Airbus rudder AD

Ummm.............. I must respectively differ..

My company also does some marine surveying, ( inspecting
pleasure boats in insuring and pre-buy situations).

Ans , yes, I have seen many examples of this "delamination" of
composiets...

....many cause factors, osmosis being the most common, poor
quality control/contamination during layup are others....

Dave

On Wed, 23 Mar 2005 03:02:04 +0000 (UTC),
(Paul Tomblin) wrote:

In a previous article, "Montblack" said:
I read that composites don't show cracks, instead they have weak 'air
pocket' spots that can't be seen during inspections. These pockets of air
bubles(?) are caused by heat/cold to the composite structures over time.

My father, who was the Chief of Non-Metallic Materials at deHavilland
Canada said that this is bunk. Once the composite is made and given the
initial inspection, there is no way in hell they could delaminate like
that.

But isn;t that just gelcoat delam. Cosmetic, and it occurs by osmotic
pressure on parts of the hull submerged in salt water?

On Wed, 23 Mar 2005 23:07:09 -0400, Dave
wrote:

Ummm.............. I must respectively differ..

My company also does some marine surveying, ( inspecting
pleasure boats in insuring and pre-buy situations).

Ans , yes, I have seen many examples of this "delamination" of
composiets...

....many cause factors, osmosis being the most common, poor
quality control/contamination during layup are others....

Dave

On Wed, 23 Mar 2005 03:02:04 +0000 (UTC),
(Paul Tomblin) wrote:

In a previous article, "Montblack" said:
I read that composites don't show cracks, instead they have weak 'air
pocket' spots that can't be seen during inspections. These pockets of air
bubles(?) are caused by heat/cold to the composite structures over time.

My father, who was the Chief of Non-Metallic Materials at deHavilland
Canada said that this is bunk. Once the composite is made and given the
initial inspection, there is no way in hell they could delaminate like
that.

Dave wrote:

....many cause factors, osmosis being the most common

This would have to be a pretty wet climate for osmosis to happen on an
airplane...

Stefan

In a previous article, Dave said:
Ans , yes, I have seen many examples of this "delamination" of
composiets...

It would be easier to understand or give credence to your points if you
knew how to spell or punctuate.

....many cause factors, osmosis being the most common, poor
quality control/contamination during layup are others....

Osmosis happens to things immersed in salt water, which hopefully isn't
the case with aircraft rudders. And the "poor quality
control/contamination during layup" are why I specified that these things
would be caught in the initial inspection. Aircraft parts are subject to
a lot more quality control and tougher inspections that your boats.

Anyway, I suspect you are seeing cosmetic flaws in the gelcoat, not full
on structural failures.


--
Paul Tomblin http://xcski.com/blogs/pt/
I've never understood why women douse themselves with things that are alleged
to smell of roses/tulips/freesias. What exactly are they trying to attract?
Bees? -- Tanuki

"Paul Tomblin" wrote in message
...
In a previous article, Dave said:
Ans , yes, I have seen many examples of this "delamination" of
composiets...

It would be easier to understand or give credence to your points if you
knew how to spell or punctuate.

....many cause factors, osmosis being the most common, poor
quality control/contamination during layup are others....

Osmosis happens to things immersed in salt water, which hopefully isn't
the case with aircraft rudders. And the "poor quality
control/contamination during layup" are why I specified that these things
would be caught in the initial inspection. Aircraft parts are subject to
a lot more quality control and tougher inspections that your boats.

Usenet grammar pedants should beware of preposition-object agreement in
their glass houses

Anyway, I suspect you are seeing cosmetic flaws in the gelcoat, not full
on structural failures.

In many older boats, osmotic blistering is going beneath the gelcoat,
sometimes several layers deep. However, I tend to agree that we are talking
apples and oranges here. The worst blistering is found on boats going back
into the 60s and 70s, and drops off with each passing year as manufacturers
understood layup better. Airbus started using composites in the early 80s,
by which time we were starting to get a decent feel for best practices in
manufacturing.

-cwk.

Way back in my aerospace days, the guy at the next desk had a casting
he used as an ashtray. (I said this was way back.)

Drifting OT to talk about the days of smoking in the workplace

When I worked as a computer operator not long ago, the master console
keyboards were the same ones used by many generations of operators before
me. They were all stained yellow from the cigarette smoke. My supervisor
(who was working there back then) was talking about the 'good ole days' when
they had an ashtray next to every keyboard.

The "industrial" version of this is an ultrasonic probe which is passed
over the surface. (Sort of like the OB/GYN's ultrasound device).

jsmith wrote:
The "tap test", as used on fiberglass homebuilts, is used to detect
voids (air bubbles) in the epoxy/glass matrix. One usually uses a
Quarter to gently tap the surface. If there are any voids, the
difference in sound will be noticeable.

George Patterson wrote:
How long do you think it will take to do this on an Airbus rudder?

Unfortuntely, no.....

To often, it goes very deep, and has caused entire hulls to be
replaced or otherwise discarded...

Repairs are very expensive, usually requiring grinding out the
affected area, thorough drying, reinstalling the glass laminations and
resurfacing/finishing etc.

It can happen in salt, brackish and fresh water, and is worse where
there is a freeze/thaw cycle in areas that have freezing temps during
layup...

I have discovered it in vessels that have only been operated in
fresh water.

I see less of it now, manufacturing techniques/quality control has
generally improved. There was a bad stretch during the '70's
and'80's...

Other cases have been topside cracks that have allowed water to
penetrate into an unsaturated laminate (usually at a corner of a
structure) freeze and open the delamination further.This can also
become a structural issue..

Cheers!

Dave

On Thu, 24 Mar 2005 05:38:19 GMT, Don Tuite
wrote:

But isn;t that just gelcoat delam. Cosmetic, and it occurs by osmotic
pressure on parts of the hull submerged in salt water?




On Wed, 23 Mar 2005 23:07:09 -0400, Dave
wrote:

Ummm.............. I must respectively differ..

My company also does some marine surveying, ( inspecting
pleasure boats in insuring and pre-buy situations).

Ans , yes, I have seen many examples of this "delamination" of
composiets...

....many cause factors, osmosis being the most common, poor
quality control/contamination during layup are others....

Dave

On Wed, 23 Mar 2005 03:02:04 +0000 (UTC),
(Paul Tomblin) wrote:

In a previous article, "Montblack" said:
I read that composites don't show cracks, instead they have weak 'air
pocket' spots that can't be seen during inspections. These pockets of air
bubles(?) are caused by heat/cold to the composite structures over time.

My father, who was the Chief of Non-Metallic Materials at deHavilland
Canada said that this is bunk. Once the composite is made and given the
initial inspection, there is no way in hell they could delaminate like
that.

Yes, it would have to be VERY wet!

Stress cracks, or gel coat cracks penetrated by rain/melting snow and
freezing during winter would be interesting though...

Cheers!

Dave

..On Thu, 24 Mar 2005 11:58:18 +0100, Stefan
wrote:

Dave wrote:

....many cause factors, osmosis being the most common

This would have to be a pretty wet climate for osmosis to happen on an
airplane...

Stefan

On Thu, 24 Mar 2005 14:12:54 +0000 (UTC),
(Paul Tomblin) wrote:

In a previous article, Dave said:
Ans , yes, I have seen many examples of this "delamination" of
composiets...

It would be easier to understand or give credence to your points if you
knew how to spell or punctuate.



Agreed, (I hate laptop keyboards!) Fortunately, I am a better with
survey tools than a keyboard.

I see you have a similar problem...

"and tougher inspections that your boats."

(your paragraph below)



....many cause factors, osmosis being the most common, poor
quality control/contamination during layup are others....

Osmosis happens to things immersed in salt water, which hopefully isn't
the case with aircraft rudders. And the "poor quality
control/contamination during layup" are why I specified that these things
would be caught in the initial inspection. Aircraft parts are subject to
a lot more quality control and tougher inspections that your boats.

Osmosis causes problems in salt, brackish and fresh water. If freeze /
thaw cycles are present after ANY moisture penetrates, delamination
will continue, and can cause structural damage in any composite.

Anyway, I suspect you are seeing cosmetic flaws in the gelcoat, not full
on structural failures.

Unfortunately, no. Entire hulls/boats have been condemmed due to this
problem in severe cases. Most are repairable, although repairs are
very costly. Physical inspection can uncover most problems, but the
x-ray equipment tells the whole story...

And the inspection process for high performance racing hulls rivals
the aircraft testing techniques, including full hull x-ray
inspections...

Thanks for your reply..

Dave