Is this white stuff on the hull mold?

[SeaGnu]

It's my first time posting here. So hello, everyone! 😊👋

I have this problem I can't seem to find an answer for. I found some white stuff on the fiberglass behind the liners in the bow cabin. Is it mold?

I have tried searching for an answer without any luck. So, I'm trying my luck and hoping someone here knows what it is. 😁👍

[Bill O]

Never really seen mold/fungal hyphae that white on a dry surface. Is it hard? Then possibly glue residue from a fabric liner.

Would wipe the area w/some vinegar. If it doesn't remove it, then would rule out salt film or mold.

[Pandor]

Looks like salt deposits.

[SeaGnu]

Originally Posted by Bill O

Never really seen mold/fungal hyphae that white on a dry surface. Is it hard? Then possibly glue residue from a fabric liner.

Would wipe the area w/some vinegar. If it doesn't remove it, then would rule out salt film or mold.

Thanks for the tip Bill O! I will try wiping with vinegar. 👍

Yes, it's quite hard and brittle. It's like chalk in the consistency. I already wiped the area with soapy water, but nothing happened. However, I could scratch it away with my nail.

I wonder if it's mold because the plywood liners I removed were black and moldy on the backside. So perhaps the mold had also grown on the walls themselves. But maybe it could also be a reaction from the polyester being moist for a long time?

[JPA Cate]

Hi, Sea Gnu,

The black stuff on the inside of the plywood may well be mold. If it is, wiping it down with vinegar, should show you if it is: some of the black will come off onto your cleaning rag, and you will be able to tell a difference between where you wiped it and didn't wipe it yet.

The white crusty deposit is more likely to be salt. Taste a tiny bit and see if it tastes salty. Try to avoid swallowing it. I would have thought if it had been salt, it would have dissolved when you wiped it down with soapy water.

I think it is mess left from the construction of the boat, and does not constitute "dirt". That said, if you want to remove it, try using plain water or vinegar, and a very stiff scrub brush. Another way would be to use a wire brush on it, but then the bits will get airborne and penetrate the fabrics, and you won't be happy with that, as they seem quite clean.

If you are planning to put the liner back, just leave it and move onto something more fun. If you are planning to paint it with matte paint, or semi-gloss, a very light sanding is in order, prior to painting, enough to rough up and give tooth to the paint that will go over the gelcoat. Matte paint will show the fiberglass roving less; semi-gloss is easier to wipe down. For me, the choice would be made on the basis of whether or not I wanted it lighter in the boat. Some boats can be dark and cavy, and the use of light paint below can brighten that look considerably; others are just fine without; and it is largely a matter of personal taste, anyway, imo. Something else you could consider, would be a thin layer of insulation, which overall, helps keep down mold proliferation in hidden places.

Ann

[SeaGnu]

Originally Posted by JPA Cate

Hi, Sea Gnu,

The black stuff on the inside of the plywood may well be mold. If it is, wiping it down with vinegar, should show you if it is: some of the black will come off onto your cleaning rag, and you will be able to tell a difference between where you wiped it and didn't wipe it yet.

The white crusty deposit is more likely to be salt. Taste a tiny bit and see if it tastes salty. Try to avoid swallowing it. I would have thought if it had been salt, it would have dissolved when you wiped it down with soapy water.

I think it is mess left from the construction of the boat, and does not constitute "dirt". That said, if you want to remove it, try using plain water or vinegar, and a very stiff scrub brush. Another way would be to use a wire brush on it, but then the bits will get airborne and penetrate the fabrics, and you won't be happy with that, as they seem quite clean.

If you are planning to put the liner back, just leave it and move onto something more fun. If you are planning to paint it with matte paint, or semi-gloss, a very light sanding is in order, prior to painting, enough to rough up and give tooth to the paint that will go over the gelcoat. Matte paint will show the fiberglass roving less; semi-gloss is easier to wipe down. For me, the choice would be made on the basis of whether or not I wanted it lighter in the boat. Some boats can be dark and cavy, and the use of light paint below can brighten that look considerably; others are just fine without; and it is largely a matter of personal taste, anyway, imo. Something else you could consider, would be a thin layer of insulation, which overall, helps keep down mold proliferation in hidden places.

Ann

Wow, I really appreciate your helpful reply! 🤗 Thanks for taking the time to help me out.

I hadn't thought of painting the hull, but that's a totally valid option. Maybe I could apply some light filler, and sand a bit before painting. I'll definitely give that some thought. I had considered insulating the hull with something like Armaflex, but since the boat will be moved from Arctic to tropical waters, I assumed that wouldn't be necessary.

My plan is to try and wash it away with vinegar first. If it doesn't come off at all, I will assume it's a mess from production as you say, and ignore it. If I choose to paint, or make new plywood liners however, I will have to make a decision!

Thanks again for your help!

[Pete7]

Originally Posted by SeaGnu

I had considered insulating the hull with something like Armaflex, but since the boat will be moved from Arctic to tropical waters, I assumed that wouldn't be necessary.

Won't insulation help to keep the heat out of the inside in the tropics? Seems a shame that whilst you have the hull exposed not to make an effort to insulate.

Pete

[Bill O]

Pete beat me to it about insulating the hull from heat penetration.

Also if you can add insulation under the deck, this will be the most helpful to keep heat out of the boat (especially if you have teak decks).

[SeaGnu]

Originally Posted by Pete7

Won't insulation help to keep the heat out of the inside in the tropics? Seems a shame that whilst you have the hull exposed not to make an effort to insulate.

Pete

Originally Posted by Bill O

Pete beat me to it about insulating the hull from heat penetration.

Also if you can add insulation under the deck, this will be the most helpful to keep heat out of the boat (especially if you have teak decks).

Thanks for the advice, Pete and Bill. I had not thought about the heat in the boat being an issue, but your suggestion has definitely given me some food for thought. 😁👍

[Pete7]

There have been days at 50'N that I wished we had done ours The only thing putting me off is getting all the nice woodwork back without damaging it.

Pete

[SeaGnu]

Originally Posted by Pete7

There have been days at 50'N that I wished we had done ours The only thing putting me off is getting all the nice woodwork back without damaging it.

Pete

Thank you for your thoughts, Pete! I'm grateful for your insight.

I'm not prepared to take down the cabinets and overhead lining yet, as I'm sure that would be a very involved project. I'm hoping I can avoid it if possible. 😄👍

I came across this photo on a Norwegian boat forum of someone who insulated their hull on their Bavaria. It looks great, however, only insulating the exposed hull won't address my condensation issue behind the cabinets and above the ceiling liner.



I'd love to know, though, how much of an issue condensation is in the Mediterranean and Caribbean? Do you have experience with it?