Removing old bitumen when blacking

[tomwillans]

I am having difficulty removing the the old blacking above the waterline. Above the water line there is a lot of old blacking which is coming off in many places in the lower layers even after the surface flakes are removed. Using the angle grinder with a wire brush seems to take it back in the most frail areas but it is starting to look like a moonscape with the poorest areas going back to the steel and the better areas stubbornly staying on and getting more polished than removed.

 

Is there a better way? I am considering a needle gun.

 

Thanks.

Tom

[Flyboy]

I've not tried it but what about trying a hot air gun & scraper.

[tomwillans]

Thanks for replying so quickly. I had not thought about a hot air gun. I am a bit worried about the insulation on the inside but will look into it.

 

Thanks.

[Bee]

Not too sure if I would bother. Above the waterline is really mostly cosmetic and you could spend an awful lot of time for not much result, bitumen is horrible to remove as you know, it melts into discs and grinding tools and clogs them, I think I would just scrape off what falls off easily and stick another coat on.

[chubby]

Me too ,

 

Scrape what comes off easily but leave the stubborn stuff on there . Why on earth would you seek to remove it - its there to protect the steel afterall . The thicker , the better i should think

Just scrape / prep where the old stuff comes off . Let it all dry out and slap on the blacking .

Edited February 11, 2017 by chubby

[pete.i]

I agree with Bee but having said that if you do not take the bitumin off fully then you are left with lumps and bumps and craters where the old bitumin still is. It depends on whether you have a shiny boat or a not so shiny one.. When I had mine done the guy used cup and twisted wire brushes and he used a lot of them. Not only do they get clogged but the wires tend to fly out like little bullets especially with the cheap ones. If you are going to use a lot of brushes then people tend to buy the cheapies. If you do use wire brushes ensure you wear full PPE. I did my roof and didn't wear eye protection and a piece of wire flew out and caught me under the eye. I only did that once. The next time I was fully geared up. Luckily I was okay but a quarter of an inch higher.

 

However you try to remove old bitumin it isn't an easy job, It took well over two full days for the guy to remove mine and I only had a 30 foot boat. Also once removed get at least one coat back on almost immediately. It's surprising how quickly rust starts to form on bare metal.

[Flyboy]

Thanks for replying so quickly. I had not thought about a hot air gun. I am a bit worried about the insulation on the inside but will look into it.

 

Thanks.

A hot air gun won't be hot enough to penetrate the plating. You can strip paint from wood without burning the wood so no problem on steel.

[Slim]

Hire a scarifier.

 

Face shield, face mask, ear defenders, gloves, disposable overalls. Horrible job but I did a 55 ' in a day. If you can get help so much the better, it's hard work. The only problem I encountered was that the teeth of the scarifier became blocked with blacking. I started off by picking it out of the teeth with a screwdriver and scriber. I discovered that a stiff brush and bowl of white spirit was much quicker.

 

As I said, I did a 55' in a day back to bare metal. Had to use a scraper and chisel in one or two places where the scarifier wouldn't fit

 

 

Frank

[dor]

my boat gets a really good pressure wash. Anything that that doesn't strip can stay there. Most of the patchy bits will be below the waterline and the bit above is going to look patchy anyway after a couple of years of touching up.

[Mike Jordan]

Haven't done it personally but I have seen it done quickly and easily with a large gas torch and a scraper. Obviously not an inside job and one requiring some care to avoid damage to paintwork.

Edited February 11, 2017 by Mike Jordan

[BWM]

I used one of those 'T' shaped scrapers with a 4" Stanley type blade, it took me two days to strip a 72' boat, complete with rivets! The only issue I had was where there were minute 'spatters' of weld which tended to snag and break the blade. No heat required.

[zenataomm]

Take your boat to the stretch of the N. Oxford between Ansty and Brinklow.

Then rock your boat side to side until it's wet as far up the sides as you can.

 

Gawd knows what they're discharging into the cut there but it should remove or at least soften your old bitumen.

[tomwillans]

Thanks for all your advice. Needle gun is out. A few bits to check out.

 

If I have to I will make her sound and live with a moonscape, but I want her to look nice. Noticed some holes breaking though in the superstructure paintwork and rust is beginning to show through on the roof which may be a priority. Painted for sale? The T scraper worked really well where the bitumen was very thin or very loose but this stuff is failing under a thick smooth top layer (it is flexing). I will let you know how I get on.

 

btw agree with PTE equipment I have a full face visor and have to keep cleaning it down due to the bits. Briefly forgot to put on my ear defenders - ouch! luckily no permanent damage, according to the docs, but was inflamation in the ear canal and a period of tinnitus.

[Machpoint005]

Thanks for all your advice. Needle gun is out. A few bits to check out.

 

If I have to I will make her sound and live with a moonscape, but I want her to look nice. Noticed some holes breaking though in the superstructure paintwork and rust is beginning to show through on the roof which may be a priority. Painted for sale? The T scraper worked really well where the bitumen was very thin or very loose but this stuff is failing under a thick smooth top layer (it is flexing). I will let you know how I get on.

 

btw agree with PTE equipment I have a full face visor and have to keep cleaning it down due to the bits. Briefly forgot to put on my ear defenders - ouch! luckily no permanent damage, according to the docs, but was inflamation in the ear canal and a period of tinnitus.

 

Inflammation in the ear canal is nothing to do with noise exposure. That affects the inner ear (only). It was likely caused by bits of sh1t from whatever you were grinding/chipping/scraping.

But do wear your ear protection, folks.

[Robbo]

I use these... http://tercoo-rotating-blaster.co.uk, they don't get the surface hot or clogged up with the blacking.

[OldGoldy]

I used a scabbler, which removed the thickest, hardened coating, but not everything. The resulting finish was a lot less 'moonscape'

 

You WILL need ear defenders, gloves and eye protection!

Edited February 11, 2017 by OldGoldy

[Grebe]

Do not forget the advice given in post no 6. Get the bare metal covered as soon as possible.

 

In my previous career when we shot-blasted steel frames we always had a maximum bare metal time of 4 hours. After that we re-blasted before coating.

[tomwillans]

I nearly got one of the rotating blaster at crick. How well do they last, was it the double you used? They seem to claim a lot. I was worried about the effect on the drill.

[cuthound]

Hire a scarifier.

Surely not.

 

https://www.amazon.co.uk/s/?ie=UTF8&keywords=scarifier&tag=googhydr-21&index=aps&hvadid=155885204345&hvpos=1t1&hvnetw=g&hvrand=6905767707960744437&hvpone=&hvptwo=&hvqmt=b&hvdev=t&hvdvcmdl=&hvlocint=&hvlocphy=1007147&hvtargid=kwd-15137680&ref=pd_sl_2k3dvpupx4_b

[Robbo]

I nearly got one of the rotating blaster at crick. How well do they last, was it the double you used? They seem to claim a lot. I was worried about the effect on the drill.

Don't use pressure is the key let the tool do the work, if you use too pressure you loose the tips. It's also only to be used on flat surfaces, so no getting in corners, etc.

I used a scabbler, which removed the thickest, hardened coating, but not everything. The resulting finish was a lot less 'moonscape'

 

You WILL need ear defenders, gloves and eye protection!

I've seen a scabbler work on the top paint, how well does it work on tar based paint? I thought it would clog up.

[OldGoldy]

Don't use pressure is the key let the tool do the work, if you use too pressure you loose the tips. It's also only to be used on flat surfaces, so no getting in corners, etc.

 

I've seen a scabbler work on the top paint, how well does it work on tar based paint? I thought it would clog up.

 

I used a WhirlAway, an american attachment for an angle grinder, but still a scabbler. It removed the thick, hardened bitumen, but just skated over the surface of a single layer. (possibly as a needle gun chips away at thickened old paint or rust, but ineffective on thin layers) - At no time did it clog, but it didn't like the odd spots of weld or splatter that it found!

[ditchcrawler]

I used one of those 'T' shaped scrapers with a 4" Stanley type blade, it took me two days to strip a 72' boat, complete with rivets! The only issue I had was where there were minute 'spatters' of weld which tended to snag and break the blade. No heat required.

Riveted and welded?

Do not forget the advice given in post no 6. Get the bare metal covered as soon as possible.

 

In my previous career when we shot-blasted steel frames we always had a maximum bare metal time of 4 hours. After that we re-blasted before coating.

Very true, nothing like a bit of shiny steel to start rusting.

[tomwillans]

Thanks everyone. I have decided to see how it goes with a rotating blaster and let you know how I get on.

[WotEver]

Thanks everyone. I have decided to see how it goes with a rotating blaster and let you know how I get on.

If you mean the Perago type heed the advice earlier to not 'push' onto the steel. Let the tips do the work.

[BWM]

Riveted and welded?

Very true, nothing like a bit of shiny steel to start rusting.

Yes, boat was in for refooting, rebottoming, knee repairs and has been partially converted - all these procedures have left some evidence..

The most annoying of which is on the porthole glass!

Edited February 13, 2017 by BWM