Advice Sought - Removing / Grinding Horiztontal Deck Welds

[PaulRainbow]

Looking at the photos ,it would appear that the rail is not solid but probably a U section. I am guessing this by the holes drilled in the top of the rails.
Hope for your sake that this is the case, as it will make the job a lot easier.

Surprisingly no one has suggested hiring a hefty angle grinder , at least a 150 mm wheel size. which will be big enough for the job and relatively easy to handle. Firstly I would cut vertically down the cross section of the rails to divide them into sections, about 400 long and then cut along the bottom of the outside face,as close to the deck as practical. Then cut along the back face but not all the way through, you might then be able to lever each length off ,(saves a lot of work.)
Then swap your cutting disc for a coarse grinding disc, and clean up the remaining welds, finish off with a finer disc .
Be very aware of safety ,, don't take chances wear proper gear .
Get plenty discs from the hire place, normally they will only charge you for what you use.
I have done this type of work very often ... don't envy you!


Awaiting incoming.

Well done for actually reading the OP

 

[Blue Seas]

Paddys milestone is a viable method. But there is a lot of awkward corners there for someone not familiar with hefty grinders so lots of opportunity for kick-back and accidents. Personally I would cut down vertically as Paddy says and then get someone decent with a gas torch (Oxy acetylene)) to run along the bottom (assuming you can get access to the deckhead below for a fire-watcher). Couple of hours tops and a big saving on discs / effort. Remove all flam stuff and use wet blankets to limit spread.

 

[MisterBaxter]

I would definitely try and get 110/240v tools to the job not cordless. I echo everything that's been said re fire risk, and I would really emphasise the physical discomfort of a job like this - you need big knee pads, tough overalls, long, thick leather gloves (welder's gloves are good) serious eye protection with no gaps down the sides (ie goggles not safety glasses) and proper ear protection. I'd wear earplugs inside ear defenders myself. And a really good mask, not just a casual paper mask but a chunky filter cartridge one. And some kind of hat to protect your hair too.
I think you'll end up kneeling on the deck with the tool braced against a knee, rather than just waving it about at arm's length - you can control it much better that way, especially if you go bigger in terms of disc size.

 

[thinwater]

Looking at the photos ,it would appear that the rail is not solid but probably a U section. I am guessing this by the holes drilled in the top of the rails.
Hope for your sake that this is the case, as it will make the job a lot easier.

Surprisingly no one has suggested hiring a hefty angle grinder , at least a 150 mm wheel size. which will be big enough for the job and relatively easy to handle. Firstly I would cut vertically down the cross section of the rails to divide them into sections, about 400 long and then cut along the bottom of the outside face,as close to the deck as practical. Then cut along the back face but not all the way through, you might then be able to lever each length off ,(saves a lot of work.)
Then swap your cutting disc for a coarse grinding disc, and clean up the remaining welds, finish off with a finer disc .
Be very aware of safety ,, don't take chances wear proper gear .
Get plenty discs from the hire place, normally they will only charge you for what you use.
I have done this type of work very often ... don't envy you!


Awaiting incoming.

Yes, all of that^^. But with the amount of grinding, cup brushing, and flap disk sanding this boat will need, I'd go larger, maybe 7" (180 mm). Not cordless, and I would buy it. A good one is only $150. Also a good corded 4.5-5" grinder for many, many smaller things. You're going to live with these. Metabo, Makita, Bosch, DeWalt, or equivalent.

I've spent a good many hours with a 9" grinder, but that is probably more than you need and they can be hard to handle. You wouldn't use it often enough to warrant.

 

[Paddys milestone]

Another couple of points, looking at the photo, it might be that the rails have been tack welded? Difficult to confirm from the image. If so this would make the job easier.
Also it it was gas welded rather than Arc welded,(or Migged or tigged ) the weld will be much softer and easier to grind.

Just a thought?

 

[DownWest]

Are we looking at a section with wood decking up against it? Is it welded under the wood? If so, complicates matters.
I would also go with a smallish grinder. 125mm and thin discs. Far easier to control in awkward places.

 

[MisterBaxter]

Honestly you wouldn't regret having two grinders for this job, a big one for blasting through the straightforward bits with easy access, and a little one for the fiddly bits. In my experience a non-cordless angle grinder is one of the power tools that it's safe enough to get secondhand, they're so simple in terms of the mechanicals there isn't much to go wrong, so you could grab a couple of decent quality ones on eBay for the price of one new one.

 

[Wansworth]

With your boat you will need a whole range of good tools and safety equipment ,my four inch angle grinder is still going…..25 years later!

 

[Rum Run]

Just to reiterate the fire risk - I have set far more stuff on fire with a grinder than by welding, mainly my own overalls or trousers . Don't keep a lighter in your pocket either, unless you really like hospital food (not me, H&S pamphlet from the early 80's). Having a spotter is good, though that did not stop a chap I once worked for setting fire to a quarry conveyor while they were 30' up over a loading bay.
Have fun!

 

[DownWest]

Honestly you wouldn't regret having two grinders for this job, a big one for blasting through the straightforward bits with easy access, and a little one for the fiddly bits. In my experience a non-cordless angle grinder is one of the power tools that it's safe enough to get secondhand, they're so simple in terms of the mechanicals there isn't much to go wrong, so you could grab a couple of decent quality ones on eBay for the price of one new one.

As the OP says he has little experience with such tools, a 2000wt 230mm angle grinder is quite a tool for getting it wrong, painfully... hence the idea of starting smaller.
My De Walt 115 is 25yrs old and used everday, but I was very unimpressed with a DW hand drill bought more recently that quit just outside the warranty. Looked inside and very low quality, so binned it.
I have had a 230 Ryobi for 19yrs and while it is heavy, it does the job with no hassles, just a new trigger switch recently.

 

[DownWest]

Just to reiterate the fire risk - I have set far more stuff on fire with a grinder than by welding, mainly my own overalls or trousers . Don't keep a lighter in your pocket either, unless you really like hospital food (not me, H&S pamphlet from the early 80's). Having a spotter is good, though that did not stop a chap I once worked for setting fire to a quarry conveyor while they were 30' up over a loading bay.
Have fun!

Agree, bloke working for me set his tee shirt on fire with a little angle grinder.. Patted it out, but it restarted as the cloth was synthetic. Pulled it off quickly, but burned the hairs in his nose, so everything smelled of that for a bit.

 

[DownWest]

Oh... On fires from welding. We went to Expo 92 in Sevilla. Great fun. But as we walked into the area, there was a delapitated burned out building. Obviously an exibit that went wrong.
Bit later, I was in a queue for a cash machine and got talking to a skirted bloke from the pacific (great hair!). His exibit had also burned and and they had a quick rebuild with a simpler theme. He had obviously travelled, but most of his crew had never left the islands. Planes were silver things in the sky and the idea of another language...
Both his fire and the other building were caused by Brit welders...

 

[MisterBaxter]

As the OP says he has little experience with such tools, a 2000wt 230mm angle grinder is quite a tool for getting it wrong, painfully... hence the idea of starting smaller.
My De Walt 115 is 25yrs old and used everday, but I was very unimpressed with a DW hand drill bought more recently that quit just outside the warranty. Looked inside and very low quality, so binned it.
I have had a 230 Ryobi for 19yrs and while it is heavy, it does the job with no hassles, just a new trigger switch recently.

Yes - I guess I was thinking about something like a 4.5" and a 7".

 

[Wansworth]

Oh... On fires from welding. We went to Expo 92 in Sevilla. Great fun. But as we walked into the area, there was a delapitated burned out building. Obviously an exibit that went wrong.
Bit later, I was in a queue for a cash machine and got talking to a skirted bloke from the pacific (great hair!). His exibit had also burned and and they had a quick rebuild with a simpler theme. He had obviously travelled, but most of his crew had never left the islands. Planes were silver things in the sky and the idea of another language...
Both his fire and the other building were caused by Brit welders...

The Opera house in Barcelona caught fire due to sparks meeting oily rags……Something similar with Norte Dame in Paris

 

[AntarcticPilot]

The Opera house in Barcelona caught fire due to sparks meeting oily rags……Something similar with Norte Dame in Paris

No need for sparks with oily rags, if it's a drying oil.

 

[jon and michie]

Get the right ppe for starters - mask, goggles, gloves & ear protection
cover any glass in the area ie wheel house - have fire extinguisher and preferably fire watcher take not of the direction of the sparks.
try not to dig into the weld that you want to remove or you will end up with gashes in the steel - let the grinder do the work without putting too much pressure on the disc.

 

[DownWest]

No need for sparks with oily rags, if it's a drying oil.

Veg oil, like linseed. Known problem for Luthieres

 

[KochADV]

Yes, perfectly feasible to grind the welds flat, its what most welders do all day long
Yes, two step is probably easier
No, sounds like a sensible approach, other option could be get a cheap Plasma cutter but then you also need a compressor
Yes, get a welding blanket or cheaper option is a fire blanket
Tools: If you havent used one before stick with the smaller 115/125mm grinders, big ones are great but can be a bit of a beast to handle until you get used to them, and access is better with the smaller ones, battery operated is OK if you buy into a particular tool range and get a good few batteries, mains is better if available - we use Ryobi battery powered tools all day long in and out of the workshop but angle grinders will eat batteries very fast, even the big ones
Both DeWalt and Milwaukee make flat head angle grinders which are great for restricted access, but pricey
Get decent quality grinding discs and flap wheel discs, ceramic / zirconia ones, the best discs are probably 3M Cubitron which are expensive but remove metal at a fair old rate and get some Norton Blaze Rapid Strip discs for finishing / polishing where the weld was
Dont forget decent PPE - proper mask, googles, gloves, and as above - knee pads

Hi Dingghyman thanks for ur detailed advice. Exceptionally helpful, this will get me going. Did some interet window shopping and think i am good to go.

Cheers
Rich

 

[KochADV]

Do want to cut at the bottom then lift the wheelhouse off with a crane, or are you cutting in sections. Is the boat on the water. With you being so close to other boats you need to inform the owners of your intentions as one spark off grinding on fibreglass will mark it .

Hi Seastoke... the wheelhouse will stay. Only the steel rail that has been welded around the wheelhouse will be removed. That is the footprint for the previous owners planned wheelhouse.

I will speak to the harbourmaster. I am kind of alone in a corner with a stone retaining wall so should be ok... but well noted thanks!

 

[KochADV]

Can I not give a new poster my experience in fabrication of steel structures over many years as you do with your claimed experience

I was taught stick and gas welding longer than you claim but it's not me or you are doing the welding it an unknown previous owner.

I currently have my own MIG and TIG welding kit in by workshop and al I no longer need to work to earn money I fiddle in my workshop and garage with boat and my classic cars o have plenty of time for make all kinds of fittings and equipment for boats and classic cars

The question really is why you are raising issues with my posts all the time you are you hoping to intimidate me to stop posting.

I have seen many knowledgeable members stop posting for this kind of comments. It's just unnecessary bickering and not productive

Roger... my first priority is to stabilise the steel and aluminium. There is a rotting corner of the wheelhouse that needs to be fixed. And given the wheelhouse is stripped i should probably check the steel to aluminium insulation. If ur set up and ibterested to do freelance work would be good to chat. Cheers