Dufour GL 350 keel support fiberglass mods

Discussion in 'Boat Design' started by Steelboat, Mar 28, 2024.

  1. Steelboat
    Joined: Feb 2022
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    Steelboat Junior Member

    I am surveying a Dufour GL350 and noted some extra glass laminate on top of the hull liner in the bilges. It looks reasonably well-executed, professionally done. The keel bolt nuts and backing plates where removed for the glass work, then re-installed. The reinforcement is under the forward and aft keel bolt backing plates. The center forward set of keel bolts are just through the smooth liner, as expected.

    Has anyone seen this extra fiberglass from the factory? If not a factory mod, then my concern is that the boat suffered some grounding damage and the extra glass was to cover cracks and or laminate damage. I will be hauling her out next week to inspect the keel join and laminate from below.

    Thanks for any first hand knowledge of this model.
     

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  2. fallguy
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    fallguy Senior Member

    Boat is going to need some xrays or other electrical UTT diagnosis now. All I can say.
     
  3. Alan Cattelliot
    Joined: Jul 2021
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    Alan Cattelliot Senior Member

    I made several inspections, at the boatyard, of boat being built, in the scope of their EC certification, and I haven't see no examples of this kind of reinforcement. Although I did not work on the 350 GL certification. My advice is to note the CIN of the unit, and directly ask DUFOUR, to get as much informations as you can from the boatyard, and its after-sale service.
    Cheers,
     
  4. Steelboat
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    Steelboat Junior Member

    Thanks for the reply Alan. I sent an email to Dufour.
     
  5. Steelboat
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    Steelboat Junior Member

    I have done a lot of Ultrasonic surveys on metal hulls, but cannot see how that could be used here, hmm. Can you explain?

    I have no direct experience with radiography. I would expect any possible crevice corrosion to be right where the bolt exits the cast iron keel. Can you get the head of your X-ray machine in at the correct angle to see anything there?

    I like the idea of non-destructive testing, but if I really suspected a keel bolt problem, sadly I think the keel would need to come off.
     
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  6. fallguy
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    fallguy Senior Member

    I think you need to be sure and the keel come off; then non-destructive testing. But I'm a casual boat lover; not surveyor. Those epoxy repairs were not done for fun. The question is are they a mask or half assed or good repair.
     
    Last edited: Mar 30, 2024
  7. fallguy
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    fallguy Senior Member

    Also, pictures never tell an accurate story, but is the glass repair over paint? Looks that way from here. I'd like to think I'm wrong here, but I see shine over a mostly homogenous white color.
     
  8. Steelboat
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    Steelboat Junior Member

    Thanks Fallguy. Just was wondering if you had some NDT tricks to share after your post suggesting it. Once the keel is off, wasted bolts will not need a flaw detector to spot. Eyeball version 1.0 does that job. I have an old graphical ultrasound that does basic flaw detection, but no good for a threaded item, it needs a smooth surface on one side.
     
  9. fallguy
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    fallguy Senior Member

    I'm just an epoxy guy, not a surveyor, but I have a hunch. If I were going to repair a hull related to grounding; it'd be more than those little pieces. My guess is there was bolt damage and they did a hole repair and figured the repair needed glass backing. But the question would be whether such a repair was engineered and whether the repair was done properly....

    I'm just offering a perspective.
     
  10. fallguy
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    fallguy Senior Member

    Another possibility is the keel bolts are rising up and out and annual tightening was showing more thread and they incorrectly assumed the hull was crushing. But all the more reason for your work...
     

  11. Steelboat
    Joined: Feb 2022
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    Steelboat Junior Member

    Thanks Fallguy, On this boat, keel is cast iron. No way keel bolts threaded into cast iron will be rising up.

    Anyhow this thread was just to ask about factory build practices. I have concluded almost certainly that Dufour did not add that reinforcing. Once I survey the underwater areas it should become clear what happened.
     
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