Author: "jaybrinkmeyer" <jaybrinkmeyer@...> Time: Wed Jan 28, 2004 9:49 am PST Link
It's been a few years, but I've had enough E&M to be dangerous... :-
) I don't buy into the argument that airplane parts don't conduct if
non-conducting primer is used. There are many thousands of
conducting rivets in metal airframes and, in fact, the airframe
itself is used as ground to complete circuits all over the place. In
addition, I contend that primer coverage never perfect and there
will always be metal touching metal in many places. Granted that
static buildup will occur regardless of precautions, but will it
really matter to a pilot who's aircraft has just been hit by
lightning?
--- In RV10@yahoogroups.com, "Jack Sargeant" <k5wiv@a...> wrote:
> --- In RV10@yahoogroups.com, "Brian Denk" <akroguy@h...> wrote:
> >
> > >I have recently received my RV 10 tailcone kit - #159. As a
novice
> > >to kit aircraft assembly, I am interested in hearing from those
> with
> > >experience, what corrosion protection I should be taking to
ensure
> > >that once my RV 10 is complete, I will spend more time flying,
and
> > >less time repairing corrosion. I live near the coast, and
although
> > >the aircraft will be hangered, it will be exposed to warm salt
> air.
> > >Vans Quick Build kits have tradionally been supplied primed
with a
> > >Sherwin Williams primer, would this coupled to annual
treatments
> of
> > >ACF -50 suffice. All advice would be appreciated.
> > >
> > >Dave
> > Dave,
> >
> > This topic has been discussed at great length in the RV forums.
> The
> > airframe even in bare metal, will likely outlive you if it is
> hangared and
> > not subject to exposure to the elements all the time. The
> aluminum coating
> > on the alloy parts are very resistant to corrosion, hence the
> term "alclad"
> > (aluminum clad).
> >
> > For additional protection, you can apply most any brand of
primer
> to the
> > mating surfaces only, to protect against water entrapment in the
> various
> > nooks and crannies of the airframe. Even the same kind of
> materials when
> > touched together will have some small amount of galvanic
> (electrical)
> > reaction which can trigger corrosion. I'm applying zinc
phosphate
> or
> > chromate to the riveted junctions only, and not coating the
entire
> interior
> > of the airframe. I primed everything on my RV8, and really
don't
> think it
> > was worth the time and expense.
> >
> > Brian Denk
> > RV8 N94BD
> > RV10 '51
> >
> > _________________________________________________________________
> > Let the new MSN Premium Internet Software make the most of your
> high-speed
> > experience. http://join.msn.com/?pgmarket=en-
us&page=byoa/prem&ST=1
>
> Brian,
>
> If you want to prime the mating surfaces on your airplane, go
ahead,
> but please don't advise others to do this potentially disastrous
> thing. Most primers are insulators, and by priming the mating
> surfaces you interfere with the electrical bond which is necessary
> to avoid many problems with precipitation static, lightning path
> conduction, and many other electromagnetic events. Yes, the
rivets
> do provide some bonding, but not enough. The use of a conductive
> corrosion inhibitor, such as alodyne or one of the rare conductive
> primers on these joints is a good idea, but the use of an
insulator
> like most primers is bad.
>
> OK, since I havent built an RV (or any other homebuilt) what are
my
> qualifications for this advice? I am an Electromagnetic
> Compatability Engineer for a major aircraft manufacturer.
>
> I'm not yet sure just what I will do when I start to build my RV,
> but I will NOT use an insulating primer on the mating surfaces.
Author: Scott Bilinski <bilinski@...> Time: Wed Jan 28, 2004 4:26 pm PST Link
I am no expert by any means but when does lightening care about .003 inches of
insulating primer? After all it is on its way to jumping 10's of thousands of
feet. What dont I understand here?
At 03:33 PM 1/28/04 +0000, you wrote:
>
> It's been a few years, but I've had enough E&M to be dangerous... :-
> ) I don't buy into the argument that airplane parts don't conduct if
> non-conducting primer is used. There are many thousands of
> conducting rivets in metal airframes and, in fact, the airframe
> itself is used as ground to complete circuits all over the place. In
> addition, I contend that primer coverage never perfect and there
> will always be metal touching metal in many places. Granted that
> static buildup will occur regardless of precautions, but will it
> really matter to a pilot who's aircraft has just been hit by
> lightning?
> --- In RV10@yahoogroups.com, "Jack Sargeant" <k5wiv@a...> wrote:
> > --- In RV10@yahoogroups.com, "Brian Denk" <akroguy@h...> wrote:
> > >
> > > >I have recently received my RV 10 tailcone kit - #159. As a
> novice
> > > >to kit aircraft assembly, I am interested in hearing from those
> > with
> > > >experience, what corrosion protection I should be taking to
> ensure
> > > >that once my RV 10 is complete, I will spend more time flying,
> and
> > > >less time repairing corrosion. I live near the coast, and
> although
> > > >the aircraft will be hangered, it will be exposed to warm salt
> > air.
> > > >Vans Quick Build kits have tradionally been supplied primed
> with a
> > > >Sherwin Williams primer, would this coupled to annual
> treatments
> > of
> > > >ACF -50 suffice. All advice would be appreciated.
> > > >
> > > >Dave
> > > Dave,
> > >
> > > This topic has been discussed at great length in the RV forums.
> > The
> > > airframe even in bare metal, will likely outlive you if it is
> > hangared and
> > > not subject to exposure to the elements all the time. The
> > aluminum coating
> > > on the alloy parts are very resistant to corrosion, hence the
> > term "alclad"
> > > (aluminum clad).
> > >
> > > For additional protection, you can apply most any brand of
> primer
> > to the
> > > mating surfaces only, to protect against water entrapment in the
> > various
> > > nooks and crannies of the airframe. Even the same kind of
> > materials when
> > > touched together will have some small amount of galvanic
> > (electrical)
> > > reaction which can trigger corrosion. I'm applying zinc
> phosphate
> > or
> > > chromate to the riveted junctions only, and not coating the
> entire
> > interior
> > > of the airframe. I primed everything on my RV8, and really
> don't
> > think it
> > > was worth the time and expense.
> > >
> > > Brian Denk
> > > RV8 N94BD
> > > RV10 '51
> > >
> > > _________________________________________________________________
> > > Let the new MSN Premium Internet Software make the most of your
> > high-speed
> > > experience.
> <http://join.msn.com/?pgmarket=en->http://join.msn.com/?pgmarket=en-
> us&page=byoa/prem&ST=1
> >
> > Brian,
> >
> > If you want to prime the mating surfaces on your airplane, go
> ahead,
> > but please don't advise others to do this potentially disastrous
> > thing. Most primers are insulators, and by priming the mating
> > surfaces you interfere with the electrical bond which is necessary
> > to avoid many problems with precipitation static, lightning path
> > conduction, and many other electromagnetic events. Yes, the
> rivets
> > do provide some bonding, but not enough. The use of a conductive
> > corrosion inhibitor, such as alodyne or one of the rare conductive
> > primers on these joints is a good idea, but the use of an
> insulator
> > like most primers is bad.
> >
> > OK, since I havent built an RV (or any other homebuilt) what are
> my
> > qualifications for this advice? I am an Electromagnetic
> > Compatability Engineer for a major aircraft manufacturer.
> >
> > I'm not yet sure just what I will do when I start to build my RV,
> > but I will NOT use an insulating primer on the mating surfaces.
> ----------
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> * To visit your group on the web, go to:
> *
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> *
> * To unsubscribe from this group, send an email to:
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> <http://docs.yahoo.com/info/terms/>Yahoo! Terms of Service.
Scott Bilinski
Eng dept 305
Phone (858) 657-2536
Pager (858) 502-5190
do not archive
[Non-text portions of this message have been removed]
Author: linn walters <lwalters2@...> Time: Wed Jan 28, 2004 4:28 pm PST Link
jaybrinkmeyer wrote:
>It's been a few years, but I've had enough E&M to be dangerous... :-
>) I don't buy into the argument that airplane parts don't conduct if
>non-conducting primer is used. There are many thousands of
>conducting rivets in metal airframes and, in fact, the airframe
>itself is used as ground to complete circuits all over the place. In
>addition, I contend that primer coverage never perfect and there
>will always be metal touching metal in many places. Granted that
>static buildup will occur regardless of precautions, but will it
>really matter to a pilot who's aircraft has just been hit by
>lightning?
>
I've had fairly extensive exposure to lightning damage ...... not in an
airplane, thank goodness. Lightning does not necessarily follow a good
conducting path all the time ..... it will jump ..... for no apparent
reason ..... across all kinds of dielectrics (non-conducting stuff) so
that it boggles the mind. I have seen what it can do to aircraft. I've
seen rows of rivets 'disappear' with no apparent damage to the holes
..... no black marks, nothing. I've also seen randomly missing rivets
in a row after a lightning strike. Go figure! There have been new
holes appear, some very small, and some very large. No 'electrical'
reason for the difference that I know of .... but it made a difference
to the lightning current. To keep this on topic (primers), I think that
the parts in the above scenarios were zinc chromated, alodined, or bare
..... so the damage can occur no matter what. For me, it's just a
natural thing to avoid lightning so I may never have the pleasure (?) of
getting some first-hand, on the spot, education.
Oh yeah ..... corrosion makes a good insulator, deteriorates the
strength of the structure, and is nasty looking. I alodine those parts
I can, zinc chromate primer in places, and ACF-50 (or similar material)
the interior of structures (no primer paint here). Remember that primer
paint can add significant weight depending on what kind, but ACF-50 (or
similar material) is significantly light if applied properly. IMHO, of
course!
Linn
Author: linn walters <lwalters2@...> Time: Wed Jan 28, 2004 6:24 pm PST Link
Scott Bilinski wrote:
>I am no expert by any means but when does lightening care about .003 inches of
>insulating primer? After all it is on its way to jumping 10's of thousands of
>feet. What dont I understand here?
>
No expert here either, but until your question I hadn't thought of 'path
of least resistance' in a while. That's probably why the rivets
disappear ..... they're carrying all the current as the energy goes from
one piece of aluminum to another as it travels on it's merry way. Then
too, there's the situation where a little moisture gets in under the
rivet ..... from condensation, if you will ...... and coupled with a
little normal current flow (the frame is used as a ground conductor)
........ and you may have galvanic corrosion. Usually this takes
dissimilar materials, but maybe there's enough difference in the alloys
of rivet and sheet. I think that the corrosion problem is minimal
though, and treatment with a wicking anti-corrosion agent (corrosion X
or ACF-50) would be sufficient. Anti-corrosion paint may hinder the
wicking action ..... don't know for sure. Just thinking out loud.
While all this noise is going on, the fact that the paint between a
riveted joint is soft (relatively) would the flexing of the frame cause
the paint to get thin and make the rivets 'looser'? Brian ought to have
a hissy on this one!!!
Sorry Brian .... couldn't resist!!! :-)
Linn
Author: "Brian Denk" <akroguy@...> Time: Thu Jan 29, 2004 1:38 am PST Link
>Scott Bilinski wrote:
>
> >I am no expert by any means but when does lightening care about .003
>inches of
> >insulating primer? After all it is on its way to jumping 10's of
>thousands of
> >feet. What dont I understand here?
> >
>No expert here either, but until your question I hadn't thought of 'path
>of least resistance' in a while. That's probably why the rivets
>disappear ..... they're carrying all the current as the energy goes from
>one piece of aluminum to another as it travels on it's merry way. Then
>too, there's the situation where a little moisture gets in under the
>rivet ..... from condensation, if you will ...... and coupled with a
>little normal current flow (the frame is used as a ground conductor)
>........ and you may have galvanic corrosion. Usually this takes
>dissimilar materials, but maybe there's enough difference in the alloys
>of rivet and sheet. I think that the corrosion problem is minimal
>though, and treatment with a wicking anti-corrosion agent (corrosion X
>or ACF-50) would be sufficient. Anti-corrosion paint may hinder the
>wicking action ..... don't know for sure. Just thinking out loud.
>While all this noise is going on, the fact that the paint between a
>riveted joint is soft (relatively) would the flexing of the frame cause
>the paint to get thin and make the rivets 'looser'? Brian ought to have
>a hissy on this one!!!
>Sorry Brian .... couldn't resist!!! :-)
>Linn
Hiss Hiss!! *pitching a fit and behaving badly*
If yer plane is a flexin, wear yer 'chute cuz yer gonna be exitin'
OK, so I'm no poet, but at least I know it. :)
The paints we use these days are very good at taking vibration and flexion.
I've abused my cowling halves numerous times over four years of oil changes,
annuals and replacing crappy chrome jugs. The only place that the paint has
shown cracks and chips is at the edges, where you'd expect them to be. No
problems with adhesion anywhere on the metal surfaces. Not a single smoking
rivet either.
Regarding that ACF stuff, I recall a post on the matronics RV list about a
builder who used it on his unpainted airplane. He was not able to get it
out of all the nooks and crannies and the finish paint job failed in these
areas as it could not bond to the metal. He was quite upset 'bout it all.
Same thing goes for the skin laps/junctions on the belly, which are subject
to Lycosaurslimybelly syndrome. I flew my -8 for several months before I
took it out of service for the paint job. It turned out great, but the
painter had to work extra hard to clean out the goop from those seams.
Paint it, alodyne it, chrome it (!), smear honey on it, do whatever turns
you on but just BUILD THE PLANE and fughedaboudit!
Adios, hombres
BD
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