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Smoothing the nose cone

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Please have a look at the attached image. This is a plastic nose cone that I sanded down and then spray painted a primer onto. However it has left rough marks on the nose cone.

I am a little new when it comes to painting. I was wondering what I could do in order to smooth the nose cone before I start to spray it again.

Thanks for any help,

004.JPG
 

InFlight

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Looks like you're using 120 grit sandpaper :confused2:

Try using some 400 grit sandpaper, it loads up faster but you will like the results. Cut it into smaller sheets like 2 x 6 and fold in half so you don't waste it.
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AKPilot

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I'll echo what Ray's stated. Use a finer grit sandpaper down to about 400 grit, then primer again. If there's still any rough spots fill them in (with the primer on) with some type of appropriate filler or putty. Then sand again with 400 and keep up the routine until you get the cone the way you like.

Hope this helps.
 

troj

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The problems with the paper clogging can be easily solved by using wet/dry paper and wet-sanding.

You'll also get a better final result if you wet sand.

-Kevin
 
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OK, I understand regarding the sand paper, and yes I am using far too rough a paper. This is another mistake I won't make again. :roll:

But my question now relates to the best method of correcting the nose cone I got. AKPilot you suggested a filler. Are you suggesting a glue of somekind? Or get a finer sand paper and continue to sand it down?
 

jj94

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What I do to get nice nose cones is to sand with rough sandpaper to get rid of the raised seam lines or what ever other imperfections there could be in the nose cone. Then I look for areas in which there are low spots, like seam lines that could form a grooved line up and down the nose cone. I fill them with filler (spackle, wood filler, auto filler, etc.) and then sand smooth. Take note that I didn't smooth the cone out with fine sandpaper before applying the filler. I like to keep it rough so the filler has something to adhere better too. After the filler is on and smoothed out with medium grit, I smooth everything out with 400 grit and then continue the filling/smoothing process until everything is exactly the way I want.
 

troj

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OK, I understand regarding the sand paper, and yes I am using far too rough a paper. This is another mistake I won't make again. :roll:

But my question now relates to the best method of correcting the nose cone I got. AKPilot you suggested a filler. Are you suggesting a glue of somekind? Or get a finer sand paper and continue to sand it down?
Get a high-fill primer; your best source of these will likely be an auto parts store. Use that and it will help; you're going to find it takes multiple coats.

-Kevin
 
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I appreciate all your help. I have been flying rockets for years, but only recently have I started to actually make them better. But at present I am making a ton of mistakes, to which one can learn from.

Thanks again, my plan is to continue sanding down the nose cone with a finer sand paper currently just brought 320. I will continue to spray primer until I have smoothed it out. Will get back to you on the results.
 

troj

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I appreciate all your help. I have been flying rockets for years, but only recently have I started to actually make them better. But at present I am making a ton of mistakes, to which one can learn from.

Thanks again, my plan is to continue sanding down the nose cone with a finer sand paper currently just brought 320. I will continue to spray primer until I have smoothed it out. Will get back to you on the results.
FWIW, there is a huge difference between "sandable primer" and regular primer, especially when it comes to how easily it sands and how much it clogs the paper.

If finish matters to you, you'll also find that it's worth the money to buy quality sandpaper. I buy either 3M or Klingspor -- hardware store brand stuff costs less per sheet, but I end up using way more of it, and in the long run, it costs me more and takes more time.

-Kevin
 

mkadams001

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troj makes a good point about the primer and sandpaper. I use Dupicolor filler primer dries fast and sands easily.

I usually end my sanding with 320 paper.

If you are using wet or dry sandpaper, ignore the dry and use it wet.

Good Luck!!
 

powderburner

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You can speed up the process a bit by only using "coarse" sandpaper (30, 40, 50 grit) for the most severely rough surfaces. When you use these grades of sandpaper (and continue using them), you will only get a surface as smooth as the size of the grit, which (for these grades) is nasty. These sandpapers will take down extreme irregularities in the surface but will leave it quite rough. I don't know anyone who uses these grades of sandpaper in rocketry.

The next step is to use a "medium" sandpaper (60, 80, 100 grit) to make the surface progressively smoother. These grades will erase part of the roughness left by the coarse sandpaper, but only down to the point where these medium grades are still leaving their own scratches and marks. This is still pretty rough stuff for any rocketry finishing applications.

The next step is down to "fine" sandpaper (120, 150, 180, 200-ish grit) to make the surface progressively smoother again. (See a pattern here?) These grades will (yada, yada...) These sandpapers will do a pretty good preliminary job of smoothing raw balsa and surfaces covered with primers.

Then (on the same project) you get to the "very fine" sandpapers (200 to 300 grit). You will probably spend twice as much time performing sanding at this stage as you did at the previous level. This is about as far as I like to go on the primer coats, but you might choose to go even farther and deeper into the realm of repetitive, monotonous, mindless, incredibly boring physical labor.

Then you get to the "extra fine" sandpapers (300 to 500 grit). You might have some paint on the rocket by now, and if you have made a painting mistake, this is probably the range of grit you need to gently remove the paint you don't want. Otherwise, I would not recommend using this grit on much more than the first coat of base color, as this grit will quite visibly scratch and damage any nice outer layer of finish paint.

Then you get to the "super fine" sandpapers (500 to 700 grit). Somewhere in here (certainly by now) you have switched over to wet-sanding, to help reduce the amount of waste that packs into your sandpaper and to help carry the waste material off the work surface you are sanding. You also have to wet-wipe (no, not those little perfumed tissues, but you do have to wipe the work surface frequently with a wet soft towel, then continue sanding with a well-wetted piece of super-fine-grit sandpaper.

Some of the guys here (who obviously don't have much to do in the way of household chores and errands) continue this nonsense down to 800, 1000, 1500 grit, and beyond. Myself, if I want an aerodynamically smooth surface for a competition model, I use car wax or Future floor polish and buff most of it back off again. For most model rockets, I don't care if I can see myself in the finish (or if anyone else can), even if it's going to be seen by many many other people (yeah, I know, that's a poor attitude).

There is a saying that "perfect" is the enemy of "good enough" and I agree. I figure that I can have 99% of the fun with 50% of the labor spent smoothing, painting, and finishing.

(Whispered: Sometimes I don't even sand or paint them at all!)
 
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InFlight

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Get a high-fill primer; your best source of these will likely be an auto parts store. Use that and it will help; you're going to find it takes multiple coats.

-Kevin
Yep, that's what I do as well. I will also smooth out the flash with a file before sanding.
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MarkII

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Some of the guys here (who obviously don't have much to do in the way of household chores and errands) continue this nonsense down to 800, 1000, 1500 grit, and beyond.
Or jobs... :rolleyes:

When I get to 1500 grit, I know that I'm about halfway there... :dark:

I'm done with the nose cone finish when I run out of sandpaper! :roll:

For most model rockets, I don't care if I can see myself in the finish (or if anyone else can), even if it's going to be seen by many many other people (yeah, I know, that's a poor attitude).
Very, very few people ever see any of my rockets. The important thing, though, is that I can see them. :cyclops:

MarkII

P.S. BTW, I'm joking. I usually stop at 1500 grit. :D
 

rokitflite

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The problems with the paper clogging can be easily solved by using wet/dry paper and wet-sanding.

You'll also get a better final result if you wet sand.

-Kevin
I second that.
 

troj

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Yep, that's what I do as well. I will also smooth out the flash with a file before sanding.
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An X-Acto knife held perpendicular to the flashing can be used to scrape it (if you've ever seen a cabinet scraper in use, it's similar).

For a good finish, the key is patience. Aggressive sanding with heavy sandpaper, especially on soft materials like plastic, just leads to a mess that you have to clean up later.

Someone mentions sandpaper below 120 grit. In rocketry, the only time I use anything more coarse than 200 is when I have a lot of material to remove from something hard, like the edge of a plywood centering ring.

For our big projects, we've been known to use 80 grit sandpaper in a belt sander. But that's also when adjusting the side of a 3/4" baltic birch centering ring.

-Kevin
 

AKPilot

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You know, I love it when I get a good finish. But, after a few launches, and a few 'landings' I realize the paints going to get chipped and scratched no matter what.
 

standardrockets

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The problems with the paper clogging can be easily solved by using wet/dry paper and wet-sanding.

You'll also get a better final result if you wet sand.

-Kevin
I've found a good way to unclog sandpaper when dry sanding is to wear an old t-shirt, then when the paper is a little clogged, rub the paper on the shirt to unclog it and make it look like I'm doing real work and getting all messy.

It works really well with those sponge sanding blocks.
 

AKPilot

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The newer 3M stuff doesn't clog no where near as much nowadays.
 

MarkII

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You know, I love it when I get a good finish. But, after a few launches, and a few 'landings' I realize the paints going to get chipped and scratched no matter what.
That's why it's good to finish two nose cones - one for flight and one for display. ;)

MarkII
 

foose4string

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I'm partial to the Norton 400 grit(and occasionally 320) 3X sandpaper. It's about all I ever use. It supposedly lasts longer than regular paper, which seems to be an accurate claim from my experience. I don't know about 3 times longer??....but longer!
Best way to avoid clogging is to make sure the primer is completely dry. If the paper is clogging with any regularity, it's not dry, and it's not ready to be sanded yet. Move on to another project while you wait. Be patient...it could take days depending on the primer used and humidity. Primers should sand off into a fine powder- not a clumpy, paper clogging, mess! It will help conserve paper too.
 

AKPilot

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I haven't used it before, but is Duplicolor primer compatible with the new Krylon formula?
 

troj

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I haven't used it before, but is Duplicolor primer compatible with the new Krylon formula?
Duplicolor makes both lacquers and enamels. You can typically put enamel over lacquer, but not lacquer over enamel.

Their high-fill primer is lacquer-based, I believe, and should work fine under an enamel color coat.

Standard Disclaimer: Always test when mixing brands, for compatibility.

-Kevin
 

astropilot

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One of the things I do is to buff the plastic parts with 00 Steel Wool, after sanding with progressively finer grits of sand paper. For me this seems to produce a very nice finish.
 
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