Today's Message Index:
----------------------
1. 03:39 AM - Ignitions harness chafe repair W/ pic (matt9923)
2. 06:47 AM - Re: Z-14 Question (Rocketman1988)
3. 07:06 AM - Re: Re: Z-14 Question (Kelly McMullen)
4. 07:59 AM - Re: Z-14 Question (Bill Watson)
5. 08:08 AM - Re: Re: Z-14 Question (Charlie England)
6. 08:18 AM - Re: Z-14 Question (Charlie England)
7. 08:26 AM - Re: Z-14 Question (Bill Watson)
8. 09:43 AM - Re: Z-14 Question (Bill Watson)
9. 02:32 PM - Re: Z-14 Question (Charlie England)
10. 03:43 PM - Re: Z-14 Question (Robert L. Nuckolls, III)
11. 08:49 PM - Re: Paint question (Matt Prather)
Message 1
INDEX | Back to Main INDEX |
NEXT | Skip to NEXT Message |
LIST | Reply to LIST Regarding this Message |
SENDER | Reply to SENDER Regarding this Message |
|
Subject: | Ignitions harness chafe repair W/ pic |
Found some chafing on the ignition harness the other day. I plan to move the harness
so it wont continue. My question is the best product to cover the shielding.
I have some PTFE film tape p422 i was going to use. Also have f4 tape and
spiral wrap. Any guidance would be helpful.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=481269#481269
Attachments:
http://forums.matronics.com//files/260729c5_3a95_4ecb_a1cf_50df33cb72ba_302.jpeg
Message 2
INDEX | Back to Main INDEX |
PREVIOUS | Skip to PREVIOUS Message |
NEXT | Skip to NEXT Message |
LIST | Reply to LIST Regarding this Message |
SENDER | Reply to SENDER Regarding this Message |
|
Subject: | Re: Z-14 Question |
Kelly,
Thanks for your opinion. I hesitate posting on these forums due to the nay sayers
when anything other than the simplest tech from the 50s is suggested. I have
chosen to use a full EFII system and fully accept the additional complexities.
I do appreciate your insight on things...
As for the previous post about the B lead current limiters, I would disagree with
putting the fuse at the other end as that would place it between the battery
and starter.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=481273#481273
Message 3
INDEX | Back to Main INDEX |
PREVIOUS | Skip to PREVIOUS Message |
NEXT | Skip to NEXT Message |
LIST | Reply to LIST Regarding this Message |
SENDER | Reply to SENDER Regarding this Message |
|
Subject: | Re: Z-14 Question |
As I said, it is all about the builder's choices. I have too many years
working on type certified airplanes as well as homebuilts, fixing self
induced errors, etc. to be very enamored of new-fangled EFII. My
experience in automotive arena tells me that the incremental
improvements from continuous flow fuel injection that arrived in the
late '50s to single cylinder electronic fuel injection of all but the
latest cars is fairly small..while the current direct injection into the
cylinder has had a much bigger improvement than anything since the
switch from carburetors to fuel injection.
I applaud your willingness to take on the challenge of EFII. When it all
works as advertised, it certainly will make starting easier and may also
help reduce maintenance.
However, I don't believe it justifies having two separate systems of
equal capacity. Still, your choice.
Kelly
On 6/29/2018 6:46 AM, Rocketman1988 wrote:
>
> Kelly,
>
> Thanks for your opinion. I hesitate posting on these forums due to the nay sayers
when anything other than the simplest tech from the 50s is suggested. I have
chosen to use a full EFII system and fully accept the additional complexities.
I do appreciate your insight on things...
>
> As for the previous post about the B lead current limiters, I would disagree
with putting the fuse at the other end as that would place it between the battery
and starter.
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=481273#481273
>
>
>
>
>
>
>
>
>
Message 4
INDEX | Back to Main INDEX |
PREVIOUS | Skip to PREVIOUS Message |
NEXT | Skip to NEXT Message |
LIST | Reply to LIST Regarding this Message |
SENDER | Reply to SENDER Regarding this Message |
|
Subject: | Re: Z-14 Question |
Help me here Charlie, I'm not quite following you. The B-lead
protection (current limiters) are installed between the Alternator
B-lead terminal and main bus line. The battery is not 'behind' the
protection and the bus. Rather the battery has no protection between it
and the bus fuse block(s).
What am I missing?
Bill
On 6/28/2018 9:56 PM, Charlie England wrote:
> Bill,
>
> Your install is obviously working, but it should be noted that your
> alternator B lead protection should be on the other end. If there's a
> fault in that wire, it should be big enough to handle everything the
> alternator can throw at it, but it'll never be big enough to handle
> everything the battery(s) can throw at it.
>
> FWIW,
>
> Charlie
>
> <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient&utm_term=icon>
> Virus-free. www.avast.com
> <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient&utm_term=link>
>
>
> <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus
Message 5
INDEX | Back to Main INDEX |
PREVIOUS | Skip to PREVIOUS Message |
NEXT | Skip to NEXT Message |
LIST | Reply to LIST Regarding this Message |
SENDER | Reply to SENDER Regarding this Message |
|
Subject: | Re: Z-14 Question |
On 6/29/2018 8:46 AM, Rocketman1988 wrote:
>
> Kelly,
>
> Thanks for your opinion. I hesitate posting on these forums due to the nay sayers
when anything other than the simplest tech from the 50s is suggested. I have
chosen to use a full EFII system and fully accept the additional complexities.
I do appreciate your insight on things...
>
> As for the previous post about the B lead current limiters, I would disagree
with putting the fuse at the other end as that would place it between the battery
and starter.
>
>
I guess I should have been more specific. The other end of the *wire*;
not the entire path. Look at the wire protection for the main alt, which
is at the hot side of the starter contactor end of the 8 ga wire
(correct). Now look at the protection on the aux alt B lead, at the
alternator end, instead of at the source end, which is the cross-tie
contactor.
When I took another look for this email, I also noticed that the 8 ga
wires feeding both fuse blocks don't have any protection. 'Conventional
wisdom' is that the battery contactor protects the 'fat wires', but
smaller wires need protection. What I see is 2 ga wires stepping down
in size to 8 ga wires, with no switching (disconnect) and protection at
the start of the 8 ga wires.
That's not a problem, as long as there isn't a problem. :-)
Charlie
---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus
Message 6
INDEX | Back to Main INDEX |
PREVIOUS | Skip to PREVIOUS Message |
NEXT | Skip to NEXT Message |
LIST | Reply to LIST Regarding this Message |
SENDER | Reply to SENDER Regarding this Message |
|
Subject: | Re: Z-14 Question |
Protection devices are to protect *wires*. In our aircraft environments
the source of damage to wires is always the battery. Alternator B leads
should be sized big enough to handle the max that the alternator can
deliver, so they need no protection from the alternator. But the battery
can deliver hundreds of amps (sometimes *many hundreds* of amps). The 4
ga and larger stuff can survive long enough to use the master contactor
as protection, but smaller stuff runs a big risk of lighting up the
insulation if there's no circuit protection.
No protection device on a wire is there to protect the battery.
Charlie
On 6/29/2018 9:58 AM, Bill Watson wrote:
> Help me here Charlie, I'm not quite following you. The B-lead
> protection (current limiters) are installed between the Alternator
> B-lead terminal and main bus line. The battery is not 'behind' the
> protection and the bus. Rather the battery has no protection between
> it and the bus fuse block(s).
>
> What am I missing?
>
> Bill
>
> On 6/28/2018 9:56 PM, Charlie England wrote:
>> Bill,
>>
>> Your install is obviously working, but it should be noted that your
>> alternator B lead protection should be on the other end. If there's a
>> fault in that wire, it should be big enough to handle everything the
>> alternator can throw at it, but it'll never be big enough to handle
>> everything the battery(s) can throw at it.
>>
>> FWIW,
>>
>> Charlie
>>
>> <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient&utm_term=icon>
>> Virus-free. www.avast.com
>> <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient&utm_term=link>
>>
>>
>> <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
>
>
---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus
Message 7
INDEX | Back to Main INDEX |
PREVIOUS | Skip to PREVIOUS Message |
NEXT | Skip to NEXT Message |
LIST | Reply to LIST Regarding this Message |
SENDER | Reply to SENDER Regarding this Message |
|
Subject: | Re: Z-14 Question |
I think Bob refers to my Z-14 in an RV-10 as 'everything including the
kitchen sink'. I other words, a bit too much.
Ten years ago when I started laying out my electrical system, I went
through the Z-schematics and frankly struggled to understand the various
backup scenarios. At one point I started sketching the Z-14 out and
everything became simple and symmetrical (I may have an excess of the
symmetry gene or something). More important, my desire coming into this
project was to have a state of the art panel which I could run for 10-15
even 30 minutes on the ground without worrying about a subsequent engine
start.
The need for this was driven home by 2 previous incidents; one being
flying in to New Orleans less than a year after the big hurricane and
finding myself sitting in my Maule staring at my Garmin 396 waiting for
a break in the usual gulf coast cu-nims. Why couldn't I sit in the FBO
and watch a Nexrad screen? Because it was still under reconstructions,
it lacked resources, and required a longish sprint to get to the
tiedowns. The other involved the Bahamas.
As my design came together, I ended up with (3) GRT HX EFIS screens and
assorted accessories. The GRTs did not have an integrated on/off switch
(or backup batts) and I wasn't interested in adding any. Main power on,
EFISs on; no accidental power-offs or reboots in the soup. Turned out
that those (3) screens are real power hogs, even dimmed down. Even now,
to run them for 30 mins on one Odyssey 680 suggests pulling a fuse on 1
or 2 might be a good idea (not really necessary). It made me question
the need for 3 screens but after encountering a couple of failures after
6 years of operation, it's cool to be able to swap out one of the 2
pilot oriented screens on the ramp at a remote location and fly with
100% of your normally used panel working.
The Z-14 has turned out to be a simple solution for me. I have 2 mags
and no electrically dependent ignition. I have 2 Odyssey 680s. Either
will start the engine, both guarantee it (I was happy to get rid of the
light weight starters in favor of the slow turning but stronger standard
starter). I can run my panel as long as I wish with the engine off.
Came in handy after the Breezy crash at Oshkosh a few years ago caused a
conga line of epic proportions. Etc etc.
I recently lost a voltage regulator. What did it require me to do?
Nothing except keep the x-feed switch on and turn off the non-working
side. No blip in the air, no shortened trip, no precautionary landing.
Flew 2 more legs like that with the same redundancy that most pilots fly
with most of the time.
Bill "I go what I wanted" Watson
On 6/28/2018 10:19 PM, Kelly McMullen wrote:
> <kellym@aviating.com>
>
> Having a flying IFR RV-10 myself I question the benefits of dual
> batteries along with dual alternators, etc. Almost all EFIS panels
> these days offer a backup battery, good for 1 hour or more. I have one
> for each of my EFIS screens. Most ship's batteries these days are good
> for an hour or more of minimized current. An Ipad can provide hours of
> moving map and GPS, and with some extras a nearly full EFIS screen.
> I can see if you choose to have dual electronic ignition systems that
> then you are vulnerable to lack of electrons for at least one. It
> seems to me that the SD-20 alternator for a backup source of power,
> with a small, Odessey 680 or less mounted on the firewall should
> handle any of those needs. You only need one good sized battery, such
> as the Odessey 925 mounted in stock rear location, for starter
> operation.s Or just keep one magneto for the backup, and eliminate
> need for dual electric power sources. You get 85% of the electronic
> ignition by replacing one mag.
> Just my opinion, but I would strive to keep the design as simple as
> possible, and avoid having totally dual everything just because you can.
> Just thinking your goals might be achieved with a simpler system.
> Kelly
>
> On 6/28/2018 6:56 PM, Charlie England wrote:
>
>>>>
>>> I have a Z-14 in an RV10. Bob's approach sounds great. I like the
>>> symmetry. Not having asked the question 10 years ago when laying
>>> my Z-14 out, I took a different approach.
>>>
>>> I have the Xfeed mounted with the other two contactors back on the
>>> battery tray. 2 AWG links them all up. Then I have a single 2AWG
>>> lead going to the starter Contactor. The other side has an 8AWG
>>> link going forward to one fuse panel (bus) and an 8AWG link going
>>> from the starter contactor to the other fuse panel (bus).
>>>
>>> The current limiters on mounted on the firewall and protect the
>>> lines going from the 2 alternators to the 2 main bus feeds.
>>>
>>> I've attached a schematic with the locations of devices implied.
>>>
>>> Bill "I love my Z-14" Watson
>>>
>> Bill,
>>
>> Your install is obviously working, but it should be noted that your
>> alternator B lead protection should be on the other end. If there's a
>> fault in that wire, it should be big enough to handle everything the
>> alternator can throw at it, but it'll never be big enough to handle
>> everything the battery(s) can throw at it.
>>
>> FWIW,
>>
>> Charlie
>>
>
>
---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus
Message 8
INDEX | Back to Main INDEX |
PREVIOUS | Skip to PREVIOUS Message |
NEXT | Skip to NEXT Message |
LIST | Reply to LIST Regarding this Message |
SENDER | Reply to SENDER Regarding this Message |
|
Subject: | Re: Z-14 Question |
I guess I didn't understand the fat wire versus the less-than-fat wire
exposure. My take on unprotected main power lines was that they can be
run and terminated in robust and simple ways with minimal exposure to
chafing, breaching of their insulation or shorting at the terminal
ends. With that view in mind, I was thinking of my 8AWG wires as 'fat
wires' just as my 2AWG wire is. So I view the 8AWG on the Aux side as a
'fat wire' with robust and simple terminations at the contactor and the
fuse block.... with a firewall stud in the path which happens to be part
of the current limiter unit. I'm quite confident that those 8AWG runs
are simple and safe.
I should note that the 8AWG runs from the current limiter firewall studs
to the fuse panels by the copilot's leg are quite short. Putting the
current limiter on the Aux side near the x-feed contactor behind the
luggage area would have required 2 long runs of 8AWG instead of 1.
I never considered the contactors as any kind of circuit protection. I
thought of them as simply switches, switches for high current loads
that can conveniently be thrown remotely by small switches. They enable
you to manually disconnect a high current line but there's no automatic
protection.
Bill
On 6/29/2018 11:18 AM, Charlie England wrote:
> Protection devices are to protect *wires*. In our aircraft
> environments the source of damage to wires is always the battery.
> Alternator B leads should be sized big enough to handle the max that
> the alternator can deliver, so they need no protection from the
> alternator. But the battery can deliver hundreds of amps (sometimes
> *many hundreds* of amps). The 4 ga and larger stuff can survive long
> enough to use the master contactor as protection, but smaller stuff
> runs a big risk of lighting up the insulation if there's no circuit
> protection.
>
> No protection device on a wire is there to protect the battery.
>
> Charlie
>
> On 6/29/2018 9:58 AM, Bill Watson wrote:
>> Help me here Charlie, I'm not quite following you. The B-lead
>> protection (current limiters) are installed between the Alternator
>> B-lead terminal and main bus line. The battery is not 'behind' the
>> protection and the bus. Rather the battery has no protection
>> between it and the bus fuse block(s).
>>
>> What am I missing?
>>
>> Bill
>>
>> On 6/28/2018 9:56 PM, Charlie England wrote:
>>> Bill,
>>>
>>> Your install is obviously working, but it should be noted that your
>>> alternator B lead protection should be on the other end. If there's
>>> a fault in that wire, it should be big enough to handle everything
>>> the alternator can throw at it, but it'll never be big enough to
>>> handle everything the battery(s) can throw at it.
>>>
>>> FWIW,
>>>
>>> Charlie
>>>
>>> <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient&utm_term=icon>
>>> Virus-free. www.avast.com
>>> <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient&utm_term=link>
>>>
>>>
>>> <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
>>
>>
>
---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus
Message 9
INDEX | Back to Main INDEX |
PREVIOUS | Skip to PREVIOUS Message |
NEXT | Skip to NEXT Message |
LIST | Reply to LIST Regarding this Message |
SENDER | Reply to SENDER Regarding this Message |
|
Subject: | Re: Z-14 Question |
Ah, the joys of trying to communicate via the interwebs. :-)
I'd agree that really short runs (the Aeroelectric 'gold standard' seems
to be 6", but I've probably fudged that in a place or two) are low risk.
But if that #8 from the right side of the x-feed contactor to the
current limiter runs the length of the plane, I'd want protection at the
source end. Not sure why moving the protection would require two runs.
If the protection is at the contactor, the #8 could run to either fuse
block #2, or to the aux alternator B lead, as 'geographically
convenient'. Then it would continue to the other component. Electrically
identical to what you have now, except the long run (and the short run)
of #8 would be protected from the battery. If the current limiter is now
on the firewall, the only #8 in that run that's actually protected is
between the limiter and the alternator B lead.
I'm not trying to tell you what to do; just wanted to mention a
potential vulnerability. If you're comfortable with the design, then run
with it. It's obviously been working ok so far. I know I've done a few
things that others wouldn't be comfortable with, but I am, with my plane.
FWIW, I have a similar arrangement for my engine bus (electrically
dependent alternative engine) to your fuse block #1, with the bus being
fed off the hot terminal of the contactor. In my case, it's the master
because everything's on the firewall in my plane, but same risk of
unprotected #8 wire. I protected it, and both my #8 alternator B leads,
by using #12 fuse link wire on the 'battery end' of each #8 wire. Just a
4"-6" long piece of the fuse link wire soldered on the end, with the
joint insulated with heat shrink. Then the fuse link gets the terminal
that connects to the contactor. The fuse link wire is an 'off the shelf'
item available from automotive supply houses; it has built-in insulation
to contain the heat if the protection is 'tripped'.
Charlie
On 6/29/2018 11:36 AM, Bill Watson wrote:
> I guess I didn't understand the fat wire versus the less-than-fat wire
> exposure. My take on unprotected main power lines was that they can
> be run and terminated in robust and simple ways with minimal exposure
> to chafing, breaching of their insulation or shorting at the terminal
> ends. With that view in mind, I was thinking of my 8AWG wires as 'fat
> wires' just as my 2AWG wire is. So I view the 8AWG on the Aux side as
> a 'fat wire' with robust and simple terminations at the contactor and
> the fuse block.... with a firewall stud in the path which happens to
> be part of the current limiter unit. I'm quite confident that those
> 8AWG runs are simple and safe.
>
> I should note that the 8AWG runs from the current limiter firewall
> studs to the fuse panels by the copilot's leg are quite short.
> Putting the current limiter on the Aux side near the x-feed contactor
> behind the luggage area would have required 2 long runs of 8AWG
> instead of 1.
>
> I never considered the contactors as any kind of circuit protection.
> I thought of them as simply switches, switches for high current loads
> that can conveniently be thrown remotely by small switches. They
> enable you to manually disconnect a high current line but there's no
> automatic protection.
>
> Bill
>
> On 6/29/2018 11:18 AM, Charlie England wrote:
>> Protection devices are to protect *wires*. In our aircraft
>> environments the source of damage to wires is always the battery.
>> Alternator B leads should be sized big enough to handle the max that
>> the alternator can deliver, so they need no protection from the
>> alternator. But the battery can deliver hundreds of amps (sometimes
>> *many hundreds* of amps). The 4 ga and larger stuff can survive long
>> enough to use the master contactor as protection, but smaller stuff
>> runs a big risk of lighting up the insulation if there's no circuit
>> protection.
>>
>> No protection device on a wire is there to protect the battery.
>>
>> Charlie
>>
>> On 6/29/2018 9:58 AM, Bill Watson wrote:
>>> Help me here Charlie, I'm not quite following you. The B-lead
>>> protection (current limiters) are installed between the Alternator
>>> B-lead terminal and main bus line. The battery is not 'behind' the
>>> protection and the bus. Rather the battery has no protection
>>> between it and the bus fuse block(s).
>>>
>>> What am I missing?
>>>
>>> Bill
>>>
>>> On 6/28/2018 9:56 PM, Charlie England wrote:
>>>> Bill,
>>>>
>>>> Your install is obviously working, but it should be noted that your
>>>> alternator B lead protection should be on the other end. If there's
>>>> a fault in that wire, it should be big enough to handle everything
>>>> the alternator can throw at it, but it'll never be big enough to
>>>> handle everything the battery(s) can throw at it.
>>>>
>>>> FWIW,
>>>>
>>>> Charlie
>>>>
>>>> <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient&utm_term=icon>
>>>> Virus-free. www.avast.com
>>>> <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient&utm_term=link>
>>>>
>>>>
>>>> <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
>>>
>>>
>>
>
---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus
Message 10
INDEX | Back to Main INDEX |
PREVIOUS | Skip to PREVIOUS Message |
NEXT | Skip to NEXT Message |
LIST | Reply to LIST Regarding this Message |
SENDER | Reply to SENDER Regarding this Message |
|
Subject: | Re: Z-14 Question |
At 11:36 AM 6/29/2018, you wrote:
>I guess I didn't understand the fat wire versus the less-than-fat
>wire exposure. My take on unprotected main power lines was that
>they can be run and terminated in robust and simple ways with
>minimal exposure to chafing, breaching of their insulation or
>shorting at the terminal ends. With that view in mind, I was
>thinking of my 8AWG wires as 'fat wires' just as my 2AWG wire
>is. So I view the 8AWG on the Aux side as a 'fat wire' with robust
>and simple terminations at the contactor and the fuse block.... with
>a firewall stud in the path which happens to be part of the current
>limiter unit. I'm quite confident that those 8AWG runs are simple and safe.
Agreed.
>I should note that the 8AWG runs from the current limiter firewall
>studs to the fuse panels by the copilot's leg are quite
>short. Putting the current limiter on the Aux side near the x-feed
>contactor behind the luggage area would have required 2 long runs of
>8AWG instead of 1.
>
>I never considered the contactors as any kind of circuit
>protection. I thought of them as simply switches, switches for
>high current loads that can conveniently be thrown remotely by small
>switches. They enable you to manually disconnect a high current
>line but there's no automatic protection.
Correct . . . powers-that-be consider them
'crew controlled protection', i.e. they're
used to disconnect sources of energy to smallest
practical footprint in times of stress . . .
like smoke or . . . short approach to the rocks.
B-lead protection is needed ONLY for the exceedingly
rare instance of shorted alternator diodes so
any such protection is located as close to the
bus/distribution node as practical.
Properly sized b-lead protection CANNOT be
opened by alternator energy.
Having recited the legacy philosophy I'll
note that all three of the vehicles in my
driveway ranging from 87GMC to 2006KIA
ALL connect the b-lead directly to the battery . . .
not even fusible links. In over 50 years
of driving alternators, never had diodes
short . . . I have had two instances of
diodes opening . . . one just two weeks
ago . . . but no shorts.
Of course, smoke from the b-lead in a
car is no big deal . . . as long as it
doesn't set the engine grease on fire.
Airplanes not so much.
Current limiters scattered around the bus
structures are very low return on investment . ..
probably zero.
Bob . . .
Message 11
INDEX | Back to Main INDEX |
PREVIOUS | Skip to PREVIOUS Message |
NEXT | Skip to NEXT Message |
LIST | Reply to LIST Regarding this Message |
SENDER | Reply to SENDER Regarding this Message |
|
Subject: | Re: Paint question |
Good point about the surface tension effect causing the conductive particles
to be completely covered and surrounded...
And, any detuning effect is probably limited - can=99t lower the reson
ant frequency of particles from GHz (?) to MHz...
How about capacitive coupling of one particle to the next? Capacitance has A
rea in the numerator and distance in the denominator... Probably not much t
here - the A is to small and the d too large. Hmm.
Regards,
Matt Prather
> On Jun 21, 2018, at 8:59 AM, Robert L. Nuckolls, III <nuckolls.bob@aeroele
ctric.com> wrote:
>
> At 09:46 AM 6/20/2018, you wrote:
>> At 07:56 AM 6/20/2018, you wrote:
>>> Hi Bob,
>>> Long time no contact... I=99m happy you=99re still in this g
ame!
>>>
>>> Regarding this topic, I wonder how much the the conductive bits are in c
ontact with each other. I don=99t know how isolated each bit of conduc
tive material is in such a paint, but I could imagine there could be billion
s of contacts between neighboring bits of flake or powder such that there wo
uld be a random resistive path across the painted surface.
>
> I've been doing some 'asphalt contemplation' on a simple
> test setup to evaluate the effects of various paints/coatings
> on antenna performance.
>
> I was trying to imagine how conductive particles suspended
> in a non-conductive 'solution' would achieve a
> microscopic version of the gas-tight contact needed
> for reliable connection between conductors. It seems
> that surface tension would cause each particle to
> be totally enveloped, thus prevented from making
> physical contact with other particles.
>
> Not sure about what happens as the solution becomes
> a solid when solvents evaporate and the paint dries.
> I've seen volume resistivity measurements on some
> coatings/fillers, like potting compounds. These
> are always VERY high . . . including those designed
> for thermal conductivity.
>
> I'm thinking that there are three potential effects
> of paint . . . the dielectric effects you hypothesized
> which would probably be limited to a lowering of
> resonant frequency, the shielding effects which
> block and or re-direct the wave fronts of interest
> and attenuation/dissipation effects that simply
> turn the RF energy into heat.
>
> I'm recalling a bit of a fire drill on the ELT
> transmitters for Beechjets where a new version
> of the ELT kept tripping off due to high SWR
> on the VHF antenna. Seems the older version happily
> existed with a pair of antennas tucked under
> the fairing at the root of vertical fin leading
> edge.
>
> <25ac6ff7.jpg>
>
> Oookkaaay . . .
>
> Now, let's lay the VHF antenna back so that it
> sorta conforms to the inside of the fairing . . .
> except . . .
>
> Fairing was also part of an air-intake ductwork
> for the A/C . . . so the antennas wound up
> looking like this:
>
> <25ac7006.jpg>
>
> There were metallic braces inside the
> fairing along with bond straps that tied
> the braces to airframe . . . for lighting
> effects. Added on top of all this was a
> composite fairing material . . .
> capped off with paint often chosen by
> the customer hence of uncontrolled pedigree.
>
> What's a poor ELT transmitter to do?
>
> <25ac7016.jpg>
>
>
> I couldn't find anywhere in the archives where
> this installation had been measured for
> performance . . . a condition that didn't
> raise its ugly head until a new ELT complained
> about an 'unsatisfactory' antenna.
>
> I suggested we design a new, top loaded vertical
> for the VHF antenna that remained vertical with
> better separation from the effects of overhead
> structures.
>
> <25ac7026.jpg>
>
> Further, we could fine tune the antenna to accommodate
> any residual effects from proximity of other structures.
>
> This got the flying fuzz all in a dither . . . a new
> antenna would violate the TSO on the ELT . . . but
> abusing the TSO'd antenna did not . . . go figure.
> I think they wound up widening the SWR trip tolerances
> on the ELT transmitter.
>
> Not one of my happier experiences with the bureaucracy.
>
> Bob . . .
Other Matronics Email List Services
These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.
-- Please support this service by making your Contribution today! --
|