Sanding Primer

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Lee

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OK – nobody likes sanding. But sanding primer is #1 on my list of undesirable tasks during a build. Loads of gray dust. I’ve resorted to wearing food handlers disposable gloves so that I don’t emerge looking like I worked in a garage all day. Just wondering how others deal with this?

Also, does anybody use 0000 steel wool on primer?
 

Back_at_it

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I have the same issue. Tons of super fine dust. During the winter I setup a little sanding booth with a fan and a hose that blows out the window. I also sand with 600 wet dry sand paper.

During the summer I do all my sanding outside.
 

Huxter

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Thats my least favorite thing to do too! I usually use paint and primer combined into one can, and only use it at the end of the build. I do sand in-between coats, but do not use it as a filler. If I choose to fill balsa grains, I usually use CWF watered down. Much less dust than the gray primer. Never used steel wool on rockets.
 

afadeev

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OK – nobody likes sanding. But sanding primer is #1 on my list of undesirable tasks during a build. Loads of gray dust. I’ve resorted to wearing food handlers disposable gloves so that I don’t emerge looking like I worked in a garage all day. Just wondering how others deal with this?
Sanding dust is unfortunate, and inevitable.
I prefer to sand outside, when the weather allows. Using fast-drying primers helps, especially when filling surface imperfections over multiple paint-sand-paint cycles.

Also, does anybody use 0000 steel wool on primer?
I've tried a few steel wool sponges on rockets, but they tend to be a bit pricier and a little harder to clean.
I'm back to 3M sandpaper of various grades of coarseness. It lasts longer, cleans more easily, and backing is strong enough to withstand an occasional water bath to clear out primer build-up from the paper.

a
 
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neil_w

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Unclear if the OP is talking about regular primer or filler/primer (a common source of confusion on the forum). In my case, it's filler/primer, and that *sounds* like what the OP is discussing.

To a certain extent this question depends on the size of the rocket. For my LPR stuff, I'm able to hold the rocket inside my garbage can while sanding, so the very vast majority of dust stays inside there. I also have a little DC fan with a HEPA filter strapped to it that I can set next to the garbage can for when I need to sand outside the can.

There will still be dust all over my hands; I keep a damp paper towel handy to wipe off frequently. I do find the dust and the task in general to be unpleasant and annoying, but also worth it: when I experimented with skipping the filler/primer step with one rocket it resulted in noticeably more surface imperfections on the finished product.

I can't imagine what it's like to sand large rockets; fortunately that is something I don't need to worry about.

(For what it's worth, I also find the dust generated from sanding CWF to be awful as well. This contributes to my preference for papering fins.)
 

Lee

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How about cleaning your primered/sanded rockets - damp paper towel?
 

neil_w

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Although I try to keep water away from my wood/paper rockets, I do often use a *damp* (not wet) paper towel to wipe it down as I go. I will eventually do alcohol wipes to get them really clean, and then maybe even a tack rag if the mood strikes me.
 

John Brohm

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I use a wet-sandable primer. No sanding dust.

Logic rightly suggests to keep water away from a paper product, but with a bit of preparation and practice, it's not a problem.
 

David Schwantz

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Use windex to clean. Ammonia takes off any grease and dries quickly.
 

John Brohm

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Regarding Lee's question about wiping the primer'ed model down, I always do this just before painting the color coat (allowing for a bit of time to make sure the model is fully dry first!), and I do this the way Neil mentions. Just a damp paper towel, and I'll also use a damp Q-tip to get into crevices where dust can hide.
 

John Brohm

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This photo shows the fin can to a model I've just finished priming. Some detail is being added just before the color coats. The primer was wet-sanded (no dust), some Q-tips were used to get at the sanding residue left in various places (like along the edges of those weld lines), and I was careful to wear a latex glove (or nitrile) while handling the model, as hand oils can be absorbed by the primer.


Fin Can Primer.jpg
 
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DigBaddy

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I use a wet-sandable primer. No sanding dust.

Logic rightly suggests to keep water away from a paper product, but with a bit of preparation and practice, it's not a problem.
I've not had good luck with the first shot of primer being able to be wet sanded. To get really smooth tubes I seem to get close enough to the paper (just back to it) that it doesn't go well. This could entirely be user error and/or lack of experience! Given your statement, perhaps I should try again and maybe I don't need to go quite as far :) I have had really good luck with Krylon automotive sandable primers, using a heavier darker gray for the first shot, that dry sands easily (3M paper), then the thinner white sandable primer second, which is wet sanded nice and smooth. Sand outside, wear a mask (when dry sanding) and gloves. Not that big of a mess to deal with. Plus, any reason to be outside is a good one.
 

John Brohm

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You're doing nothing wrong - one coat of primer isn't a sufficient moisture barrier. I lay down two successive coats, drying time in between, no sanding. Wet sanding (with a #400 grit) following the curing of the second primer coat.

Make sure to CA the ends of the tube, and any other openings. This waterproofs the other moisture entry points that wet-sanding might see.
 

rklapp

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I think this gets to the basic question, is it better to look good or to feel good? Is it a model or a rocket? The more time I spend on the details of the rocket, the more anxiety I have about putting an E12 into it. Granted it didn't take too much repair on the Saturn 1B I just pulled out of a tree. I used a lot of CA gap filler on the broken blow mold bits. Maybe someday I'll eventually put that E12-4 into it.

To get back to the OP, I use the 0000 on the primer. I should be using the alcohol to wipe the fine steel wool bits off. Someone suggested using talc powder on the sand paper to prevent the primer from gumming up the grit but haven't tried it yet.

 

neil_w

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I think this gets to the basic question, is it better to look good or to feel good? Is it a model or a rocket? The more time I spend on the details of the rocket, the more anxiety I have about putting an E12 into it.
I would have anxiety about putting an E12 into a roll of paper towels, but that's another issue.

For me, the anxiety of flying a highly crafted rocket (i.e. pucker factor) is part of the fun. Of course it's also nice to have some less "treasured" rockets that you can fly with less stress.
 

caveduck

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Not so unpleasant for me, but I probably use a different primer than most (2 part Klass Kote oxide primer). The dust is white and non-sticky, unlike the rattle can primers that can be really gummy. I do use steel wool for nooks 'n crannies...John Boren put me on to that a couple of years ago. The Klass Kote does not load up sandpaper much, especially if you use the purplish 3M pro stuff. These days I'm always looking to machine sand whenever possible...Dremel Multi-Maxx for flat stuff, and even an orbital sander with a very soft interface pad for 4-6" rockets. Mostly I go outdoors now and use a mask too. The dust will brush off clothes pretty well.
 

Bruiser

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John Brohm, that looks a lot like a Black Brant...

I also wet sand the primer, even when I wasn't quasi-glassing the body tubes. Two nice coats of primer then wet sand. I also seal the ends of the tubes with thin CA. There have been times when I did go thru the primer. I just let it dry then spray a little more primer and be more careful when I sand. I also try to remember to wear gloves between the final sanding and the top coat/s

-Bob
 

mbeels

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I also wet sand the primer, even when I wasn't quasi-glassing the body tubes. Two nice coats of primer then wet sand.
That's pretty much what I do as well, either one or two coats of primer and then wet sand. Some are concerned about a porous primer letting water through to the cardboard tube, but I just haven't experienced that as a problem. I don't think enough water gets through to do any damage. Wet sanding is faster, less dust, the paper doesn't clog at all, and good results.
 

teepot

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I use automotive sandable primer. 2 coats and dry sand. The dust doesn't bother me because it doesn't become airborne. I vacuum the dust off the rocket and I use denatured alcohol to wipe it down before the color coat.
 

Dawgbert

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I'm a newbie here, not brave enough to wet sand, but would get extremely frustrated with primer sticking to the sandpaper. Tried using talcum powder on a my 4" Hawk, works great but makes a terrible mess. Seems like the primer sticks to the powder and weighs it down, not as much dust in the air, sandpaper doesn't clog as long as a little powder is added along.
 

Mike Haberer

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Although I try to keep water away from my wood/paper rockets, I do often use a *damp* (not wet) paper towel to wipe it down as I go. I will eventually do alcohol wipes to get them really clean, and then maybe even a tack rag if the mood strikes me.
Wet sanding with 320/400 grit, tack cloth for the dust first, then isopropyl alcohol. Two coats of color, then 600 grit wet sanding, then tack cloth and isopropyl alcohol before the final light color coat. Then decals. Then clear coat.

Then again, a lot of the time I prime and sand, then fly and maybe get to the color coats. Paint is truly optional.
 

Lee

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When sanding a flat surface we use a sanding block to maintain the flat surface. But what about the body tube where you want to maintain the curvature? Seems to me a curved sanding block is called for. I'm tinkering with a piece of core from a roll of tape. Seems to be working. Any other ideas on this?
wetsanding 4.jpg
 

Back_at_it

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Wet sanding by hand on body tubes. I use a block on flat surfaces.

When doing the tubes I use a 45 degree cross pattern so I don’t sand grooves or flats into the tube.

done a lot of body work in my life 😕
 

Lee

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I am wet sanding now also. I coated my "tape core sanding block" with TBIII so that it doesn't absorb water. So far, pleased with the results.
 

Rory Gin

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I use a sheet of medium-coarse paper free handed (some edges require a sanding block) then follow up with extra fine conformal foam sanding. I tried wet sanding but I prefer dry for better control.
 
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