Paint, to sand or not to sand

[BrAdam]

I am painting the fin can portion of my darkstar jr and then want to clear coat the entire thing. I have painted the fin can and it feels rough. Like 400 grit sandpaper. Should I just spray over that and will that result in a smooth glossy finish? Or, is there something I need to do to the paint? Sand buff….?

New territory for me, help.

 

[samb]

You may get a few different answers to this but here's my 2 cents:

Do not spray anything yet. A rough surface should be corrected if you want a "smooth glassy finish". In my experience, the results you've described have two possible causes:

The surface for color coat was too rough - needed another iteration of fill/sand/prime. Your last coat of primer should be smooth with maybe a light rub with 600 grit to level it out.

or

You sprayed a "dry" coat of color. If you're too far away the paint dries and hits the surface in fine drops.

IMO you have two choices: sand smooth with no more than 400 grit. It may take a while but aggressive sanding at this point is bad. Respray and try for a better, wetter coat. Yes, it's an art and it's frustrating sometimes.

choice 2 - Stick a woosh generator in that puppy and light the candle ! They all look the same at 1000 feet. Try for the "smooth glossy finish" on the next one.

 

[BrAdam]

I think a dry spray. Surface prep was pretty good. So sand and des pray another color coat? If wet enough it should be smooth, then clear?


Sent from my iPhone using Rocketry Forum

 

[samb]

Yep. Take your time with the sanding so you don't add any gouges. Stop often and feel with your fingers. When you're satisfied with it, wipe of the sanding dust and respray.

 

[Micromeister]

I wouldn't use sandpaper, I'd use two 3m products to straighten out the rough surface
start with Perfect-it III on a damp rag in a circular motion working a small area at a time. then finish with Finesset-II on a damp rag same procedure. This is how we remove orange-peel, dust, dirt and other minor imperfections from Auto finishes before and after the basecoat/topcoat are applied.

 

[cjp]

I found the more you sand the better the finish.I had a rocket finish that cracked.I sanded, primed and sanded again.Best finish I have ever had.All from a mistake.But it depends what your happy with in a finish.They all look the same at 150mph going up off the pad.

 

[stealth6]

A concept that is foreign to most people is: that in order to get a REALLY great finish, you need to "finish the finish". This IS well known amongst professionals who do fine woodworking, auto painting, etc., but most civilians want to believe the marketing hype that all they have to do is apply some miracle product, let it dry, and then sit back and admire thier "professional" hi-gloss finish. Unfortunately, it doesn't really work like that.

Here's the deal - there are essentially no paints or finishing products out there that if you simply apply them and let them cure they will come out perfect. ESPECIALLY anything that comes in an aerosol. Yes, some go on smoother than others, but for a truly "glass-like" finish you will still have to buff and/or polish (which are really just very fine "sanding" to some degree). Sometimes quite a bit of buffing/polishing in fact. And yes, the smoother the subsurface is (meaning more sanding), the smoother the top-coat will be. But you WILL still need to buff/polish/wetsand that last coat. And you MUST wait until that coat is fully cured before doing so (which can be a very long time if you use aerosol paints).

So, if you are really going for superb results, you must sand between all coats. And you must "finish the finish" on that last coat, which means more sanding/polishing/buffing/etc.

That said, this IS "just a rocket" and there is absolutely nothing wrong with just grabbing a can of Krylon, spraying a bunch of it on, letting it dry and calling it good, as long as you are not expecting it to be perfect. And sometimes you do get quite good (if not "perfect") results. If this makes you happy, it's all good. Rockets are for flying.

s6