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Over plating, MIG, TIG or MMA? (first timer)


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Which type of welding is best suited to boats? I have been looking at some boats on the walk down the canal home and it would appear that some have concave welds and some convex, will MIG welding be ok for over plating below and above the water line? how bigger plate should I use? what type of machine should I use? is there any process used in over plating to attach the plates other than the welds all the way round?

Thanks.

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Hi kida.

 

All depends on your pocket for a welder, for slight rusty steel them Arc is best, if you can clean it back dam good them Mig is best as doing Arc upsdie down is anohter art that is not easy to do, never mind Mig upside down..

 

Thickness of steel you will want to use at a guess 4mm then i would get a good the best rig you can for the duty cycle, the longer cycle the better. A 200amp will do but for thicker then a 250amp but then you go to 3 phase for power, 200amp is pushing single phase supply at full wack. 

 

The bigger the amp of the rig the better your chance for a longer duty cycle ;)

I would look to spend over £500 for a good one, more than that then better still.

 

Parweld and Portamig are good gear

 

http://www.weldequip.com/mig-welders.htm

 

 

 

 

 

 

 

 

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56 minutes ago, firstboat said:

Which type of welding is best suited to boats? I have been looking at some boats on the walk down the canal home and it would appear that some have concave welds and some convex, will MIG welding be ok for over plating below and above the water line? how bigger plate should I use? what type of machine should I use? is there any process used in over plating to attach the plates other than the welds all the way round?

Thanks.

If I had to ask those questions I wouldn’t trust my welding for overplating, I would want an experienced welder to do it.  It’s not worth cheaping out on a job like that.

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In a workshop, with clean steel, mig (often actually mag) is fantastic as well as easier for a beginner to get an ok weld. However as said, it's poorly suited to outdoor work as while small odd jobs can be done, any wind will take away the sheild leaving an appalling weld.

Stick/arc/mma is more tolerant of imperfect prep and much less effected by wind, if harder to to master. Welding sets are a bit cheaper and have less wear parts.

Never heard of Tig being used on a narrowboat although I'm sure it has. More common for thinner gauges and stainless/ali.

 

Equally I do wonder, if you are asking these questions what your experience is. I can weld reasonable well for someone who basically doesn't weld and has limited tuition, enough to put in a skylight, make an engine mount, or secure a bracket to the hull, but I wouldn't tackle replating a boat.

 

Daniel

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Doubling plates on the bottom must be plug welded to the original baseplate along the bottom of the boat so that the new plates are structurally supported and cannot flex away from the original plate. 

It must be difficult to get a good fit on curved sections and you will probably not know if there are voids and if all your welding work is truly water tight.

It's a job for a specialist.

JP

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1 hour ago, Tony Brooks said:

Me neither and I had to pass a welding trade test as a youngster.

happy to cobble non-structural parts for the boat together but hulls are another thing altogether.

Me as well, I did a night school welding course, conclusion was that my welds were structurally sound, ugly and if doing a long run would have a few pin hole leaks, especially where I changed rods.  Not what you want for overplating.

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I have had much of my barges bilges (rounded) and bottom overplayed in the last10 years and it has always been done by the shipyard welders using rods. The steel is 5.5mm. They cut a number of holes in the new plate to weld to the bottom as well as the edges the plates being 3.8 m wide. The last time a Romanian welder who had been shipyard trained made such a good job that the other welders came to admire his work, I was very pleased.

By the way my barge is 100 years old and was originally made of 5.5mm steel. Parts of the bottom had gone below 4 mm and the starboard bilge towards the stern down to 3 mm in places. Rubbed through over the years.

Docking in sept for insurance survey so hope no mor work needed.

david

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3 hours ago, firstboat said:

Which type of welding is best suited to boats? I have been looking at some boats on the walk down the canal home and it would appear that some have concave welds and some convex, will MIG welding be ok for over plating below and above the water line? how bigger plate should I use? what type of machine should I use? is there any process used in over plating to attach the plates other than the welds all the way round?

Thanks.

hi what is the age of your boat is it a steel iron or mild steel

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i have just over plated my 1936 using both stick and mig , stick for mild to old steel hull, i used 7018 low hydrogen rods as 6013 tend to burn to hot and will laminte / fracture and you have to peen for you life to destress welds , i carried out a few test prior to starting the  job to get best match rods in a fracture test 6013 were very brittle whilst 7018 were very ductile , the new base to new side mig welded to save time as my boat is 21.6 mtrs long which is a lot of welding and normal modern day mild is fine with mig , mig in wind over 4-5 miles an hour you will probably get porosity unless you use flux cored wire 

, concave welding is bad mayby vertical downhand , should be convex , plate size depends on your pockets iv used 10mm base 6mm walls which i believe is the standard used on modern boats now but you could use 8mm depending how bad your base has worn / overplating fully weld , there are diffrent way to weld base you can place plates on floor fully weld top then place boat on to plates put sides on weld then lift v out underside weld overhead , i didnt have that option so on stands fitted base plates welded sides , then v out base underside root run 2 run then capping run full penetration , rather that puddle weld as the boat is 80 years old even though was only a few places where it was 4mm thick , i cut holes in floor welded tubes through to new floor then plated over to sandwhich old floor this allowed me to support the new floor and keep level underside , iv also put 50mm x 12mm flat bar around base to side wall to act as ware plate and triple up on welded joint , if you use stick you can get decent invertor welding sets for £200-£250 200 amp can use 3.25 or 4mm rods  np at all

Edited by kevin123
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Thanks for your input, the bit I'm actually thinking about doing is only a couple of patch repair jobs above the water line and welding on my own anodes though its interesting to hear the responses for the whole picture.

The boat is 1988 mild steel originally 4mm thick but down to small holes near the gas locker as someone added a shelf  to the gas locker in the past and it has collected water and not done the joint to the hull any favours.

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7 hours ago, firstboat said:

Thanks for your input, the bit I'm actually thinking about doing is only a couple of patch repair jobs above the water line and welding on my own anodes though its interesting to hear the responses for the whole picture.

The boat is 1988 mild steel originally 4mm thick but down to small holes near the gas locker as someone added a shelf  to the gas locker in the past and it has collected water and not done the joint to the hull any favours.

Go for Mig, just gtesome practice done untill you get good length runs. Mig is best as you can grind back and try again, as with Stick/Arc it leaves slag behind and that just cocks up the whole job and the whole weld will need grinding back to get rid of the slag in between the messy weld.

If it is only a small few areas i can recomend this rig that i have . it will do the job and you have all three, Tig, Mig and Stick to play with. The Tig is not HF start but still dam good. 

It was my last rig so i can vouch for them being good, shop around but dont forget the cost of the extras like a good auto mask gloves etc etc , gas, BOC do a good deal with the Volkzone deal. I pay about £90 rent and £35 refill for a 20l Argon. 

If you have a frindlt pub then as you are ding above water line then you can use drinks pub gas CO2 gas, i used it for years on my cars and is fine, even on building winch bumpers, it is not as pure a gas as commercial but a help of a lot cheaper at about £10 a 10l cylinder with no rent. 

 

https://www.unitedwelding.co.uk/thermal-arc-fabricator-181i-multi-process-inverter-package-230v-ce-for-mig--tig--arc-welding-168-p.asp

 

 

Good luck, it is a joy to learn a new skill ;) 

 

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I can't weld but I'm always interested to hear what experts have to say.  I had this conversation with the late Bob French (of French & Peel) some years ago and he maintained there was no place for MIG welding below the waterline and other welders I have spoken to have said though MIG welding is great, don't use it routinely for anything that has to be watertight.  I emphasise not my opinion, just repeating what others have said.  No doubt there are respected boat builders out there using MIG.

I suspect there's a few members on here who often contemplate learning to (stick) weld, I have a question for those who have learned - is it one of those "motor skills" that once learned you never forget eg like riding a bike, or do you have to stay "in practice"? 

 

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7 hours ago, firstboat said:

Thanks for your input, the bit I'm actually thinking about doing is only a couple of patch repair jobs above the water line and welding on my own anodes though its interesting to hear the responses for the whole picture.

I'm a first timer and needed to fill in a few skin fittings and structural frames, etc.  I went for MIG as it's meant to be the easiest, mine is no-gas / gas version.  I find no-gas is a lot easier.    It's well worth getting a half decent one if you have the urge as it's quite satisfying, however you may find getting someone to do it cheaper and better work.

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Fair enough. While I would never overplate a while boat and we have not needed patches, I have changed anodes and welded up some poorly designed above waterline deck drains, all done with a 160amp inverter mig, in drydock or on a still day. For small areas you can take the time to achieve the required cleanliness for mig. Some recommendation gasless mig for outdoor work, but I have not personal experience.

I have an Esab Caddy 160i from weldequip, their recommend regulator, BOC I'm volkzone deal. Not the cheapest, but nice to use and can get refills with ease.

 

Daniel

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2 hours ago, Neil2 said:

I can't weld but I'm always interested to hear what experts have to say.  I had this conversation with the late Bob French (of French & Peel) some years ago and he maintained there was no place for MIG welding below the waterline and other welders I have spoken to have said though MIG welding is great, don't use it routinely for anything that has to be watertight.  I emphasise not my opinion, just repeating what others have said.  No doubt there are respected boat builders out there using MIG.

I suspect there's a few members on here who often contemplate learning to (stick) weld, I have a question for those who have learned - is it one of those "motor skills" that once learned you never forget eg like riding a bike, or do you have to stay "in practice"? 

 

Used Arc Welder for the Hull of my  70 Foot Narrow Boat,and Mig for the Superstructure,I too have heard of Mig Welds liable to Porosity.

Boat was built 21 Years ago and has thus far had no Leaks:)

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5 hours ago, Neil2 said:

 

I suspect there's a few members on here who often contemplate learning to (stick) weld, I have a question for those who have learned - is it one of those "motor skills" that once learned you never forget eg like riding a bike, or do you have to stay "in practice"? 

 

As an apprentice I took six month of welding lessons consisting of arc (MMA), gas, and gas brazing and bronze welding. As this was for a motor trade trade test I concentrated on gas and braze but could make a decent looking run of MMA. (nothing clever like welding backwards or overhead). Jump forward about 50 years and the end fell off my "hire boat" stern fender. Much to  my surprise I managed to weld a new end plate into it using a Lidle arc welder. Much to my surprise it stuck and is still in place three years on. However if one of my students had produced the result pre-fettling it would have been justifiably called "sparrow crap" . So once you have the basics you will always have a rough idea of how to set up the welder, the size of rod to choose and what weld defects look like BUT in my view to do a neat job you do need to keep your hand in or do several hours practice before doing the actual job.

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18 hours ago, firstboat said:

Thanks for your input, the bit I'm actually thinking about doing is only a couple of patch repair jobs above the water line and welding on my own anodes though its interesting to hear the responses for the whole picture.

The boat is 1988 mild steel originally 4mm thick but down to small holes near the gas locker as someone added a shelf  to the gas locker in the past and it has collected water and not done the joint to the hull any favours.

depending how big a job and your welding experience , above water line just minor repairs mig will be fine on your boat , if you havent welded before practice iv taught people to weld with mig in about 20 mins and they would be fine to horizontal weld ( thats why they call it monkey wire ) as it can be picked up quite quickly if you have to do vertical and havent had much experence you could pulse weld , meaning start weld with a spot weld and repeat in about 1-2 second intervals moving slowly vertical allow weld puddle to cool then repeat , it will keep weld from dropping away and looking like bird  sh.. t  i believe the term is lol ,but practice first good luck

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10 hours ago, Neil2 said:

I can't weld but I'm always interested to hear what experts have to say.  I had this conversation with the late Bob French (of French & Peel) some years ago and he maintained there was no place for MIG welding below the waterline and other welders I have spoken to have said though MIG welding is great, don't use it routinely for anything that has to be watertight.  I emphasise not my opinion, just repeating what others have said.  No doubt there are respected boat builders out there using MIG.

I suspect there's a few members on here who often contemplate learning to (stick) weld, I have a question for those who have learned - is it one of those "motor skills" that once learned you never forget eg like riding a bike, or do you have to stay "in practice"? 

 

iv been welding 30 some years and if i dont weld for while it is like riding a bike on easier welds like horizontal but vertical and overhead you would need a bit of time just to angles and flow rates but you soon back into it ,also depending which rods you use can make a diffrence like iv said iv been using low hydrogen rods 7018 which i took to like duck to water, but one of my work pals carnt use but is fine with standard 6013

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8 hours ago, cereal tiller said:

I too have heard of Mig Welds liable to Porosity.

My understanding is that while you can get porosity and or a pinhole in a weld created with a mig welder, its rare and certainly not something you would expect in a mig weld.

Porosity: http://www.steelconstruction.info/File:800px-Weld_defects_-_Surface_porosity.jpg
Cross section: https://makemoneywelding.com/wp-content/uploads/2015/07/porous-weld.jpg
Extreme example: https://makemoneywelding.com/wp-content/uploads/2013/04/welding-porosity.jpg

Given the number of things that are mig-welded these days (almost everything thats welded...) including only from my own personally experience, the hydraulic tanks of every telescopic handler JCB has ever made, if its good enough to hold thin hydraulic fluid at 80degrees and 3bar for 20 years, it will probably keep the Trent and Mersey out 2ft6 under.

 

Daniel

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5 minutes ago, DHutch said:

My understanding is that while you can get porosity and or a pinhole in a weld created with a mig welder, its rare and certainly not something you would expect in a mig weld.

Porosity: http://www.steelconstruction.info/File:800px-Weld_defects_-_Surface_porosity.jpg
Cross section: https://makemoneywelding.com/wp-content/uploads/2015/07/porous-weld.jpg
Extreme example: https://makemoneywelding.com/wp-content/uploads/2013/04/welding-porosity.jpg

Given the number of things that are mig-welded these days (almost everything thats welded...) including only from my own personally experience, the hydraulic tanks of every telescopic handler JCB has ever made, if its good enough to hold thin hydraulic fluid at 80degrees and 3bar for 20 years, it will probably keep the Trent and Mersey out 2ft6 under.

 

Daniel

Agreed,have always considered that that those porous Welds were likely caused by the Gas shield being lost by Wind or poor pressure.have never had the problem myself.

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3 minutes ago, DHutch said:

My understanding is that while you can get porosity and or a pinhole in a weld created with a mig welder, its rare and certainly not something you would expect in a mig weld.

Porosity: http://www.steelconstruction.info/File:800px-Weld_defects_-_Surface_porosity.jpg
Cross section: https://makemoneywelding.com/wp-content/uploads/2015/07/porous-weld.jpg
Extreme example: https://makemoneywelding.com/wp-content/uploads/2013/04/welding-porosity.jpg

Given the number of things that are mig-welded these days (almost everything thats welded...) including only from my own personally experience, the hydraulic tanks of every telescopic handler JCB has ever made, if its good enough to hold thin hydraulic fluid at 80degrees and 3bar for 20 years, it will probably keep the Trent and Mersey out 2ft6 under.

 

Daniel

like you daniel i to have had the pleasure of welding the main frames of quite a few main frame chassis at jcb and mig is fine as you say most welding is carried out using mig as faster to lay down , and structurally sound , but depending on material you would have to find the right wire for the job and also conditions inside outside flux cored argo etc , great pictures of porosity first one shows 3 small pin hole but if you were to grind that back you would find it would look like a areo chocolate bar upto a least 1" or more either end , just a note always grind start and stops of welds with  before next run to make sure of good penetration

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18 minutes ago, cereal tiller said:

Agreed,have always considered that that those porous Welds were likely caused by the Gas shield being lost by Wind or poor pressure.have never had the problem myself.

you are lucky if you have never had porosity with mig , every welder i know of including myself get porosity but just make sure if you do grind back compleatly and reweld , there are many reasons for porosity if you are laying long runs spatter in shroud can stop gas coverage wind is big factor lose of gas,  gun kinks contaminats in steel to name few , i have my weld mpi tested regular and to the naked eye you can not see some pin holes but when mpi is carried out they soon stand out ,

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