Main bulkhead replacement

Discussion in 'Boat Design' started by N2everythg, Dec 4, 2018.

  1. N2everythg
    Joined: Dec 2018
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    N2everythg Junior Member

    after considerable searching on the net and not finding any solid advice..... thought I would ask here and see what response I got.

    I recently purchased an amel 46 project boat that fell off stands during a hurricane. starboard hull midship was compromised when landing on a jack stand. 3 midship bulkheads; companionway, main saloon and 1/2 wall at chart table also received damage. I suspect both compression of starboard hull and potentially from the mast whip when she hit the dirt.. baby stay chain plate on port side also seems to have suffered damage and both the toe rail and chain plate will need to be addressed - again probably due to the excessive force of mast torque/snap when the boat landed.

    needless to say I have my work cut out for me for some time to come.

    question is this... main forward bulkhead runs from mast step to starboard hull. way too big to fit through companionway hatch at full size. It is cracked at 2 locations above hatch to forward berth and likely will need to be retabbed to starboard hull. Prefer to replace the whole thing but what is the strongest way to replace a bulkhead that wont fit through a companionway door? 6-8" scarfed joins in approx 3' sections and do the scarf inside the boat? epoxy thinner ply bulkhead sections up in the boat with overlapping joints?

    existing bulkheads are made up of 3/4 inch ply if it helps.

    all this is at least a month or 2 down the road as I am currently working to remove and expose the hull for repair and gain access to the bulkheads...

    thanks in advance.
    N2
     
  2. Bruce Woods
    Joined: Sep 2007
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    Bruce Woods Senior Member

    I worry for you and the success of your project when you require help from internet forums.

    However regards a ply bulkhead, cut out the broken/cracked bits, wedge the hull back into shape, scarf in new wood and reinforce with UNI glass and epoxy, either repaint or dress with surface finish to your taste.

    I doubt that the bulkhead was originally done in one piece due to its sheer size.
     
  3. N2everythg
    Joined: Dec 2018
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    N2everythg Junior Member

    What I was actually hoping to determine from the wealth of online knowledge was a bit more technical than that.

    What I was hoping for was a discussion regarding different methods of repair to existing bulkheads that were installed prior to the deck being laid on top.
    For example. ...is it stronger to scarf in a 3/4 “ piece of ply with a 1:12 ratio or would it be better to use say 1/2 “ ply biscuit joined and then laminate 1/4” ply over the top of the Seam for at least 12”.
    Or are there other alternatives out there that would prove stronger.

    Thanks .
    N2
     
    Last edited: Jan 5, 2019
  4. fallguy
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    fallguy Senior Member

    My first inclination when I read your post was wow, sounds like a big job. Not sure I am qualified to answer. Everyone wants you to succeed, but it does sound daunting.

    Actually, if I were you, I would consider trying to do repairs with infusion.

    You would tack the glass on with 777 and bag the job and test vac and avoid inferior work with sagging glass on verticals and the nightmare of applying prewetted glass to verticals.

    The other thing vac ensures is no voids, etc.

    Also, despite my lacking a credential to help you, I can say the post was a little hard to interpret and I figured you'd post some pictures.

    Best of luck in the work.
     
    Last edited: Jan 5, 2019
  5. N2everythg
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    N2everythg Junior Member

    Thanks fallguy. Interesting approach. something I will look into further. That is what I was hoping for. options and suggestions to evaluate.
    perhaps my first post was vague. Sorry if I took offence to bruces first statement and reacted. I will fix it.. one way or the other... Just trying to determine the best way. or at least the intersection of cost effective, time input, and strength....
    I hadn't considered infusion and glass sandwich.
    here is a pic of the forward bulkhead. Mast step is encased to the left in the picture.

    oh and as far as I can tell that bulkhead is one piece.. from the mast step amidship to the starboard hull. I assume laid in prior to the deck being attached to the hull.
     

    Attached Files:

  6. fallguy
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    fallguy Senior Member

    I wasn't advising foam in a ply build.

    I was advising considering vacuum to get resins into difficult places like those cracks.

    Yeah, super tricky work.

    In order for the BH to crack like that; there were some major hull problems I'd say. Did it fall off the stands or take a ride in the wind?

    I think you would repair the BH as part of the rest of the repair. Assuming the BH is tabbed into the hull, the tabbing would be damaged as well, right? Your picture doesn't show that as there seems cosmetics in the pic.

    I would be less concerned about 12:1 scarfing and more concerned about making the boat stronger; especially if a jackstand fall caused a BH to crack like that. I would probably fix the BH and tabbing and glass the entire BH.

    It might be a blessing that deficiencies were revealed....what do i know...

    And you can go back and edit your reply to Bruce. He is well respected here.
     
    Last edited: Jan 5, 2019
  7. N2everythg
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    N2everythg Junior Member

    thanks fall guy. When I said sandwich I didn’t mean foam core. More ply core. I understood what you were suggesting by vacuum bagging the existing BH and using glass.

    Re the existing tabbing.: from what I have uncovered so far it is 99% intact and still connected to the hull. Which I find strange. From what I can ascertain the hull flexed enough with the bh in place and tabbed to hull that the weak places in the bh ply split rather than either the tabbing or the glass. There is no identifiable damage to either the hull or the deck that I can see through the gelcoat. And I would expect the gelcoat to at least crack with that much force exerted on the bh to split it. Will know more as I dig deeper.

    Edit completed but with your quote won’t matter. Apologies. Shouldn’t have reacted to his concern that I couldn’t complete a build..
     
  8. fallguy
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    fallguy Senior Member

    I fixed on my end. You need to realize he has a valid point and the vaguity added to his remark.

    I'm really curious about how much you paid for a hurricane damaged boat. Just a general curiousity. Then does the title get changed to a salvaged boat?

    The BH cracked internally and the hull flexed and rebounded...hmmm. What is the hull made of? Hard to believe ply hull would flex without an issue unless it has an issue elsewhere...
     
  9. N2everythg
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    N2everythg Junior Member

    Dirt cheap. In my book anyway. As in even if for some reason I couldn’t fix the structural bh damage and the glass hull even after paying for disposal of the carcass I would come out ahead or at the very least break even selling components motor, electronics, etc.
    But that aside. I know I can fix it.
    It’s an 1983 amel maramu 46. Full fiberglass hull deck etc. ketch rigged. Interior bulkheads are 3/4 approx ply. Are you familiar with them?
    It’s a CG documented vessel so no title. If somone pulled the HID I would assume that there might be a salvage record from the insurance claim.
    To answer your previous question re how the damage was done. During Florence she fell to starboard and landed on a stand. A side
    Flop. I saw pics and they equaled the seller and other descriptions I got from other folks in the yard and yard owner. The stand was Flattened and created an approx 6’ compression tear in the starboard hull almost directly mid ship. It pushed the center 1/2 BH inward (almost right at the hull breach) that BH split diagonally.... well here. Watch this YouTube vid. It will show the whole boat and the issues. .....ahh it looks the the P.O. took down the vid. So I will try to describe best I can. That center BH tabbing did let go. And the inward and upward force along with the diagonal split applied pressure to the walkway above and cracked the porthole window. So fiberglass and BH repair to be done there.
    The weird thing that I haven’t quite gotten to the bottom of is that forward BH in the pic in prev post. I haven’t gutted that section yet. I can tell you that the forward BH is still tabbed to hull despite those cracks in the BH above the door.
    What I “think” happened at this point...... that mast whipped when she hit the dirt. And I know that there is some form of damage to the port baby stay and likely chainplate as it is a bit loose and the toe rail where the chainplate enters hull sound taps as damaged to some degree. What I think happened is that the mast whiped to starboard upon impact and compressed the BH and caused the split over the hatch tho I can find no indication of any damage to the fiberglass where the mast goes through the deck.
    I will know more as I dig further into that forward bulkhead and the sole underneith.

    I know.... I got a project on my hands ..... but I ain’t skert.
    She may never round the Horn of Africa again but that is not my intent.
     
  10. N2everythg
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    N2everythg Junior Member

    here's a pic of that mid 1/2 bulkhead during the tear out and after it has been removed. you can see the compression tear in the hull just to the left of center line of pic where the BH was removed.
     

    Attached Files:

  11. fallguy
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    fallguy Senior Member

    Did you fix the tear, yet?

    No, not familiar with these, but it looks like something that would be repaired best with vacuum to ensure you get the best bonding.

    There are a few other guys with LOTS more experience. Perhaps they will coin in as sometimes these posts get more interesting with photos. I might encourage you to markup the photos on a smartphone if you can and highlight the tear, although I was able to see it pretty easily.
     
  12. BlueBell
    Joined: May 2017
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    BlueBell Ahhhhh...

    Hi FG,
    See original post.
    Cheers
     
  13. fallguy
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    fallguy Senior Member

    It was a rhetorical challenge to the OP. I found it a little hard to believe it had that much damage falling off a stand until he explained the mast whip issue. I would have expected a vessel to have less damage from a stand fall is all. Make sense or no?
     
  14. BlueBell
    Joined: May 2017
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    BlueBell Ahhhhh...

    Ahhh, okay, I understand.
    Hmmmm, good question.
    I suppose it would depend on the robustness of construction, the weight of the vessel and it's condition.
    No offence to the OP, but I pity the individual who next buys that boat...

    I too am curious how much the boat sold for.
    If insurance was paid out as a "write-off", then perhaps any $$$'s received would be a bonus AND the boat is gone.
     

  15. fallguy
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    fallguy Senior Member

    Boat is gone?

    Boat is held by salvage buyer.
     
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