Today's Message Index:
----------------------
1. 04:28 AM - Epoxy to Aluminum ()
2. 06:55 AM - Re: Mechanical question - Bond Studs (Robert L. Nuckolls, III)
3. 08:30 AM - Re: Copper Bar vs "FAT" wire (grjtucson)
4. 08:37 AM - Re: Epoxy to Aluminum (Eric M. Jones)
5. 09:03 AM - Re: Re: Mechanical question - Bond Studs ()
6. 11:06 AM - Fuses vs Circuit Breaker Fuses (Henry Trzeciakowski)
7. 11:22 AM - Re: Strange Exp-Bus Problem (Mark Doble)
8. 12:11 PM - Re: Re: Mechanical question - Bond Studs (Ed Anderson)
9. 05:34 PM - Re: Copper Bar vs "FAT" wire (n277dl)
10. 06:44 PM - Re: Re: Mechanical question - Bond Studs (Robert L. Nuckolls, III)
11. 06:46 PM - Re: Re: Copper Bar vs "FAT" wire (Robert L. Nuckolls, III)
12. 06:47 PM - Re: Fuses vs Circuit Breaker Fuses (Robert L. Nuckolls, III)
13. 07:50 PM - Re: Epoxy to Aluminum (Speedy11@aol.com)
14. 08:18 PM - Re: Mechanical question (Speedy11@aol.com)
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: | Epoxy to Aluminum |
4/28/2008
Hello Dennis, Thanks for your interesting input.
One technique that may be used, if appropriate to the situation, to improve
joint holding, is to make holes in the aluminum. This permits the epoxy to
ooze through and form sort of a rivet effect for the glue line.
'OC' Says: "The best investment we can make is the effort to gather and
understand knowledge."
-----------------------------------------------------------
Time: 10:11:16 AM PST US
From: "Dennis Johnson" <pinetownd@volcano.net>
Subject: AeroElectric-List: Epoxy to Aluminum
Greetings,
As part of building a composite airplane, I studied everything I could
find about epoxies, materials, and adhesive bonding in general. I
concluded that I did not have the ability to make an epoxy bond to
aluminum that I could be confident that it wouldn't fail.
The problem is that aluminum begins oxidizing immediately after
cleaning. No matter how quick you are, unless you use extraordinary
measures, there will be aluminum oxide on the surface you are bonding.
Aluminum oxide has relatively low strength. The epoxy bonds well to the
aluminum oxide, but the aluminum oxide isn't stuck very well to the
underlying aluminum. After some number of hot/cold and wet/dry cycles,
the bond may weaken enough to fail.
Obviously, Boeing and others solved this problem long ago. However,
based on the great reference book, "Composite Basics," by Andrew
Marshall, their methods aren't practical for most of us homebuilders.
>From chapter 11, Marshall says, "Unfortunately, both the FPL etch and
the PAA treatments (the ones widely and successfully used in the
industry) involve extensive chemical control and a large investment in
equipment."
As an interesting aside, he describes an industry standard "wedge" test
where two .125" thick aluminum pieces are bonded together. After
curing, a wedge is driven into the end of the assembly, between the two
pieces of aluminum, which forces the bond to break at that point. A
mark is placed at the point where the fracture stops. The test piece is
then placed into a warm, wet chamber for one hour. The assembly is then
removed and the additional distance the crack propagated during the
warm/wet test is measured. If the crack grew less than three-fourths of
an inch, the bond is considered to be good for life. Marshall says that
if the aluminum was cleaned but not chemically treated, the assembly
will likely totally delaminate during the one hour test!
Since I didn't have the ability to duplicate Boeing's chemical treatment
process, I didn't make any bond to aluminum that would cause anything
more than inconvenience if it failed. Heat and humidity seem to be the
culprits, which might explain why some people report long lasting bonds
and others have failures.
Best,
Dennis
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: Mechanical question - Bond Studs |
At 06:03 PM 4/27/2008 -0400, you wrote:
>Very Cool! Thanks for pointing them out to me.
>Stan
>Do not archive
>
>Take a look at Perforated Base Binding Nuts and Studs on page
>3120 of the
>
>http://www.mcmaster.com
Agreed! Many of you will recall that for a time
a few years ago, the 'Connection offered "bond studs"
for the purpose of securing non-structural support
studs to the surfaces inside airplanes. We went through
several batches of a manufacturer's surplus product
in less than a year . . . over 3500 parts as I recall.
I've toyed with then notion of having something made
that would duplicate or improve upon the utility of
that technique but it's been one-project-of-many and
is pretty far back on the stove.
In the mean time, it seems our friends at McMaster-
Carr have cataloged a variety of similar products that
are almost sure to be equal to or better than the
junk-yard gizmos I sold out of. See:
http://aeroelectric.com/articles/Bond_Studs.pdf
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
----------------------------------------
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: Copper Bar vs "FAT" wire |
nuckolls.bob(at)cox.net wrote:
> At 12:12 PM 4/27/2008 -0700, you wrote:
>
> Yeah . . . I stuck my foot in it. I was tangled up
> in some numbers recalled from a different case
> and blew it.
>
>
> As another Lister pointed out, brass has a higher
> resistance than copper. A quick measurement of
> some stuff in my metals bin from K&S Engineering
> shows their brass alloy to be about 4x the
> resistance of equivalent copper sheet. So, the
> same stud-to-stud strap of .062 x .75 brass strip
> would drop about 45 millivolts . . . on the same
> order as a shunt . . . but unnecessarily high.
>
> When I get the drive stand running, I'll be
> strapping some high current contactors in the same
> manner as those on your airplanes and I'll get some
> actual drops and temperature rises for the various
> materials available to us. In the mean time,
> the K&S metals 16142 0.060 copper sheet is the
> better material from which to fabricate stud
> jumpers than the brass strip cited earlier.
>
> Bob . . .
Ouch.
Bob,
Per your earlier recommendation to me, I standardized on 4 awg fat wires for my
60amp RV-7 and I went with .75 x .062 brass for the strap between master and
starter contactor and between starter contactor and anl. You had actually suggested
.032 but that seemed thin to me, particularly since Van's calls out .125
copper.
Now you're suggesting copper for these and I'm wondering if I should swap out my
brass? It's not a huge amount of work but if the .062 brass will still work
fine, I'm likely to leave it.
Also, is .032 brass still OK for the ground buses? I haven't installed those yet
though the tabs are soldered on.
Thanks,
George Jenson
RV-7
Tucson, AZ
--------
George Jenson -
Tucson, AZ - RV-7 Standard Build
Empennage Completed 1/06
Wings Completed 11/06
Fuselage in Progress
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=179827#179827
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: Epoxy to Aluminum |
> Greetings,
>
> After proper dry preparation per the manual, West System epoxy technical manual
(catalogue number 002-950, 1994) on page 9, item 5, in bonding hardware ( continued
from page says: "Coat the bottom contact surface of the hardware with
unthickened epoxy. Wire brush or sand the wet epoxy into the surface with 50
grit sandpaper. Sanding the base with, coated with epoxy, will expose the epoxy
directly to fresh metal with no chance for the metal to oxidize."
> Raymond Julian
> Kettle River, MN
The West System method seems brilliant to me. It seems to use the approach often
used in soldering aluminum where a stainless-wire brush removes the oxide while
being protected from re-oxidation by the solder (and flux). Nice.
--------
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones@charter.net
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=179832#179832
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: Mechanical question - Bond Studs |
"Perforated Base Binding Nuts and Studs on page 3120 of the
http://www.mcmaster.com"
For what its worth I have used McMaster perforated base studs. I used the
Stainless ones. They are very shiny, guess you could hand sand them,
blasting with aluminium oxide does a better job. I used the 1/4-20 studs,
but needed small nuts so tapped some aviation small outside diameter nuts
and gave them a bit of a squishing, and used a dab of Loctite. They are
easy to cut, and in my instance tack weld together (TIG) for easy
installation with exact dimension between studs for holding two Flowscan
201B transducers.
They are heavier than Aircraft Spruce aluminium studs, but the ability to
weld made them my choice for the Transducers.
As far as bonding to aluminium, you can not do much better than Redux 420
(or Huntsmans Epibond 420) which has rubber added to it, also has glass in
its brew so you can not squeeze out all adhesive. My Europa is held
together with this stuff! Far superior to Laminating Epoxy or JB Weld.
Scuff sand with 80 grit or if scratches will not cause stress cracking use
40 grit. Then wet out with pure Redux, then make a bed of Redux and Flox
(toothpaste consistency, Flox is chopped cotton and makes structural mix)
and set stud in place. Aluminium studs from Spruce or Wicks work great
with Redux, I drill some holes in it for rivet effect. Note McMaster studs
allow a flat base even with adhesive because of integral stand off. If it
is something I don't want to come off ever, can put 2 BID on it. BID is
BiDirectional fiberglass cloth as used by Rutan. What you do is take a
piece of clear plastic and draw a circle on it with a magic marker, turn
sheet over and place 2 pieces of BID on it, then wet out with Redux and
squeegee out excess, make a hole in center for stud, cut circumferance and
apply to stud, then peel off plastic.
Again Redux has rubber in it, so it is somewhat flexible, it prevents
point loading and peeling. Boeing uses Epibond 420. I am pretty certain
that if you anodized it would probably make a better bond, but I am pretty
certain that studs stuck only with Redux to scuffed aluminium will be
around for life of aircraft, and with 2 BID, foreverrrrr.
Side note, I bond zip tie blocks or other nylon hold downs to aluminium,
by scuffing nylon with 40 and aluminium with 40 or 80, then JB KWIK in
place, after 15 minutes Redux/Flox fillet and 1 Redux/BID. If you don't
have Redux, you could probably plastic sheet 1 BID with long cure JB Weld.
If you don't have BID could probably plastic sheet a few layers of gauze
style Spackle tape with long cure JB Weld, both of which are available at
the aviation isle of Home Depot or your local home center or hardware
store. Test first as I have not, but pretty certain it will be a winner.
On Fiberglass, I JB KWIK, then Aeropoxy/flox fillet then 1 Aeropoxy/BID.
Redux would work but harder to work with (mix and mess and expense).
Back to studs, you will need to try, but on aluminium or fiberglass, scuff
stud with 40 grit, and aircraft with 40 or 80, wet stud and aircraft with
thin layer of JB long cure, then mix some JB long cure with some flox
(toothpaste consistency) and install stud, then plastic sheet a few layers
of spackle tape and JB long cure, cut center hole and scissor OD and
install.
If cold, or damp just leave the plastic on and remove after cure, will be
a nice smooth surface.
If you are not working in 70 plus temperatures with less than ~60%
humidity, warm up stud and airplane.
Warm up first, scuff sand and apply adhesive, wait as Little time as you
can after scuff to apply adhesive.
Ron Parigoris
I could have installed 4 studs with JB Long and Spackle tape in the amount
of time it took me to write this.
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: | Fuses vs Circuit Breaker Fuses |
Bob:
I was "surfing the net" the other day and came upon a couple of sites that
sell ATC Circuit Breaker fuses. They fit a standard fluse block that B & C
sells. I found these quite interesting and pondered the question:
if they are worth the investment (not a huge difference in cost between the
CB fuse and regular fuse)?
are they more robust and would they make a good substitute for fuselable
links?
and serve any "better" or improve upon the electric architecture than
standard fuses? - especially in your Z diagrams: Z-11, 12 and or 13?
Henry
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: Strange Exp-Bus Problem |
Hey Peter,
Check the electrical system closely for wire connector rings of the
incorrect size. Eg. A too large ring over a connector stud.
If the connector rings are bigger than the stud, over time they vibrate and
the resulting residue makes a poor contact. This will give you the exact
fault you have.intermittent electrical faults.
I would check all the contactors connections, alternator connectors,
etc..anything with a big ring connector. The culprit ring connector will
look black when you take the nut off.
Don't ask how I know so much about this problem :-)
Cheers,
Mark.
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: Mechanical question - Bond Studs |
I found that copper tubing used for gas lines can be beaten flat and used as
the copper bar - the advantage is you can find it almost anywhere.
Ed
----- Original Message -----
From: "Robert L. Nuckolls, III" <nuckolls.bob@cox.net>
Sent: Monday, April 28, 2008 9:50 AM
Subject: AeroElectric-List: Re: Mechanical question - Bond Studs
> <nuckolls.bob@cox.net>
>
> At 06:03 PM 4/27/2008 -0400, you wrote:
>
>>Very Cool! Thanks for pointing them out to me.
>>Stan
>>Do not archive
>>
>>Take a look at Perforated Base Binding Nuts and Studs on page
>>3120 of the
>>
>>http://www.mcmaster.com
>
> Agreed! Many of you will recall that for a time
> a few years ago, the 'Connection offered "bond studs"
> for the purpose of securing non-structural support
> studs to the surfaces inside airplanes. We went through
> several batches of a manufacturer's surplus product
> in less than a year . . . over 3500 parts as I recall.
>
> I've toyed with then notion of having something made
> that would duplicate or improve upon the utility of
> that technique but it's been one-project-of-many and
> is pretty far back on the stove.
>
> In the mean time, it seems our friends at McMaster-
> Carr have cataloged a variety of similar products that
> are almost sure to be equal to or better than the
> junk-yard gizmos I sold out of. See:
>
> http://aeroelectric.com/articles/Bond_Studs.pdf
>
> Bob . . .
>
> ----------------------------------------)
> ( . . . a long habit of not thinking )
> ( a thing wrong, gives it a superficial )
> ( appearance of being right . . . )
> ( )
> ( -Thomas Paine 1776- )
> ----------------------------------------
>
>
>
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: Copper Bar vs "FAT" wire |
grjtucson wrote:
>
> nuckolls.bob(at)cox.net wrote:
> > At 12:12 PM 4/27/2008 -0700, you wrote:
> >
> > Yeah . . . I stuck my foot in it. I was tangled up
> > in some numbers recalled from a different case
> > and blew it.
> >
> >
> > As another Lister pointed out, brass has a higher
> > resistance than copper. A quick measurement of
> > some stuff in my metals bin from K&S Engineering
> > shows their brass alloy to be about 4x the
> > resistance of equivalent copper sheet. So, the
> > same stud-to-stud strap of .062 x .75 brass strip
> > would drop about 45 millivolts . . . on the same
> > order as a shunt . . . but unnecessarily high.
> >
> > When I get the drive stand running, I'll be
> > strapping some high current contactors in the same
> > manner as those on your airplanes and I'll get some
> > actual drops and temperature rises for the various
> > materials available to us. In the mean time,
> > the K&S metals 16142 0.060 copper sheet is the
> > better material from which to fabricate stud
> > jumpers than the brass strip cited earlier.
> >
> > Bob . . .
>
>
> Ouch.
>
> Bob,
>
> Per your earlier recommendation to me, I standardized on 4 awg fat wires for
my 60amp RV-7 and I went with .75 x .062 brass for the strap between master and
starter contactor and between starter contactor and anl. You had actually suggested
.032 but that seemed thin to me, particularly since Van's calls out .125
copper.
>
> Now you're suggesting copper for these and I'm wondering if I should swap out
my brass? It's not a huge amount of work but if the .062 brass will still work
fine, I'm likely to leave it.
>
> Also, is .032 brass still OK for the ground buses? I haven't installed those
yet though the tabs are soldered on.
>
> Thanks,
>
> George Jenson
> RV-7
> Tucson, AZ
George,
I was doing the annual on my 7A this past weekend. It'd began to get difficult
to start the prop spinning when cold. The battery was only a couple years
old but I decided to replace it. Also, just for good measure I replaced the original
starter contactor and battery contactor with new ones from B&C, original
ones from Vans. Rumor (un-proven by me) that the B&C were better quality.
Anyway, had to replace the copper bus bars as the original doesn't work anymore.
Couldn't find copper anywhere local so came back, found the post in early April
where brass was recommended instead of copper.... purchased .063 x .5, installed
on the 7A and it all worked fine. Only a couple starts but didn't have
any problems so the brass will work. Guess time will tell how well.
Doug
--------
Doug
"Fools" are always more creative than process people and will always
find ways to ruin a perfectly good set of processes.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=179943#179943
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: Mechanical question - Bond Studs |
At 03:07 PM 4/28/2008 -0400, you wrote:
><eanderson@carolina.rr.com>
>
>I found that copper tubing used for gas lines can be beaten flat and used
>as the copper bar - the advantage is you can find it almost anywhere.
>
>Ed
If one is attempting to get gas-tight connections to
the sheet-material bus-bars, they need to be as flat
as possible with parallel and smooth front and back
surfaces. While you can certainly drill holes in and
bolt up chunks of flattened tubing, the finished product
leaves some concerns for long-term joint integrity.
Suggest you stick with manufactured sheet materials.
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
----------------------------------------
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: Copper Bar vs "FAT" wire |
>
> > Bob,
> >
> > Per your earlier recommendation to me, I standardized on 4 awg fat
> wires for my 60amp RV-7 and I went with .75 x .062 brass for the strap
> between master and starter contactor and between starter contactor and
> anl. You had actually suggested .032 but that seemed thin to me,
> particularly since Van's calls out .125 copper.
> >
> > Now you're suggesting copper for these and I'm wondering if I should
> swap out my brass? It's not a huge amount of work but if the .062 brass
> will still work fine, I'm likely to leave it.
> >
> > Also, is .032 brass still OK for the ground buses? I haven't installed
> those yet though the tabs are soldered on.
> >
> > Thanks,
> >
> > George Jenson
> > RV-7
> > Tucson, AZ
>
>
>George,
> I was doing the annual on my 7A this past weekend. It'd began to get
> difficult to start the prop spinning when cold. The battery was only a
> couple years old but I decided to replace it. Also, just for good
> measure I replaced the original starter contactor and battery contactor
> with new ones from B&C, original ones from Vans. Rumor (un-proven by me)
> that the B&C were better quality.
>
>Anyway, had to replace the copper bus bars as the original doesn't work
>anymore. Couldn't find copper anywhere local so came back, found the post
>in early April where brass was recommended instead of copper.... purchased
>.063 x .5, installed on the 7A and it all worked fine. Only a couple
>starts but didn't have any problems so the brass will work. Guess time
>will tell how well.
I think you're going to be okay. It will warm up some
during cranking. I'll know more about the details later
this year. Weather is warming up - spent several good
chunks of time in the shop cleaning up around the drive
stand. My son is going to strip out all the old system
wiring next weekend in anticipation of installing a mock-up
of Z-11/13-8/14 electrical systems.
Bob . . .
Message 12
| 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: Fuses vs Circuit Breaker Fuses |
At 02:09 PM 4/28/2008 -0700, you wrote:
><hammer408@comcast.net>
>
>Bob:
>
>I was "surfing the net" the other day and came upon a couple of sites that
>sell ATC Circuit Breaker fuses. They fit a standard fluse block that B & C
>sells. I found these quite interesting and pondered the question:
>
> if they are worth the investment (not a huge difference in cost between the
>CB fuse and regular fuse)?
>
>are they more robust and would they make a good substitute for fuselable
>links?
>
>and serve any "better" or improve upon the electric architecture than
>standard fuses? - especially in your Z diagrams: Z-11, 12 and or 13?
You can't get any simpler/more-reliable protection than the
fuse. Breakers add moving parts in a device that will probably
never be called upon to protect a wire but . . .
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
----------------------------------------
Message 13
| 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: Epoxy to Aluminum |
Dennis,
Very interesting information. Thanks for sharing it.
I had never thought about it, but your explanation makes sense. It also may
explain why I had such poor results with the Click-Bond nutplate adhesion.
Perhaps the Click-Bond products are most ideal for composite airplanes and
regular nutplates are better for aluminum airplanes.
Thanks again,
Stan Sutterfield
Do not archive
Greetings,
As part of building a composite airplane, I studied everything I could
find about epoxies, materials, and adhesive bonding in general. I
concluded that I did not have the ability to make an epoxy bond to
aluminum that I could be confident that it wouldn't fail.
The problem is that aluminum begins oxidizing immediately after
cleaning. No matter how quick you are, unless you use extraordinary
measures, there will be aluminum oxide on the surface you are bonding.
Aluminum oxide has relatively low strength. The epoxy bonds well to the
aluminum oxide, but the aluminum oxide isn't stuck very well to the
underlying aluminum. After some number of hot/cold and wet/dry cycles,
the bond may weaken enough to fail.
Obviously, Boeing and others solved this problem long ago. However,
based on the great reference book, "Composite Basics," by Andrew
Marshall, their methods aren't practical for most of us homebuilders.
>From chapter 11, Marshall says, "Unfortunately, both the FPL etch and
the PAA treatments (the ones widely and successfully used in the
industry) involve extensive chemical control and a large investment in
equipment."
As an interesting aside, he describes an industry standard "wedge" test
where two .125" thick aluminum pieces are bonded together. After
curing, a wedge is driven into the end of the assembly, between the two
pieces of aluminum, which forces the bond to break at that point. A
mark is placed at the point where the fracture stops. The test piece is
then placed into a warm, wet chamber for one hour. The assembly is then
removed and the additional distance the crack propagated during the
warm/wet test is measured. If the crack grew less than three-fourths of
an inch, the bond is considered to be good for life. Marshall says that
if the aluminum was cleaned but not chemically treated, the assembly
will likely totally delaminate during the one hour test!
Since I didn't have the ability to duplicate Boeing's chemical treatment
process, I didn't make any bond to aluminum that would cause anything
more than inconvenience if it failed. Heat and humidity seem to be the
culprits, which might explain why some people report long lasting bonds
and others have failures.
Best,
Dennis
**************Need a new ride? Check out the largest site for U.S. used car
listings at AOL Autos.
(http://autos.aol.com/used?NCID=aolcmp00300000002851)
Message 14
| 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: Mechanical question |
Considering how many people have had success with them, the fault obviously
lies with me.
I was adhering to bare aluminum.
I have already switched to all normal riveted nutplates and I'm very happy
with them.
Stan Sutterfield
I add my data point on them. Not to be contrary, but I have never had one
come off and indeed when I have misplaced one I found it very difficult to
remove. I wonder Stan, what kind of surface you were adhering to? Boeing,
Lockheed and Airbus use them, can't be all that bad.
Tim Andres
**************Need a new ride? Check out the largest site for U.S. used car
listings at AOL Autos.
(http://autos.aol.com/used?NCID=aolcmp00300000002851)
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! --
|