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Fybridge - Reseal the Seam

Discussion in 'Technical Discussion' started by dewald, Apr 7, 2020.

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  1. dewald

    dewald Member

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    It’s time to reseal the seam between the flybridge and the cabin hardtop. Could use some words of wisdom. So far, I have removed the old sealant to even or just recessed past the front edge of the lip, in some places the sealant was so bad/dried out under the lip it just fell out leaving a hollow space under the lip going back ½ - 3/4”. My thinking is I should I dig out more of the old sealant that is even with the front of the lip to make sure there’s no bad stuff behind it; plus it would give a little more surface for the new sealant to adhere to.

    For the new sealant I’m thinking 3M 4000 UV or Sika 295 UV. Is there something better to use?

    Old Sealant/Seam
    CIMG1265.JPG
    Removed even with lip
    CIMG1266.JPG
    Hollow under lip
    CIMG1264.JPG
  2. chesapeake46

    chesapeake46 Senior Member

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    I used 4000 UV for the exact same issue on my bridge.
    I was disappointed in the result but did get about 3 years out of it before it began to flake off.
    My boat is in a covered slip so only in direct sunlight while in use.
    Every Single Weekend over that time period from April to November.
  3. PacBlue

    PacBlue Senior Member

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    I tested both and had the 3M 4000 UV stay brighter/whiter than the Sika 295 in direct sunlight.

    It’s all about prep and removing surface residue/contaminants.
  4. Capt Ralph

    Capt Ralph Senior Member

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    Blow out the cracks, no dirt, bugs, green or water. Scrub the contact area with denatured alcohol. Tape off the lines that make the caulk width.
    Find or make a grout corner tool that shapes the corner within the tape lines. You don't want the caulk to thick or to thin, just plump. Push the Sika into the cracks and ahead of the tip. Use the grout corner tool to shape the caulk before it starts setting. Use the denatured alcohol to wet the Sika if needed. If your good at pushing caulk with your finger, wear a blue glove and go for it, dip your finger in the alcohol (not booze) and squeeze your lines following the tape. In 5 minutes pull the tape. Pour a cold one, tomorrow it will look great.
    You have to have a clean and dry contact surface for the caulk. Order fresh Sika and have it at room temperature. Not hot or cold.
    Re-doing this will be a pain. Practice on some scrap if your not sure of a technique.
    Last edited: Apr 7, 2020
    YachtForums likes this.
  5. Capt Ralph

    Capt Ralph Senior Member

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    Ozone, pollutants and contaminated dust that normally would blow or wash off with wind & rain messed up your 4200.
    Covered slips help keep the sun off but brings other problems.
  6. Capt Ralph

    Capt Ralph Senior Member

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    Your pictures look great with out sealant. Is there a factory gasket under the seam?
    Any way to seal from the inside and not have any exposed caulk at all?

    If you must caulk, scratch my plumb caulk comment above, just fill the gap with no radi caulk exposed at all.
  7. cleanslate

    cleanslate Senior Member

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    I've used both 3M 4000 UV and Sika flex 295UV currently on my three large forward salon windows. Both seem to last around three years or so then start to chalk and flake. 5200 will turn yellow-ish over time, but will last longest. Never really used Boatlife stuff maybe that would last longer, and you can paint over their stuff if need be with semi-gloss paint.
    I would use one of the Sika Flex products. Look at the various Sika products on there site and match the best one that meets your needs.
    You want to dig out all the old loose stuff the best you can for a good seal. Before you seal it I would go around the entire seam with a small 1/4'' wide wire wheel in a cordless drill to clean the seam further and to lightly scuff the surface to give more bite for the new sealant to hold to.
    Tape it off before you seal it, and have a small container of kerosene , nitrile gloves and rags ready to smooth out the joint with you finger , lightly wet with kerosene to keep it form sticking and it helps to make a nice bead. Clean up is easy with the rags and kerosene.

    Some of those gaps are big , I think the 3M 4000 UV may roll out on you. The 295UV will keep it's shape and stay put.
  8. dewald

    dewald Member

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    Thanks for the feedback. I think I will use the Sika 295 UV. Used it late last year when I did my first ever attempt at replacing the acrylic lens on Bomar bow hatch. I did a good job if do not say so myself. I’m **** about working on things and do a let research on how to do it, so I can avoid stepping into the mess kit as much as possible. Now if I can just figure out how to tie myself on to the front of flybridge to work on that seam, I will be all set.
  9. cleanslate

    cleanslate Senior Member

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    Hum that is a long reach by hand from standing on the port and starboard deck. You should get close...
    Be careful! Maybe find a younger nimble friend / volunteer to get the rest of it.
    Or hang out over from the bridge perhaps . Good luck !