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colind
Joined: 10 Jan 2006
Posts: 32
Location: Sydney, Australia
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 Posted: Tue Jan 23, 2007 5:05 am Post subject: Rust behind battery tray |
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After many delays, I am finally ready to put the fabric on the KF4. I just need another inspection to be done by our local RAAus inspector, and that's booked for next Monday. I can't believe that its taken so long to get to this point (its been 18mths since we brought the part finished kit home).
The last job I did in preparation for the inspection, was to remove the old rear-mounted battery tray. The tray had been welded in place at the factory, between three braces on the right side of the fuselage. There were two small weld beads on each side of each brace, which I cut through using a very fine cutting disk.
The fuselage had been powder-coated at the factory.
After removing the tray, I noticed that both the tray and the three braces showed significant rust where they touched. The powder coating had not penetrated or sealed those contact points, hence the surface was left unprotected, and oxidation had started. The surface of the braces was pitted. Had I not discovered this, the rust would have continued to the piont at which the integrity of these braces may have been compromised. The kit had been stored for many years in a very dry location prior to our purchasing it, hence this limited the progress of the oxidation. Once the aircraft began operations however, the amoint of moisture able to get into thease areas would have been much higher, so I believe that the speed of oxidation would have increased significantly and, because of its location, would not have been easily noticed.
I suggest that anyone with a battery tray that has been welded in place at the factory, especially if their fuselage was also powder-coated, should check the brace contact points closely. Standard spray painting would not guarantee that these areas were properly coated either, due to their akward position.
The rust shown on the battery tray edge in photo #0121 is similar, but slightly less than what I found on the brace where the tray contacted it. Sorry, but by the time I thought of getting the camera, I had already cleaned and primed the brace tubes.
Regards
Colin Durey
Sydney - Australia
+61-418-677073
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_________________
Colin Durey
Sydney
+61-418-677073 |
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pwmac(at)sisna.com
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| Posted: Tue Jan 23, 2007 7:48 am Post subject: Rust behind battery tray |
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Two ways to prevent rust in this location. 1) Use the plastic box in the kit which has a closely fitting top with a vent to relocate the fumes from a flooded cell battery. 2) Use a sealed battery. The sealed battery is especially good as they use a plastic case which does not let battery vapors out from inside the battery. In this case the Skystar plastic box is not necessary.
In any case a small amount of rubber vetween the battery or plastic box will keep the paint from wearing off due to vibration.
Of course if you are criticizing the weld integrity then all the welds would be subject to similar corrosion. I dont think the batt tray is peculiar to bad welds where paint that did not seal the weld. Anyway It is my belief that battery vapors is the root cause of corrosion. Otherwise other welds would have the same problem.
BTW, Powder coating will not cover a weld defect. Any significant pin holes or cracks would not be sealed by the process.
Regards, Paul
===============
After many delays, I am finally ready to put the fabric on the KF4. I just need another inspection to be done by our local RAAus inspector, and that's booked for next Monday. I can't believe that its taken so long to get to this point (its been 18mths since we brought the part finished kit home).
The last job I did in preparation for the inspection, was to remove the old rear-mounted battery tray. The tray had been welded in place at the factory, between three braces on the right side of the fuselage. There were two small weld beads on each side of each brace, which I cut through using a very fine cutting disk.
The fuselage had been powder-coated at the factory.
After removing the tray, I noticed that both the tray and the three braces showed significant rust where they touched. The powder coating had not penetrated or sealed those contact points, hence the surface was left unprotected, and oxidation had started. The surface of the braces was pitted. Had I not discovered this, the rust would have continued to the piont at which the integrity of these braces may have been compromised. The kit had been stored for many years in a very dry location prior to our purchasing it, hence this limited the progress of the oxidation. Once the aircraft began operations however, the amoint of moisture able to get into thease areas would have been much higher, so I believe that the speed of oxidation would have increased significantly and, because of its location, would not have been easily noticed.
I suggest that anyone with a battery tray that has been welded in place at the factory, especially if their fuselage was also powder-coated, should check the brace contact points closely. Standard spray painting would not guarantee that these areas were properly coated either, due to their akward position.
The rust shown on the battery tray edge in photo #0121 is similar, but slightly less than what I found on the brace where the tray contacted it. Sorry, but by the time I thought of getting the camera, I had already cleaned and primed the brace tubes.
Regards
Colin Durey
Sydney - Australia
+61-418-677073
Attachments:
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http://forums.matronics.com//files/img_0121_121.jpg
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pulsair(at)mindspring.com
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| Posted: Tue Jan 23, 2007 6:01 pm Post subject: Rust behind battery tray |
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Colin,
That has always bothered me since I built my Fox. I remember hearing
rattling noises when I moved powder coated items like the horizontal
stabilizer and rudder. Of course they were powdercoated and I couldn't do
anything about it. I ordered a set of powdercoated wing support brackets so
I could tow my aircraft. As I was fabricating the supports to fit I tapped
them on the garage floor after I heard rattling. Out came all sorts of rust.
I don't know if anyone else has experienced that? I also wonder if the
factory treated the tubing with linseed oil before they sealed them? I built
my Fox 1993-1996. Jeff
---
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smokey_bear_40220(at)yaho
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| Posted: Wed Jan 24, 2007 10:51 pm Post subject: Rust behind battery tray |
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Before covering my -5 I did a thorough check of the
airframe and found bubbles in the powder coating on
the front spreader between the bottom engine mounts
and the horizontal stab. I decided to pop a 2" bubble
and found, sure enough, it was rusted. Cleaned off
all the bubbles and it ended up with several feet of
rusted surface under the coating.
I think it was possible that the frame wasn't properly
cleaned before coating, or that it was then left to
sit and rust a bit again.
In any case, I had to clean and repaint these areas
before covering.
Kurt S.
--- jeff puls <pulsair(at)mindspring.com> wrote:
| Quote: | Colin,
That has always bothered me since I built my Fox. I
remember hearing
rattling noises when I moved powder coated items
like the horizontal
stabilizer and rudder. Of course they were
powdercoated and I couldn't do
anything about it. I ordered a set of powdercoated
wing support brackets so
I could tow my aircraft. As I was fabricating the
supports to fit I tapped
them on the garage floor after I heard rattling. Out
came all sorts of rust.
I don't know if anyone else has experienced that? I
also wonder if the
factory treated the tubing with linseed oil before
they sealed them? I built
my Fox 1993-1996. Jeff
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