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View Full Version : Proper use and application of MEK


TroyW
02-03-2006, 08:22 PM
I'm working on my practice kit, and will be using the Sherwin Williams 988 GBP primer. I'm getting ready to clean and prime the stiffeners in the airfoil section, but can't find a reference on how to use the MEK to clean the alumimum.

Dan Checkoway's site has a great page with pictures; he suggests using a spray bottle to spray it on the part, scrub the "bejeesus" (his words) out of it with a scotch-brite pad, rinse it with water, hang it up to dry, then prime it when it's dry.

Is that what you all do? I was wondering if I could keep some MEK in a large container (wash basin with a sealed lid) to use to submerse/wash/scrub the parts--would that put enough contaminants in the MEK to render it unusable?

Just curious what you all suggest...

Troy Whistman
Fort Worth, TX
Build blog: www.whistman.com

jcoloccia
02-03-2006, 08:43 PM
I wouldn't want to be in the same room with a uncovered bucket of MEK and I wouldn't want to be in the same state with that stuff misting around out of a spray bottle :eek: . It's absolutely nasty except in small quantities where it's merely noxious :)

I don't want to talk for him, but I've got to think he's spraying Metal Prep, not MEK. Personally, I just wipe down my parts with some MEK, Acetone or Laquer thinner (whatever I'm in the mood for that day), and spray. Some people use Dawn and warm water.

This has been working for me, but I'm also kinda' curious what other people are doing. The whole metal prep, scrub, alodine, epoxy thing's been done to death, but I haven't read much on prepping before rattle can stuff. Like I said, I just wipe it clean with no scrubing and it appears to stick like the dickens, whatever THAT means.

rzbill
02-03-2006, 08:55 PM
I too, simply use an MEK paper towel for a final wipe down. No comments on primer prep. That is covered elsewhere. I would not recommend a large open container of MEK. It evaporates very fast and is flamable. When wiping down a part or two, I usually don't bother with a breathing filter. However, when doing my tanks and cleaning cleco's afterwards, I learned to use the filter mask. I skipped it for the first two session and noticed some bronchial irritation afterwards (the next day). It was just a matter of having my face in the stuff for a long time. The filter mask cured it. I wore it while cleaning cleco's not while dancing with the proseal.

TroyW
02-03-2006, 10:33 PM
I too, simply use an MEK paper towel for a final wipe down. No comments on primer prep. That is covered elsewhere. I would not recommend a large open container of MEK. It evaporates very fast and is flamable. When wiping down a part or two, I usually don't bother with a breathing filter. However, when doing my tanks and cleaning cleco's afterwards, I learned to use the filter mask. I skipped it for the first two session and noticed some bronchial irritation afterwards (the next day). It was just a matter of having my face in the stuff for a long time. The filter mask cured it. I wore it while cleaning cleco's not while dancing with the proseal.

Thank you both for your comments. rzbill, you say "use an MEK paper towel"; is this just a normal paper towel soaked in MEK, or something special?

Also, will MEK remove finger oils, etc., or is there a need to wash with Dawn and water first, then MEK wipe before spraying?

Do you rinse with water after the MEK, or just let it evaporate?

Amazing how hard it is to find this "basic" info! I couldn't find a thread with the answers, so figured I'd start one!

TroyW
02-03-2006, 10:36 PM
I don't want to talk for him, but I've got to think he's spraying Metal Prep, not MEK.

Oops, you're right, sorry Dan! It's AlumiPrep he's spraying, not MEK.

I noticed the MEK takes the sharpie marks right off the metal. Van's instructions say do not EVER scribe or punch the metal to mark it. So what do you do to keep the sharpie 'orientation' marks for reassembly? Do you clean the metal then immediately re-write your marks?

jcoloccia
02-03-2006, 11:06 PM
Also, will MEK remove finger oils, etc., or is there a need to wash with Dawn and water first, then MEK wipe before spraying?

MEK will pretty much take everything off of anything. Acetone works nearly as well...maybe better since it doesn't evaporate as fast so it's easier to work with. I personally like acetone better...not as noxious. I happen to have a can of MEK lying around so I'm using that. These are the solvents I happen to have experience with through work and it's my comfort zone. YMMV. Priming is a hotly debated topic....check out the neverending debates. Just to give you an idea, do a google search on:

"what kind of primer to use"

The very first link is to www.vansairforce.com (no, I'm not kidding )

I'll also say ignore anything I say and chalk it up to it's just what one schmuck trying to build a plane happens to be doing. Also, I've switched primers 4 times looking for a good balance of "easy" and "warm fuzzies". Hey, I'm allowed.


Do you rinse with water after the MEK, or just let it evaporate?

Good luck trying to make a puddle of MEK. By the time you get the ball loose in the can of 988, the MEK is halfway to China. Acetone evaporates a bit slower....it only makes it to California. :)


I noticed the MEK takes the sharpie marks right off the metal. Van's instructions say do not EVER scribe or punch the metal to mark it. So what do you do to keep the sharpie 'orientation' marks for reassembly? Do you clean the metal then immediately re-write your marks?

Actually, somewhere in there he says it's okay to use light punch marks or an engraving tool (very light marks with the engraving tool). Maybe not in the instructions for the practice kit, but he says it in the preview plans/instructions for the real deal. I tried using punches on some scrap, but I don't have a light enough touch with the hammer....lol....wasn't pretty) So I use the engraving tool. This was back when I was MetalPrepping because it was totally inconvenient to wash the parts with water, dry off a little bit and remark with the sharpie (doesn't seem like a lot of work, but just try to do this dripping wet wearing goggles, a respirator full of snot, and heavy chemical gloves). Now that I'm just wiping with Acetone (or whatever) I'll probably just remark them as I wipe them off.

Some guys have come up with some pretty cool marking systems using pieces of wire stuck through rivet holes, or laying things out a certain way when they prime. Search through these boards and on the net. Lots of really clever people out there.

rv9aviator
02-04-2006, 07:38 AM
I used the hot water (Dawn) scrubdown with scotchbrite, let dry, wipe (no lint paper towel) with your favorite carcinogen (MEK, acetone) and spray with whatever self etching primer (my second favorite carcinogen) P-60 or 988. The P-60 stuck like glue and the rattle cans did OK.

Red
02-04-2006, 07:50 AM
I use the PPG automotive line except for the primer. The process that I use is a wipedown with Wax and Grease Remover (DX330), Aluminum cleaner (DX533, acid etch), Aluminum conditioner (DX503, alodine), prime with PPG Super Koropon.

Super Koropon is a very good fluid resistant primer used by the military and commercial airplane builders. I have wiped down cured primer with various paint solvents, MEK, acetone... nothing I have found so far affects the cured primer. It is also less expensive than what I could get the PPG automotive epoxy primer (DX50) locally.

TroyW
02-04-2006, 08:55 AM
Actually, somewhere in there he says it's okay to use light punch marks or an engraving tool (very light marks with the engraving tool). Maybe not in the instructions for the practice kit, but he says it in the preview plans/instructions for the real deal.


I was looking at section 5C of the instructions, titled "MARKING PARTS". He says, and I quote:


NEVER use a scribe to make layout lines or other marks on aircraft parts. The lines can cause failure of the part along the lines with the vibration of the engine. The use of an ordinary lead pencil will cause corrosion of the aluminum. We recommend that you use only an extra fine point "Sharpie" pen. For some unexplaiend reason the blue ones seem to last longer than other colors. The sharpie ink will bleed through primer, so you can still see the ID marks after priming the parts.

TroyW
02-04-2006, 08:58 AM
Dang, these could be convenient!

http://www.aerocraftparts.com/ItemForm.aspx?item=KSW0107

jcoloccia
02-04-2006, 09:17 AM
I was looking at section 5C of the instructions, titled "MARKING PARTS". He says, and I quote:

Originally Posted by Vans
NEVER use a scribe to make layout lines or other marks on aircraft parts. The lines can cause failure of the part along the lines with the vibration of the engine. The use of an ordinary lead pencil will cause corrosion of the aluminum. We recommend that you use only an extra fine point "Sharpie" pen. For some unexplaiend reason the blue ones seem to last longer than other colors. The sharpie ink will bleed through primer, so you can still see the ID marks after priming the parts.


LOL....yes, but in Section 6 of the instructions that come with the airplane kit, he says, and I quote:

Despite earlier admonitions about scribing or scratching aluminum, it is permissible to use a vibrating pencil or a system of light punch marks to make identifying marks that will be visible after priming
:D

dan
02-04-2006, 09:45 AM
Anybody who is afraid to "engrave" their parts (I'm just talking about lightly scribing with a vibrating pencil), take a look at the WING SPARS and center section. Scribed like crazy with numbers -- from the factory.

The admonitions are overblown imho. If all you're doing is lightly "scratching" or "etching" little pits in the web of a rib or stiffener, seriously, what is the worst that could happen? I have yet to be convinced that there would ever be the slightest repercussion structurally. After all, the reason we're doing this marking is because we're friggin' priming. So it's not like corrosion is gonna get ya. Structurally what could happen as a result of a few little pits in the web of an aileron rib?

I would love to be corrected about my assumptions if they're overly cavalier. But then again, how do you explain all the engraving of numbers Van's Aircraft itself does on mission critical parts?

)_( Dan
RV-7 N714D (807 hours)
http://www.rvproject.com

ptrotter
02-04-2006, 10:26 AM
Dan, I noticed the engraving on the wing spars and thought the same thing I use a little electric engraver to mark parts. I just make sure that I don't make any marks on places that have any stress.


With respect to MEK, the only problems I have with it is that I'm starting to like it too much :-)

szicree
02-04-2006, 12:53 PM
I think all this wash, scrub, etch, wipe, dry, rescrub, alodine, wash, sprinkle with chicken blood, do the hokey pokey, prime stuff is WAAAYYYY out of control. Throughout my project I've simply wiped with acetone, etched, alodined, rinsed and primed with AKZO. No fancy towels, no MEK, no scrubbing. This primer has shown absolutely no tendency to lift, peel or flake in any way despite pretty rough treatment. As a matter of fact, I had to remove it once (long story) and it was **** to get it off. If you don't mind ink showing through the primer here and there you could easily substitute soap and water for the acetone. I wear a repirator whenever using acetone cuz it gives me headaches (probably a little cancer too). Furthermore, I usually spray this stuff in my driveway and have had no issues with contamination except one or two suicidal flies whose toes are now entombed inside my tailcone. Having said all this, I will be more thorough when shooting the outside of the plane. The film build is much thicker there and consequently much more susceptible to peeling from skin flexing/expansion/etc. YMMV.

ptrotter
02-04-2006, 01:45 PM
Chicken blood... I knew I missed a step somewhere. :-)

4kilo
02-04-2006, 07:04 PM
Who knows of a supplier of aviation grade chicken blood?

jcoloccia
02-04-2006, 07:47 PM
Who knows of a supplier of aviation grade chicken blood?

Have you tried Aircraft Goose? :p

alpinelakespilot2000
02-04-2006, 11:12 PM
Rather than die a slow death with MEK, I just use lacquer thinner to clean my parts that are going to be Variprimed or GPB988'ed. I'm not alone here. This is what George Orndorff recommended and I picked up the same tip from numerous other builders who have flown a lot and not seen any adhesion problems. When I get to the exterior, I'll religiously follow whatever instructions re: primer that my topcoat requires. However, for the interior parts, I think we already overkill on the priming thing anyway. So, my vote is save your liver, save $$$, and save the MEK for the fuel tanks.

glenmthompson
02-05-2006, 10:52 AM
As a Cheme, with a great respect and knowledge of solvent dangers. Lemme throw out my recommended technique for maximum corrosion removal, etching and cleaning prior to priming.

1. Mix up per man. recs. aluminum acid etch (buy at car paint store) and add about 1 tsp of Dawn dishwashing soap per gallon to this solution. This is to etch the aluminum and remove the corrosion that exists and oils/greases. Yes, there is corrosion whether you can see "chalking" or not, alclad or 6061 T6, it is ALWAYS THERE. Ask any metallurgist.

2. Scrub with scotchbrite and the above solution. Look at Van's quick build parts, make your parts look to this degree on your slow build parts. No need to go nuts, just take off the shine, rubbing moderately, over entire surface and scrub HARD where any visual signs of corrosion might be. Keep surfaces nice and wet.

3. Rinse with COPIUS quantities of water from your garden hose. For those a little more anal and corrosion paranoid like myself, use polyethylene gloves and your respirator (carbon/filter mask is ok and safe), and spray the parts immediately with ACETONE (water soluable solvent, cheaper, and MUCH LESS carcinigenic then MEK) using your paint gun and say 25-30 psi in a conventioal spray gun. HVLP is ok too. This is extremely safe, fast and thorough since you can rinse every square inch of every part and all nooks and crannies. Just stay away from ignition sources and OBVIOUSLY do this outside!!

4. Paint/prime ASAP with your favorite ETCHING primer.

5. I challange ANYBODY to accomplish part cleaning any faster or safer or more thorough than me using the above technique.

Sorry for the caps here but this is EXTREMELY IMPORTANT!

NOW,..... ANY BODY WHO DOES NOT ALREADY KNOW, MEK, ISOBUTYL ETHANOL, ACETONE, TOLUENE, BENZENE AND OTHER SOLVENTS WE USE ARE KNOWN/GUARTANTEED CARCINIGINS ! ! ! ! ! ESPECIALLY KIDNEY AND LIVER CANCER! ! ! ! THEY ALSO, EACH TO A VARYING DEGREE, PENETRATE EASILY THROUGH YOUR SKIN DIRECTLY INTO YOUR BLOODSTREAM! ! ! ! (DMSO (Dimethylene Sulfoxide) is a great solvent for example and pentrates the skin INSTANTLY!!!!!! They even use this to instantly put drugs directly into the bloodstream! Ever wonder why you get heartburn after "playing" with MEK? Don't believe me? Ask your doctor, and a week after swimming in MEK, check your liver enzymes, then watch the doc's face as he reads the results.......

Please guys, respect these solvents like they are asbestos. They will/can kill you faster.

Parting note, NEVER, NEVER, NEVER, NEVER, NEVER, NEVER, NEVER ,NEVER, NEVER,.... PAINT A CYANOACRILATE CATYLIZED PAINT OR PRIMER WITHOUT A "FRESH AIR" SUPPLY BREATHING SYSTEM, ie. "HOBBY AIR". NO CARBON FILTER MASKS ALLOWED, NEVER, EVER, PERIOD. This is all for your own good and longevity.
Strong words, but must be heeded.

Glen

KTM520guy
02-05-2006, 11:24 AM
Don't use MEK to kill Black widow spiders. They just shake it off. :D

I wear gloves and a respirator when using MEK. It has it's uses but in the future you won't be able get the stuff. It kinda a shame for what MEK can be used for there are no good replacements.

szicree
02-05-2006, 11:41 AM
Glen,

From what source do you draw the conclusion that acetone is readily absorbed into the bloodstream through unbroken skin? Also, all information I have seen says that it is not believed to be carcinogenic in humans.

Finally, why would I bother using an etching primer when I've just acid etched and scrubbed?

KTM520guy
02-05-2006, 12:00 PM
As a Cheme, with a great respect and knowledge of solvent dangers. Lemme throw out my recommended technique for maximum corrosion removal, etching and cleaning prior to priming.

1. Mix up per man. recs. aluminum acid etch (buy at car paint store) and add about 1 tsp of Dawn dishwashing soap per gallon to this solution. This is to etch the aluminum and remove the corrosion that exists and oils/greases. Yes, there is corrosion whether you can see "chalking" or not, alclad or 6061 T6, it is ALWAYS THERE. Ask any metallurgist.

2. Scrub with scotchbrite and the above solution. Look at Van's quick build parts, make your parts look to this degree on your slow build parts. No need to go nuts, just take off the shine, rubbing moderately, over entire surface and scrub HARD where any visual signs of corrosion might be. Keep surfaces nice and wet.

3. Rinse with COPIUS quantities of water from your garden hose. For those a little more anal and corrosion paranoid like myself, use polyethylene gloves and your respirator (carbon/filter mask is ok and safe), and spray the parts immediately with ACETONE (water soluable solvent, cheaper, and MUCH LESS carcinigenic then MEK) using your paint gun and say 25-30 psi in a conventioal spray gun. HVLP is ok too. This is extremely safe, fast and thorough since you can rinse every square inch of every part and all nooks and crannies. Just stay away from ignition sources and OBVIOUSLY do this outside!!

4. Paint/prime ASAP with your favorite ETCHING primer.

5. I challange ANYBODY to accomplish part cleaning any faster or safer or more thorough than me using the above technique.

Sorry for the caps here but this is EXTREMELY IMPORTANT!


Glen
Let me give an alternative method.

1. Wash the part with a solution of soap and water and scotch brite. Use a clear soap like Clear Tide or Ajax. My favorite is Eldorado ED-500. It's an industrial grade soap. Can be found at AIRCRAFT paint suppliers. Rince well when done.

If you want to use a self-etching primer this as far as you need to go. Just make sure your parts a very clean and really well scuffed. Primer does not like an unclean or smooth surface.

2. If you are not going to use a self etching primer then you need to etch the part yourself. I use Eldorado AC-12 to etch my parts. I buy 5 gals at a time in concentrate. My water/etch ratio is about 4:1. I like my etch strong so I need to work fast. Alumi-prep is not very strong so you need to spend more time with your parts. Rince really well and check for "water brakes" If you missed a spot the rince water will go right around it. Etch that spot again and rince.

3. Now that your parts are nice and clean and etched it's time to alodine them. Alodine is a conversion coating. It helps prevent corrosion and makes the primer stick. For big parts I spray it on. If I have a bunch of little stuff I'll use a bucket and dip them. After you get a nice light gold color rince your parts with clean water and set aside to dry. Wear gloves when do this and don't get any on your clothes. The stains never come out.

4. Let dry over night. It's best to start priming within 24 hrs.

5. Now that you are ready to prime you need to clean one more time. Put your gloves back on and get some lint free rags and Acetone or MEK. With a damp rag wipe down the surface. You will be suprised how dirty your parts still are. A lot of it is the crud that's in your water.

Total time to wash your RV, 3-4 hours.

:)

bearair
02-05-2006, 04:16 PM
Glen,

From what source do you draw the conclusion that acetone is readily absorbed into the bloodstream through unbroken skin? Also, all information I have seen says that it is not believed to be carcinogenic in humans.

Finally, why would I bother using an etching primer when I've just acid etched and scrubbed?


Just a quick FYI. I use a parts washer at home and at work that have acetone based solvent in them. OSHA says to wear gloves when using them as it is absorbed through the skin and builds up in your liver and can cause liver damage and cancer at higher concentrations. The MSDS say to avoid contact with skin. You don't need to have any cuts or sores for it to be absorbed.

It's not bad stuff since it doesn't require a mask to use, but the affects are cumulative since your body metabolizes it slowly. You'd be more prone to cancer if you were using it regularly over a period of years for sure.

Basic precautions (gloves) will protect you as long as you use it in a ventilated area.

I personally am using isopropyl alcohol to clean with (empennage) since it also leaves no residue, is easy to use and is inexpensive. Doesn't smell up the house either. I'm doing most of the work in my indoor work area as my shop still isn't heated. I'll have it insulated and heated by next winter hopefully!

jarhead
02-06-2006, 12:56 AM
Glen,

From what source do you draw the conclusion that acetone is readily absorbed into the bloodstream through unbroken skin? Also, all information I have seen says that it is not believed to be carcinogenic in humans.

Finally, why would I bother using an etching primer when I've just acid etched and scrubbed?

The oils in your skin help block contaminants from crossing the skin barrier into the bloodstream. They also keep your skin flexible. Solvents that are great at removing grease and oil from metal (acetone, MEK, other choices) are also great at removing grease and oil from your skin. Ever noticed that your fingers get "chalky"-looking after the "I'm not gonna bother with gloves for just one quick solvent wipe" routine? This is called "de-fatting" of your skin; also known as "contact dermatitis". This is bad, mmm-kay?

Too many repetitions of this act will result in "chronic dermatitis", where your hands are always dry and chalky-looking because all the solvents you used to clean your hands/aircraft parts over the years (before you knew better) have damaged/destroyed the cells that generate the oils in your skin. You end up being the guy with the skin that cracks open on your hands when the weather's real dry. Ask me how I know this...

Re: acetone being/not being a carcinogen - I'm waiting for a password to an MSDS website so I can look it up. But I recall seeing acetone as carcinogenic the last time I looked at the MSDS for it (admittedly, a while ago). I'll look up MEK just for grins, too...


***UPDATE***
Got the password.
According to Ashland Chemical Corp.'s MSDS, acetone is not a carcinogen.

And for a shocker...




...neither is MEK! :eek:
Cancer Information
Based on the available information, this material cannot be classified with regard to carcinogenicity. This material is not listed as a carcinogen by the International Agency for Research on Cancer, the National Toxicology Program, or the Occupational Health and Safety Administration.

I'll be damned...

szicree
02-06-2006, 08:38 AM
FYI: Acetone is the main ingredient in nail polish remover. This would not be legal if it were known to be a carcinogen.

glenmthompson
02-06-2006, 07:43 PM
My source for my info, besides of course my college degree, work experience, plant OSHA rep., etc... info is....Perry & Chilton's Chemical Engineers Handbook.


Etching primer is for ensuring a thorough bond by removing surface corrosion and extra etching. I dare anybody, I said anybody to scrape off any of my primer/paint without scratching the aluminum underbeath. Not gonna happen, nuh uh,... Once agin, the pre etching, is to remove existing corrosion.. This is not necessary of course, if you have your parts shipped directly from the aluminum plant in a perfect vacuum, then.... assemble, drill, deburr, dimple, assemble, dissasemble and paint within minutes in an arid environment., Then, go right ahead and just paint away with your self etching primer.

For those people that care for their health, consider the following...Doctors used to say:.... go out in the sun white boy, and it will dry up your acne......Smoking does not have long term health effects,...Thalidamide is ok for your unborn baby.....Etc...

If there are doctors with experience in toxoclogy out there in this forum that feel/are more qualified than myself, and disagree/find fault with me, then go ahead all,... feel free to take their advice. For most,who want to enjoy their CORROSION FREE RV well into their 80's, treat these solvents with great respect like the poisons they are.
Glen

PS ...Szicree, you easily exceed the maximum daily recommended exposure to Benzeze/aliphatics (KNOWN AND PROVEN CARCINIGENS) every time you fill up your car with GASOLINE !
As of 09:30 PM this evening, gasoline was still legal to sell, and oh yea, cigarettes, booze, oak wood (dust is carcinogenic), drywall compound, cement (silicosis), perchloroethelene---PERC---dry cleaning solvent-(major carcinogen found in chlorinated brake cleaner),etc, etc, etc, etc,etc,etc


Questions? OBJECTIVE comments?

szicree
02-06-2006, 08:55 PM
I certainly never meant to imply that acetone is not potentially damaging to one's health. My point was simply that I could find no referrence to acetone being carcinogenic, nor readily absorbed throught the skin and into the bloodstream. So far nobody has directed me to one either. As for the legal sale of gasoline, it is sold as a fuel, not a cosmetic. Even so, the stations and gas cans are plastered with legally required signs warning of the dangers. My can of acetone bears no such cancer warning, which in California is required for all products proven to be carcinogenic. Again, I'm not saying that these things are vitamins, I was just trying to find out where the acetone/cancer info was coming from (and I guess for MEK too).

rzbill
02-07-2006, 07:38 PM
Dang! All this talk of FINE smellin' chemicals and nobody has mentioned the top of the heap... 111 Trichloroethane...

TYPO UPDATE: Sorry for that. I originally typed Trichloroethylene (Still a very undesireable chemical) rather than the ethane that I meant.

KTM520guy
02-07-2006, 07:53 PM
Trichloroethylene...


Thanks for bringing that up. :mad: Now you have brought back memories of a job I hated. Thanks a lot :rolleyes:

:D

szicree
02-07-2006, 10:12 PM
Dang! All this talk of FINE smellin' chemicals and nobody has mentioned the top of the heap... 111 Trichloroethylene...

I use that stuff for hot sauce. Mmmm, good ol' 111.

Captain Avgas
02-08-2006, 04:56 AM
Anybody who is afraid to "engrave" their parts (I'm just talking about lightly scribing with a vibrating pencil), take a look at the WING SPARS and center section. Scribed like crazy with numbers -- from the factory.

The admonitions are overblown imho. If all you're doing is lightly "scratching" or "etching" little pits in the web of a rib or stiffener, seriously, what is the worst that could happen? I have yet to be convinced that there would ever be the slightest repercussion structurally. After all, the reason we're doing this marking is because we're friggin' priming. So it's not like corrosion is gonna get ya. Structurally what could happen as a result of a few little pits in the web of an aileron rib?

I would love to be corrected about my assumptions if they're overly cavalier. But then again, how do you explain all the engraving of numbers Van's Aircraft itself does on mission critical parts?

)_( Dan
RV-7 N714D (807 hours)
http://www.rvproject.com

Hi Dan, actually the truth is that Vans approves of "peen" type engravers (they engrave by hammering rather than cutting) and light punching. I think you'll find that the engraving on the RV wing spars is done with a vibrating "peen" type tool.

On the other hand scribes and standard engraving tools are definitely a no-no. The trouble is not corrosion but that the sharp discontinuity creates a "work-of-fracture" situation (infinitely high stresses) which can lead to cracking of the aluminium under constant vibration and or cyclical stresses. This happens quite happily under a painted surface.

Even on Boeing airliners there have been cases where serious cracking of the skin has been dicovered some years after maintenance. Investigations have pointed to the cracking running along scratches caused by maintenance workers.

jarhead
02-08-2006, 06:06 AM
Even on Boeing airliners there have been cases where serious cracking of the skin has been dicovered some years after maintenance. Investigations have pointed to the cracking running along scratches caused by maintenance workers.

Apparently there are two 767's out there that have a special 50hr fuselage skin inspection requirement, brought on by a maintenance contractor's personnel that used razor blades to help strip old paint off the fuselage before re-painting. They might have been retired or re-skinned by now, but they were definitely out there (I think it was a non-US airline). Ooops...

apatti
02-08-2006, 08:49 AM
I use that stuff for hot sauce. Mmmm, good ol' 111.


Yeah, it is almost twice as good as Heinz 57. :)

glenmthompson
02-08-2006, 07:38 PM
Dang! All this talk of FINE smellin' chemicals and nobody has mentioned the top of the heap... 111 Trichloroethylene...
Gatcha! This was mentioned in my previouse post...Also known as PERC... (I like the smell of this too...Can be found in chlorinated brake cleaner for those stubborn stains....PS, sorry, black death, eerrrr uuuh proseal cannot be removed with perc. )
Glen

rzbill
02-09-2006, 11:39 AM
Gatcha! This was mentioned in my previouse post...Also known as PERC...
Glen

Nah... Missed me! :D Perc (CCl4) smells fine too but it ain't exactly Tri (CL3C.CH3). Different chemical structure even though similar degreasing uses for the pair of them. I'm not proud, I liked both of them.. so yeah I'm brain damaged! :o