bradycros
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Posted 20th September 2011, 02:22 AM
By: luke strawwalker
BAR jack of all trades Join Date: 18th January 2009
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The post below is reprinted with luke strawwalkers permission. He accurately discribes the damp (wet) sanding technique he and I use. I see no need to reinvent the wheel on this one.
bradycros
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I recommend a technique I call "damp sanding"...
I typically use a 440 grit or 600 grit as the final sanding on my rockets before painting (sanding the primer "glass smooth"-- don't worry, it still has MORE than enough 'tooth' for the paint to hold on to). It makes the surface SO smooth that the final color coats go on like silk and flow out perfectly without the need for color sanding (IMHO). Here's how you do it.
Get a bowl of water and keep it where you're sanding, and your sandpaper (I use roughly 2x3 inch blocks of sandpaper at at time and sand everything by hand (without sanding blocks). I usually sand while watching TV, so I set the bowl on the table by my chair and drape an old towel over me to keep the crud off. Have a couple paper towels handy too. Dip the paper in the water bowl, and then shake the excess off. You basically only want a few drops of water spread evenly on the paper. Start sanding, ALWAYS sand in a circular motion, and CONSTANTLY rotate the rocket in your hand very slowly as you sand, NEVER sand in the same spot continuously to avoid flat spots and sand-thrus. Sand easy with VERY little pressure-- let the paper do the work. The sanding will liberate "sanding mud" consisting of the primer you've sanded off the surface of the rocket, mixed with moisture from the sandpaper. About every minute or so, when the paper "loads up", drop it in the bowl, and take the paper towel and wipe the excess "sanding mud" off the rocket. Run your finger over the submerged paper to free the paint particles from the grit, pull the paper out of the bowl, shake the excess water off, and if you start getting too much water, daub the paper a bit on the towel before returning to sanding. Actually you can keep sanding without wiping the mud off that often-- about every third dip of the paper in the bowl is fine. The main thing is, you DON'T want water 'running everywhere'... you need JUST enough water to lube the paper a bit and keep the liberated primer particles flowing out as 'sanding mud'.
It's a REALLY easy process to learn once you get the hang of it and it works VERY well. You can LITERALLY make primer "shine" using this technique. Of course you don't have to take it THAT far (and it's probably better that you DON'T) because all you REALLY need to do is get rid of ALL the imperfections in the surface before you paint, and you'll have a GORGEOUS paint job (if you don't screw up applying the paint!)
I usually inspect the rocket by holding it up at eye level in front of me, with a sunlit window or bright light above and on the other side of the room. This will create a "glint" off the surface of the tubes or fin surfaces that will readily show any imperfections as specks, spots, craters, waves, or breaks in that "glint" of reflected light off the surface-- imperfections FAR too small to see directly, or to feel with your finger... but they stand out EASILY when looking at their effect on the reflection of light off the tube/surface. Once you have it to the point your satisfied, wipe it down with a DAMP paper towel to remove any remaining sanding mud and let it dry THOROUGHLY (overnight usually) and then paint as normal.
I regularly sand balsa fins, un-CA-sealed paper tubes, balsa transitions, etc. with this method and have had ZERO problems-- just terrific finishes!
Later and good luck! Hope this helps! OL JR
__________________
The X-87B Cruise Basselope- THE ultimate weapon in the arsenal of homeland defense and only $52 million per round!
__________________
The process is continuous...
By: luke strawwalker
BAR jack of all trades Join Date: 18th January 2009
-------------------------------------------------------------------------------
The post below is reprinted with luke strawwalkers permission. He accurately discribes the damp (wet) sanding technique he and I use. I see no need to reinvent the wheel on this one.
bradycros
--------------------------------------------------------------------------------
I recommend a technique I call "damp sanding"...
I typically use a 440 grit or 600 grit as the final sanding on my rockets before painting (sanding the primer "glass smooth"-- don't worry, it still has MORE than enough 'tooth' for the paint to hold on to). It makes the surface SO smooth that the final color coats go on like silk and flow out perfectly without the need for color sanding (IMHO). Here's how you do it.
Get a bowl of water and keep it where you're sanding, and your sandpaper (I use roughly 2x3 inch blocks of sandpaper at at time and sand everything by hand (without sanding blocks). I usually sand while watching TV, so I set the bowl on the table by my chair and drape an old towel over me to keep the crud off. Have a couple paper towels handy too. Dip the paper in the water bowl, and then shake the excess off. You basically only want a few drops of water spread evenly on the paper. Start sanding, ALWAYS sand in a circular motion, and CONSTANTLY rotate the rocket in your hand very slowly as you sand, NEVER sand in the same spot continuously to avoid flat spots and sand-thrus. Sand easy with VERY little pressure-- let the paper do the work. The sanding will liberate "sanding mud" consisting of the primer you've sanded off the surface of the rocket, mixed with moisture from the sandpaper. About every minute or so, when the paper "loads up", drop it in the bowl, and take the paper towel and wipe the excess "sanding mud" off the rocket. Run your finger over the submerged paper to free the paint particles from the grit, pull the paper out of the bowl, shake the excess water off, and if you start getting too much water, daub the paper a bit on the towel before returning to sanding. Actually you can keep sanding without wiping the mud off that often-- about every third dip of the paper in the bowl is fine. The main thing is, you DON'T want water 'running everywhere'... you need JUST enough water to lube the paper a bit and keep the liberated primer particles flowing out as 'sanding mud'.
It's a REALLY easy process to learn once you get the hang of it and it works VERY well. You can LITERALLY make primer "shine" using this technique. Of course you don't have to take it THAT far (and it's probably better that you DON'T) because all you REALLY need to do is get rid of ALL the imperfections in the surface before you paint, and you'll have a GORGEOUS paint job (if you don't screw up applying the paint!)
I usually inspect the rocket by holding it up at eye level in front of me, with a sunlit window or bright light above and on the other side of the room. This will create a "glint" off the surface of the tubes or fin surfaces that will readily show any imperfections as specks, spots, craters, waves, or breaks in that "glint" of reflected light off the surface-- imperfections FAR too small to see directly, or to feel with your finger... but they stand out EASILY when looking at their effect on the reflection of light off the tube/surface. Once you have it to the point your satisfied, wipe it down with a DAMP paper towel to remove any remaining sanding mud and let it dry THOROUGHLY (overnight usually) and then paint as normal.
I regularly sand balsa fins, un-CA-sealed paper tubes, balsa transitions, etc. with this method and have had ZERO problems-- just terrific finishes!
Later and good luck! Hope this helps! OL JR
__________________
The X-87B Cruise Basselope- THE ultimate weapon in the arsenal of homeland defense and only $52 million per round!
__________________
The process is continuous...
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