Interesting discussions on the pros/cons of powder coating. In the end I
decided to paint it using enamel. After all of the racks were in place and
with avionics removed, I prepped the metal, zinc-chromate primer, and then
just a few coats of Rustoleum gloss grey. The final coat was lightly wet
sanded with #600 grit and then top coated with Rustoleum matte clear coat.
This came out pretty well. The paint does not have much glare with the matte
clear coat. The clear coat hides scratches better than glossy enamel alone.
Tests trying just clear coat touch ups worked well.
Definitely not bullet proof like powder coat, but seems okay.
The clear vinyl labels look like they were silk screened in most light. They
also have UV treatment when produced so they shouldn't yellow over time.
Eric
-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com] On Behalf Of
rognal@dcsol.com
Sent: Monday, December 01, 2008 9:05 AM
To: rebel-builders@dcsol.com
Subject: [rebel-builders] Powder Coating Rebel Panel
Eric & Dave,
FWIW, this is a copy of an email response from Robin at MAM (3+ years ago)
regarding powder coating of the Rebel instrument panel.
R Hoffman R687
Eugene, OR USA!
*********************************************
Hi Roger,
There is no problem structurally with powder coating the instrument panel.
Cheers, Robin
----------------------------------------------------------------------------
----
From: Roger Hoffman
Sent: Wednesday, March 02, 2005 9:01 PM
To: Murtech Mailbox
Subject: Rebel Instrument Panel & Powder Coating
Hi Robin,
I'm thinking about having my Rebel instrument panel powder coated, but
wanted to check with Murphy Aircraft for your approval/disapproval or other
thoughts on the matter.
I'm told that powder coating requires curing the coated parts in an oven at
approximately 400 deg farenheit for several hours. I was wondering if this
might have any kind of adverse affect on the structural integrity of the
panel, especially since it is said to be a structural part of the aircraft.
Appreciate any comments you might have.
Thank you,
Roger Hoffman #R687
Eugene, OR USA!
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[rebel-builders] Powder Coating Rebel Panel
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Dave Ricker
[rebel-builders] Powder Coating Rebel Panel
Hi Roger
I'm not sure what to make of Murphy's statement, but here's some information for
anyone who wants to inform themselves before going the powder route. BTW, I won't
use it on any structural parts myself.
This excerpt form MIL-HDBK-5, Rev H points out the risk of overheating 6061-T6:
"3.1.2.1.8 Elevated Temperatures
In general, the strengths of aluminum alloys decrease and toughness increases with
increase in temperature and with time at temperature above room temperature; the
effect is generally greatest over the temperature range from 212 to 400F. Exceptions
to the general trends are tempers developed by solution heat treatment without
subsequent aging, for which the initial elevated temperature exposure results in
some age hardening and reduction in toughness; further time at temperature beyond
that required to achieve peak hardness results in the aforementioned decrease in
strength and
increase in toughness [Reference 3.1.2.1.8]."
(BTW, MIL-HDBK-5 is a good source of info on Engineering materials and well
applicable to aircraft design).
First they are talking about steps in the tempering process (heat treatment &
aging), material which is T6 condition (temper) has completed the treatment and
aging process so it will be at the peak hardness developed in the process and can
only be degraded.
When they say the strength decreases the important parameter for us is the yield
strength, that is the strength at which the material will not return to the shape it
was before it was loaded, it permanantly deforms. This yield strength reduces when
the material is annealed. They speak of toughness, this can also be measured by
ductility which is roughly how far from the original shape you can deform the
material after you have exceeded the yield strength. An example of this is the
difference from spring wire and a coathanger. Try to bend (permanantly) a spring,
it's a lot harder to do than a coathanger and if you try to bend it as far as the
coathanger it will break first because the coathanger has a lot higher ductility.
All Greek?? When you're an Engineer geek it's hard sometimes to speak plain English
LOL!
Anyhow, normal powder coating, from the web:
(http://www.powder-coater.com/convection_cure_ovens.htm)
"Different powder materials require different cure temperatures, commonly in a range
between 350 °F and 400 °F (177 - 204 °C). The part is heated by the hot air in
the oven and it in turn conducts heat into the coating. powder coating cure ovens.
The coating must be held at temperature for a predetermined length of time to reach
full cure."
These would be the general use powder coatings although some lower temperature
coatings are emerging, driven by concerns like the heat treated aluminum problem.
This site discusses the low temperature cure issue and progress made.
http://www.estcp.org/Technology/WP-0614-FS.cfm, it's a US military technology site.
They're talking about 250F cure which is still greater than the 212F lower limit of
MIL-HDBK-5.
At my office we design & build military cranes in welded aluminum and we send the
6061 out to be returned to T6 condition after welding to re-gain the full strength
so risking the strength on powder coat is not considered even though a lot of our
non-military equipment is powder coated. That equipment isn't as highly loaded
though so we can accept the lower yield strength.
Whew, that was a lot of info to answer a one-liner!
Cheers,
Dave
rognal@dcsol.com wrote:
David A. Ricker
Fall River, Nova Scotia
Canada
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I'm not sure what to make of Murphy's statement, but here's some information for
anyone who wants to inform themselves before going the powder route. BTW, I won't
use it on any structural parts myself.
This excerpt form MIL-HDBK-5, Rev H points out the risk of overheating 6061-T6:
"3.1.2.1.8 Elevated Temperatures
In general, the strengths of aluminum alloys decrease and toughness increases with
increase in temperature and with time at temperature above room temperature; the
effect is generally greatest over the temperature range from 212 to 400F. Exceptions
to the general trends are tempers developed by solution heat treatment without
subsequent aging, for which the initial elevated temperature exposure results in
some age hardening and reduction in toughness; further time at temperature beyond
that required to achieve peak hardness results in the aforementioned decrease in
strength and
increase in toughness [Reference 3.1.2.1.8]."
(BTW, MIL-HDBK-5 is a good source of info on Engineering materials and well
applicable to aircraft design).
First they are talking about steps in the tempering process (heat treatment &
aging), material which is T6 condition (temper) has completed the treatment and
aging process so it will be at the peak hardness developed in the process and can
only be degraded.
When they say the strength decreases the important parameter for us is the yield
strength, that is the strength at which the material will not return to the shape it
was before it was loaded, it permanantly deforms. This yield strength reduces when
the material is annealed. They speak of toughness, this can also be measured by
ductility which is roughly how far from the original shape you can deform the
material after you have exceeded the yield strength. An example of this is the
difference from spring wire and a coathanger. Try to bend (permanantly) a spring,
it's a lot harder to do than a coathanger and if you try to bend it as far as the
coathanger it will break first because the coathanger has a lot higher ductility.
All Greek?? When you're an Engineer geek it's hard sometimes to speak plain English
LOL!
Anyhow, normal powder coating, from the web:
(http://www.powder-coater.com/convection_cure_ovens.htm)
"Different powder materials require different cure temperatures, commonly in a range
between 350 °F and 400 °F (177 - 204 °C). The part is heated by the hot air in
the oven and it in turn conducts heat into the coating. powder coating cure ovens.
The coating must be held at temperature for a predetermined length of time to reach
full cure."
These would be the general use powder coatings although some lower temperature
coatings are emerging, driven by concerns like the heat treated aluminum problem.
This site discusses the low temperature cure issue and progress made.
http://www.estcp.org/Technology/WP-0614-FS.cfm, it's a US military technology site.
They're talking about 250F cure which is still greater than the 212F lower limit of
MIL-HDBK-5.
At my office we design & build military cranes in welded aluminum and we send the
6061 out to be returned to T6 condition after welding to re-gain the full strength
so risking the strength on powder coat is not considered even though a lot of our
non-military equipment is powder coated. That equipment isn't as highly loaded
though so we can accept the lower yield strength.
Whew, that was a lot of info to answer a one-liner!
Cheers,
Dave
rognal@dcsol.com wrote:
--Eric & Dave,
FWIW, this is a copy of an email response from Robin at MAM (3+ years ago)
regarding powder coating of the Rebel instrument panel.
R Hoffman R687
Eugene, OR USA!
*********************************************
Hi Roger,
There is no problem structurally with powder coating the instrument panel.
Cheers, Robin
--------------------------------------------------------------------------------
From: Roger Hoffman
Sent: Wednesday, March 02, 2005 9:01 PM
To: Murtech Mailbox
Subject: Rebel Instrument Panel & Powder Coating
Hi Robin,
I'm thinking about having my Rebel instrument panel powder coated, but
wanted to check with Murphy Aircraft for your approval/disapproval or other
thoughts on the matter.
I'm told that powder coating requires curing the coated parts in an oven at
approximately 400 deg farenheit for several hours. I was wondering if this
might have any kind of adverse affect on the structural integrity of the
panel, especially since it is said to be a structural part of the aircraft.
Appreciate any comments you might have.
Thank you,
Roger Hoffman #R687
Eugene, OR USA!
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David A. Ricker
Fall River, Nova Scotia
Canada
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rognal
[rebel-builders] Powder Coating Rebel Panel
Hi Dave,
I wasn't convinced either and painted mine.
Roger
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I wasn't convinced either and painted mine.
Roger
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