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Thread: How to smooth a dash and door panels

  1. #1
    Newbie wildbill22's Avatar
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    How to smooth a dash and door panels

    I am new to fabrication and need some help. I have painted my dash and some of my door panels but i didnt know how to smooth them as you can see from the pics below. please help me out and tell me how to make is look good.


  2. #2
    Variable Bitrate Arrow's Avatar
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    Use a high-grit sandpaper, then clearcoat if you want that shiny wet look.

  3. #3
    Variable Bitrate
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    yeah, use a 80 grit paper or lower to take the texture off, then smooth it out with higher grit paper, you may need to hit it with a high build and then sand that back to make it real smooth. Remember to give a couple coats of a plastic primer or adhesion promoter onto bare plastics before anything else or the paint will chip off over time.
    Continued Worklog... Upgrades in progress:
    *15.4" WXGA LED backlight touchscreen upgrade
    *Custom fiberglass dash bezel

  4. #4
    Newbie wildbill22's Avatar
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    thanks, now do i need to wet sand it or just plain sand it.

  5. #5
    Low Bitrate kazzxtrismus's Avatar
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    220 is plent rough enoug with a 1/3 sheet electric sander (for larger project / larger flat surface).

    then go down to about 400 grit
    plastic / flexible body panel primer
    filler primer
    sand with 400
    look for high spots and low spots (where the sandpaper didn't hit)
    if they dont look to bad just sand 'em to make the txture match the sanded parts.

    if you need to flatten and fill use a putty then sand
    prime with primer or filler primer when done sanding
    look at the shine from an angle as you spray...this will help you see if there are any low spots to care for.

    sand with 400 to get everything evenly smooth / rough...
    (i sometimes will then cover with fresh primer and go right into sanding if orange peel is not a concern)

    paint with your fave colour

    clear coat if you want shiny-er

    when painting and clearing make sure the paint has gone tacky (gluey) before the next coat is applied.
    (i use a pc of carboard...i paint it at the same time to check for tacky,.. then i can touch that and not muck up the panel I'm working on)

    2-3 coats of paint minimum (if your good and cheap with it)...paint that needs clear-coating is ONLY THERE FOR COLOUR...so just do thin coats till the colour is even across the surface.

    2-3 coats of clear is a good finisher..... if you let the 2nd last coat go a little past tacky it will hold a heavier final coat (better gloss)

    wet sanding should be done with 600 or 800 grit paper minimum then BUFFED with a rotating buffing pad and polishing compound (farecla G3 is my fav).

    you can wetsand down to 1000 and 1500 and 2000 but its rarely ever worth it cause any imperfection shows up like a giant pimple or scar.

    if you need to go waay more than these 2-3 coats of colour and 2-3 coats of clear to get everything even...you will be pushing the limits of the paint.

    it may not harden enough (ever really) and be easy to gouge.
    it can sag because of the weight of the paint
    it can "fisheye" which is outgassing being trapped in microbubbles in the surface or just below.

    so make sure you wait for the paint to get tacky before the next coat....if it looks like 3-5 coats wait a little longer than tacky.

    you cannot fix fisheye...you have to wait for it to dry then sand with 400 and go at it again with the colour then clear....luckily NOT start all over again

  6. #6
    Newbie wildbill22's Avatar
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    well i went down to my local scrap yard and pick up a piece of a dash like mine so if i messed up i would not mess mine up. well here is after a day of sanding.

  7. #7
    Newbie wildbill22's Avatar
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    how long do you wait before you put the clear coat on?

  8. #8
    Raw Wave shotgunefx's Avatar
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    One thing I've found is that some types of plastic are MUCH easier to sand than others. Parts of my interior are polypropylene, and they are easy, others (door panels, rear interior panels) are talc-filled polypropylene.

    Those parts are virtually impossible to sand. It more just kind of shreds, like the whole piece was made out of tons of shrink wrap compressed into a piece. A few people with my car have done it, but literally, over a 100 hours of sanding. I gave up on those after a couple of hours.

    How do you tell what's what? There are various burn tests, etc, I happened to have a manual that specified what was what.

  9. #9
    Variable Bitrate Bimmerstyle's Avatar
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    Those parts are virtually impossible to sand. It more just kind of shreds, like the whole piece was made out of tons of shrink wrap compressed into a piece. A few people with my car have done it, but literally, over a 100 hours of sanding. I gave up on those after a couple of hours.
    You don't have to sand the structure out of these materials. It's, as you say, virtually impossible.

    Slightly sand the plastic so it's ready to paint (don't mind the structure yet)

    Put plastic primer on it

    Put a lot of coats of spray filler on it (minimum 3 coats, wait long enough between coats)

    Then sand this with 220 grit paper and you wil notice it becomes smooth. This is actually the part of the process where you get rid of the structure. You get it out of the spray filler actually without touching the plastic. It's important not to touch the plastic here so that's why a lot of coats of spray filler are important.

    Put primer on it.

    Sand with about 800 grit (more if you like but for interior parts i don't find it necessary)

    Now your pieces are ready to be painted in any colour you want.

    Your result should be something like these. (examples done by ourselves not just taken from the internet)











    EDIT: The doors of the BMW (black and orange) were a little more complex. It involved removing the original fabric on the doors and put polyester (fiberglass) on them. Also the speaker openings were made with polyester. But the entire dash was done the way I explained in this post.
    BMW 525tds -Biostar I94GM-I4 -Celeron M44O 1,86GHz, M2-ATX, 1Gb, 320GB -HQCT RDS tuner -Creative Extigy -iBus controller -Lilliput 7" touchscreen -DLS Ultimate A7 amplifier -Focal 130K, 130V, 27V2 speakers

    Bezel Worklog-My Install -iDrive F01 RR Skin

  10. #10
    Low Bitrate kazzxtrismus's Avatar
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    ya use filler primer or finishing putty to fill the texture.

    i like finishing putty or bondo better because it can be mixed to go harder than regular filler primers.

    but to each is own.

    either way tho i wouldn't paint over anything smoother than a "600 wetsanded" smoothness...paint has a bit of a tendancy to not really grab well at these levels.
    especially for anyonne new to this kinda work.

    but ehhh whatever works best for you.

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