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Corroded bow foil  Bottom

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  • i think it is epoxy or something
    it is too much for it to be foil material - there isn't a giant hole on foil, just heavy pitting
  • MN3, I think you are right. It is most likely a polyester adhesive bedding material like 3M-5200 pr 3M-4200 that has failed. The color is right, and this is how it fails in hardware that has been in use a long time and has some movement https://www.3m.com/3M/en_…002385+3293241623&rt=rud

    We have moved away from this material because it does dry out and fail and started using the butyl rubber I showed in a previous post. While 3M-5200 is a strong adhesive as well as sealant, the adhesive is just not needed where fasteners like rivets, bolts and screws are providing a mechanical attachment. On monohulls it is a pain in the ass to remove, and its failure results in soft decks. The butyl rubber never dries or fails and moves in shear, tension and compression without losing its seal.



    Edited by tominpa on Dec 23, 2020 - 08:07 PM.

    --
    Tom
    NACRA 5.7 (1984 Sail 181)
    Pennsylvania
    --
  • waiex191
    MN3
    AndinistaI just realized that I can turn the foil around and rivet the piece at the other side... and invert the end caps. That makes more sense.
    icon_smile icon_smile
    Will check the suggestions about corrosion protection now

    YES!!!!

    what is this you are holding ? some anti fouling or silicone or something? can't be aluminum oxide is it? (looks thicker than the foil metal to me)

    https://www.thebeachcats.com/gallery2/main.php?g2_view=core.DownloadItem&g2_itemId=134154&g2_serialNumber=4&g2_GALLERYSID=fabfe0b93bcfa0d347017aa2710c7f8c

    I was assuming aluminum oxide. It's pretty ugly looking!

    Clever idea to turn the foil around. Will you patch the other side?

    Yes, it is the aluminum oxide!! It grows thicker than in its previous state.. it’s taken from all the crap visible in other pictures.
    The hand would be my daughter’s, so adjust scale a little bit :)
    Yes, I will probably patch the corroded part, not sure how necessary it is, but for peace of mind
  • Before disassembling it didn’t look as bad, the worse was closer to the center that in the edges.But I had not realized that the white stuff was the aluminum itself, I thought that the rivets were coming loose and that the white stuff was some sort of buildup coming from outside.



    Edited by Andinista on Dec 23, 2020 - 10:19 PM.
  • MN3i there isn't a giant hole on foil, just heavy pitting

    At one spot all the material is gone and there is a little hole. In another small spot the the original surface is still there. Very uneven, but it’s actually pretty bad.
  • Tom, I don’t think it’s adhesive bedding material, because its thickness is uneven and matches the lack
    of thickness on the aluminum. Makes sense?
  • Not sure. I would expect if it was used as a sealant or adhesive, the thickness could be uneven. Aluminum oxide corrosion can expand to fill any space, and in the oxide form is much larger than the metal it came from. It is soft, flaky and usually retains moisture. I guess, photos have their limits, and from here in Pennsylvania, I just can't tell you. Is the material "friable"? Does it fall apart easily when rubbed between your fingers? I can't tell if the material is a chalky, friable metal or a chunk of plastic caulk.

    --
    Tom
    NACRA 5.7 (1984 Sail 181)
    Pennsylvania
    --
  • Quite friable and definitely chalky
  • This is very common with stainless and aluminum. I’ve run across it a lot. Maybe you have, but wire brush the corrosion to see how bad it really is. Ultimately, I would suggest replacing the foil. I have built a foil for my boat out of a H-16 boom. My second option would be to have the base of the full striker built larger. I would stay away from flipping the foil over. If the corroded area is compromised, you’ll add a weak spot to a pretty high load area. I think the foil will fold. Which ever you do, make sure you use a corrosion inhibitor paste in between all dissimilar metals.

    --
    Scott

    Prindle 18-2 Mod "FrankenKitty"
    Tornado Classic "Fast Furniture"
    Prindle 19 "Mr. Wiggly" - gone
    Nacra 5.8 "De ja vu"
    Nacra 5.0
    Nacra 5.8
    Tornadoes (Reg White)
    --
  • I was looking for CRC 06026 and its cheap but shipping to chile adds up consierably, it's probably considered hazardous or something. Not to kill me but I'd rather go the double bridles way, considering that I have some wires and would just need to swage them.
    But I do have a small pot of TEF GEL that should be enough. According to the video below it's the right thing, what do you think?
    How bad would it be to skip the butyl tape and just apply the TEF GEL? I'm not planing to sail this boat other 20 years anyway... And to sell it I'd probably swage those wires anyway.
    https://corrosionandmarine.com/



    Edited by Andinista on Dec 29, 2020 - 10:05 AM.
  • I have never used it in marine, but plumbing uses TEF all the time, and it works well. It's worth remembering it took a long time for the corrosion to occur the first time, and any solution you apply will likely be effective in preventing it or slowing it down now.

    --
    Tom
    NACRA 5.7 (1984 Sail 181)
    Pennsylvania
    --
  • That’s what I needed to hear, thanks :)
  • AndinistaI was looking for CRC 06026 and its cheap but shipping to chile adds up consierably, it's probably considered hazardous or something. Not to kill me but I'd rather go the double bridles way, considering that I have some wires and would just need to swage them.
    But I do have a small pot of TEF GEL that should be enough. According to the video below it's the right thing, what do you think?
    How bad would it be to skip the butyl tape and just apply the TEF GEL? I'm not planing to sail this boat other 20 years anyway... And to sell it I'd probably swage those wires anyway.
    https://corrosionandmarine.com/Edited by Andinista on Dec 29, 2020 - 10:05 AM.



    I have used tef gel for years
    it is superb as a barrier to reduce galv. corrosion

    i suggest you don't use your fingers to spread the product like the man in the video
    it is nasty stuff and while not caustic - probably not a good idea to use like that. i always wear disposable gloves and use it after dry fitting everything
  • The last couple of times sailing, I notice my bow foil acting funky - weird bending going on. Doing some winter maintenance, I noticed the thimble for the gull striker had compressed. It is a 3/16" sailmaker thimble. I do push the boat hard, just didn't realize how hard. Tried to post a pic, but it wouldn't stick.

    --
    Scott

    Prindle 18-2 Mod "FrankenKitty"
    Tornado Classic "Fast Furniture"
    Prindle 19 "Mr. Wiggly" - gone
    Nacra 5.8 "De ja vu"
    Nacra 5.0
    Nacra 5.8
    Tornadoes (Reg White)
    --
  • QuoteTried to post a pic, but it wouldn't stick.

    you can email it to my old free email account and i will post if you want
    asn1987 at aol
  • Andinista,

    Given your corrosion issue, as a former Nacra 5.5 owner, if you have not yet, I would suggest you inspect the front beam at the inner ends where the dolphin striker horizontal support bolts to the beam (3 bolts per side). By boat had corrosion there and I put small plates inside the beam to improve the structure where the corrosion had weakened it.

    Patrick
  • Thanks Patrick, i will. Still haven’t done much, I will report whatever I do
  • Hi!
    After quite a while I repaired my bowfoil, here are the pictures.
    Conclusions:
    * I seriously considered to make double bridles instead, but then realized that I like to roll the jib on the forestay (even without roller furling), so I didn't.
    * I will seal the rivets and plates edges to keep water away
    * I love Tef-Gel
    * There is little room for the plate that I added. I had to press the foil with my foot to bend it a little bit to be able to connect again the wires at both ends

    Before:
    https://www.thebeachcats.com/gallery2/main.php?g2_view=core.DownloadItem&g2_itemId=134144&g2_serialNumber=3
    https://www.thebeachcats.com/gallery2/main.php?g2_view=core.DownloadItem&g2_itemId=134152&g2_serialNumber=3

    After:
    https://www.thebeachcats.com/gallery2/main.php?g2_view=core.DownloadItem&g2_itemId=135722&g2_serialNumber=4
    https://www.thebeachcats.com/gallery2/main.php?g2_view=core.DownloadItem&g2_itemId=135719&g2_serialNumber=4
    https://www.thebeachcats.com/gallery2/main.php?g2_view=core.DownloadItem&g2_itemId=135713&g2_serialNumber=4
    https://www.thebeachcats.com/gallery2/main.php?g2_view=core.DownloadItem&g2_itemId=135716&g2_serialNumber=4

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