How do you prevent clogging your random orbital sand paper from cured resin?

Discussion in 'Boatbuilding' started by magentawave, Aug 25, 2013.

  1. magentawave
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    magentawave Senior Member

    Is there any solution to preventing your random orbiat sanding discs from clogging while sanding cured polyester laminating resin? I tried one of those big rubber eraser thingee's which actually work great for a lot of stuff but it was totally useless with resin. I googled the question and someone said to wipe down the area you're sanding with kerosene first and he guarantee's your sand paper won't clog. Has anyone used that technique before? Is there any downside to using kerosene on a fiberglass surface that will be glassed more after sanding, and then primed, and then painted? Would a good wipe down with alcohol remove any remnants of kerosene?

    Thanks!
     
  2. Mr Efficiency
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    Mr Efficiency Senior Member

    What is the kero supposed to do I wonder ? Seal the surface long enough for the resin to cure tack-free ? It is the tackiness of unwaxed resin that blocks the discs. I would be cautious about using anything like that, that might leave an oily residue. Try using a coarser grit, fine grit always clogs faster.
     
  3. upchurchmr
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    upchurchmr Senior Member

    Don't know about polyester, but on epoxy I use a knife blade to scrape off the clogged spots (if it is not too bad). doesn't last long once the clogging has started and it makes you sharpen the knife after your done also.
     
  4. SamSam
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    SamSam Senior Member

    Don't use kerosene, it will contaminate the glass with oil and make any following laminations or painting very questionable if even possible.

    You say laminating resin, so I assume it's unwaxed. So I assume you know you don't actually have to sand the last laminate before applying the next, if you do it within a certain amount of time.

    You can use a sharp paint scraper to do most of the "sanding" you have to do. They are easy to clean and sharpen and are usually faster that sanding. For the rest use a coarse sanding disc, 40 grit or less. All you have to do is get rid of the bumps and nubs and random 'hairs' that will hold the next layer of glass off the surface and allow air pockets. Unless you used too much resin or have puddles and need to get back to actual glass to laminate to.
     
  5. magentawave
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    magentawave Senior Member

    Just speculation but I'm thinking that since kerosene is kinda oily feeling that it helps the sand paper glide a little.

    I'm using 36 grit so its pretty gnarly stuff.

     
  6. magentawave
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    magentawave Senior Member

    So if I can't use kerosene then I'm back to clogging up these expensive discs. Dang.

    Yes, it is laminating resin so has no wax in it.

    I clogged it using 36 grit.

    I'm not sanding between laminations. The sanding is being done after laminating.

     
  7. magentawave
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    magentawave Senior Member

    BTW: I found these two links about minimizing sand paper clogging...

    This link mentions using kerosene.

    This link recommends running the sander at a lower speed setting and keep it moving quickly over the area with very light pressure to avoid heating up the disc which then heats up the stuff you're sanding thus causing the build up. One guy also said he did all of the above but sprayed high temperature cooking spray on his discs.
     
  8. Mr Efficiency
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    Mr Efficiency Senior Member

    I think you need waxed resin to avoid clogging discs, it is the uncured resin that doesn't go off because it is exposed to air that really can't be sanded. Fairing with resins filled with microballoons and the like will encounter the same problem, if in unwaxed resin.
     
  9. messabout
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    messabout Senior Member

    Mr Efficiency has it right I believe. Polyester has the property of failing to cure in the presence of oxygen. The topmost part of the resin in the laminate is in fact exposed to oxygen. The inclusion of wax is the common solution. When the resin polymerization process generates a bit of heat, the wax floats to the surface and insulates the outermost film from the atmoshphere.

    The end result is that non waxed resin will remain sticky enough to clog the sanding disk. Other methods for isolating the surface film include peelply or something as simple as a plastic sheet such as visqueen. A tightly and carefully laid sheet of plastic not only insures surface cure but can save a ton of subsequent sanding. Vacuum bagging is even better for surface quality and resin cure.
     
  10. SamSam
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    SamSam Senior Member

    PVA will work too.

    The OP could apply another coat of resin with provisions so it would surface cure and then go to sanding.
     
  11. michael pierzga
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    michael pierzga Senior Member

    With gummy resin youre up the creek without a paddle.

    For normal sanding, gumming paper means high temperture at the sandpaper to surface interface. Slow down, use less pressure and choose the correct random orbital. Random orbitals are ratde by thier sanding orbit. Small orbit is for fine paper and finish sanding, large orbit is for coarse paper and heavy sanding.

    A small orbit with course sandpaper will clog fast.

    What is the orbit of your random orbital ?
     
  12. magentawave
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    magentawave Senior Member

    I'm not sure what the orbit is but its the 6" Porter Cable configured like a little grinder. Here it is: http://www.portercable.com/products/ProductDetail.aspx?ProductID=21428. I've had it for over 20 years and its one of my all time favorite tools.

    Right now for the major grinding I'm using my big Makita 7" grinder with 40 grit discs. I'm happy to report that the discs aren't clogging now running it at half speed with very little pressure and moving it quickly across the surface. Yay!
     
  13. Petros
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    Petros Senior Member

    how about trying wiping it with water? some moisture on the surface of the sanding disk should keep it cool and prevent the clogging. Usually with wet sanding the more water present the less risk of clogging the sandpaper.
     
  14. magentawave
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    magentawave Senior Member

    Wet sanding with a sanding disc on a grinder or RO sander? Doesn't that F up the machine?
     

  15. Petros
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    Petros Senior Member

    keep the water on the surface, and off the machine. Spray some LPS1 into the vents as it is running and it will protect the windings from any possible moisture issues. It will not really harm it, but it could cause some running issues, and long term corrosion. LPS-1 will not harm the motor, protect it from moisture and lubricate any moving parts.
     
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