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Discussion Starter · #1 ·
I am a relative newbie to fatbikes. My first, a Surly Moonlander, is now about 3 months old. I'm hooked. It is a riot.

It was a LBS demo. I completely disassembled it. Treated the frame and fork with Framsaver. I also replaced the stock Andel BB with a Shimano unit and added the Chris King BB sleeve to address any potential moisture issues.

The BFL tires throw AN AWFUL LOT of road/trail crap into my face and into the drivetrain. Not fun! So I started looking for mudguards...

I've been searching for something suitable for the last several months. A tip steered my to Big O manufacturing. About two weeks ago they announced that they had brought their Moonlander set to market, so I ordered some. Pretty decent.

The set from Big O look to be a softer ABS plastic and have a crinkle/irregular finish to the outer surface. Have any folks painted them? If so, what did you do to get a smooth gloss finish?


I have never shot (painted) this softer - flexible pastic. How do you smooth it out? Multiple heavy coats of two part epoxy primer/filler sanded between coats? Any/all tips and suggestions are appreciated.
 

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There used to be a product called plasticoat. I used it on the soft vinyl on my jet ski chin pad 10+ years ago and it still looks great. Google it!
 

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Discussion Starter · #3 ·
If I am reading the Plasticoat information correctly, it seems like it is a rubberized paint. I'm looking for someing that will adhere well to ABS plastic, and fill in/level out the surface irregularities and serve as a appropriate base coat for a subsequent gloss finish coat which I can stripe/detail/decal.

Thoughts?
 

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Look to the automotive industry for a rattle-can for flexible plastic parts. Like the plastic fascia over bumpers. If they say to use a particular primer paint, or a degreasing prep step, then do so. Once of the biggest causes of failure in painting is not doing sufficient prep work. (On diluting surface grease vs. degreasing http://forums.mtbr.com/fat-bikes/bead-seating-my-wits-end-904073.html#post11076347)

I'm guessing that the Big O fenders are made from heat-formed ABS sheets. ABS sheets are typically available smooth both sides or textured one side. Google images for "abs sheet texture" to see if textured one side is what you have, be it from sheet stock or from Big O's forming process, or from a textured paint.

I read somewhere that someone had sanded the Big O fenders smooth before painting them. I would expect sanding to be a lot more likely to have a good outcome than trying to fill in a texture with paint.

I haven't read how they sanded them smooth, but when cutting or sanding plastic, watch the speed of your saw/drill/sander so you don't end up melting the plastic instead of cutting it. So sand by hand with a sanding block or turn that sander speed down.
 

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Nemophilist
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Nope;

Painting plastic is NEVER very successful. You CAN do it, and it will "work"... AS LONG AS YOU NEVER BUMP, BEND, TAP, TWIST, SCRAPE, OR OTHERWISE TWEAK IT. Then you will be sorry because the paint will blow right off.

Bottom line; buy the color you want. Black is always nice.
 

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Nope; Painting plastic is NEVER very successful. You CAN do it, and it will "work"... AS LONG AS YOU NEVER BUMP, BEND, TAP, TWIST, SCRAPE, OR OTHERWISE TWEAK IT. Then you will be sorry because the paint will blow right off..
Gee. I guess all of the dented painted plastic bumper covers that I got to spring back out with a heat gun without needing repainting were just my imagination.

The "trick" is to use the paint intended for flexible plastic, and do the proper prep. They take thermal cycling too. There are limits to the flex, but they're pretty good.

Even with the correct paint, if you don't do the prep properly, be it sanding or to remove manufacturing release agents, blooming or post manufacturing grease contamination, it will often be exactly as you describe.
 

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Nemophilist
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You want to tell me how to paint plastic parts?

I might say that what was in your imagination is that you really know what you are talking about, but that would be even snarkier than your response. I've been doing it for near 30 years, FOR A LIVING! Go ahead and tell me how it is done...........

There is NO process, NONE, NOT A SINGLE ONE, in the after market that can come even close to replicating automotive OE flexible part finishes. Much to our utter dismay, I might add. The only reason you were able to push a boink out was because it was an OE finish. I've tried all the gee whiz stuff that has come out over the years; scrub pads, squirt bottles, conversion coatings, etch primers, you name it. Some of it is better than others, but you can take the best and do it all right and it still doesn't replicate the amazing properties of OE finishes. The ONLY plastic paint that is impressive is vinyl interior dye, and that stuff is pretty freeking incredible.

Take it for what it is worth, but don't suggest that someone you don't know doesn't know what they are talking about. I do.

To the OP. Go ahead and get some plastic paint and give it a go. Report back what you learn.
 

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Sorry, but my first hand personal experience is different than yours. It's always interesting when someone tells me it's impossible to do something that I've done. If I can do it, it can't be that hard.
 

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Sorry, but my first hand personal experience is different than yours. It's always interesting when someone tells me it's impossible to do something that I've done. If I can do it, it can't be that hard.
Canoe don’t question Trailmaker:nono: he knows everything about everything you are wrong just ask him.:skep:
 

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Others have painted plastic successfully. I've painted plastic successfully. What can I say.


~edit.
If it's any help:
  • the parts, paint or rattle-can were always room temperature or slightly warmer (not preheated),
  • parts were prepped and bone dry in advance, allowed to settle to room temperature overnight, and not touched by bare hand once degreased,
  • air temperature was always 60F or higher, and never over 80F, typically 65F to 72F, and
  • relative humidity: never above 50% (never even tried it); ; shoot over 40% under duress (particularly for priming or first coats), shoot with confidence if under 40%, and I'd hold off for under 30% if it looked like conditions would co-operate. Usually 20% to 40%.
  • And I've had surprisingly good results violating the above rules with cheap parts using standard indoor/outdoor solid colour Kyron rattle-cans, and as low as 40F and as high as 55%, with a simple detergent wash and an RO or RO/DI water rinse. Thin coats.
 

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Nope;

Painting plastic is NEVER very successful. You CAN do it, and it will "work"... AS LONG AS YOU NEVER BUMP, BEND, TAP, TWIST, SCRAPE, OR OTHERWISE TWEAK IT. Then you will be sorry because the paint will blow right off.

Bottom line; buy the color you want. Black is always nice.
I have Quad/ATV rider friends who use the plasticoat/plastidip products successfully. They don't expect a permanent forever fix, actually the point is that you can change to another colour next year!
But, the best refinishing of old ABS is not paint, it's acryilic floor polish!. it rejuvenates old honda big reds to look like new!
 

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I have to check which brand was recommended if your'e interested, but it's the second part after you use a floor stripper, it's specifically the kind for refinishing vinyl tile floors
 

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Discussion Starter · #13 ·
All,
Thank you for your input, passion, and candor. Generally got the following steps:
Hand sand to remove the crinkle surface. Probably the most effort here.
Surface prep/degrease with appropriate stuff.
Prime/base coat with appropriate stuff.
Dry.
Repeat until satisfied with surface.
1st color coat.
Dry
Prep for finish coat
Finish coat.

Caveat - it's plastic. You get results proportionate to your level of prep, skill and what the materials can yield.

Thanks for the input. Appreciated.
 

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Nemophilist
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Canoe don’t question Trailmaker:nono: he knows everything about everything you are wrong just ask him.:skep:
Don't you worry;

Everyone's reputation - and what they know - is very evident. You are obviously happy with where you are. We're both safe.
 

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Well...

You can put paint on anything. You can paint a balloon and as long as the amount of air in it doesn't change, the finish will stay the same. Yeh, right.

My idea of painting something is that there exist a reasonable expectation that it will stay that way. Take a strip of OE car bumper, and then a like strip that has been refinished using the best materials available. Bend both pieces back and forth and see which one fails. It won't be the OE piece. If you're lucky you get a few cycles before the refinished paint cracks. Funny... the examples parts the paint reps bring around to show off their latest and greatest flex system never fails, but when you try it yourself, using the exact methods, it fails. Why is that?

Painted plastic looks great until you bend it, and then all bets are off. That's not my idea of success. There simply is not enough mechanical adhesion - like on sheetmetal - for it to resist failure. There is simply too great a disparity in the flex of the base material and the paint on top of it. You have a chance on ABS plastic only because it doesn't bend very easily. However, it is also incredibly "greasy" and NOTHING likes to stick to it. Most flex agents that you add for plastic parts only keep the paint flexible long enough for you to get them installed, and the companies TELL YOU THAT (in fine print). When it fails, what you end up with looks worse than before it was painted (repaired). In the case of car bumpers, a walk through a crowded parking lot will give you all the evidence you need.

Send your fenders - and forks - to exp18. He can do anything. Unlike him, I am well aware of all I don't know, and govern myself accordingly.
 

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In my early years, my painting plastic almost always failed. But once I was taught to degrease properly, and to stop putting paint on so thick :)madman:), problem gone. I have no idea why your experience is different from mine, or from those in the shop where I worked. We weren't taking special care, nor were any of us specifically trained. Just using the supplier's manuals & tech sheets. We had the equipment, mixed it and shot it.

Back before the VOC restrictions, in addition to shooting on metal, we would shoot glasurit (spelling?) with a flex agent on ABS fender extensions and some other plastic parts. Sometimes with vinyl wash, sometimes without. If it was textured ABS, just the shop degreaser (don't remember what it was), if it was smooth, we'd sand first to scuff the surface. For the ABS, usually a flash coat of thinned epoxy primer as an adhesion promoter, but we did this as standard for our metal parts & chassis too. On ABS with the flex agent = no problem; without flex agent = eventually a problem, usually sooner than later, particularly if the equipment was garaged, so likely due to the thermal cycling. If they used the glasurit with extra hardener (they kept insisting on that for some metal parts, for 'extra gloss for appearance', or 'for better salt resistance') on plastic, we were guaranteed a problem, as that was hugely brittle, but some of the guys would shoot that on plastic as it 'was already in the gun'. The equipment was used year round in temps from -30F to +95F. We used the glasurit for the plastics as that was what we already had in the shop for the heavy steel and the sheet metal, and it worked without creating warranty work. All high pressure guns, no HVLP in the shop. Except for one of the guys who always put paint on too thick, the paint would stick and flex with the plastic or the sheet metal, to a surprising degree, well past what was required.

I wasn't around when they had to switch to low/no voc, so I have no idea how that worked out, but they did switch to having one guy do all the painting so perhaps those materials needed skill instead of 'just shoot it'. (curious, that guy was the one who'd always applied the paint too thick...)

Some body shops are fixing dents in metal work from the backside, with the paint on the front, coming back out to the original shape without defect in the paint. Labor intensive, but if they don't have to shoot a metalic-clearcoat again and again to satisfy the customer, it can be worth it. While somewhat of a novelty today, this was not uncommon back in the day with 2nd gen Imron, if it was prepped properly and not applied too thick (like I did at first), it would stay with the sheet metal, and without cracks. This was very common when using the glasurit, except when instructed to use the extra hardener. And if the catalyzed polyurethane was applied at proper thicknesses, it was also common that there was enough flex in the paint that rocks would flex the paint, primer & metal and bounce off without chipping; applied too thick, all bets off. Same for sheets flexing in accidents, depending on the radius of the bend.

So nothing special, but it worked. And as there was nothing special, there's little chance of there being anything in there to help you. No idea why you have issues with plastics where you are.
Speculating: any chance you have some odd component in the air, maybe even a particular humidity range, that affects how it dries?
 

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Another option might be pin striping. Comes in many sizes and there are decals that you can apply also.
 

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Nemophilist
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Maybe it was my expectation;

I wanted paint to stick to bumpers like the factory did. Too bad, but that is impossible. I've painted hundreds of car bumpers, and I deliver them with the caveat; It will look factory until you bump something. Then, all bets are off.

Bike fenders. I like them black because then they recede visually don't spoil the style of my bike! You just want them to work if you have to have them. You don't really want to see them.
 

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