Repairing transom delaminate

Discussion in 'Fiberglass and Composite Boat Building' started by nikous, Nov 30, 2010.

  1. PAR
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    PAR Yacht Designer/Builder

    This isn't entirely correct. Rot needs a fairly specific environment to survive. Wood embalmed in epoxy, can't have this environment and dies, though the damage is done and the high moisture content isn't helping anything. In colder climates, the trapped moisture will likely freeze, testing the durability of the epoxy encapsulation, which if breached, will permit rot to continue it's destructive ways.

    As a rule there are some resin systems that can tolerate higher moisture contents, but nothing like what is seen in well soaked or saturated wood. The usual trade off for these resin types is strength, particularly tensile and compressive, which may be self defeating in this application.

    You can drill holes if you want, but I find this a waste of time usually, because you pretty much already know where the moisture is. With my "L" shaped tool trick, you'll very quickly find out how extensive the core damage is and you can then make a decision about inner or outer skin removal or an over size hardware bonding situation (fill hole then re-drill for the thru hull).

    To me, you have to remove the soaked core anyway, so I'd start with the "L" shaped tool, just because you can remove the core and preserve the hull shell and liner. Vacuum it out, fill with goo and call it a day.

    Another option that's less destructive then ripping out the inner or outer skin is to wedge a hunk of wood in the current hole, then using a large hole saw (4" or so) drill though the laminate enough to free it from the core. With this fairly small, circular piece removed, you'll see how much damage the moisture has done. You can glue this disk back in as part of the eventual repair.

    The bottom line is how much damage has been done. Drilling little holes isn't especially conclusive, especially if this is your first transom "rodeo". Removing large hunks of wet core until dry core is encountered ("L" shaped hook thingy) or exposing a moderate size area around the expected damage (hole saw trick) location are the reasonable choices here, besides I'm running out of tricks to relay.
     
  2. LMB
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    LMB Junior Member

    West System recommends g-flex if you are dealing with a damp area - I don't think I said wet.
     
  3. nikous
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    nikous Junior Member

    Thanks again
    It will take too long to repair because I have to build up a small penthouse. The boat is in an outside place. I hope I will ready for the next spring. I've no free time for final working now.
    I'll came back with photos during I work and I'll wait for your advices.
     
  4. nikous
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    nikous Junior Member

    bad news

    Hi everybody. I’m coming again.
    I tried to find the wet area. I’ve cut the outside skin around the hole and I disappointed. The plywood is very wet and a little rotten. I couldn’t find whole the wet area because I must get out the engine. I have to replace the core. (PAR, you've won the bet.)
    [​IMG]

    Questions:
    1) After removing the motor, if I’ll find no wet onto the upper half portion and the starboard of the plywood, can I replace only the down/wet portion? In this case my transom will have 2 pieces and less work. Is this right? Will be the transom strong? The boat is 2200 lbs (empty) and the engine 115 HP.
    2) Could I scrap the old wood from outside and replace it, without touching the inside skin and the stringers? (I have difficult access from inside, because I must cut out the engine well). If yes, I will ask you how.
    [​IMG]

    3) What is the white solid material between the plywood and the thin mat fiberglass, which the manufacturer has built up the transom?
    [​IMG]

    That’s all now. Thank you very much.
    Any suggestion would be welcome.
    PS. The white around the hole is dust from cutting
     
  5. PAR
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    PAR Yacht Designer/Builder

    Yea, this ain't my first picnic either. You can save yourself a fair bit of laminating if you remove the outer skin, though you'll have a bit more fairing to do.

    Leave a 100 mm flange all around the edge of the transom, which will greatly reduce you new fabric requirements and retain the factory transom edges.

    Some think you can patch the transom core, but I'm not one of those types. Since it's compromised, it all should come out and be replaced. It's not much more work and insures a solid transom when finished. I think you'll be surprised at the amount of damage, inside the transom.
     
  6. stilloutoffocus
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    stilloutoffocus dealership repair flunkie

    yeah im sorry to say that this looks like what i refer to as a "rake out" transom. which is nice when youre doing your removal because the rotten wood will just rake out with your hands or a tool rather than having to cut and chisel the whole mess. im not one to go around contradicting PAR but ive done several partial transoms and i would say that especially with such a small boat and engine that if you have solid wood on the other side i would just go with replacing whats rotten, maybe take that one half out. my one stipulation would be that you must make sure to have an extremely good layup between the new wood and the existing fiberglass. and i would lay at least one layer of roving over the entire outdrive hole to give it a more even strength.

    this is the first time ive heard of doing the transom replace from the outside. i guess we always just done ours from the bilge because its so much easier to finish out bilge paint than the gelcoat on the outside.it certainly seems like it would be much easier to access from outside though! so i guess its a trade off either way.
     
  7. stilloutoffocus
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    stilloutoffocus dealership repair flunkie

    and yes that white substance looks to be some sort of filler putty that the factory used as a leveling compound to get a good even bed for the wood to lay in.
     
  8. LMB
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    LMB Junior Member

    Sorry to see your situation. I admit, I'm surprised on a boat only 5 yrs old. I was about to agree with Par on removing the outer skin when I realized that your hull stern may not be flat. If it's like the one on the new boat in the earlier post, then removing the outer skin may not be an option. Alot of bass boats have funky stern designs and complicated transom bracing. If its like that then things start getting a little more complicated.
     
  9. nikous
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    nikous Junior Member

    Is this an epoxy substance? I'm asking if could use polyester resin over this.
     

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  10. PAR
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    PAR Yacht Designer/Builder

    No that's not an epoxy, judging by the looks of things. I'd resist the temptation of polyester on this type of repair, you just don't get reliable strength and durability.

    If it is one of the curved and reinforced transoms, the more for using epoxy and removing the external skin. This is because of the structure you'd have to cut through to get at the inside transom skin.

    A patch to the core will just test the bonding techniques you employ (more reason to use epoxy) and expose more glue lines to potential strain and rupture. You can try it and hope for the best if you like, but in the end, I've found this type of repair approach isn't cost effective in the long run.
     
  11. LMB
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    LMB Junior Member

    I was just looking back over the posted photos and noticed the one where you pointed out the transom edge. That edge is well inside of the stern corners if I'm looking at it correctly. Are you certain the transom core stops at that edge? If it does then removing the outer skin for a recore will be fairly straight forward, as you can stay within the flat area. I would caution you here that the core may extend all the way to the outside corners of the boat. I just finished a bass boat with a similar design. If the manufacturer is still in business, you may be able to get some design info from them before doing much cutting.
     
  12. PAR
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    PAR Yacht Designer/Builder

    Not having the boat in front of me presents some issues, more internal photos would be helpful though. The one picture on the previous page of this thread was for the location of a pump outlet on a newer boat. I'm fairly confident that the pictures above are the actual boat and it seems the transom is flat all the way across and I'll assume the core does as well.
     
  13. nikous
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    nikous Junior Member

    Ok PAR, I will use epoxy.

    LMB, Yes this is the transom edge, but the manufacturer has build up a "strength" (sorry i dont know the term) next to the transom at both sides and at the bottom of the boat a few inches towards bow, as you can see at the pics.

    Many thanks. I need your helps please. I live in a small city. We have not any good foremen and I have no confidence to them.

    What excatly I have to do?

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]
     
  14. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    LMB, it looks like you were right and the transom is just cored in the center section. I'll bet the two knees are at each end of the transom core and the outboard ends are just laminate.

    Nikous, the first thing you need to do is get that engine and controls off the boat. The controls can usually be pushed out of the way, as can electrical harnesses and other items. Take lots of pictures, so you can put it back together again in the proper locations.
     

  15. nikous
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    nikous Junior Member

    yes, you are right.
    My question is, if i'll remove the outter skin (as PAR describes), could i epoxied the plywood on the inner skin, without remove the skin, the two knees and the stringer?
     
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