Using Ethylene Glycol on rot damaged GRP covered stringers and bulkheads to arrest further decay

Discussion in 'Fiberglass and Composite Boat Building' started by Martin Upton, Feb 14, 2020.

  1. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    Just continue here.

    Do not use glycol. You will never be able to get rid of that slimy ****.

    If your boat is not so bad; now is a good time to fix it instead of running it to the ground.

    And if you have ingress; you need to determine sources.
     
  2. Martin Upton
    Joined: Feb 2020
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    Location: Australia

    Martin Upton Junior Member

    ok I’ve dropped the ethylene glycol thoughts. Thanks all for your thoughts.
    I got hold of an article thanks to Brenden in this forum that showed the renovation of a Southwind SF20 (an older version of my boat). This was very helpful to understand the under deck structure.
    The deterioration in my frame is nowhere near as bad as the boat in this article (yet) but there is dampness there.
    In an attempt to reduce (not eliminate) the dampness what to you think of attaching an evacuation compressor near the site of the original water ingress (and seal it up to create a negative pressure in the wood? to draw the water back and reduce the moisture level in the wood frame?
    Something like this 3 Gallon Vacuum Chamber and 4CFM 1720RPM 1/4HP transparent cover Pump Degassing | eBay https://www.ebay.com.au/itm/3-Gallon-Vacuum-Chamber-and-4CFM-1720RPM-1-4HP-transparent-cover-Pump-Degassing/223581398803?hash=item340e7d6713:g:RZYAAOSwwQ5dJUOk
     
  3. trip the light fandango
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    trip the light fandango Senior Member

    I'm pretty sure you need to remove the moisture with heat,/ evaporation, which rises so make slots or holes at the high points ,use the sun, black plastic ,however you can heat the wet areas. This is like that game whack the mole when he pops his head up,.. ready.. The saturated timber may act like a sponge at night when cool so seal it temporarily until you can heat it again. An electric blanket ,electric fan heater. could help in difficult spots. Reinforcing the top and base of the transom with extra glass and pay extra attention to where it meets the hull sides. This is assuming you're not replacing the rotten timber, if you are don't cut the glass shear with the hull sides , leave one side and stubs on the side you remove, preferably the inside. Form ply has been used for this before, it needs the surface taken off a little to get mechanical grip, triple coat the edges/ any cuts with slow drying epoxy. When you're pretty sure all the moisture has gone and your glass is nearly finished get plenty of salt into the dodgy timber spots, Just a few thoughts ., I stopped reading the other posts ,..ha. good luck
     
  4. Martin Upton
    Joined: Feb 2020
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    Martin Upton Junior Member

    Ah that is interesting. One of the concerns I had about the vacuum idea is that it would probably draw air into the damp timber thereby potentially exacerbating the problem. Salt could be a potential alternative to stop the rotting fungus?
    With regard To the transom. When it is appropriate I probably wouldn’t muck around just replace it properly.
    with regard to the heating ... that’s interesting ... I’m thinking your homes with some sort of enclosure over the boat with a heater and dehumidifier (for a long time) . What do you think?
     
  5. Martin Upton
    Joined: Feb 2020
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    Martin Upton Junior Member

    This boat has pretty thick glassing around the ply frame so I’m loathed to rip it up if I can help it. The other option I was thinking of was to glass a new stringer and / or bulkhead next to the existing. Any thoughts on that?
     
  6. trip the light fandango
    Joined: Apr 2018
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    Location: Rhyll Phillip Island Victoria Australia

    trip the light fandango Senior Member

    I re read llan voyagers post and it is a well detailed description of the job required, you will get better access by cutting most of the outside glass off,but yes all that quality finish will need to be replicated. The nature of rot is that once dry the spores are active and searching for any dampness, salt will put them off. chlorine is another, but you may want to look up any chemical reaction that may occur,..like a bomb..ha .
    Martin you have lots of research to do on this site and others.
    If you are going to leave the rotten timber then you have to key in and lay plenty of woven matt over probably rovings/ unidirectional Glass laid across the transom top and bottom and around the outboard mounts, run layers of glass tape directly to the bottom and top outer corners I would also glass in 4 triangles [think holding up a shelf or step but vertical] where the transom meets the hull making sure that the inner and outer skins are connected at those points.. I would do the same for the across where the t transom meets the bottom of the hull .The problem you are having[I'm guessing] is that when someone describes a procedure in nautical terms you have to search for the words and understand them then come back to the description, I'm very familiar with this procedure. I've explained the how to previously in laymans terms and llan has given you the correct approach, you should be able to work out what to do.
    As far as putting up a tent ,well yes bearing in mind the stinky moisture/spore laden air has to relocate somewhere so you will be wiping off moisture from non absorbant surfaces presumably. I think the inner and outer skin need to be attached to each other with a series of plugs,with glass patches bonded integral to the surfaces on each side , which will affect the outside surface of the transom but is less work to finish than cutting it off. They will also indicate to you whether your fix has worked if they crack. Draw pictures of your approach, take more photos with your descriptions and ask the knowledgeable people what they think of each step you are thinking of taking. You could bolt in stainless angle and brackets and carefully glass/ re enforce the holes the bolts go through as an alternative. Make a wooden pattern and have them cut/welded up.
     
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  7. Martin Upton
    Joined: Feb 2020
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    Location: Australia

    Martin Upton Junior Member

    Thanks for your detailed reply.
    The transom at the moment is a low concern as I aim to replace it when it’s needed. The only rot I have round is forward where fresh water has been getting it. I have only found dampness (no rot) (saltwater)) aft.
    You raise an important point about killing off the spores which I’ll consider in my deliberations.
    I will do as you suggested and post photos, sketches and descriptions of what I’m thinking.
    The approach I’m thinking at the moment is do what I can to dry out and kill off the rot before it gets too bad and based of what I find / how successful that is decide what to do next.
    Thanks
     
  8. brendan gardam
    Joined: Feb 2020
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    Location: east gippsland australia

    brendan gardam Senior Member

    if you went to all this trouble you just replace the transom not cut out bits and pieces. i have done a few transom replacements on my own boats and always do them in epoxy. 40 grit discs give a good key to bond epoxy to poly. but martins boat doesn't sound like it is any where near that stage.
     
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  9. Ilan Voyager
    Joined: May 2004
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    Ilan Voyager Senior Member

    Start a new thread, as it's a vast subject but the answers are rather short, unhappily for many hoping a fast simple fix. There are a lot of snake oil products claiming improbable results.
    But precise the type of boat building. Timber degradation has very different cures in classic wood, double planking, cold molded or in composite building using wood as core and/or structural element.
     
  10. fallguy
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    fallguy Senior Member

    A small bit of rot here n there is a lucky catch. Dry the boat up and fix it.
     
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  11. Martin Upton
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    Martin Upton Junior Member

    Thankyou Ilan, you clearly have a lot of experience around this topic. I will get photos and sketches and start a new thread. Thankyou all!
     
  12. Capm Kurt
    Joined: Jul 2021
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    Location: State of Louisiana, USA

    Capm Kurt New Member



    Trip the Light Fandango,

    I'm glad to see your response on drilling holes/injecting resin. I have a 32ft Sutphen "cigarette" type boat made for rough water. Twin 502's.
    That's exactly what i am doing in the transom. Just trying to get something solid between the fiberglass laminates in the transom especially where the multitude of items that are attached and the laminates squeezed together by bolts (2 trim tabs, 2 hydraulic steering brackets, besides the drives, thru hull exhaust, and the usual other stuff. Tapped with wooden stick everywhere, and drilled quite a few 3/8" holes to check for rot where suspected. But doesn't take too long to do. Completely drying it out first.

    This boat has been thru a lot of rough riding before i saw one small transom crack at a stringer, so it must be a very well built transom for the engines/drives to stay perfectly aligned after that much abuse even with the rotting spots. It does have offshore front engine mounts. Next time i will pull both motors and everything, but for now, it's holes and injected resin with a filler, and a good repair at that crack at the top of one stringer.

    Thanks for your suggestion. Should work for a stringer as well which I've seen hold up just with the fiberglass and some of the wood gone. Glass is tough. Glad to see somebody mention this. You don't see this done much. But since it's held up, and I now keep the transom dry since I've bought it, I really believe this will make it last quite a while. Mostly to keep the existing laminates in there place, although i agree, not at all as strong as everything properly glued together, but should be more than enough.

    Kurt
     
  13. gonzo
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    gonzo Senior Member

    The problem you describe is structural. Drying it out is virtually impossible unless you put the boat in a heated vacuum chamber and wait a long time. Making holes and injecting resin will make the rot hard, but will not accomplish anything to repair the failed structure. You will be adhering a lump of hardened rot to the end of decayed fibers. There is only one proper way to repair a wooden boat: cut out the rot and replace with new wood.
     
  14. bajansailor
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    bajansailor Marine Surveyor


  15. gonzo
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    gonzo Senior Member

    I know, but the wooden bulkheads and stringers are structural. I should've written "the wood in any boat"
     
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