My turn to tackle the hull to deck joint.

Discussion in 'Sport Cruisers' started by skibum, May 18, 2018 at 12:09 AM.

  1. skibum

    skibum Well-Known Member

    Jul 30, 2007
    Perry Hall, MD
    2005 Sundancer 260
    496 Magnum HO
    I was going to do it last year, but life was happening at blazing speed and the boat had to take a back seat for a couple of months. Last weekend I took the plunge and removed my rub rail. What a mess. The entire port side from just forward of the forward port light back until about a foot and a half from the back of the boat was not connected. There were a couple of screws still in their holes, but they were so loose I could spin them out with my fingers. 2 or 3 of them had been bent into a z shape. I'll try to find them and snap a picture of them next time I get down there. I should have done this much earlier. The starboard side also has a few spots where the screws were loosening up, but all of them still had good purchase into the hull. From the front port light on each side and around the tip of the bow, all of the screws seem to be tight and there is no apparent gap. The two pieces seem to be flush with each other. It appears to be "sealed" with a bead of soft silicone along the outside of the joint. I'm not sure if this sealant is between the 2 parts, or simply applied externally. The situation seems to be the same across the stern. There is one small, 1/2" wide gap in the externally applied bead. I can't tell if the 2 halves are touching, or if there is a gap between them because of the sealant. I think there is a small gap.

    I've managed to get about 85% of the sealant off of the hull on the port side. There were 3 broken off screws in a 4" section that I had to spend an hour removing with needle nose pliers. That was fun. Mineral spirits has been doing a decent job of softening whatever it is. Scraping it off has required more finesse than force, so it really hasn't been too bad. I'm planning on just using a bit of 60 grit to roughen up the underside of the deck a bit because I really can't see it well enough to scrape it "clean". I'll hit it with some acetone right before I start buttoning her up. I hope that will be sufficient.

    I'm going to replace all of the screws. Do y'all think it would be worth it to "upgrade" the hull to deck screws to #10s as opposed to the standard #8s? I believe the 5200 will provide the strength once it sets, so I'm leaning towards sticking with the #8s. Is my logic sound?

    As to the bow and stern. I'm inclined at this point to leave well enough alone as I don't see any apparent issues to fix. I'm debating about removing the old sealant from the surface so when I seal the sides of the boat I'll have a continuous bead (more like a filet) around the perimeter. Do you guys think that is the proper course of action?

    Last question. Is there anything wrong with using Marine Tex to fill in the extra holes in the deck. I have several to fill. I'd like to restore some structural integrity to the section with 5 holes in a 6" stretch. Or should I just fill them with 5200?

    I've lost 4 days due to rain. I've got 4 tubes of 5200 ready to go. All I need are a few dry hours.

    Edit: I forgot to mention. Just in case anyone else has a problem with a bit of rust stain appearing on the vinyl headliner around the bottom perimeter of the port light inside the cabin. I took it off 3 years ago to reseal it, but it was obviously not leaking when I took it apart. Everything was clean and dry. While scraping the sealant, I noticed that some excess interior headliner material was sandwiched between the hull and the deck. Apparently, water would go under the rail and soak the foam backing of the vinyl and wick its way up to the bottom frame of the port light, causing rust where there was no leak.
    Last edited: May 18, 2018 at 12:25 AM
  2. importmonkey

    importmonkey Opinionated Member SILVER Sponsor GOLD Sponsor

    Jul 9, 2015
    Middle River, MD
    2007 44 Sundancer
    QSC 500s
    Good luck. This project really tries your patience but it isn't too hard. I only have reservations about the 5200. I think there was a lot of debate on that in past threads - something about wanting more flex in that joint instead of a rigid one. Could be wrong though. See you on the bay soon.
    skibum likes this.
  3. ttmott

    ttmott Well-Known Member GOLD Sponsor

    Apr 3, 2012
    Space Coast Florida
    2006 52 Sedan Bridge
    Cummins QSM11
    I would consider the screws non- structural as their purpose is to pull, align, and hold the deck to hull joint together until the bonding adhesive cures. It is the adhesive that is the structural component in that deck to hull mating. If you are looking to re-bond the items back together then 5200 is not the right material but rather use Plexus MA series Structural Adhesives. Sika also makes a suitable bonding material. So, if you have a debond issue then remove all of the screws, drive some wedges in the gap to slightly open it up then with a long drill bit or something, get in there and clean/abrade the surfaces to be bonded. Final clean the mating surfaces with Acetone. Mask off the hull so the adhesive doesn't run down it and inject the adhesive to completely fill the joint. Remove the wedges as you fill the seam then drive the screws (I would use #10's if going into existing holes) and pull the two halves tight together creating a good bond. Regarding the screws - the box store material will be 18-8 stainless which can leave rust stains as time goes by so order 316 stainless screws from McMaster or the like.

    As an edit - much of the strength of the boat's hull is derived from the deck (the hoop and torsional strength) and that bond between the deck and hull is critical. Modern boat construction has reduced the traditional bulkheads which support the sides of the hull and now those have been replaced with the deck connection.
    Last edited: May 18, 2018 at 7:45 AM
    importmonkey likes this.
  4. quality time

    quality time Well-Known Member

    Oct 30, 2007
    Upper Chesapeake Bay
    2003 480DB and Kencraft 190 CC
    I don't have any experience with this project but keep in mind that nothing sticks well to silicone. I assume you'll have a hard time removing all of the residue in the joint.
  5. skibum

    skibum Well-Known Member

    Jul 30, 2007
    Perry Hall, MD
    2005 Sundancer 260
    496 Magnum HO
    I do recall discussions about plexus versus 5200, but I don't recall seeing a consensus answer. I certainly want to use the correct material for the job, but to keep things in perspective, a 260 Sundancer is a bay boat, not an ocean-going vessel. The maximum she will ever see is 3 1/2 footers. The biggest complaint that I ever heard about 5200 is that it won't come apart. I tend to think it might be sufficient for the use it will see. I'm still open to changing my mind though.

    I've managed to clean up the hull pretty good. I've been cleaning it up with mineral spirits, compounding it with rubbing compound, followed up by wiping out down with acetone as I go. The parts that I've done feel very clean. The underside of the deck is a different story. Fortunately, there really wasn't a whole lot of sealant in there. Mostly 1/8" to 1/4" lines of it. That leaves plenty of uncontaminated surface area for the new adhesive to work with.

    Does anyone have any thoughts on whether I should disassemble the bow and stern considering that they appear to be attached pretty well currently?
  6. skibum

    skibum Well-Known Member

    Jul 30, 2007
    Perry Hall, MD
    2005 Sundancer 260
    496 Magnum HO
    Heads up if you need new screws for your rub rail inserts. Fastenal has boxes of 100 #8x1" 316 SS oval head screws for $3.21. That is not a typo. I ordered 3 boxes for under $22. $10 of that was shipping.
    Last edited: May 18, 2018 at 6:48 PM
    importmonkey likes this.
  7. b_arrington

    b_arrington Member SILVER Sponsor

    Feb 21, 2007
    Setauket, NY
    270 Amberjack (2006)
    AB Ventus 9 VL RIB
    350 Mag MPI Horizon w/ BIII
    1998 Envinrude 15 HP 2-stroke
    I did this last year and wrote up a lot of detail. I would caution you not to remove all the fasteners at one time especially at the bow. I found the bow would spring up and if all the fasteners were out I would never have been able to get it back in place. Remove enough to clean out, use a wedge to open the joint and get 5200 in their, then screw down and move on.

    Also, an oscillating tool with a long caulk scraping blade was invaluable for cleaning the caulk from the joint.

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