wierd stain

Z

Z50

New member
Took the boat out this past weekend for four days and a brown stain appeared under the port side gunnel near the cabin. Where is this coming from? I was in clear water the entire time. Pictures are in my album.
 
Looks like this is weeping out of a pinhole between the tabbing for the bulkhead, the hull and underside of the gunnel deck. What penetrations are there on the top of the gunnel? It is possible that water travels feet from the point of entry. Most likely you will end up pulling each piece of hardware on top of the gunnel, under cut any core, and then fill with thickened epoxy, re-drill any pilot or bolt holes, and then properly bed with a adhesive/bedding compound--such as 3M 4000.
 
There is nothing on the top of the gunnel. No holes. Its coming out of the side. Ill take a better closeup.
 
Might be water from the rub rail attachments. Your picture might be showing the inside of the fastening of the rub rail (bump in the upper right of the image). They can rust and the water run down under the interior spray on speckle finish until a break in the finish lets the water come out. You'll probably find that pressing on the interior surface somewhere directly in line above where the water runs out will indicate a blister or bubble in the finish. There may be a noticeable vertical distance between where the water seeps out and a rub rail rivet, but where the water comes out will likely be vertically below where a rub rail rivet goes through the hull.

My boat had these in one or two places. If you seal the rub rail top and bottom with 5200 and press the water out you should be ok. The hull sides are not cored, so a little water seepage down the side is not an issue (IMO). In my case the amount of water was just several drops.
 
is this inside the cockpit? Is there a bulkhead with tabbing next to it? There will be cleats and perhaps public's, screws holding hatch covers all of which all be on top of the deck.

Tabbing is a narrow strip of fiberglass which holds bulkheads and furniture in place. It is clearly seen in the photo is as a pin hole. Water get into the deck core and travel the length of the boat.

Not tea or coffee stain.

This appears to material from either the core and / or even some un-cured resin by products which will turn dark.
 
Z50":1xwh7xz9 said:
Took the boat out this past weekend for four days and a brown stain appeared under the port side gunnel near the cabin. Where is this coming from? I was in clear water the entire time. Pictures are in my album.
Click to expand...

In my 25, that would be called a rusting rub rail rivet :wink:

Aluminum pop rivet with a STEEL mandrel, when they POP the steel ball stays in the rivet. I drilled all mine out & replaced with STAINLESS. :wink:
 
thataway":rfmb50lh said:
is this inside the cockpit? Is there a bulkhead with tabbing next to it? There will be cleats and perhaps public's, screws holding hatch covers all of which all be on top of the deck.

Tabbing is a narrow strip of fiberglass which holds bulkheads and furniture in place. It is clearly seen in the photo is as a pin hole. Water get into the deck core and travel the length of the boat.

Not tea or coffee stain.

This appears to material from either the core and / or even some un-cured resin by products which will turn dark.
Click to expand...

yes this is inside the cockpit
 
It could be from a pop rivet. My initial impression was that it was above the "hull to deck joint/rub rail". But if this is at the same level as the outside rub rail, then I would agree it is a pop rivet. Also concur with questioning why a non stainless steel mandrel is used?
 
Z50, have you called the factory in Fairhaven, Washington where your boat was made at NMI? I notice your Venture is a 2018 and I would think they have some provision as warranty to make a repair for you even though you are located in Florida. We had a couple of minor issues with our boat, took it to them and they corrected them for free. Gary.
 
i called TMI a couple of years ago when I was replacing the pop rivets that had popped out. At that time they said they weren't using the same fastening method. One might check what was used and how they could leak. I replaced them with 1/4 in bolts where I could reach the back and sheet metal screws where I couldn't.

Also, if one mixes aluminum and stainless, there is corrosion. So an al pop rivet with a SS core is guaranteed to corrode.

Boris
 
journey on":3aw0jzbj said:
i called TMI a couple of years ago when I was replacing the pop rivets that had popped out. At that time they said they weren't using the same fastening method. One might check what was used and how they could leak. I replaced them with 1/4 in bolts where I could reach the back and sheet metal screws where I couldn't.

Also, if one mixes aluminum and stainless, there is corrosion. So an al pop rivet with a SS core is guaranteed to corrode.

Boris
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All mine were replaced with Stainless pop rivets or #10x32 machine screws all w/ back up washers 10 years ago all good so far :wink: :beer
Expensive @50 cents each but only have it do it once. Back then my time was worth something :mrgreen: :thup
 
Boris is correct, but the replacement rivet would be all SS. I used a bunch of them on one of my RV's, You to use a higher leverage tool, but it works very well. I have built up several sailboat masts using SS pop rivets multiple times and the rigs stood up for years with minimal corrosion..

I save aluminum pop rivets for aluminum projects. If you use Tuf-Gel there should not be bad interactions. If you replace with SS bolts you have the same issue--Maybe in 30 years replace the rub rail??
 
Well, to beat this to death, if you're going to use all stainless fasteners, pop rivets or bolts, please use a plastic washer under the fastener head. The rub rail is aluminum and gets filled with salt water. I also drilled a couple of weep holes to make sure the water had a way out.

I first found out about that corrosion on our sailboat, where the mast was corroded around a ss fastener. That was in Mexico, so that boat was only a couple years old.

Boris
 
Our Cal 46 was 18 years old when we bought it. I checked the SS fittings and all were good, plus I added another winch and some other mast fittings. The difference may have been that the Cal 46 mast was an oversized extrusion, and the mast had been painted from the beginning. If there was any corrosion it was addressed and touched up immediately. I would go up the rig and inspect each fitting before we made any offshore passage, as well as yearly.
 
I did speak with the factory. They said they used SS screws and ground them flush and then glassed over them. He said grinding down the SS screw would cause them to rust. I cant believe a rusty screw could produce that much brown water in a short period of time. They said they would fix it. I think the water is coming from somewhere else. Just don't know where.
 
Well, at risk of providing a lonely opinion again, why would grinding down the bolts make them rust? I've ground them, cut them and filed them, no rust. The ss alloy is the same thru-out. And if there is a surface layer, it'll reform.

And Bob, I congratulate you, Cal must of had better alloy. I had a Catalina, the Ford of the sailboat fleet.

Boris
 
journey on":32odi5mw said:
Well, at risk of providing a lonely opinion again, why would grinding down the bolts make them rust? I've ground them, cut them and filed them, no rust. The ss alloy is the same thru-out. And if there is a surface layer, it'll reform.

And Bob, I congratulate you, Cal must of had better alloy. I had a Catalina, the Ford of the sailboat fleet.

Boris
Click to expand...

yeah I dont believe the screws would cause this problem
 
Beach Donkey,
Sadly sourcing high quality stainless steel is very difficult. Stainless steel comes in different grades (such as 316 and 318). The least (rust) staining stainless steel that is the benchmark for the marine industry for fasteners that are going to be visible is 316.
When you go to Lowes and Home Depot you can buy stainless steel fasteners. Most hardware stores do not list the grade of the stainless steel, so you won't know if it will bleed rust, till down the road.
Vendors like West Marine really got caught up in this a while back, as the grade and quality of the fasteners was not high on their list of QA until they had many customers go back to them with thousands of complaints about weeping rust from a fastener that had been installed 6 months previous (this applies to hose clamps as well).
So, back to your new boat...Even though the fasteners purchased were most likely procured as high quality 316 stainless, they could have gotten some that had a higher carbon content.
 
Z50, glad to hear that Northwest Marine Industries will make the repair for what caused the stain on the inside of the cockpit deck hull. NMI is trying to be a very responsible manufacturer of C-Dory boats to keep the legend of C-Dory alive. We should all be thankful for that. We all have great boats and the C-Dory name deserves to be kept alive, hopefully for many more generations to come!

Please let us know what the problem turned out to be after the repair. This information could be helpful to many of us in the care for our boats.

Thanks for sharing.

Gary.
 
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