Which grit to dry blast old FRP hull interior?

Discussion in 'Fiberglass and Composite Boat Building' started by powerabout, Jul 21, 2008.

  1. powerabout
    Joined: Nov 2007
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    Location: Melbourne/Singapore/Italy

    powerabout Senior Member

    Guys

    I have an old yacht that has been repainted (inside) over the flowcoat but the paint is failing so I need to remove it and I dont care if the flow coat goes with it.
    I am thinking of dry blasting but I am not sure of what grit to use?

    Thanks

    Powerabout
     
  2. Landlubber
    Joined: Jun 2007
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    Location: Brisbane

    Landlubber Senior Member

    powerabout,

    I assume the boat has been stripped of everything and you are going to start again, cos grit blasting is going to fill every nook and cranny that ever was hidden inside.

    The simple answer is anything that will remove paint from a board, try a sample test piece on a piece of ply using the finest grit that you can get.

    Mediums like almond husks, walnut husks, soda and sand will all do the job, there is absolutely no need for course blasting, but if that is all you have, lower the gun pressure and also hit the job from at least 2 feet away, the nozzle will blast right into the glass if you get too close.

    I remove the antifouling from glass boats with a wet sand blaster and a very small nozzle, it is only 1/2 inch, yet strips the paint very fast and controllable.

    Furnace grit may be available in Singapore, if so be very careful as it is very abrasive.

    The other way is to use a flap disc on a 4 inch grinder, slow, but very controllable, if you can get a small nozzle for the blaster, i would go that way too.
     
  3. powerabout
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    powerabout Senior Member

    Landlubber thanks,
    Yes I was thinking of a half inch hand held gun I just wondered if there was a specific medium to use.
    I am sure I will be able to get anything in Singapore.
    Its only a J24 so not that much area but and there arent any nooks and crannies so to speak of.
    It looks like the flow coat has been painted over without so much of a sand.
    Thanks
    Powerabout
     
  4. Landlubber
    Joined: Jun 2007
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    Location: Brisbane

    Landlubber Senior Member

    powerabout,

    I would just use a random orbital disc sander on a J24 mate, there is only a few hours work there, it would be far quicker than setting up and cleaning out the blaster!

    Use 120 grit on a 6" foam based pad, it will be gone before you even have time to get thirsty. Good sanders are festool and Rupes, also there is a sander that is not random it is geared to work the same pattern, they are excveptional, but may not be easy to get in Singapore. the crash shops will have a sander you may be able to rent for half a day.
     
  5. powerabout
    Joined: Nov 2007
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    powerabout Senior Member

    Landlubber
    I just found out that there is a process for fibreglass and that it is low pressure and uses granulated polycarbonate.
    People who restore fibreglass car bodies use it?
    Regards
    Powerabout
     
  6. the1much
    Joined: Jul 2007
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    the1much hippie dreams

    the big thing here now is baking soda blasting,,,,havent seen it yet,,,,but they say its safer and works as good as sand or beads.
     
  7. powerabout
    Joined: Nov 2007
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    powerabout Senior Member

    or..even better and no clean up is dry ice blast
     
  8. the1much
    Joined: Jul 2007
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    Location: maine

    the1much hippie dreams

    neva heard of that,,,wow.
     

  9. Kaptin-Jer
    Joined: Mar 2004
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    Kaptin-Jer Semi-Pro

    I did pretty much the same thing to a 38' sailboat. I used a wire brush in an electric drill. Woked very well, but invest in a full face mask.
     
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