bottom job on metal (steel) boat and sandblasting..

Discussion in 'Metal Boat Building' started by rawley2, Aug 4, 2008.

  1. rawley2
    Joined: Jun 2007
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    Location: Florida

    rawley2 Junior Member

    Am I to belive that you would need to sandblast a steel hull every year when you do your bottom paint..

    OK lets say you move a lot and use hard bottom paint and get 3 years between bottom jobs..

    Do you really need to blast to white steel and start from there?

    Can you just pressure wash, give it a light sanding and put another coat of anti fouling on it?? Just spot blasting (or grinding) and rust spots you see? Not the whole bottom.
     
  2. tazmann
    Joined: Aug 2005
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    Location: California

    tazmann Senior Member

    No you would not sandblast every year, you should have a good epoxy berrier coat under the bottom paint. preping and doing any repairs then add another bottom coating.
    Tom
     
  3. Landlubber
    Joined: Jun 2007
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    Location: Brisbane

    Landlubber Senior Member

    rawley2,

    The hull is sandblaste only from new, done to white metal and then a minimum of 300 microns epoxy protective coatings. I can recommend the Altex Devoe range of products as being exceptionally good. They are called Devoe Ameron in your part of the world. They have beem making protective coatings for off shore structures for decades, so if they can survive in those circumstances, they have a good chance of survival on a boat.
    Contact your local rep and discuss the best system they have, forget the price, quality is remembered long after price is forgotten.
    Do exactly as they say, do not listen to all the local experts that know more than the manufacturer, theyreally have a good track record.

    I made scrapers from 1/2" acrylic plactic that we used especially for the steel boats, it removed barnacles quite well and never dug into the substrate paint system. The only time you would ever have to sandblast during normal yearly slippings would be if there was damage for some reason or other, the paint system could last for 20 years, my last one did!
     
  4. Landlubber
    Joined: Jun 2007
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    Location: Brisbane

    Landlubber Senior Member

    Just looked up a spec sheet from Altex Coatings (NZ)

    Abrasive blast to SSPC SP10 (Sa2.5) to achieve a uniform jagged blast profile of between 35 and 50μm.
    Apply coat Epoxy Primer N°.1 - full prime to the prepared SP10 substrate.
    (thickness 110micron WFT)
    Apply a full coat of coat Epoxy High Build Surfacer N°.2 - full coat
    (thickness 350 micron WFT)
    Apply another Epoxy High Build Surfacer N°.2 - full coat
    (thickness 350 micron WFT)
    Epoxy Primer N°.1 - full coat
    (thickness 110 micron WFT)
    No.5 Anti-Fouling - full coat
    (thickness 200 micron WFT)
    No.5 Anti-Fouling - full coat
    (thickness 200 micron WFT)
    All surfaces must be clean and dry before painting
    NOTE:
    1. Apply No.5 Antifouling before last coat (Epoxy Primer No.1) has cured i.e. tack free but still soft to finger pressure.
    DO NOT allow the Epoxy Primer No.1 to cure hard before applying No.5 Antifouling. (My comment:This allows the paints to chemically lock into each other)
    2. Allow 12 hours cure of the final coat of No.5 Antifouling before relaunching.
    NB: DO NOT exceed maximum recoat times.

    Ask the rep for a gauge, he will show you how to read it, well worth while.
     
  5. mastcolin
    Joined: Jun 2005
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    Location: The Netherlands

    mastcolin Senior Member

    antifouling

    There is absolutley no need to blast to bare substrate at lifting.

    Just high pressure wash off any fouling (and loose paint!). Let it dry, scrape off any remaining fouling and scuff it all up with some rough sandpaper. (remember to wear gloves, goggles etc)

    You can overcoat normally with fresh antifouling.

    However - take care with changing brand of antifouling. Some are incompatible and can cause problems (eg cracking, blistering) . If you are considering changing brand/type then speak with the new supplier. They normally have list of any compatibility issues and solutions.

    If you do get a build up of old antifouling then if it does start to build up and crack off in sheets, then the worse you should have to do is a light grit blast back to the primer system. You could of course scrape it off but it is horrible job. "You pay your money and make your choice" as they say.

    Then just re-apply tiecoat and new antifouling.
     
  6. rawley2
    Joined: Jun 2007
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    Location: Florida

    rawley2 Junior Member

    Thanks guys,

    I thought better than that but had to make sure.

    I know steel hulls are a LITTLE more maintenance but sandblasting every year.. I was like come on. LOL
     

  7. Brent Swain
    Joined: Mar 2002
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    Location: British Columbia

    Brent Swain Member

    My steel boat is 24 years old , in excellent condition and has never been sandblasted.
     
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