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My Crazy Idea. Will It work? (paint related)

Discussion in 'Technical and Troubleshooting Torque' started by Manny, May 4, 2005.

  1. The big wrap around fairing on my bike has a big ol crack in it. It's just above the indicator, but doesnt go all the way to the edge of the fairing. I was wondering if rather than having it plastic welded, i could put a vinyl sticker over the crack, then spray over it. I figure if the sticker is covering the crack, then you wont be able to see the crack in the paint work.

    Ordinarily i would probably just have it plastic welded, but Im going to be a learner soon, and chances are I'm going to drop it.

    Whats the verdict? Do it right, or do it with a sticker? =p
  2. why dont you dry duck tape or bandaids?!?!?
  3. when i fixed up missa's GPX, i just popped some fibreglass behind the crack to strengthen it. looked fine and would have been sandable and paintable and it even held up to another stack :LOL:
  4. fiberglass you say... how expensive would it be? what would i need to buyyy
  5. araldite it and use some plastic from a milk bottle on the back of the fairing to add strength.
  6. Yeah, fiberglass would be the next best bet, as coconuts has suggested. You should be able to buy what you need at bunnings or any hardware store. It may even come in a kit - fiberglass matting and laquer together.

    Maybe a filler to fill the crack over on the outside before respray to flatten the surface.

    I think you'd have real trouble with a) the paint reacting with the decal and bubbling or get the orange peel effect happening, and/or b) Seeing the outline of the decal under the paint - it would be very difficult to spray over the decal to get it flush and a nice flat surface on the fairing. This wouldn't be a problem of course if you put the same decal on over the top of the paint as well. ie decal, paint, decal. But i still think you'd have trouble with the paint reacting on the sticker.
  7. not only will the paint react with the sticker, also vinyl will stretch over time and alow the crack to re open, better off glassing it up
  8. aight cool

    thanks for the tips! ill go down to bunnings tomorrow n see how much it costs..
  9. I'm not the bigest fan of fiber glass on plastic fairings... you might want to scratch up the area where you are going to stick the fiber glass to... I have seen paches like that come off... does not look preaty...
  10. Patch goes on the back, for stength only, not looks.

    But scratching it up to give the reson something to bond to is a great idea.
  11. Don't go buying a big tin of car repair bog for this.

    Get the fibreglass repair kit from Bunnings. For his job you want woven cloth, not the random chopped mat. It is too difficult to get the chopped mat to sit flat against the surface if there are any curves in it.

    You also need a garbage bag and some sand. You'll use this as a weight to hold the woven mat against the fairing. The poor-man's vacuum bag.

    Rough up a area the full length of the crack, about 5cm either side. Use coarse sandpaper - 180 grit. Because you're gluing to a surface that has already set, you're just creating a mechanical bond not a chemical one, so you need a very clean, rough surface to "key" into.

    Now cut the cloth into strips, the length of the crack. Use sharp scissors to reduce fraying. The first strip will be 10cm. The next with be 8, then 6 and 4.

    If the cloth isn't long enough to go the full length of the crack you can make up the lengths in two pieces, but you must allow 5cm of overlap AND the joins must be in different spots so the 10cm strip has its join in a different spot from the 8cm strip, which in turn is in a different spot from the 6cm strip. The idea here is to avoid getting stress concentration points.

    10cm strip: -----|----------------------------------
    8 cm strip: ---------------------|------------------
    6 cm strip: ------------|---------------------------
    4 cm strip: ------------------------------|---------

    Ok. Here's where you need to work fast. Polyester resin sets fast. This part is easier if you have a sheet of glass handy (old shower doors are great).

    Make up enough resin to paint a wet layer 10cm wide onto the inside of the fairing 5cm either side of the crack.

    Paint a 6cm wide stripe of resin onto the glass, lay the 4cm strip onto the wet resin and dab it with the brush until the woven mat all changes from white to translucent. Add more resin if you need to but be sparing. Too much resin weakens the repair. Carefully pick up the 4cm strip and lay it onto the inside of the fairing, equally spaced over the crack.

    Repeat the last step with each of the strips of cloth, so you've built up layers of wet cloth that has the narrowest strip at the bottom and the widest strip at the top. As you put down each layer give it a good dab all over with the brush to remove any air bubbles.

    When you've layed all the wet cloth down, lay the fairing on the ground, get the garbage bag and put it over the cloth without disturbing it. You may need to put some wooden blocks under the fairing to stop it from rolling around. Pour the sand onto the garbage bag so the sand puts some weight over the wet cloth. You need a layer of sand about a centimetre thick. This will help compact the layers and reduce air bubbles.

    HINT - it is better to mix small quantities of resin than to make up too much. Although the resin sets fast, you still get a chemical bond when the resin is in its "gel" stage so its ok to stop for a few minutes and mix more while the last layer sets a little. This is much safer than maxing a huge amount and having it all go off while you're working on the first few layers. Also, a large volume of resin sets faster than a small one because the reaction is exothermic - it produces heat - which, in turn, speeds the setting. A large volume disipates heat less quickly so a cup of resin cures faster than a teaspoon full.

    Put the cup you mixed the resin in near the fairing. You'll need this later. To avoid the temptation to lift the garbage bag and see how things are going, just check the resin in the mixing cup. When it is set, the fairing is ready.

    When the glass is fully cured, get the resin again and make up enough to fill the lid of a Coke bottle. Mix in talcum powder (yes, the stuff you put on your feet) until you get a paste about the consistency of peanut butter. Work this into the crack from the outside of the fairing and let it set. It makes a great filler - light, flexible and easy to sand.
  12. 30 minutes. Easy. But that plastex stuff looks clever - "Plastex is excellent for reproducing knobs"

    But do we need more Martys? :p
  13. that doesn't work, will cause a stress concentration and crack willeventually get through it. in the mean time the crack will just find an alternative path to progress through. Fixing it properly is the only way to get rid of it.

    You should just take all your fairing off ya bike and ride it naked if your worried about binning it.
  14. dont get the drilling a hole bit, its not needed if your gonna use that plastex stuff. Many people believe that drilling a hole at the end of a crack will stop it progressing any further, just wanted to clear up that it is not the case. I can verify this from both my own ignorance in trying to do this a couple of years ago when i binned my bike, then last year i did some fatigue work and learnt some of the theory behind it.
  15. just ride the bloody thing and treat it as a battle scar :LOL:
    once you drop it do what roderz does then go naked :LOL:
  16. Wow. thanks for the feedback.
    Special thanks to you Chairman, very detailed. Thanks a lot for the effort.

    god it'll be sweet to get this shit all finished up. woowoowooo!
  17. Re plastex. Have people used this product. What is its strength like. How much stress will it take compared to the original part? Is plastic welding a better option?

    Like to hear some thoughts.