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Sandblasting

 
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DougJ



Joined: 10 Dec 2006
Posts: 41
Location: Kernersville, NC

PostPosted: Fri Jun 18, 2010 11:47 am    Post subject: Sandblasting Reply with quote

I'm getting close to sandblasting time. What is the best way, what to look out for, what never to do, etc...???
I did a search for sandblasting on the forum and found only one warning which didn't say anything other than to use no more than 120 psi. Any other warnings??
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Doug Jewell
N9776 - Starduster II
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jsh



Joined: 19 Dec 2005
Posts: 354
Location: Burnet, TX

PostPosted: Fri Jun 18, 2010 2:03 pm    Post subject: Reply with quote

Doug, I wrote an article for Starduster magazine some years ago detailing my experience.....I think all the issues are available on this BB? Let me know if you can find it. I will tell you this.....it is one of the messiest, most unenjoyable, dirtiest, most distasteful tasks I did on the airplane. John
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bmcj



Joined: 05 Dec 2005
Posts: 810
Location: California, Fresno

PostPosted: Fri Jun 18, 2010 9:45 pm    Post subject: Reply with quote

Sand is not the only medium. There is also (glass) bead blasting... just as messy, but less dust and less abrasive.

If you can find a unit for rent, there is also dry ice blasting. You drop big blocks od dry ice in the machine and it chops and grinds it as you blast. It works good, is less abrasive for delicate parts, cools the metal as you blast (rather than heating it), removes paint quickly because it freezes and blasts at the same time. Best of all, the only cleanup is the paint and rust that you blast off because the dry ice evaporates. You don't have to worry about sand getting caught in crevices.

The DOWN SIDE: The dry ice can be more expensive than sand. Also, dry ice sublimates into carbon dioxide... not poisonous, but can cause suffocation if allowed to collect because it is odorless and symptomless. Best to use a forced air respirator if you have one, but at a minimum, you should use it in an open area with good ventilation and not in a low spot where the heavy gas can collect.

ALSO... don't stick your tongue on the block of dry ice!!! Rolling Eyes

Bruce Smile
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planebuilder



Joined: 28 Nov 2008
Posts: 46
Location: Midland Ontario Canada

PostPosted: Sat Jun 19, 2010 11:04 am    Post subject: Reply with quote

Sand, as in beach sand, works well, however, treat it as you would very toxic paint. Beach sand
usually has silica in it, that is frowned upon by most regulatory bodies because it causes silicosis
of the lungs, VERY BAD. There are other media, like ďBlack BeautyĒ,.. ďBlack diamondĒ ... that
donít contain silica. I think itís dangerous to think if it doesnít have silica itís safe. Whatever
media you use I would NEVER blast without a full fresh air supplied hood. Keep your neighbors
in mind, sand dust will float in the air and travel 100 feet in a breeze. I know one guy who had to
pay to repaint a Mercedes because the abrasive dust traveled to the neighbors yard, when the
owner complained, an employee brushed the ďdustĒ off the car, scratching the high gloss finish.
You will need a pressure pot blaster, for a fuselage a siphon feed blaster is a waste of time.
If you can do it in a room (with exhaust fan) great, then you can recycle the sand, sift it through a
window screen and reuse it, if outside some very big tarps on the ground might save some sand,
you will need lots to do a fuselage. Even new sand needs to be sifted, just one small stone can
plug the blaster. Pro blasters will tell you the sand wonít work as well when reused, they donít
do aircraft. I recycle my sand many times, until itís so fine it goes out the exhaust fan. You want
the finest grit you can get, if itís a little coarse turn down the pressure and keep more distance.
Also, especially with coarser sand, blast at ~45 degrees, 90 is too hard on the thin wall tube.
You might find a classic car restorer that has fine sand. You probably donít need more than 60
PSI, but thatís at the blaster, at full flow rate, Your compressor should be higher, you will have
losses through filters, water separators, hoses, etc. You also need the air to be DRY, Not an easy
item. Sand in damp ďsand castlesĒ sticks, in a blaster, it wonít flow, it only takes a few drops of
water to stop it. If working inside, you will need lots of light, and if hit by the sand, light bulbs
and flourescent tubes donít last long. Sorry this wasnít better organized, and shorter,but I hope it saves you
some headaches. I hope this doesnít discourage you, It can be done, and You will probably end
up with a better job because you did it yourself. Oh yea, one more thing, you might want to keep
your welder nearby. This will be the best opportunity to inspect every detail of your fuse, Itís not
uncommon to find a spot or two you might want to touch up.
Morgan
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jsh



Joined: 19 Dec 2005
Posts: 354
Location: Burnet, TX

PostPosted: Sat Jun 19, 2010 6:23 pm    Post subject: Reply with quote

and obtw, a local blasting company here advertises that they use soda (like baking soda I guess) supposed to be very easy on the parent material
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bmcj



Joined: 05 Dec 2005
Posts: 810
Location: California, Fresno

PostPosted: Sat Jun 19, 2010 7:55 pm    Post subject: Reply with quote

I forgot about soda blasting. JSH is correct, loke dry ice, soda is "kinder" to your delicate thin-walled tubes.

Bruce Smile
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Bruce

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DougJ



Joined: 10 Dec 2006
Posts: 41
Location: Kernersville, NC

PostPosted: Sat Nov 17, 2012 9:36 am    Post subject: Metal Protector Reply with quote

I decided to go with soda blasting and am very pleased with the results. The tube came out very clean without any apparent pitting or loss of material. I had a local guy do the work for me (he does it for a living) and he charged me $602 for the fuselage. This did not include the rudder, horizontal stabilizer, elevator, landing gear, engine mount, etc. Based on his charges, I'm expecting it will cost another $200-$250 to do the rest.

After blasting, he sprayed Holdtight 102 "to help remove soda residue". I read up on Holdtight 102 and can't figure out why he used it, but it doesn't seem like it would be a problem. Does anyone know anything about this stuff?

Now I'm seeing a very small amount of surface rust (dusty looking and easily rubbed off). I know this will become a problem, so I'm looking for something to protect the metal until I can finish my welding and get it primed and painted. I am considering using a PPG DX Metal Cleaner and Conditioner (DX579 and DX520). Does anyone have experience with this stuff and is it the best stuff to use?

Thanks,
Doug
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Doug Jewell
N9776 - Starduster II
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Don Adamson



Joined: 08 Dec 2005
Posts: 242
Location: Lonoke, AR

PostPosted: Sun Nov 18, 2012 6:34 pm    Post subject: Limestone Reply with quote

The last fuselage I had powdercoated (J-3 in July) was blasted with limestone sand. It was less aggressive than other media, lots cheaper than soda.
We chemically stripped old paint, glue and fabric so they only had to do a light blasting cleanup prior to powder coating.

Limestone sand should work well on a virgin fuselage.
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