Interior welding while in water?

Discussion in 'Metal Boat Building' started by svbravo, Apr 23, 2020.

  1. svbravo
    Joined: Apr 2020
    Posts: 3
    Likes: 1, Points: 3
    Location: Treguier, France

    svbravo New Member

    I'm installing a watermaker in an aluminum sailboat, recently launched. I'd like to mount the HP pump/motor in the engine compartment. The floor in the area is inside of the hull plating. Ideally I'd like a small platform just a couple of inches off the floor that I could bolt the motor to. This platform will need to sit on a couple of sleepers attached on the floor. I'd prefer these be welded to the floor. The boat is currently in the water.

    I'm not a welder, so would hire this out. My question is, can a bit of interior welding like this, on the inside of a hull, be done while the boat is in the water, or must it be hauled out to get a decent weld?
    Thanks.
     
  2. BlueBell
    Joined: May 2017
    Posts: 1,226
    Likes: 230, Points: 63
    Location: Victoria BC Canada

    BlueBell Ahhhhh...

    I don't know.
    Have you asked your welder?
     
  3. svbravo
    Joined: Apr 2020
    Posts: 3
    Likes: 1, Points: 3
    Location: Treguier, France

    svbravo New Member

    Not yet. I thought perhaps there might be some with more knowledge of it than you or I who could weigh in with either an "absolutely not.....a whacky idea", or a "no worries....done all the time".
     
  4. BlueBell
    Joined: May 2017
    Posts: 1,226
    Likes: 230, Points: 63
    Location: Victoria BC Canada

    BlueBell Ahhhhh...

    Fair enough.
    However, we don't have much info.
    No pictures, no sketch, etc.
    I would find a marine welder that knows.
    And then get two more estimates.
     
  5. Blueknarr
    Joined: Aug 2017
    Posts: 891
    Likes: 175, Points: 43
    Location: Colorado

    Blueknarr Senior Member

    The devil is in the details.
    Welding Al is a bit tricky.
    Floating adds a bit more trickyness.
    Welding in a confined space is a lot more tricky.
    Explosive fumes in bilge is spectacular

    Call your welder. Floating isn't a serious problem.
     
    BlueBell likes this.
  6. svbravo
    Joined: Apr 2020
    Posts: 3
    Likes: 1, Points: 3
    Location: Treguier, France

    svbravo New Member

    Happy to hear that being afloat (water on the opposite side of the plating from the weld) isn't in and of itself a deal breaker. I'll discuss the details with a welder, thanks
     
    BlueBell likes this.
  7. kapnD
    Joined: Jan 2003
    Posts: 692
    Likes: 79, Points: 28, Legacy Rep: 40
    Location: hawaii, usa

    kapnD Senior Member

    I’d be exploring adhesives for that job.
    Might be an opportunity to isolate the water maker from the hull with a layer of nonconducting, vibration absorbing material.
     
    Dejay and bajansailor like this.
  8. bajansailor
    Joined: Oct 2007
    Posts: 1,161
    Likes: 307, Points: 83, Legacy Rep: 37
    Location: Barbados

    bajansailor Marine Surveyor

    How far apart are the transverse frames and the longitudinal shell plate stiffeners in your engine room?
    Can you post a photo of your chosen location?
    As Kapn D says, this is an ideal way of making sure that your water maker is insulated from the hull.
    Would it be feasible to build a suitable bracket for supporting the water maker, and then mount it across two frames or stiffeners?
    The bracket could be bolted or glued to the frames / stiffeners - preferably with an insulator strip in between.
    If using bolts, make sure that the bolts are insulated from the aluminium structure.
     
  9. Barry
    Joined: Mar 2002
    Posts: 1,303
    Likes: 146, Points: 63, Legacy Rep: 158

    Barry Senior Member

    Don't consider welding anything to the floor plating when it is in the water or you will more than likely blow a hole through the hull plating.
    I am assuming that the plating is say less than 1/4 inch

    As aluminum conducts heat extremely fast the water pressure on the outside of the hull will just blow through the weld pool

    Fab the pieces, get to a hull sling, pull it up, weld them in and you are done. Dry the outside of the boat where the weld beads will be on the inside
     
    bajansailor likes this.
  10. BlueBell
    Joined: May 2017
    Posts: 1,226
    Likes: 230, Points: 63
    Location: Victoria BC Canada

    BlueBell Ahhhhh...

    SVBravo,

    Have you consulted a competent marine welder yet?

    If so, what did they say?

    Please, let us know.
     
  11. Ad Hoc
    Joined: Oct 2008
    Posts: 6,566
    Likes: 592, Points: 113, Legacy Rep: 2488
    Location: Japan

    Ad Hoc Naval Architect

    If the welding is above the waterline... then yes, it is ok.
    If the welding is below the waterline - then no.
     
  12. BlueBell
    Joined: May 2017
    Posts: 1,226
    Likes: 230, Points: 63
    Location: Victoria BC Canada

    BlueBell Ahhhhh...

    There you have it Bravo, two no's and a yes.
    Now what are you going to do?
    Hmmmm, I have an idea...
     

  13. Manateeman
    Joined: Oct 2019
    Posts: 40
    Likes: 1, Points: 8
    Location: Kennebunk ME

    Manateeman Junior Member

    Hi. Barry is correct. Above the waterline, ok. Not above...you weld alu on AC. Blown out weld, dead welder.
    I have a TIG onboard and when on AC ...I’m very careful about any water source, diesel fumes, rain, fire...always have my wife at the welder to shut it off because I’m under the hood concentrating. Even near the waterline, a wake can kill you.
    Liquid aluminum. Amps. A fire can smolder out of sight long after you finish. Lightning. You are holding AC in your hand.
    I’m an old, manatee because I’m a careful manatee.
    Mark
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.