Rust behind PU foam from waterline to decking

Discussion in 'Metal Boat Building' started by Bengy, Sep 21, 2019.

  1. Bengy
    Joined: Sep 2019
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    Location: Indiantown fl

    Bengy Junior Member

    I am currently trying to restore a 42' Colvin gazelle that I have discovered surface rust underneath most of the sprayed PU foam from waterline up.
    I am hoping to paint the outerhull and float the boat and then begin removing sections of the interior foam and roving rust with cup brushes and recoating with amercoat 2. Will the boat be safe to live in the water while I begin the interior retrofit which will probably take me at least 2 .onths to complete? Does anyone have any experience with this issue and the value of such a refit? This boat is not something I can easily walk away from as its a family heirloom. However I am a young person and I need to be able to go back to work in the next w months to continue paying for restoration. The rest of the boat (engine, spars etc) are all in great shape. Any help and suggestions would be greatly appreciated.
     

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  2. Bengy
    Joined: Sep 2019
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    Location: Indiantown fl

    Bengy Junior Member

    Also what is the quickest way to remove PU foam
     
  3. Bengy
    Joined: Sep 2019
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    Location: Indiantown fl

    Bengy Junior Member

    Also what are your thoughts on rust doctor?
     
  4. Blueknarr
    Joined: Aug 2017
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    Blueknarr Senior Member

    Welcome to the forum.

    The surface rust looks minor, so I think it would be safe to float. BUT there could be a major issue you haven't shown a picture of. A marine surveyer could use ultrasound to determine hull plate thickness.

    I would use a scraper blade on a "Sawaall" to remove most of the foam.

    Two months is a very ambitious time frame for this project.

    Good luck
     
  5. Bengy
    Joined: Sep 2019
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    Location: Indiantown fl

    Bengy Junior Member

    Thanks for Ithe reply!
    don't have the money for an inspection however I have inspected the waterline down and that's in great shape as well as structural connections as the builder cut in all the ribs with coal tar epoxy and all of the areas I've pulled off the structure have been in perfect shape. It's just the flat areas in between structure that are only primed and showing the conditions above.
     
  6. Deering
    Joined: Feb 2005
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    Deering Senior Member

    I agree with Blueknarr. The sections in your photos don’t look that bad. Since they’re above the waterline you’re probably safe splashing it.

    If you can’t afford a survey, then pause and do an honest estimate of what this refit will cost. Then triple it. Will you still be able to afford it and will it still be worth it?

    You could always pick a few of the worst sections and drill a tiny hole through the hull to visually examine thickness/integrity of the metal. Plug them with thickened epoxy.
     
  7. Bengy
    Joined: Sep 2019
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    Location: Indiantown fl

    Bengy Junior Member

    As far as affording a refit as it stands I'm currently not working and chewing up savings to get it floatable so I can go back to work. Once I'm working I can afford the refit. I'm a very skilled carpenter and by what I'm hearing I will be able to address the not so bad rusting spots over the next 6 months. The boat was free from a family member and the only costs I have left is time stripping and painting the interior in piecemeal sections as I am also living on the boat during refit.
    I have the benefit of being young and very motivated.
    I've gone thru and inspected all portions of the boat and what is pictured is the worst of it and is located mainly on the upper hull and deck. Bilge and lower 2' of hull above waterline are great. The worst sections of which are just beginning to develop scale maybe 10% of boat and have not lost appreciable thickness yet.
    Pray for me and wish me luck lol
     
  8. Blueknarr
    Joined: Aug 2017
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    Blueknarr Senior Member


    Deering's is some of the best advice you will ever receive!!!!

    If you can't afford a survey, then you CAN'T afford to do the project.

    The surveyer should find everything wrong with the vessel. Then you can determine how much it will cost (time, money and emotional)

    A good survey is the first step in a restoration. Proceeding without one is foolish.
     
  9. Blueknarr
    Joined: Aug 2017
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    Blueknarr Senior Member

    Bengy,

    Just read your post. I fully understand your position. I've been there myself. I admire your ambition and hope to support you as well as I might.

    Living in a work project is tough. Make it a boat project and hellish nightmares are recalled.

    Your living space WILL be inundated with hazardous and toxic fumes and dust. Please protect your health. Have somewhere else to go.

    Piecemeal work in an occupied space will drive up the cost by at least a factor of ten.

    Best of luck
     
  10. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    If you don't have a survey carried out on the boat, then the next best thing would be to acquire your own ultrasonic thickness meter - this will become your best friend on board (or your second best after your partner).
    I just did a search for ultrasonic thickness meters on Amazon, and about 1,000 results came up - there are all types, and all prices.
    However this one generally seems to have positive reviews, and it only costs US$70 -
    https://www.amazon.com/Signstek-Digital-Ultrasonic-Thickness-1-2-225mm/dp/B071YN23T1/ref=sr_1_7
    Even though the hull bottom appears to be in good condition, it would still be worthwhile to do a detailed ultrasound survey yourself of the whole bottom while the vessel is out of the water.
     
  11. Nick.K
    Joined: May 2011
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    Location: Ireland

    Nick.K Senior Member

    What is the last photo showing? Is that a hole or a reflection?
    The advice you've been given here is good, especially, not to live on the boat during your work. Removing the PU foam and cleaning back the steel will be very dusty and whatever coating you use for the steel will have heavy fumes and will off-gas for many days after. You'll be ingesting these 24/7 in the air, on your clothes, bedding and food.
    Is it necessary to do the work? The corrosion in the photos doesn't look too bad. To remove the interior, remove the PU foam, clean off the steel, coat it and then replace it all is a massive project, much more than two months work if it is done properly. Wire brushing is an ineffective way of cleaning steel, it only cleans the high spots leaving the active rust pits untouched. It's possible that after all the work you may still have corrosion issues.
    Is the boat dry or are there leaks from the deck or portlights? Is there a lot of condensation inside? If the boat can be kept dry inside then the rate of corrosion will be very slow.
    My advice is to investigate the thickness of the hull, paying special attention to areas that you know are corroded inside. If the thicknesses are ok then keep the interior dry and focus on what you want to do in the future with the boat and finding employment. If you feel you must do work on the boat then keep it to small limited areas of work, starting and finishing each area before you move on. This will avoid a situation where the boat isn't usable as a home, isn't saleable and you may not have money or time to progress.
     
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  12. Bengy
    Joined: Sep 2019
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    Location: Indiantown fl

    Bengy Junior Member

    I hear what you guys are saying and I completely agree. I have enough time in dry dock here to strip foam and rust and paint the aft living quarters which I can seal off from the rest of the boat as I am all too aware of the joys of construction and living. By living I strictly mean sleeping. I will be using marina facilities until the boat is complete. I am definitely going to get that $70 meter posted above as I would love to painstakingly assess every part with out stripping all the foam unnecessarily (and saving 5k for the surveys I've had priced) for 5k I'd rather pay myself to strip the interior and be sure myself then find out yes it needs to be stripped and I'm 5k lighter in the wallet. The picture above is in fact a hole and the main reason why I want to strip that entire compartment asap while I have facilities and can stay off the boat. Once that is complete and I can identify which areas to address based on thickness then I can better plan my route to reconstruction. I have been going through and taking a hole of foam out of every section of the boat trying to get an idea of severity and have been pleasantly surprised that the area with the hole is by far in much worse shape that anywhere else by a pretty big margin. My original plan was also to replace the interior in stages as it's old and only partially functional so I believe I am still on track to have a liveable compartment and floating boat in 2 months and to be able to address the rest of the PU and rust over the next year.
     
  13. Nick.K
    Joined: May 2011
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    Nick.K Senior Member

    If the hull has holes then it is almost certainly a bigger project than two months.
    Do you know any steel worker who has done a lot of boat repairs? Employ an experienced marine steel worker for a day to look at the hull and tell you what plate needs replacing and where.
    You need also to assess the under deck condition. Assuming that the hole is from internal corrosion, that much corrosion suggests a long term leak from somewhere. If the deck has been leaking and it is also covered in PU then probably the deck plate is also very thin in areas.
     
  14. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    I was optimistically hoping that the apparent hole in the hull shell was the camera flash reflecting off a shiny area of steel, but alas, it isn't.
    Finding a hole like that adds a whole new dimension to the potential scope of work - if there is one hole, there is a good possibility that there are others - they might be hiding behind a composite coating of rust and paint holding hands.
    In addition to a meter, a big hammer will also be very useful - don't be afraid to sound the hull with it in the meantime, while you wait for your meter to arrive.
    Don't just tap the hull, give it good thumps.
    If the hammer goes through, well, the steel is too thin..... if it starts to flex, even slightly, it is too thin.
    You can then use the meter to do a sort of contour map of thicknesses, a bit like a land map showing heights.
    Do you know what the original shell plate thicknesses were? If any localised areas are less than 50% of the original (or less than 3 mm / 1/8" on the hull bottom shell - with a larger margin in way of the keel), I would be looking at cutting out these areas and welding in new plate.

    I met a young couple (in their 20's) here a few weeks ago - they had just bought a 40' steel ketch (built in Holland in the 60's) in the water (no survey, not even a look at the bottom by snorkelling.......) for US$ 19,000 and were planning on sailing off into the sunset with her..... I told them how I had seen this ketch out of the water here two years ago. The previous owner had sounded the bottom then with a hammer, and welded in new sections of plate where the hammer had gone through. But these new areas of plate were very small, and literally were not much bigger than the holes that had been created. And a visual inspection of the bilges and the anchor locker showed serious rusting everywhere - a lot more plate could have been corroded in the last 2 years. They left last weekend, on an overnight sail to the Windward Islands - they were going to find somewhere to haul out there to do the work required. I just hope that they do not find too many nasty surprises when they get there.
     

  15. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    If you don't have $1000 for a survey of the hull plating, this boat is probably beyond your means. Further, it may have severe corrosion and section loss on the plating. The boat may float, but fail structurally in heavy weather. The last photo appears to exhibit a through hole.
     
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