Deck hull joint and rub rail caulk

Coz

Active Member
Oct 9, 2018
443
Boat Info
2008 Sundancer 310
Engines
Merc Mag 350 DTS w/Bravo III
Anyone know how searay joins the deck and hull on an 08 sundancer? I can see the deck overlaps the hull. Is the joint glued and screwed?
I’m trying to understand why my vinyl rub rail is caulked on the bottom and not on top.

I don’t see how water could get in that joint
 
Yes, it's like a shoe box then glued and screwed - both directly and indirectly via rubrail screws. Sea Ray doesn't caulk the bottom, or top, of the vinyl rubrail. A previous owner did that.

IF a previous owner was getting water (splashing up as the boat moves) through a gap where the glue failed, then they may have done a quick fix to try and stop the water. Or, in most cases, owner's did that to try and mitigate the mascara effect.
 
I don’t have pictures of the joint, but I’ve seen it.

On my boat, once I took the rub rail off, I could see the joint was fused together somehow and tight. I don’t think the caulk at the top or bottom of the rub rail does a whole lot, although it may just be there to keep dirt from getting in behind the rub rail.

I had leaks caused by unused screw holes - the vinyl rub rail is screwed into the hull (those screws should have sealant on them). Then the stainless portion of the rub rail is screwed on top of that (those screws should have sealant on them too). On my boat, Sea Ray had drilled a couple of holes though the vinyl rub rail and through the hull, but they abandoned those holes without sealing them or using them for any screws, and this was the cause of some leaks into my bilge. I sealed them with LifeCaulk.
 
IMG_4230.JPG
After years of dealing with leaks I came to the conclusion that the hull/joint connection on my 370 Express was not strong enough to withstand the torsional flexing that comes with running the boat in rough water on Lake Michigan. It was not fixable under warranty, and I spent a lot of money dealing with leaks when it was out of warranty.
The shoebox design works, but SR did not execute it well with my boat. I believe this is true with many of the boats that left their factories. They also did not add an element that would have made them better, wooden spacers between the decks and hulls. To work properly, the deck and hull joints need a good overlap. A strip of material such as wood needs to be adhered to the joint with construction adhesive. Then the deck and hull needs to be through bolted with robust fasteners including the liberal use of 5200. The rub rail goes on after the joint is sealed. Boats built with this technique do not leak at the joint.
 
IMG_4059.jpg
IMG_4058.jpg
IMG_4057.jpg
On my 06DB it is a "shoebox" joint which the deck and hull are bedded in an adhesive then through bolted with 1/4" screws with nuts and washers in the inside. After that the joint is laid up with fiberglass on the inside then the gap caulked with a silicone like caulking on the outside. The rub-rail is then screwed with 2 inch #10 screws and the stainless trim screwed to the rub-rail with 3/4" #8 screws. We just finished re-caulking the joint with 5200 so here are a couple of pics. We filled these long neck syringes with 5200 and injected up inside of the joint then with putty knives worked the 5200 throughout the entire joint. Make sure you put that rub-rail back on the boat every night at least with a couple of screws to ensure it's shape is held otherwise the rub-rail shape will relax and you will play hell getting it to fit the boat again. Tom
 
Last edited:
My 2006 270 AJ had a leaking hull-deck joint. I found it when I had the helm storage box out. I stuck my head in the hole and saw daylight streaming in through a huge open gap in the deck joint.

I ended up removing the entire rub rail and the stainless screws that held the deck joint together (not all at once though!). I found there was virtually no caulking in many areas of the joint, and what was there was very minimal. It certainly was not structurally glued together. The flexing of the hull over time, combined with a lack of structural adhesive, caused the screws to back out and the joint to open up in several areas.

Once the screws were removed and the joint cleaned up, I thoroughly caulked the joint with 3M 5200. I never wanted the joint to come apart again. I reinstalled the rub rail but did not caulk either side. The area behind the stainless insert was very dirty so I cleaned that thoroughly too.

Here's my write up of the repair project.
http://www.clubsearay.com/index.php?threads/resealing-the-hull-to-deck-joint.83083/#post-939082
 
Thanks for the info. makes more sense now. I have no known leaks.......so I think I will just recaulk the bottom of the rub rail. Guessing that was to prevent mascara effect like LazyDaze said.

If I wanted to inspect the joint. Sounds like its ok to take the rub rail off right? there are separate screws that hold the deck and hull together?
 
This is on the list for this winter, just the transom.
 
If I wanted to inspect the joint. Sounds like its ok to take the rub rail off right? there are separate screws that hold the deck and hull together?

yes. 1 set for the stainless insert, 1 for the plastic rail, and 1 for the deck joint.
 

Forum statistics

Threads
112,944
Messages
1,422,715
Members
60,927
Latest member
Jaguar65
Back
Top