Repairing and/or drying GRP covered stringers and bulkheads

Discussion in 'Fiberglass and Composite Boat Building' started by Martin Upton, Apr 8, 2020.

  1. gonzo
    Joined: Aug 2002
    Posts: 15,500
    Likes: 1,040, Points: 123, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    If you have rough fiberglass surfaces, it is easier to use a sandblaster than grinding or sanding. It will remove a layer of resin and rough up the surface without taking off a lot of glass like grinding does. It should also remove all or most of the mold.
     
    Martin Upton likes this.
  2. Blueknarr
    Joined: Aug 2017
    Posts: 1,233
    Likes: 290, Points: 83
    Location: Colorado

    Blueknarr Senior Member

    Bleach work's well on taw wood. It can take awhile to completely dry. As with all surfaces, there is a possibility of color loss.
    Be aware that "wood bleach" is not the same as the laundry bleach that is most useful as a fungicide.
     
    Martin Upton likes this.
  3. Martin Upton
    Joined: Feb 2020
    Posts: 39
    Likes: 7, Points: 8
    Location: Australia

    Martin Upton Junior Member

    Yep that is right.
    I’ve removed the outer layer of glass and the timber and only left with the glass on the other side. There is evidence of mold in spots on the inaccessible side of that glass (there is also foam on the other side too ) (See photo ). If I use a composite material for the new stringer then it probably doesn’t matter that much but seeing as I’m this far it makes sense to me to address it.
    Re attacking the transom. The transom is actually in pretty good nick. I think the stringers and bulkheads / floor) (missinginaction :) ) we’re subjected to fresh water ingress and the transom whilst damp was subjected to saltwater (sitting in the ocean for years).
    Thee is no movement in the transom when roughing the motor round and when I pulled the motor off whilst the mounting holes were damp the timber was still solid.
    Thanks for the tips on the epoxy troweling falloutguy ... very helpful.
    Re bleach type Blueknar .... I was thinking of pool chlorine (I’ve gat about 70 litres of it in the shed)? Discolouration is not an issue here.
     

    Attached Files:

    Last edited: Apr 12, 2020
  4. Martin Upton
    Joined: Feb 2020
    Posts: 39
    Likes: 7, Points: 8
    Location: Australia

    Martin Upton Junior Member

    Hey gonzo,
    thanks for the sandblasting tip. I plan to re flow-coat most of the boat. Would your sandblasted tip work for roughing up the existing flo-cote at all? Cheers
     
  5. gonzo
    Joined: Aug 2002
    Posts: 15,500
    Likes: 1,040, Points: 123, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    Yes. I love sandblasters.
     
  6. trip the light fandango
    Joined: Apr 2018
    Posts: 472
    Likes: 94, Points: 28
    Location: Rhyll Phillip Island Victoria Australia

    trip the light fandango Senior Member

    I just remembered there is a product made by sikoflex that chases out water from substrate under flooring tiles in bathrooms. Put a hole at the far end and keep adding until it comes out. It may be your solution, good luck
     
    Martin Upton likes this.
  7. Martin Upton
    Joined: Feb 2020
    Posts: 39
    Likes: 7, Points: 8
    Location: Australia

    Martin Upton Junior Member

    Ahhh ... just saw your post now. Sounds like a good product.
     
  8. Martin Upton
    Joined: Feb 2020
    Posts: 39
    Likes: 7, Points: 8
    Location: Australia

    Martin Upton Junior Member

    UPDATE. I connected a vaccum Pump to a silicone based suction cup I made and started evacuating water from the stringers. My gadget worked well however I was concerned about the amount of water coming out so I cut more inspection holes.
    One of you forum Contributors suggested that the issue is always worse than imagined when it comes to rot and stringers etc. you ARE right.
    I ended up cutting all of the stringers, bulkheads, internal transom stingers and bunks out and leaving one side of the glass intact removing all the wet and rotten ply. (Sone it was so rotten it was just dust) Most of the boat! I’ve replaced it all with a composite material (thermalite) board and epoxied it to the existing glass and reglassed the outside of the new structure. Just in the finishing stages of flow coating and putting in trim and electrics. Fortunately I didn’t need to rip the top deck off but was able to wiggle in to do all the work. Tough going and A lot of work but now I have a rot/water free boat.
    Thanks for all your advice guys it all makes a difference.
     
  9. tpenfield
    Joined: Dec 2016
    Posts: 233
    Likes: 19, Points: 18, Legacy Rep: 10
    Location: Cape Cod, MA

    tpenfield Senior Member

    Late to the party . . . Post some more pictures when you can. Your investigation seems to have led you along the proper path by replacing the wet/rotted bulkheads and stringers. Not that it is impossible to dry out a wet structure . . . it's only nearly impossible, and few if any of us can create the proper conditions to do so. Also with a wet boat, to the extent that you showed us, some areas are going to be rotten rather than just wet. So, you end up cutting out a bunch of stuff anyway. BTDT . . .

    Most of the pro's will do the cut & gut then rebuild, because taking the time to dry out the structure is not a money making proposition. There was a process that appeared a few years back called 'Dry Boat' ( www.dryboat.com ) which tries to dry out saturated areas of a boat by injecting dry air and sucking out the moisture in the effected areas. Not sure how the use of this process had stood the test of time though.
     
  10. gonzo
    Joined: Aug 2002
    Posts: 15,500
    Likes: 1,040, Points: 123, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    Drying rotted wood will do nothing for the structural integrity of a boat.
     
    fallguy and Blueknarr like this.
  11. Blueknarr
    Joined: Aug 2017
    Posts: 1,233
    Likes: 290, Points: 83
    Location: Colorado

    Blueknarr Senior Member

    As Gonzo says.
    And it takes like a billion years.

    Try this experiment:
    1. Take a kitchen sponge and weigh it. Hold it under water for 5 minutes, then weigh it again. Periodically check its weight until it returns to the original weight. (Probably a few days)
    2. Incert a second sponge into a sealing sandwich baggie. Follow the same submerging and weighing procedure as above. (Return to start weight in a few minutes)
    3. Now stab the sealed sponge with a fork a few times. Repeat the soaking and weighing procedure. (It will take weeks to dry)

    I have found that most waterproofing is far better at keeping moisture in than preventing it's ingresses.
     
  12. fallguy
    Joined: Dec 2016
    Posts: 5,264
    Likes: 1,007, Points: 123, Legacy Rep: 10
    Location: usa

    fallguy Senior Member

    One thing that still bothers me Martin. Did you find the sources of ingress?

    With all that top deck structure, you really need to verify what caused the original failures.

    Did you try the pump on the transom?

    Just seal up one of the existing holes or a couple of them and see if the pump sucks water out. You use 6 mil or vac bag plastic and some butyl tape to seal off the hole. Or silicone can also work, but is messy and hard to clean up.
     
  13. Martin Upton
    Joined: Feb 2020
    Posts: 39
    Likes: 7, Points: 8
    Location: Australia

    Martin Upton Junior Member

    Hi
    Hi tpenfield, you are so right!
    Yeah the vaccum pump process was a learning curve. Heres a few pics. I made a seal at the base using silicone in a mold (let it dry for a week).
    Up to that point getting a good seal to vac was the challenge. It did indeed pump a fair bit of moisture out however after I made the decision to remove and replace the stringers it became apparent as to the extent of the problem.
    When you own the boat everything in you wants to believe that your case is somehow better. Someone in this forum said that ‘when it comes to rot it’s always worse than you think.‘ so true.
    my plan was to try to evac the moisture and use something like west system to strengthen.
    When I pulled it apart in some cases the wood was just damp and weak. In other areas it was crumbly powder. Had I persued my original plan I would have ended up with a weak (non structural), heavy, expensive outcome.
    Replacing the stringers was more work but stronger, lighter and now gives me confidence that it’s right.
    Honestly what I hate is that the boat looks no different on the outside for all that work :).
     

    Attached Files:

    fallguy likes this.
  14. Martin Upton
    Joined: Feb 2020
    Posts: 39
    Likes: 7, Points: 8
    Location: Australia

    Martin Upton Junior Member

    Hey fallguy,
    Yeah ingress was coming from a couple of places. On the transom and connected rear stringers. the boat was in the water for 17 years and the engine mount bolt was loose letting water seep in. It wicked it’s way through over time.
    the front the boat had been left uncovered letting rain enter the cabin, which pooled and then with crap boat construction techniques created a moist environment that allowed the moisture to be wicked through the top of the exposed stringers (grp hadn’t been laid all the way to the top) and into the subfloor which had only been glassed on the top not underneath.
    so glad for the advice from you guys and for making the decision to do it the hard but proper way.
    In the end I got pretty good at removing one side of the grp and the wood underneath which left the other grp side intact. The helped me keep the boat form intact and gave me an exact location to replace and epoxy the new stringer to.
     

  15. Martin Upton
    Joined: Feb 2020
    Posts: 39
    Likes: 7, Points: 8
    Location: Australia

    Martin Upton Junior Member

    To any other Southwind SR655 owners out there who are contemplating this kind of work. The good thing about this boat is you can do the work without taking to top off.
    If you’d like to know about the structure/ layout or techniques to get to difficult spots just message me and I’d be happy to help out.
    Cheers
     
    Last edited: Oct 7, 2020
Loading...
Similar Threads
  1. Midday Gun
    Replies:
    21
    Views:
    567
  2. UtahSignature
    Replies:
    4
    Views:
    421
  3. Ronjon
    Replies:
    55
    Views:
    3,410
  4. Smj1
    Replies:
    12
    Views:
    1,969
  5. Phil Canoe
    Replies:
    12
    Views:
    3,154
  6. abourgault
    Replies:
    9
    Views:
    4,246
  7. Duck
    Replies:
    15
    Views:
    3,308
  8. BC Chris
    Replies:
    2
    Views:
    2,221
  9. pmack
    Replies:
    2
    Views:
    4,533
  10. trailrunner
    Replies:
    29
    Views:
    11,395
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.