Plastic Repairs

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John Vardanian
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Plastic Repairs

Postby John Vardanian » Tue Dec 06, 2016 1:47 am

I'd appreciate anyone advice on repairing/refinishing plastics, like the knobs of the window handles. What would be an appropriate filler? Thanks.

john
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afwrench
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Re: Plastic Repairs

Postby afwrench » Tue Dec 06, 2016 11:36 am

Hi John,I have repaired and remade a number of parts with cold cure resin.I made new knobs for my C4 that are a perfect match.Various colors are available and you should be able to add to and then contour and polish to a high sheen.I think that the products I have used are from Aero Marine . They have a website .I made some hinge blanks for Tom Y that he was able to use as patterns .Good luck,Mike
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peterp
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Re: Plastic Repairs

Postby peterp » Tue Dec 06, 2016 12:28 pm

It might help to post pictures so that we can see exactly what you are trying to repair, but I've found the JB Weld "stick" products to be very useful for this type of repair. The JB Weld comes in various forms steel, wood, plastic, ec. The "steel" stuff sets up way too fast (less than 5 minutes after you activate it) and it is nearly impossible to sand once it hardens. The "wood" version gives a much longer working time (more than 10 minutes) and can be sanded easily after curing, but is still very very strong. I think their "plastic" version is somewhere is somewhere in between the two, but I would recommend the wood version just because it's much easier to work with and is plenty strong.

It is a putty that has a very nice consistency that allows you to very accurately shape it to fill the hole and, once it is cured (an hour or so later), you can sand it fairly easily to get a perfect match.

This is the stuff (home depot usually stocks it, but not always -> https://www.amazon.com/J-B-Weld-8257-Kw ... +weld+wood
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John Vardanian
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Re: Plastic Repairs

Postby John Vardanian » Wed Dec 07, 2016 12:50 am

Thanks Peter. I'd like to use something that is black and can be polished. I'm trying to fill in some divides in the window crank knobs.

afwrench, can you tell me more about your product, name, model, etc., so I can find it? Thanks.

john
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peterp
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Re: Plastic Repairs

Postby peterp » Wed Dec 07, 2016 9:12 am

John Vardanian wrote:Thanks Peter. I'd like to use something that is black and can be polished. I'm trying to fill in some divides in the window crank knobs.


I think you could easily add pigment to make it black. It can definitely be shaped, sanded, and polished to exactly match the shape and sheen of the existing plastic. Just start with slightly coarser sandpaper (220 or so) to shape it and then using progressively finer paper down to 2000 or 3000 grit to get the finish you want, followed by polish if you find it necessary. Since you are trying to match something old, you might find that the ultra-smooth, but relatively matte, finish you get with 2000 might be preferable to following it up with a polish that might make it too shiny. Just don't use the metal version of JB Weld, that stuff is too strong and nearly impossible to sand. This thread talks about about pigments and filling black plastic -> http://forum.pafoa.org/showthread.php?t=166944
Peter P
1966 330 2+2 series 2 #8169

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John Vardanian
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Re: Plastic Repairs

Postby John Vardanian » Wed Dec 07, 2016 12:59 pm

Peter, how do you add pigment to exactly match the black cellulose?

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peterp
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Re: Plastic Repairs

Postby peterp » Wed Dec 07, 2016 2:30 pm

Unfortunately, John, I haven't had to use any pigment in my repairs, so I can't help regarding which pigment to use or how to use it. That said, for matching a vintage-weathered color, it seems like it might be easier to get a color match with a pigment-based approach (where you can tweak the amount of pigment as needed) than it would be to find something off the shelf that will be an exact match. I would try mixing up a bit of putty, slicing it into portions and try various amounts of pigments in each to see which combination is the best match, then sand the best matching test piece to see how both color and sheen match the existing.
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afwrench
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Re: Plastic Repairs

Postby afwrench » Wed Dec 07, 2016 3:52 pm

Hi John, try aeromarineproducts.com .A small mix and you should be able to fill voids with ease. Mike
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John Vardanian
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Re: Plastic Repairs

Postby John Vardanian » Wed Dec 07, 2016 9:40 pm

afwrench, when I go to their website, I see a boatload of products. Which one did you use?

Here's the plastic piece in question.

john

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afwrench
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Re: Plastic Repairs

Postby afwrench » Thu Dec 08, 2016 8:42 am

Hi John, I will check tonight and get specific info for you. All the best,Mike
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afwrench
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Re: Plastic Repairs

Postby afwrench » Sun Dec 11, 2016 1:09 pm

Hi John, no part number but what I got from them is Black Casting Resin part A and part B.Hope this helps. They were very helpfull on the phone. Good luck,Mike
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John Vardanian
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Re: Plastic Repairs

Postby John Vardanian » Mon Dec 12, 2016 1:01 am

Mike, that's very helpful. Thank you.

john
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