Stain on hull.

[Bransher]

Does anyone have any idea what is creating this stain on my hull?

The boat is four years old, and the bottom paint is the original Micron that was dealer installed. I hit it briefly with the pressure washer today and it had no effect. The boat spends most of it's time on the trailer in a covered shed.

It just seems odd to me that it suddenly originates right at the point where the bottom paint and the unpainted surfaces meet.

[K9Kampers]

Where is the side-stay chainplate in relation to the location of this stain?

[NiceAft]

Odd indeed. Just for the heck of it, when you looked inside the nearest bilg, was there any stain in there? Does the stain look organic? It just seems strange that it originates suddenly, with a clean line denoting its begining.

When I magnify the picture, there appears to be lines similar to the stain, but clean instead of stained. Has there been any other running stains before

Ray

[K9Kampers]

If the stain came from a dripping from above... say a rusty nail / bolt, wood joist, bird poo... from the shed and grazed the smooth, waxed surface of the gelcoat while flowing down to the textured, porous bottom paint surface...

[Bransher]

No rusty nails as the shed is galvanized metal. The stain is about 4 foot forward of the chainplate. I have not looked inside the bilge, but will do that in the morning. The “lines similar to the stain, but clean instead of stained” are probably just some runoff from earlier today when I gave the boat a quick wash. Never had any running stains before.

The stain started to appear several months ago and gradually increased in size. The color is similar to a light oil or rust color. Nothing like that on the deck that could have run or dripped down. When I hit it with the pressure washer today, there was no change. However, just now I went outside with a flashlight and rubbed my finger over it. Two or three passes with my finger took some of it off and it seemed to have a greasy feel to it. I have not used any petroleum products anywhere that could have created this. That clean line where it starts is what baffles me.

[seahouse]

Hi Bransher!

So there are no grommeted screws in the roof where water would drip from? They don’t necessarily have to be rusty themselves to leave a rust stain, the water can pick up and carry the stain along from the galvinizing. I’ve seen it.

Might it be that each new stain line is where the boat was parked in a slightly different location each time you took the boat out, and the length of time it was parked there corresponds to the size of the stain? (Just guessing). Next time it’s raining go out and check maybe?

As mentioned previously, two different paint chemistries can explain the horizontal difference, one more porous, the other more hydrophilic, or pH differences, etc.

To remove it; there are a myriad of dedicated products for this, but easiest to use whatever you have on hand, diluted at first, such as CLR, oxalic acid, muriatic acid etc. I’ve found Mr Clean Magic Erasers to be very convenient and work well, are less noxious, and I highly recommend them. Start at the bottom to see what works, and rinse well, including the ground.

- Brian.

[Bransher]

Actually Brian, there are probably several hundred grommeted screws in the roof. Your theory certainly is a possibility.
The stains do not bother me, and so far I have not tried to remove them. I was just curious about their origion. The fact that there is no trace of anything on the gel coated surface above the waterline seemed odd to me, but I suppose it could be that rust just does not adhere to gel coat as easily as bottom paint.

[Catigale]

I doubt it is originating at the bottom paint interface rather than it happens to stick to the bottom paint, but not the gelcoat. Is it possible you washed off residue (colourless) from the gelcoat when you power washed?

Other than that, I confess Im clueless. If you were closer I would have a friend run a mass spec on it for you.

[K9Kampers]

Research condensation & sweating of metal roofs.

[c130king]

I doubt it is originating at the bottom paint interface rather than it happens to stick to the bottom paint, but not the gelcoat. Is it possible you washed off residue (colourless) from the gelcoat when you power washed?

I agree with the good Dr. I have a bottom paint with some "texture" to it. Some things that wash off the deck...like bird poop and sometimes just plain old dirt/dust...will not stick to the gel coat but will stick to my bottom paint. I also have sailed through some dirty water and gotten a similar effect...didn't stick or show on the gel coat but did show on the bottom paint.

I was able to get it off using a brush when I washed the boat. Simply rinising with a hose didn't seem to work.

Good luck.

Cheers,
Jim
Sailing on König
Sailing on König YouTube Channel

[NiceAft]

Totally aside from the line of thinking of this thread, I want to say that your boat has a wonderful shine to it. When the picture is enlared, one can clearly see your reflective image. You need a haircut

Ray

[Bransher]

K9Kampers…….. I did the research shown below. My galvanized metal shed is only closed on three sides. The front is completely open so it is well ventilated. However, this time of year in Florida we tend to have large swings in temperature. The non-insulated roof will be exposed to bright sunlight with ambient temp. around 70 degrees, and at night the temp. will sometimes drop into the 40’s. We have high humidity year round.

“If the air outside is moist and you bring that air inside the attic (via vents) and then the temp goes down (like it does most every night); if it goes down below the dew point temp, condensation will occur. How much condensation; it depends on how far below the dew point the air temp went. Will that condensation drip down on anything else; depends on how saturated the condensing surface is with moisture. Fully saturated; it will drip (or at least run down the sloped surfaces of the rafters or trusses or sheathing or metal roof material) once the water drops get large enough to overcome surface tension.”

While the conditions are there to support your theory, a visual inspection of the interior shed roof shows no rust stains. The trusses are four sided galvanized channel but the screws only penetrate the top surface. Any rust created at the drill holes would run down the inside of the channel. The metal roof sheets are factory painted on both sides.

[Bransher]

Catigale........I guess anything is possible, but I did not see anything before I power washed.

NiceAft........ Thanks for the observation. Do you think my green shirt clashes with my tan pants???

c130king........ From my research I have determined that most bird poop in my vicinity is white in color. The stain on my hat supports that research.

[K9Kampers]

Thanks for the observation. Do you think my green shirt clashes with my tan pants???

Pants? Oh... I thought... oh never mind...


Is the surface area around the stain unusually cold? Is there any unusual smoke or mist in the vicinity? What does the stain smell / taste like... putrid / fleshy / blood-like? If any of these questions answer yes, then you may have an inter-dimensional portal to h3ll at your waterline!!
Be warey cauwful with that!

[Bransher]

So, you think it may be time to call in an exorcist?

No way am I going to taste that stuff.