prep, prime/paint and fair bottom on aluminum boat

Discussion in 'Metal Boat Building' started by Northeaster, Jan 5, 2016.

  1. Northeaster
    Joined: Sep 2011
    Posts: 265
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    Location: Eastern Canada

    Northeaster Senior Member

    Andy - thanks for advice - I checked out their website - what kind of prep work and materials do you use before using that product? \i.e. do you blast, sand, use strong cleaners, etchers, etc prior to applying?
     
  2. Andy Jr
    Joined: Jan 2016
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    Location: Grand Isle, La

    Andy Jr Junior Member

    I do a sweep blast SSPC-7 then apply 2 coats coat of Aluthane. It's a moisture cured aluminum. Talked with a guy named Paul Oman. He knew his stuff
     
  3. Northeaster
    Joined: Sep 2011
    Posts: 265
    Likes: 8, Points: 18, Legacy Rep: 45
    Location: Eastern Canada

    Northeaster Senior Member

    Hi Folks,

    I am about halfway done prep and paint work but have some questions...or a dilema I guess..re: bottom paint.

    This 25ft aluminum hull, planing power boat will spend about 4-5 months per year (albeit much less this summer) docked on a tidal river, about 1/2 mile upstream of the salt water bay / Atlantic ocean. Water at the dock is slightly salty but mostly fresh as the river has a good flow rate all year.

    I have kept my older 30ft sailboat there for the last 5 years and regardless of bottom paint choice, or some years even only lightly sanding existing bottom paint, the most "growth" I get is some slime which easily pressure washes off after 4 months.

    I have followed mfgr's instructions and (after first sanding the hull) have applied 1 coat of Inteprotect 2000E and then faired low spots with Interlux's "watertight" brand epoxy filler.
    I have a bit more sanding / fairing to do and then I will be ready for a few more coats of I2000E and then bottom paint - but here is my dilema.

    The boat is far from finished but I am hoping to get enough done to do some sea trials and have a bit of fun this summer, knowing many items will not be finished till the following winter.
    The boat is upside down now, so it is much easier to apply bottom paint now, but that causes some issues as the boat will not be submerged for a few months, and even then, perhaps not for long, if it requires major tweaking..

    As I see it I have the following choices:

    1. As originally planned, while final coat of I2000E is still tacky, apply
    first coat of Trilux II bottom paint, followed by subsequent coat(s).
    Pro - don't have to sand I2000E to apply this bottom paint.
    Cons - Mfg says boat must be submerged within 90 days or bottom paint will not be effective- this would be hard to do... I could hold off on last coat of I2000E and bottom paint till it's close to ready for water, but this means painting those final 2-3 coats while boat is then right side up - much more difficult
    - Trilux II is a one season paint so no good the following year, need to re-apply - very expensive for only limited use this year.


    2. Use a "non" bottom paint such as VC performance epoxy instead of bottom paint.
    Pro - less expensive. would not reapply year to year
    - can do while upside down - much easier
    Con - no antifouling, pressure wash when needed.
    - need to cure and sand the I2000E before applying

    3. Leave last coat of I2000E as final coat (nothing on top if it).
    Pros - do while upside down. less expensive, no repeat each year.
    Cons- no antifouling, need to pressure wash as needed
    - would texture of I2000E allow growth faster than "slicker" paint?

    4 . what other options?

    In summary, I am not really trying to save money, but more importantly to not waste money and effort by applying a paint that will be worthless when submerged. Also, trying to do as much while upside down as reasonable.

    Note- I have faired since these pics were taken, including rounding out the keel bottom.

    I would appreciate any advice!
     

    Attached Files:

    Last edited: Mar 14, 2016

  4. Northeaster
    Joined: Sep 2011
    Posts: 265
    Likes: 8, Points: 18, Legacy Rep: 45
    Location: Eastern Canada

    Northeaster Senior Member

    Hi Folks,

    Finished applying 4 coats of I2000E primer and am holding off on bottom paint until closer to launch, as the bottom paint I had bought was only good if launched within 90 days of painting.
    Will likely do sea trails when ready with primer alone and then paint next winter.
    I will have to touch up a few small bubbled paint areas later, as I have a few hull welds left to do, for top-of-strut bracing, engine girder bracing, etc. I should have done it before painting, but that's how it is.

    Finally....lifted the large 4"x4" framed jig off of the boat, after flipping right side up for the final time...
    I will start next weekend, to final align/install shaft and drill gearbox mount holes and then align and install engine.

    Looking forward to not having to climb up, over and around that jig anymore....
    here is a before and after pic.
     

    Attached Files:

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