Brown/ black scaly hull marks - how to remove??

[Soggytreehugger]

Hi, I have some really stubborn hard scaly marks on the hull just down from the gunnel, well clear of the waterline. They are raised.

anyone have any idea what might be??

and how to remove? I feel like I want to give a good scrape but that would damage gel coat.

Thanks
Rachel

 

[Concerto]

Welcome to the forum.

A little bit more detail of the boat and a photo would assist us a lot to be able to give the correct advice.

Have you tried anything yet. My initial thought would be to put on some rubber gloves, then soak some towelling in neat bleach and hold it on the affected area. Hold for 5 minutes and see if that has softened or dropped off. If your boat is in the water, use another cloth to wash the bleach off trying not to allow any bleach in the water.

 

[William_H]

If it is raised then careful use of a sharp chisel might remove much of it. Gel coat should be fairly tough but be careful. The thing is, if it has a build up, so fairly thick chemical cleaning will have a lot of bulk to dissolve. Once you have removed the bulk (or if you decide not to chisel) then I would suggest a regime starting with detergent then try bleach followed by oxalic acid and lastly acetone. My guess is that it is rubber from a rub up against a tire or similar fender. In which case go to acetone first. ol'will

 

[Stemar]

Is it a lichen? They can stick like the proverbial to a blanket. One suggestion I've seen is to soak it in IPA (the alcohol, not the beer) and it'll die and drop off. If you decide to scrape, round the edges of the scraper so they don't dig in

 

[johnalison]

I would start with the solvent approach described above and progress from cloth through to scraping. In the end it doesn’t really matter if you rough up the gel coat a bit as it is not hard to polish out, even if 1200 grade sandpaper is used.

 

[Soggytreehugger]

Thank you everyone, I didn’t see your replies until just now. I tried Concerto’s bleach suggestion first thing and it worked a treat! Thank you, good to know about 1200 grit paper & chisel suggestions too, ‘gel coat’ sounds very sensitive but I must not be afraid!!

I still have no idea what it was, pics attached though if you are interested

thank you so much
Rachel

 

[Soggytreehugger]

Can’t seem to add photos

 

[Concerto]

Rachel.

It was probably a fungal growth which came from a tree.

Gel coat thickness depends on how it was applied in the mould. If your boat is from about 1990 or earlier, then it most likely has brushed on gel coat and will be 1 to 2mm thick, except Westerly who used a double coat and this is 2 to 3mm thick. You may find the PowerPoint presentation I created worth reading.
https://wiki.westerly-owners.co.uk/images/8/86/Gel_coat_renovation_19May2020.pdf

My Westerly Fulmar Concerto has undergone massive renovations over the past 8 years and will be at the Southampton Boat Show in September as the Westerly Owners Association boat at the show. To get an appreciation of the changes have a look at this presentation I made to a RYA Conference just before Covid hit.If you are going to the show, I will be on board most of the time so you can have a chat.
https://wiki.westerly-owners.co.uk/images/3/3f/Concerto.pdf

 

[Soggytreehugger]

Rachel.

It was probably a fungal growth which came from a tree.

Gel coat thickness depends on how it was applied in the mould. If your boat is from about 1990 or earlier, then it most likely has brushed on gel coat and will be 1 to 2mm thick, except Westerly who used a double coat and this is 2 to 3mm thick. You may find the PowerPoint presentation I created worth reading.
https://wiki.westerly-owners.co.uk/images/8/86/Gel_coat_renovation_19May2020.pdf

My Westerly Fulmar Concerto has undergone massive renovations over the past 8 years and will be at the Southampton Boat Show in September as the Westerly Owners Association boat at the show. To get an appreciation of the changes have a look at this presentation I made to a RYA Conference just before Covid hit.If you are going to the show, I will be on board most of the time so you can have a chat.
https://wiki.westerly-owners.co.uk/images/3/3f/Concerto.pdf

thanks Concerto that’s interesting, I need to look in to the Fisher Freeward spec. I’ll join the association. Good luck with the show, hope all goes well. We’ll be doing quite alot of renovation over the next few years so I’ll check out. Thank you very much.
Rachel

 

[johnalison]

thanks Concerto that’s interesting, I need to look in to the Fisher Freeward spec. I’ll join the association. Good luck with the show, hope all goes well. We’ll be doing quite alot of renovation over the next few years so I’ll check out. Thank you very much.
Rachel

Just out of interest. Are you soggy or do you only hug soggy trees?

 

[Soggytreehugger]

Just out of interest. Are you soggy or do you only hug soggy trees?

Mostly the former but I’d never rule out the latter, true wet woodlands are hard to come by in the UK!!