match though. The gap is identified, but not how far it is from the wingtip support for instance.



 

   Did a little Autocad layout and found that the top

   capacitor plate doesn't come all the way to the end

   of the capacitor di-electric. Given that it's

   a 60-60-60 triangle with an inside dim of 5.00

   inches, the details come out something like this:



 

    Just discovered that I had the elements of the gamma-match

    swapped end for end in the drawing. Here's the corrected

    version.



  http://tinyurl.com/7wol3jx 



 

 

   Bob . . .    [quote][b]

Alfio

Joined: 05 May 2008
Posts: 6

Posted: Wed Mar 28, 2012 2:04 am Post subject: Re: Source for Bakelite - 1/32

 	  nuckolls.bob(at)aeroelect wrote: 	
		  At 11:09 AM 3/27/2012, you wrote:

 

   Did a little Autocad layout and found that the top

   capacitor plate doesn't come all the way to the end

   of the capacitor di-electric. Given that it's

   a 60-60-60 triangle with an inside dim of 5.00

   inches, the details come out something like this:

  http://tinyurl.com/7wol3jx 



   Bob . . .    	




Just what I was looking for. Thanks.



Alfio

racerjerry

Joined: 15 Dec 2009
Posts: 202
Location: Deer Park, NY

Posted: Wed Mar 28, 2012 7:29 am Post subject: Re: Source for Bakelite - 1/32

Be careful when substituting non-reinforced plastic material for Micarta sheet.  Often, you will need a phenolic laminate material with resin impregnated layers of linen cloth to provide support and to preserve electrical spacings at elevated temperatures.  Many non-reinforced plastics will begin to flow when heated.  Impregnated cloth or paper will maintain some electrical spacing even when charred.



Aircraft Spruce still sells “Grade L (linen base) phenolic sheet” 1/16 and thicker, which is the generic equivalent of Micarta.

_________________
Jerry King

nuckolls.bob(at)aeroelect
Guest

Posted: Wed Mar 28, 2012 8:04 am Post subject: Source for Bakelite - 1/32" thick

At 10:29 AM 3/28/2012, you wrote:

 	  Quote: 	
		  



Be careful when substituting non-reinforced 

plastic material for Micarta sheet.  Often, you 

will need a phenolic laminate material with 

resin impregnated layers of linen cloth to 

provide support and to preserve electrical 

spacings at elevated temperatures.  Many 

non-reinforced plastics will begin to flow when 

heated.  Impregnated cloth or paper will 

maintain some electrical spacing even when charred.



Aircraft Spruce still sells “Grade L (linen 

base) phenolic sheet” 1/16 and thicker, which 

is the generic equivalent of Micarta.


	


    Good thoughts. At least this case doesn't raise

    critical questions as to structural integrity. The

    parts being joined are exceedingly light.



    The substitution problem here is two-fold. Structural

    as you've correctly deduced PLUS electrical. The insulating

    material is the dielectric for a high frequency capacitor

    that is expected to TUNE out some reactive components of

    the gamma-match elements.



    A List member is sending me a store-bought antenna.

    I'll mount it on a ground plane and get some SWR data.

    Then I'll measure the VALUE of the as-purchased capacitor.

    Then we'll have a basis for evaluating the electrical

    qualities of any proposed substitution.



    I'm thinking that we can fabricate the struts, insulator

    and capacitor from a single piece of double-sided etched

    circuit board material. I have lots of the material to

    play with and can pretty easily test it against the store

    bought design for optimal dimensions.



    In fact, I'm considering a 'mod' to the design that

    uses a variable capacitor soldered down to the ECB

    material . . . which must be adjusted but it's pretty

    easy to do with the ship's comm transmitter or a hand

    held and an SWR meter.

   Bob . . .

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