MASTERCLASS - DIY plastic body panel repairs.

A load of posts that show you how to do various projects, step by step.
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johnr
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MASTERCLASS - DIY plastic body panel repairs.

Unread post by johnr » Mon Mar 09, 2009 3:43 am

Right firstly the usual denials and warnings.
I'm not taking any responsibility if you set fire to your garage or poison yourself. repairing plastic is relatively simple and the repairs can be as strong as the original part. however, don't blame me if your badly cobbled together effort falls to bits on your way to work, or the sharp edges you failed to remove shred the mot testers hand.
also, plastic when melted gives off a heady cocktail of toxins in its smoke. I did mine outside where the car port provided a wind tunnel effect to whisk the smoke and nasty stuff away. if you choose to do yours in your bedroom with the door shut, don't blame me if you spend a week in hospital with the after effects,
realise also, that molten plastic is hot, as are soldering irons, so don't rest it on your leg whilst welding it up wearing shorts.
basically guys, common sense ok?


Right, this is what we have to start with. broken in a low speed tumble, also theres a crack in it which we will repair the same way. this is a mudguard off a honda 90, but it could just as well be any other plastic motorcycle fairing or sidepanel, I've repaired katana panels using this method. as theyre expensive and hard to find. and it works well and has lasted for years since I did it.

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johnr
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Re: DIY plastic body panel repairs!!!!!

Unread post by johnr » Mon Mar 09, 2009 3:51 am

Ok, so its broken. but, we have all the bits and the breaks are relatively clean.

So to begin with this is what we need, a sander, a soldering iron (this small butane gas one was under a tenner from maplin electronics) some zip ties. only other thing I used was a dremel, but its not necessary, I'm just lazy!

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now the most important part of any job like this is preparation so dont cut corners, I know you are dead keen to start melting stuff but be patient. it needs cleaning off first.
Last edited by johnr on Mon Mar 09, 2009 4:21 am, edited 1 time in total.

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johnr
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Re: DIY plastic body panel repairs!!!!!

Unread post by johnr » Mon Mar 09, 2009 3:57 am

first job is to sand off the existing paint finish, this avoids getting paint into the plastic, and just makes it easier to see what you are doing.
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Re: DIY plastic body panel repairs!!!!!

Unread post by johnr » Mon Mar 09, 2009 3:59 am

next thing we need to do is get the dremel out and smooth over the edges. now in order to make the job strong, we need to get maximum penetration of the melted plastic into the join. so using the dremel, chamfer the edge of the plastic over, both inside and outside. when put together, this hollow is what we are going to fill with melted plastic.

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now the hole I have drilled is to prevent the end of the crack from spreading, the hole prevents it from cracking right across, and we will be filling it with weld later, so wont be seen.

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Re: DIY plastic body panel repairs!!!!!

Unread post by johnr » Mon Mar 09, 2009 4:01 am

so here we are, nicely chamfered edges, hole drilled, on both pieces, all ready to go.

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it all fits together, and the edges are nice and smooth. so test fit it together to just make sure
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Re: DIY plastic body panel repairs!!!!!

Unread post by johnr » Mon Mar 09, 2009 4:04 am

right. now you get to melt it!!

ok, using a nice hot soldering iron as the heat source, this is a butane gas powered one, and as a filler we use zip ties!! yes, the good old cable tie is the right type of plastic to use to weld these panels and when cool is as hard and strong as the original plastic.

first of all, on the inside of the guard touch the hot iron against the surface and melt the 2 sides of the plastic together. no filler required, this is just to tack them for welding, so make sure they are straight and everything lines up,

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the technique is, and we are on the crack here first, put the zip tie onto the crack, and press the soldering iron into it, the melted plastic will be forced into the crack. dont press too hard though, we are going to do the inside after this side, and dont worry about how much plastic you put in, too much is better than not enough.

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eventually you will have got to the end of the join, and if you are just welding cracks, then you will need to fill the hole you have drilled too.

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Re: DIY plastic body panel repairs!!!!!

Unread post by johnr » Mon Mar 09, 2009 4:09 am

next repeat the process on the inside. I tend to put plenty on the inside of joins as I'm not planning to clean this off so the extra material here will reinforce the plastic.

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sometimes you need more hands than you have so its useful to have something to hold part of the job still, leaving you a hand free to hold the other half,

again as before, just tack the 2 halves first, tack on both sides about an inch apart. then check that everything lines up as it should before welding it.

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now as before weld the plastics together, using the zip ties as before. this whole repair used up 5 zip ties only, and I used white ones as I had them, but as its being paited afterwards, use whatever colour you can get hold of.

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Re: DIY plastic body panel repairs!!!!!

Unread post by johnr » Mon Mar 09, 2009 4:12 am

here we have the finnished mudguard, welded inside and out, and ready for the final tidy up.

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Re: DIY plastic body panel repairs!!!!!

Unread post by johnr » Mon Mar 09, 2009 4:14 am

now its out with the dremmel, and clean up the welds that are visible , just grind them smooth with the surface like so,

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leaving us with this kind of finish,

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Re: DIY plastic body panel repairs!!!!!

Unread post by johnr » Mon Mar 09, 2009 4:18 am

a final quick fit on the bike to make sure its all still ok,
as you can see, the majority of the welds arent visible due to the forks, so I only need to make a good clean job of the ones at the top

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next I give it a quick blow over with filler primer. a wonderful product that will provide a thick layer of primer that will fill any surface imperfections, and I can sand through to get a smooth finish,

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and thats pretty much it, it just needs rubbing back and then spraying the colour of your choice. simple eh! and if your panel is already broken. what have you got to lose?

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