Overplating with thick steel - opinions?

[paultheg33k]

Hi all,

I've been lurking and reading the forum on and off for a couple of years now - it's a great resource.

Despite being on my second (cheap) MIG, I've never really done much more welding than a few patches on cars at MOT time - and some occasional repair of other bits and bobs.

But.... Myself and my better half have now bought a (nother) narrowboat, this one in need of some overplating - much of which has been started but not finished.

I thought I'd have a quick go with my MIG to see how it handled welding the 5mm plate to the existing c. 4mm hull.

The following is about 6-8" of first quick go, from the outside.

And this from the inside:

What do you think - apart from the general bad start and end?

This is at full power on the Clark 131TE, with (I think, if I remember correctly) 0.6mm wire, and a disposable CO2/Argon mix.

Cheers!

PC

 

[Wozzaaah]

Are we talking plating above or below the waterline? I don't know much about boats but I know I wouldn't want a 'cold' weld below the waterline and mig is great for making good-looking welds with poor penetration and wall fusion, especially when welding downhill.
I'd say your little Clarke is a bit underpowered. If you're already using it at full power then you need more power. You might just about get away with a short run but once you hit the thermal cutout during a long run (and you will ) you'll have another cold start to contend with.
0.6mm wire is too small, 0.8mm or above would be better.
Have you thought about using a stick welder instead? A little more difficult to use maybe but I'd have thought much better than a small mig for boat stuff.
What happened to the tip by the way?

 

[paultheg33k]

Are we talking plating above or below the waterline? I don't know much about boats but I know I wouldn't want a 'cold' weld below the waterline and mig is great for making good-looking welds with poor penetration and wall fusion, especially when welding downhill.
I'd say your little Clarke is a bit underpowered. If you're already using it at full power then you need more power. You might just about get away with a short run but once you hit the thermal cutout during a long run (and you will ) you'll have another cold start to contend with.
0.6mm wire is too small, 0.8mm or above would be better.
Have you thought about using a stick welder instead? A little more difficult to use maybe but I'd have thought much better than a small mig for boat stuff.
What happened to the tip by the way?

The plating amounts to the four 'corners' of the boat - so mostly below the waterline - and the flat uxter plate, or counter - which sits around the waterline with any luck, across the back of the boat.

To be honest, with the exception of the uxter plate, there aren't any holes being covered up here, just thin steel - although I'm still keen that water not get between the two metal surfaces.

What do you think of the penetration in terms of the reverse of the weld, shown from inside the boat? My faithful watcher was keeping an eye on things and seemed to suggest that it was doing a good glowing hot-hot-hot impression on the inside.

I can see what you mean about the duty cycle of the welder, although I've not pushed this fan blown one very hard yet. My old 90A blue one would cut out if pushed properly hard on full power.

The 0.6mm wire was just what was in it, I need to verify that it is in fact 0.6mm and change it for 0.8 - but I wanted a quick go to see whether I could get the penetration required.

In terms of stick welding, I've had a go a few times in the past and I'm just no good at it - I can't get on with the technique required and it drives me up the wall. I'd rather pay someone to do it than risk my stick work! On that topic, quotes so far have ranged from £700 towards £2000+, which is driving motivation to do it myself!

The tip was already a bit shagged from lots of Rangie welding a while back, and suffered a bit from me playing with the wire speed set a bit low, with burn back - the end of it's erroded away.

Thanks for the comments anyway - all good stuff!

PC

 

[astro_al]

Ha - i read the title and knew it would be about a narrowboat.

I got into welding through my old narrowboat. It was a Springer (yeah yeah) and I had the whole hull overplated. You think you have problems? Try a V-hull from a single sheet!

Whiloe it was in the dock, I got curious about welders, so I started having a go to 'help' in the evening, then the guys would come back the nest day, grind out all the pigeon poo I'd laid down, and do it all properly! Ahh happy days - not for them!

Accepted technique is to cut holes in the existing plate where the middle of the new one will be, and use that as extra joining access between the two plates (ie weld them together through this hole as well as at the edges). Hope that makes sense.

The forces on narrowboat hulls are pretty low - its mostly a question of getting it water tight. Check c-a-r-e-f-u-l-l-y for pin-holes etc, and plenty of bitumen when done!. take the opportunity to fill any small (coin sized, usually) pits in the hull with weld. These can show up alarmingly thin with an ultrasonic tester.

Check the rubbing strakes and replace the anodes while you're at it.

Personally, I think you're pushing it with that little welder, but you have ok signs of heat on the reverse.

Good luck, Al.

 

[paultheg33k]

Ha - i read the title and knew it would be about a narrowboat.

I got into welding through my old narrowboat. It was a Springer (yeah yeah) and I had the whole hull overplated. You think you have problems? Try a V-hull from a single sheet!

Whiloe it was in the dock, I got curious about welders, so I started having a go to 'help' in the evening, then the guys would come back the nest day, grind out all the pigeon poo I'd laid down, and do it all properly! Ahh happy days - not for them!

Accepted technique is to cut holes in the existing plate where the middle of the new one will be, and use that as extra joining access between the two plates (ie weld them together through this hole as well as at the edges). Hope that makes sense.

The forces on narrowboat hulls are pretty low - its mostly a question of getting it water tight. Check c-a-r-e-f-u-l-l-y for pin-holes etc, and plenty of bitumen when done!. take the opportunity to fill any small (coin sized, usually) pits in the hull with weld. These can show up alarmingly thin with an ultrasonic tester.

Check the rubbing strakes and replace the anodes while you're at it.

Personally, I think you're pushing it with that little welder, but you have ok signs of heat on the reverse.

Good luck, Al.

Lol, always a narrowboat eh?

I'm impressed you managed to plate the v-bottomed hull with a single sheet - that sounds like good work!

Aye, I'm aware of the concept of cutting through the existing hull sheeting to weld to the plate from the inside - but at least this isn't a full overplate - just the swims, bows and counter.

It's the counter that concerns me the most, as unless I get a pattern made and it cut from a full sheet, it'll be more than one piece of steel - meaning butt welds, which I'm less confident with, with this welder.

I'm glad you think there're reasonable signs of penetration from the reverse side - I thought so too. It might well improve using 0.8mm wire - we'll see.

New anodes are a given, as are replacement of the rubbing strakes which have been cut off to put the new plates in place.

With the pitting, the welder employed at Streethay Wharf, on our other boat, suggested that filling the pits with weld might generate stress concentrations and hence it might be better to do something else. With that boat, that I'm posting from now, I used a phosphoric-acid rust-converter:

...for the pits and filled with 2-pack epoxy resin, then blacked over the top:

I'm not sure if that was a good idea or not!

Thanks for the vote of good luck!

PC

 

[astro_al]

Well, sounds like you're on top of it!

Not sure about that resin - should be ok I guess, I think welding is too well tried and tested to go wrong, but whatever works for you.

For the counter, just make up a cardboard template as crudely as you like - stick bits together, tear it, whatever, just end up with a decent final profile and cut it out of a plate - plasma is good if you can find one - ideal for that sort of thing.

Butt welds will be fine (you really can't get it from a 3 x 1.5 sheet?). Just grind a V half way on both sides - zero penetration required! (Kind of...) - anyway - its perfectly do-able, just needs more prep. If you weren't so far away I'd offer to help.

Re-pack the stern tube while you're under there?

Al.

 

[paultheg33k]

Well, sounds like you're on top of it!

Not sure about that resin - should be ok I guess, I think welding is too well tried and tested to go wrong, but whatever works for you.

For the counter, just make up a cardboard template as crudely as you like - stick bits together, tear it, whatever, just end up with a decent final profile and cut it out of a plate - plasma is good if you can find one - ideal for that sort of thing.

Butt welds will be fine (you really can't get it from a 3 x 1.5 sheet?). Just grind a V half way on both sides - zero penetration required! (Kind of...) - anyway - its perfectly do-able, just needs more prep. If you weren't so far away I'd offer to help.

Re-pack the stern tube while you're under there?

Al.

Yeah, the resin, as I say, was on the advice of the welder in the yard at the time, who was worried about stress concentration caused by welding large numbers of individual pits. Is that how you did yours?

I'm glad you reckon the butt welds will be okay, if they're necessary - I'll have a go with some spare plate when I'm down there next, just to make sure I'm up to it. It's been suggested that brushing the weld with paraffin is a good method of weld-testing in lieu of a dye testing kit?

Cheers for the help anyway - all good stuff.

The stern gear will be getting some attention, especially as there appears to be a fariy-liquid bottle wrapped around it on the inside, which presumably existed for some reason... Mind you, the fact that the prop's missing completely is likely to be more of an impediment to actually going anywhere!

In terms of the template for the counter - I certainly don't have any large enough sheets to do it in one go without sticking bits together, but I presume I could take the pattern somewhere and get it cut out?

This is some of the work that's been started by the previous owner:

Interesting eh?

Cheers! PC

 

[danny s]

for real

Hi new to board,
I weld boats for a living stretching, side plating, base plates, cosmetic alterations act.
As for mig welding on boats and your description photo's ect forget it the weld pictured is domed from the start as the lack of cleaning you have done.
mig welding is not tolerant to any dirt, rust or draught you are supposed to be welding mild steel to mild steel not mild steel to iron oxide or bitumen.
ass for the "clake" mig welder it is only capable of diy welding on cars,
0.6 mm wire is for welding thin plate as in cars
the mig of gas you’re using with the co2 content is more suited for heavy plate
(15 mm to 20 mm)
the weave that has been used will have done nothing to have helped apart from causing a cold lap
the chances are there will be water ingress though the cold lap
the chances are that the weld will be really brittle through the lack of heat on such a mass of metal cooling the weld so quickly
will this really take a collision from a hire boat with 6 drunken students at the helm?
why are you trying to weld to the rubbing strake that will only be stitched underneath so allowing water ingress straight into your new plate?
sorry I see this type of welding done quite often and have to re-plate, on the plus side it’s easy to remove.
you will need a mig with a minimum of 300 amps with quality coils, quality wire 1mm and an argon-co2-o2 mix with probably 5% co2 only and no draughts to blow the shielding gas away
I personally would prefer mig to weld boats as its cleaner, better penetration characteristics, faster and less distortion - but I will spend 6 days preparing and cleaning to do a 50 ft base plate but weld it all the way round in 6 hours-
get the prep Wright and it will weld its self
hope this helps remember boats sink
Danny

 

[backpurge]

I think Danny has just about covered everything

One common misconseption to clear up, just because it glows on the back doesn't mean it's penetrating, it jus tmeans it's getting hot

 

[Wozzaaah]

14-07-2009

I think he's probably sorted it by now!

 

[Shox Dr]

Or it's sitting on the bottom

 

[backpurge]

Or it's sitting on the bottom