Sandblasting antifouling

Discussion in 'Fiberglass and Composite Boat Building' started by simon, Dec 14, 2009.

  1. simon
    Joined: May 2002
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    simon Senior Member

    Good day everyone,

    I would be interested in experiences in sandblasting antifouling on fiberglass hulls. My boat does not have gelcoat and below the antifouling is immediately the fiberglass.
    Anything I do have to pay attention? I want to preserve the fiberglass layer and think that this would be also a good preparation for painting.

    Cheers

    Simon
     
  2. wardd
    Joined: Apr 2009
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    Location: usa

    wardd Senior Member

    i believe it would dissolve your hull

    you could try dry ice blasting
     
  3. Submarine Tom

    Submarine Tom Previous Member

    I soda blasted (baking soda) my Fiberglas on plywood houseboat hull to

    remove epoxy bottom paint and Gelcote in order to apply epoxy barrier and

    it was brilliant!

    -Tom
     
  4. simon
    Joined: May 2002
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    simon Senior Member

  5. Itchy&Scratchy
    Joined: Jul 2008
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    Location: Oxford & South Africa

    Itchy&Scratchy Senior Member

    There should be no reason to sandblast, unless you have water ingress, which you would probably only know if you had osmosis, which is unlikely if you have no gelcoat below the waterline- as I thiink (I may be wrong on this, but I have only seen this in the last few years) this is a new thing leaving the bottom clear.

    The other question , you need to possibly find out is whether or not your hull has been epoxied in the area with no gel? , also a fairly standard practice nowadays.

    If the hull has already been keyed up and antifouled properly, you shouldnt need to remove it,but if you really must, use a DA sander with about a 60 or 80 grit disc.
    J
     
  6. Submarine Tom

    Submarine Tom Previous Member

    Sodablasting was cheap for me. The guy gave me the machine for the day

    for 100 bucks (US85). It took me the better part of the day, with breaks.

    Like I said, it was slick. I'd do it again in a heartbeat.

    -Tom
     
  7. missinginaction
    Joined: Aug 2007
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    Location: New York

    missinginaction Senior Member

    FWIW I'm going to second Itchy&Scratchy here. While replacing thru hulls and seacocks last summer I found it necessary to fill and repair a couple of holes in the bottom of my Silverton that were no longer necessary. As part of the repair I had to remove the ablative antifouling paint in the area. I used a dual action (da) sander and found it cut right through the paint to the gel coat very quickly with a #40 disk. I'd also recommend a good OSHA approved canister type respirator to save your lungs.

    Regards,

    MIA
     
  8. SamSam
    Joined: Feb 2005
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    Location: Coastal Georgia

    SamSam Senior Member

    There are different grades of sand available according to mesh size used to screen it, the higher the number the finer the grains, the finer the grains the more controllable as to how fast or it eats away whatever you're blasting and how deep it cuts. Gravestone makers can probably steer you to sources.

    Protect your lungs. You not only have the danger of silicosis from the powdered sand but the danger of powdered heavy metal dust from the bottom paint.

    MIA, you do realize to do thruhull repairs with fiberglass, that a repair won't stick to gelcoat and you have to grind through the gelcoat to get to actual FG laminations ?
     
  9. Herman
    Joined: Oct 2004
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    Location: The Netherlands

    Herman Senior Member

    About blast media, there are more options than (various grades of) sand.

    glass
    walnut shells
    metal spheres
    soda
    solid co2
    solid n2

    And probably more...
     
  10. missinginaction
    Joined: Aug 2007
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    Location: New York

    missinginaction Senior Member

    Hi samsam,

    Regarding the hull repairs.....I did the repair from the inside of the boat, layering up about 5 laminations of biaxle cloth and mat that I had leftover from making my stringers. I filled the hole with epoxy resin (the hull is actually about 1/2 inch thick solid laminate in that area), then applied increasingly large pieces of fiberglass cloth to the inside of the hull building up the laminate.

    I sanded off the paint so that I could apply a piece of tape to the outside of the boat (over the hole) to keep the epoxy goo from running out while I made the repair.

    Thanks for the concern, I'm grateful for folks like you that keep an eye on me:)

    Regards,

    MIA
     
  11. Herman
    Joined: Oct 2004
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    Location: The Netherlands

    Herman Senior Member

    Solid laminate? You mean single skin I suppose. Cored laminates can be solid as well.
     
  12. missinginaction
    Joined: Aug 2007
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    Location: New York

    missinginaction Senior Member

    Nope Herman....it's a 1973 Silverton 25 1/2 foot sedan. I've been restoring it over the past 3 years. Built like a battleship. The bottom of the hull is 1/2 inch thick solid fiberglass laminate in the aft area under the engine. No core, just layup. I was amazed when I pulled the old thruhulls and saw how heavy they made it. The laminate appears to be even thicker at the chines. It thins a bit as you go forward. Ah for the good old days....when petrochemicals were cheap and the livin was easy!:D :D

    Didn't want to hijack the thread though so back to the original question about sandblasting. I think that sanding might be cheaper. How much would sand blasting off the paint cost?

    Regards,

    MIA
     
  13. simon
    Joined: May 2002
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    simon Senior Member

    I have had a sample patch done and it looks very well. Going to do the rest next week.

    Simon
     

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  14. Guest62110524

    Guest62110524 Previous Member

    I have done plenty of blasting, you just cut back the pressure, and distance off, for instance balsting steel 120psi, but I would start at 20 psi and work up
    a good resharpenable scraper like a skarston is perfectly controllable too
    cheerrs
     

  15. souljour2000
    Joined: Aug 2009
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    Location: SW Florida

    souljour2000 Senior Member

    On this topic...is there a reason anyone might not recommend pressure washing to get rid of really old and flaky bottom paint on a good condition sailboat hull from the mid-80's that has been on a trailer most of it's life?
     
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