electrolysis in wood

Discussion in 'Wooden Boat Building and Restoration' started by skaraborgcraft, Jan 2, 2024.

  1. sdowney717
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    sdowney717 Senior Member

    That picture is a very close up one. Here is how it really looks. reminds me of Sunbrella
    This fabric sheds water, ran under the tap.
    Idea is to protect high wear area, like the keel and the bow wood.
    Plan to cover whole keel wit this, so as to run strips from where planks meet keel, down, around keel bottom and back up other side.
    And protect forward bow keel area, similar plan.

    upload_2024-10-6_12-11-39.png

    My close up pic, it looks to be keyed well, so it should stick really well to 5200, maybe even epoxy.
    upload_2024-10-6_12-12-54.png
     
  2. sdowney717
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    sdowney717 Senior Member

    I did not actually give up on Sanitred, but it has some issues, as in sometimes lets go of wood and then fits like a tight glove against wood, but it stuck all the time on the Loctite PL premium polyurethane I used in the plank seams. It is a drippy coating painting upside down, I hope the 5200 being paste like wont do that too me. I got it all over everything when painting the hull.
    The Sanitred protected the exterior from worms and the wood underneath is in like new condition after 20 years in the salt water, which is pretty good. It can be torn, as in you can rip it but it is hard to do that. Sanitred Permaflex never had 250% elongation which 5200 says it has, I would estimate 20%. Very hard to sand with tremendous effort, but can be planed off with an electric power planer pretty fast. I like the idea of coting a wood hull in rubber, and I figure 5200 is one of the better polyurethanse. Another idea is Durabak, but it is also a paint, which will drip on me again.
     
  3. Dave G 9N
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    Dave G 9N Senior Member

    The Nylon fabric from Amazon is coated on one side with urethane. That would concern me. You should test it before you commit to using it on your boat. I would be very hesitant to try the coated fabric without some testing. If it doesn't wet and adhere well, get the uncoated (greige) cloth that Corey sells. The uncoated fabric wets easily with water and wets well with a fairly low viscosity 2-part PU. I doubt that the coated fabric will drape very well. As for wetting and adhesion, only a test can answer the question. The uncoated fabric does not drape like fiberglass cloth, but it does well enough on the outside of a canoe. My suggestion to wet and stretch it is is not going to work on the coated fabric. While in general PU adheres well to PU, without a test, I would never assume that any particular PU will adhere to another particular PU. It might work out well, but it is a major headache if you find out too late on the boat.

    Applying Sanitreed on a vertical surface had me worried when looking at it for a dome. An overhead surface... I see your problem and it sounds bad. I would consider adding about 2 wt% fumed silica to it before adding the catalyst. And, yes, I would tend to look for something more viscous. From what I have read, the mixing of fumed silica with resin has to be very thorough with a high shear mixer. It will make the material thixotropic without increasing the viscosity appreciably. That does normally reduce sags on a vertical surface. Sanitred sells a thickener for their liquid rubber base, but not for the Sanitred PU topcoat. If you do try fumed silica, it absorbs moisture in humid weather and that can shorten the pot life of the PU. The silica may need to be dried in a warm oven for a while if it isn't a new batch.

    You may be correct when you say Sanitred Permaflex never had 250% elongation. Their data sheet says something very different, and I have no way to verify their claim. You have hands on experience. What they claim and what you found may not match.The data sheet also says that the hardness is Shore D 80. I think they meant Shore A 80. The typical comparison charts liken Shore A 80 to a shoe heel and Shore D 80 to a hard hat. If you can dent it with your thumbnail, it's Shore A. It would not be the first time I found typos an a data sheet.
     
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  4. skaraborgcraft
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    skaraborgcraft Senior Member

    Are going to use some kind of roller to apply that cloth? Im wondering how you are going to get enough 5200 into the weave to get a good bond. I would definately do a small test panel before starting on the hull.

    I removed a "cascover" nylon sheaving on an old plywood boat, the glue had given up in a few spots causing bubble spots and it was easy to just peel off. I believe it was put on when the boat was new, so it had lasted over 40 years. I was considering the whole epoxy-glass sheathing, but i had time and weather constraints. I finally used Chlorinated rubber, as used on ships, oil rigs and under sea steel pipes. I did the entire boat with maybe 6 coats. It worked well while it was still in my ownership and it was dirt cheap.

    Look forward to seeing how your test works out.
     
  5. sdowney717
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    sdowney717 Senior Member

    yeah, cannot be dented with a fingernail, is a harder rubber than shore 70 which is a car tire.
    I will test the cloth, but I am confident 5200 will stick well to it.

    Yes, it can form drippy runs, and the runs are like very slow moving. I did the coating in summer and the stuff very slowly gets thicker and thicker till it gels. You can add more as it does that and get thick layers. I did that for reinforcement on some interior boat framing at the chine which I had repaired due to broken frames. That made the repairs very solid and strong.

    I have also thought having a layer of 5200 on the wood, then a top coat of Sanitred would be nice. I use Loctite PL polyurethane in all the plank seams and the Sanitred stuck fast to that without issue for those 20 years. Cured sanitred permaflex feels very slick and smooth. If you let a coat cure, it needs washing with dishsoap as it can form an oily layer, I don't know if today that is still true.
     
  6. sdowney717
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    sdowney717 Senior Member

    Since 5200 is slow cure, and sticky I figure strips of cloth when pressed in it will adhere good.
    I was thinking a stiff putty knife dragged across the cloth which will also stretch and get out wrinkles. Then rub my hands all over it.
    It does not gas as it cures. Seeing it is moisture cured, anything mixed with it will have air humidity adding moisture and I think might speed up the cure. I have been thinking a 1/8" thick layer of 5200

    Got a link to the chlorinated rubber paint idea? I have thought of that also. Is it like pool paint?
     
  7. sdowney717
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    sdowney717 Senior Member

  8. skaraborgcraft
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    skaraborgcraft Senior Member

    Certainly it wont stretch like 5200. I would use it on a planked boat if it had been splined and the planks where not overly large , and perhaps on a narrowly planked deck. Its ease of overcoating is a plus, just a wash required. Xylene based so bit of a head-banger if you forget to wear a decent respirator. It did fill a butt joint without problems, but sure, no movement in plywood compared to trad plank.
     
  9. Dave G 9N
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    Dave G 9N Senior Member

    Good technical data sheets for chlorinated rubber paints are hard to find. The closest thing to information about elongation is that someone used it to seal a canvas covered SOF boat. At least that implies that it isn't too brittle. As far low cost chlorinated rubber coatings, the least expensive one was the one used on the canvas boat, and that was $380 per [EDIT: 5] gallon [bucket]. That is less than the $587 for [5 gallon bucket of] Sanitred. The CR paint does appear to be non-toxic once cured since it is recommended for Koi ponds. There are consistent comments that it can not be overcoated with any other type of paint, but there are antifouling CRR paints.

    As far as coating Nylon, I have read that nothing but PU will adhere to Nylon. I would not assume that those comments were made by people familiar with CR, so a test would be in order. Considering the fact that sdowney already has 3M 5200 on hand, it is something of a moot point. I would be surprised if 5200 did not stick to the urethane coated cloth, but it is unlikely to saturate that cloth. A test is the only way to find out how well it will work. I have some confidence in the user's judgement here, so while I may have my misgivings, the best advice I can provide is to proceed with caution, which he appears to do anyway.
     
    Last edited: Oct 9, 2024
  10. gonzo
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    gonzo Senior Member

  11. skaraborgcraft
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    skaraborgcraft Senior Member

    That i would agree with. Once you have gone down the CR road, the only way back is to strip off the entire coating. Many anti-foul paints are/were xylene based, hence the compatibility. A friend used it to seal the inside of a plywood water tank, much with the same comment, if its good enough for fish....
     
  12. sdowney717
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    sdowney717 Senior Member

    Saturating the Nylon cloth is not the goal. I think of it like wood, you glue wood side to side, the glue does not saturate through the wood.
    The nylon cloth is very strong, holds together by itself and abrasion resistant by nature. I figure with its inbuilt surface texture, bottom paints will stick well to the cloth.
    I also was wondering if since it is water repellant, would a hull made of the cloth and no paint not leak in water? Or might leak only a small amount.

    If it passed no liquid water, that also is another water barrier effect to prevent worms, rot, and fastener corrosion for an otherwise wood boat which swells up in water.
    I been around long enough that I know bronze screws always corrode on wood boats, especially with salty ocean water saturating the wood planks. Coating the hull with multiple resistant to water layers is good idea for longevity. The reason wood and metal degrade is they get wet.
     
  13. skaraborgcraft
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    skaraborgcraft Senior Member

    It will leak. The yarns are not tight enough to prevent it.
     
  14. sdowney717
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    sdowney717 Senior Member

    Ok, I should show you all an ugly result of 54 years of electrolysis in white oak wood caused by OEM construction method which long term is a very bad idea.
    Of course OEM did not care, all they care is about selling boats, not what happens decades later.
    Has to do with them drilling a 1/2" hole and pounding galvanized steel rod through boat floors into keels.

    If that wood gets sea water wet, or wet, then the steel rusts into the oak and it destroys the wood for several inches around the hole. It won't destroy all the wood just close by wood.
    I got one such spot to fix this haul and I chiseled out the weakened wood to form a slot into which will glue new white oak with the Loctite PL. Basically had to reconstruct the white oak floor on top, I had to side cut a slot to remove the iron spike. It is at the most forward first floor of the inner keel. There is large oak timber skeg keel unaffected below which is bronze bolted with 1/2 long bolts. Surprisingly and good, the bolt holes in the inner keel nearby are full strength. What I understand is acids eat the oak and it is like burns the wood black, and the wood loses its integrity. This part of the hull is the lowest part and all water collects here. All the other floors and keel going aft never have sitting water on them. The underwater profile of the hull reminds me of a goldfish, it is curved so the front area is like its belly.

    What I have done over last several years with boat in water is either pull or cut those spikes out, and have not found inner keel damage elsewhere. I have pulled the forward 7 spikes out and doubled up those floors with new oak on both sides of those floors. I also thought it awful of OEM to drill a 1/2 inch hole straight thru a nice strong 2" wide white oak floor, it does lower its strength. I asked about deadrise boats and was told their floors are laid to keel and not spiked to the keel.

    I glue and screw oak boards to the sides of the oak floor wood (floor is like a joist sits on keel) I have a lot of red oak 4/4 here I cut for flooring, so using it. It won't get wet and it is sealed all sides in Loctite PL. I use the PL as I had bad experience with epoxy on this white oak keel, it does not hold to the wood, but the PL Polyurethane glue does hold great.

    I chiseled the slot clean all the way to the skeg keel bolted underneath. And the length is about 6 or 7 inches and up to 3" depth and 1.5" wide
    Today will get a pic, just don't be horrified as everything is fixable with effort.



    My repair doubles up the floor so it will be stronger than new.
     

  15. skaraborgcraft
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    skaraborgcraft Senior Member

    I have personal experience with iron in oak after 70 years, its not pretty. Lets face it, 50 year life expectancy for a wooden pleasure boat is good going. Wooden beach boats might have an expected life of 5-10 years, boats on moorings 15-25 years.

    If they lasted forever, builders would be out of a job, but GRP did that to most traditional builders anyway. The beauty of wood is that is is always repairable if the budget is big enough, and even if its half a plank at a time.
     
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