Center board trunk leak

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Center board trunk leak

Postby DavidOakland » Fri Jul 17, 2020 1:25 pm

Help! I have recently acquired a 1984 DS made by Precision. It leaks. After a half day of sailing, about 5 gallons + of water must be drained from the inner cavity between the cockpit deck and hull.

To find the leak, I filled the cavity with water while on the trailer. Water soon began seeping from the joint between the fiberglass "trunk" that holds the centerboard and the fiberglass cockpit deck. But,I saw no leak in the hull below the boat. How can sea water get into the inner cavity if it does not come out when filled? I don't get it.
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Re: Center board trunk leak

Postby GreenLake » Fri Jul 17, 2020 2:06 pm

The source of water clearly sits above the cockpit sole. When you sail, there can be significant pressure build-up in the CB trunk, and this can lead to leaks while sailing. You could try to see whether sitting in the water for, say, half an hour, generates less leakage than sailing vigorously (or motoring with the CB down) for the same time.

I don't know the newer DS1's that well: I assume you still have the lever, and that that one is the only other opening in the CB trunk. In that case, I'd look for leakage from there getting into the bilge. Is the trunk doubled as well? That would be the easiest route for water to run down. However, if the sole just surrounds a standard (single) trunk, then look for water seeping down through that crack w/o puddling in the cockpit. (If a CB gasket leaks, that leak may be one-way, as water pressure in the reverse direction may seal the leak).

Best guess I can offer remotely.

Another theoretical alternative is a hole somehwere in the hull above the waterline. Do you sail in choppy waves? With the boat heeled to the gunwales? Esp if the latter, you might look for gaps in the hull-deck joint (possibly along the cockpit where freeboard is least). Neither of these options lend themselves to detection by filling the boat from the inside - that much water is going to damage it sitting poorly supported on the trailer.

Again, a test comparing sitting at a protected dock vs. active sailing may give an indication how high on the hull you have to search.

Finally, there's a possibility that a leak exists for some fastener only when loaded. Theoretically, the lower gudgeon could get submerged and if there's stress on the rudder, there may be a leak there that isn't present at rest.
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Re: Center board trunk leak

Postby DavidOakland » Fri Jul 17, 2020 2:50 pm

IMG_0369 (1).jpg
IMG_0369 (1).jpg (82.43 KiB) Viewed 428 times


GreenLake: Thank you for your response. I'm thinking the joint between the trunk and the hull is the source of the leak. You can see it has been sealed in the past. Perhaps more water than I think is coming into the cockpit!

How should the joint be sealed? What do I see if I remove the plastic cover?

Thanks again, David
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Re: Center board trunk leak

Postby GreenLake » Fri Jul 17, 2020 7:09 pm

David, let me make sure I understand what I am seeing in the photo. You mention an inner space (bilge) between cockpit sole and hull. So, what we are looking at in the picture is not the hull, but the cockpit sole, or the "roof" of that inner space. However, the CB, while it has a nice "cap" isn't fully enclosed, so what we are seeing there is the actual wall of the trunk.

So, where can water get in? It ends up in the bilge, but when you fill that inner space with water, it does not exit from the hull (meaning the hull below the level of the cockpit sole is water tight). (Including the plug: as a leaky plug would also allow water into that space).

You reported that water seeps around the base of the CB trunk into the cockpit, after you filled the inner space. So, I concur the seam is probably not watertight. But even if you caulk that seam, will you have stemmed the leak? You could try some white 3M 4200, but because your cockpit is off-white it would show.

Now, while you are sailing, is there any water puddling in the cockpit? If yes, sealing the cockpit sole may keep that water out of the bilge. However, if there is no puddling, then you still need to look for a source.

Once the CB gasket gets old, you may notice a leak there, however, it would leak into the cockpit first and should be visible. (Do plan on replacing that gasket regularly; replacements are sold by DR Marine).

If you did not see any water in the cockpit while sailing, your source would have to be higher than the cockpit sole in the hull (including hull-deck joint) or it would have to be something that acts like a one-way valve, letting water in, but not out (or a crack etc. that opens up only when the boat is being sailed).
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Re: Center board trunk leak

Postby DavidOakland » Sun Jul 19, 2020 3:56 pm

Thanks again for you thoughts and concern. I apologize for my poor nautical vocabulary.

When I filled the bilge with water, it soon seeped up through the cracked joint around the base of the CB trunk. This seam is definitely not watertight! I continued to fill the cockpit to a depth of about a foot of water, well above waterline of the boat. At this point I carefully looked for leaks in the hull but found none.

While sailing, I do tend to get water in the cockpit and of course it can get through the seam. I had no thought until now that this could be the source of the large volume of water in the bilge. But, it seems so. Next, I'm going to put the boat in the water at a calm small lake nearby and let it sit for perhaps a day or so without possibility of water in the cockpit, except rain.

I need to seal the joint in any case. If water is coming down from the top, it will not be under pressure and sealant might work (3M 4200). Sounds like you think I should replace the CB gasket in any case.

How is the trunk secured to the hull? Should the joint be fiberglassed?

I appreciate your experience. David
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Re: Center board trunk leak

Postby GreenLake » Sun Jul 19, 2020 4:37 pm

The CB trunk should be securely fiberglassed to the hull (because the cockpit mold is separate, the trunk is not attached to it, but sticks through an opening that is intended to be sealed, but, as you found out, not perfectly). Sealing this opening should prevent rainwater and splashed water from draining down into the bilge - as well as any water that might drip slowly from the CB gasket. But in all cases, I would have expected it to visibly puddle in the cockpit - and that's not something you reported.

I would look under your boat and look around the edges of the CB trunk. Are there any (deep) cracks in the laminate? (Anything more than light surface crazing) Sometimes the connection between hull and trunk can get damaged over time and any cracks in that area may be such that water can come in when the CB is in use, but possibly not come out when everything is on the trailer. Some cracks have this "one-way valve" type behavior.

The only other source of water that possibly might apply would be from some place like the hull-deck joint, assuming you sailed your boat heeled far enough (or in waves high enough) that those areas were underwater for a while during sailing. Alternatively, any other cracks or areas of damage to the hull that are above the waterline but may be immersed while sailing.

And, although I think that would be more theoretical, your plug could be worn in such a way that it won't let water out, but may let water in. Just something to rule out. Water can be incredibly "creative" when it comes to finding leaks.
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Re: Center board trunk leak

Postby Brianl289 » Sun Jul 19, 2020 6:07 pm

While doing some hull prep on my boat for paint I found a 2 inch gash that was only visible when I had the sander putting pressure on it. If I didn't touch it it blended right in perfectly. For me it was directly under my passenger bench. May be something like that causing water to get in?
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Re: Center board trunk leak

Postby DavidOakland » Tue Jul 21, 2020 12:08 pm

Water does of course puddle when a wave comes over the bow into the cockpit and I now think this water is going through the crack between the CB case and the deck. I wish I could see a section drawing showing how the CB trunk is secured to the hull. I fear a similar crack in the inside between the hull and case. I cannot see that joint.

Do you think I should seal the outer leaking joint with fiberglass or just sealant? Thanks again, David
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Re: Center board trunk leak

Postby GreenLake » Tue Jul 21, 2020 4:53 pm

David, thanks for clarifying that you were taking on water via splashing. That was not a given; I sail in locations/conditions where that is rare. But if that's the source of your water, it will drain below.

Unlike the connection between cockpit sole and CB trunk the connection to the hull has to handle the actual forces acting on the centerboard. Normally, that connection is therefore strong. The CB trunk most likely forms part of the mold in which the hull is laid up, making it a single piece with the hull. Nevertheless, if abused, it can crack. One look from below would tell you whether you got cracks in that area.

Rather than speculating how to deal with those, we'll let you have a look first and give us an update on the condition of that area of your hull. (Note, you may have gelcoat crazing, because it's a stressed area - that's different from a real crack in the laminate).

The joint for the cockpit sole doesn't need the same strength, so caulking it should be fine. I was suggesting 3M 4200 (white) which is an adhesive caulk with the idea that it might better resist any stress from movement. You could also try Marine Tex epoxy paste (white). Making sure all grease and wax is removed, then grinding a bit of a groove so you can lay down a nice bead - that's what I would try.

(You could, of course, lay up a couple strips of fiberglass, but that repair would extend a few inches in every direction and possibly look unsightly unless you paint your cockpit. Therefore, the suggestion to first try a bead of adhesive sealant or epoxy paste. If that fails, for example if the cockpit sole flexes too much from foot traffic or the CB trunk too much from sailing, you can always go the next step).
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Re: Center board trunk leak

Postby DavidOakland » Wed Jul 29, 2020 5:26 pm

I put the boat in the water yesterday and just let it sit for a couple of hours, tied to the dock with no wind, or waves. No water could have come in from the top.

When I pulled it out, about a 2 cups of water drained from the bilge. So, looks like I have small leak that did not show up when the bilge was filled. The leak seems so small that I think I'll go forward with resealing the trunk and replacing the centerboard gasket and keeping an eye on the water quantity draining from the bilge.
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Re: Center board trunk leak

Postby GreenLake » Thu Jul 30, 2020 11:03 am

On my (old-style) DS1, that amount of leakage would have been from a slow drip from the CB gasket. Don't remember right now whether you discussed this, but I would suggest you replace yours. DR Marine sells them, they are not expensive and they do age. Good thing to replace on spec and to make sure the little triangular plate is pushing hard enough for an effective seal. Good luck!
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Re: Center board trunk leak

Postby DavidOakland » Sun Aug 02, 2020 5:04 pm

Thanks. I have a gasket on the way. The existing sealant between the trunk and the deck is hardened. Should I chip or grind it away before new sealant?

It's going to take more than the one tube of 4500 that I bought! You can see in the photos that this has been done before.
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Re: Center board trunk leak

Postby GreenLake » Sun Aug 02, 2020 5:26 pm

Can you tell what it is? If it's rock hard, it might not be sealant. If it's resin of some sort, it may not come off that easily.
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