Double Welded Cabins

[Gary Peacock]

Just taken delivery of a hull, very happy generally but the steel on the cabin roof was only welded from the inside, the rest is all double welded. Called the builders who said this was normal as distortion could occur, our fitters say this is not normal practice and ALL welds should be made from the inside and outside. Before I kick up a fuss are there any readers out there who can throw some light on this, is it something which is normal practice or are the builders right?

 

Load of Bollocks!

 

Get them to sort it!

[bag 'o' bones]

Load of Bollocks!

 

Get them to sort it!

 

That's settled that then!

[steelaway]

Hi

 

There is not 1" of filler on my boat, my builders prided them selfs on that. They will aways sooner weld and polish a joint, done properly it will not ripple.

The 10mm base plate is welded on both sides, to ensure full penetration and strength

The cabin sides are made of only two lengths of 5mm, press formed with gunwhales and a window cut out on the joint. You cannot the remaining 6" top or bottom.

The roof is also 5mm. The steel work (and boat) is as straight as a die. There is not one ripple or joint to be seen and definetly NO FILLER!!!

You gets what you pay for, but quality will out.

 

Alex

[blackrose]

Hi

 

There is not 1" of filler on my boat, my builders prided them selfs on that. They will aways sooner weld and polish a joint, done properly it will not ripple.

The 10mm base plate is welded on both sides, to ensure full penetration and strength

The cabin sides are made of only two lengths of 5mm, press formed with gunwhales and a window cut out on the joint. You cannot the remaining 6" top or bottom.

The roof is also 5mm. The steel work (and boat) is as straight as a die. There is not one ripple or joint to be seen and definetly NO FILLER!!!

You gets what you pay for, but quality will out.

 

Alex

 

Not bad for a Springer!

[steelaway]

Not bad for a Springer!

 

 

 

NORTY STEP FOR YOU MY BOY!!!

 

 

 

 

Alex

[gazza]

Hi

 

There is not 1" of filler on my boat, my builders prided them selfs on that. They will aways sooner weld and polish a joint, done properly it will not ripple.

The 10mm base plate is welded on both sides, to ensure full penetration and strength

The cabin sides are made of only two lengths of 5mm, press formed with gunwhales and a window cut out on the joint. You cannot the remaining 6" top or bottom.

The roof is also 5mm. The steel work (and boat) is as straight as a die. There is not one ripple or joint to be seen and definetly NO FILLER!!!

You gets what you pay for, but quality will out.

 

Alex

 

the shaded red text is not needed if the welder knows what they are up to.

 

According to a coded welder I know the Americans only 'V' one side of the butt!

 

the AWS and TWI are mostly in agreement with each other on matters welding related, shame the yanks cant spell and use funny terminology

[ChrisPy]

on a typical pipeline we weld hundreds of thousands of 48" pipes 25mm wall thickness using v-prep joints from the outside only, with 1.5mm root gap.

 

and that is to the highest standards of non-destructive testing including ultrasonic and radiography.

 

 

 

But on most Liverpool Boats an integral handrail was put over the top, so it's not quite the same as there is no exposed join.

I was talking about the athwartships welds, Mike, which of course are not covered up. I assumed that is where the issue is.

 

Another point - LB did not omit welding the roof from the outside to save costs, because it would have been much easier to weld from above on the outside. Of course on 4 or 5mm steel that would be probably a full penetration weld anyway.

Edited December 24, 2009 by ChrisPy

[Batavia]

The welding of the annular plates on a large oil storage tank is analogous to welding the base plate of a boat.

 

In the past, we used to weld these from both sides - do the top first and then lift the plates up onto stools, a section at a time, and get the welder to crawl undeneath and do the bottom part of the weld. This is no longer considered, by some companies, to be acceptable.

 

Consequently we now do all the welding from the top, with the plates lying on the tank foundation, but with ceramic backing strips under the welds, as these can then be removed once the welding has been done (as opposed to using steel backing bars, which are normally un-removeable). The NDT is then UT and MPI.

 

The downside is the cost of the ceramic strips - which is probably why it has not caught on with the boat-building fraternity!

 

Chris G

[Madmark62]

The welding of the annular plates on a large oil storage tank is analogous to welding the base plate of a boat.

 

In the past, we used to weld these from both sides - do the top first and then lift the plates up onto stools, a section at a time, and get the welder to crawl undeneath and do the bottom part of the weld. This is no longer considered, by some companies, to be acceptable.

 

Consequently we now do all the welding from the top, with the plates lying on the tank foundation, but with ceramic backing strips under the welds, as these can then be removed once the welding has been done (as opposed to using steel backing bars, which are normally un-removeable). The NDT is then UT and MPI.

 

The downside is the cost of the ceramic strips - which is probably why it has not caught on with the boat-building fraternity!

 

Chris G

 

That sounds bloody good, I wish I knew what it all meant!

[DHutch]

The downside is the cost of the ceramic strips - which is probably why it has not caught on with the boat-building fraternity!

For the base plate, most yards i expect make use of the concreate floor....

[Martin Kedian]

i wonder how much is to do with confidence in your work i too would prep the plate with a single v butt, sufficent root gap for plate thickness then nail it together.

 

i mentioned in a previous post, narrowboat fabrication is not typical of the wider weldingindustry standards. it shocks me more do not use mags to produce a complete boat. it is a low hydrogen process that can produce joints in quite thick sections. mags is a much quicker and lower cost process, that said, mags is the easiest process to get wrong.

 

 

HI sorry to hear of your dilema Not a practice that we would do filler tends to crack with time the cabin should not distort in this area if welded at the right temprature I personaly would be unhappy to take delivery of a boat that hade been made this way It is not common practice most shell bullders weld the outside and tack at regular intevals the inside ther will of course be other opinions I base mine on working in the industry since 1972 I hope you sort it out without to much difficulty Regards Martin Kedian

[gazza]

That sounds bloody good, I wish I knew what it all meant!

 

it means the guy that typed it knows what he is on about

[Bobo]

The welding of the annular plates on a large oil storage tank is analogous to welding the base plate of a boat.

 

In the past, we used to weld these from both sides - do the top first and then lift the plates up onto stools, a section at a time, and get the welder to crawl undeneath and do the bottom part of the weld. This is no longer considered, by some companies, to be acceptable.

 

Consequently we now do all the welding from the top, with the plates lying on the tank foundation, but with ceramic backing strips under the welds, as these can then be removed once the welding has been done (as opposed to using steel backing bars, which are normally un-removeable). The NDT is then UT and MPI.

 

The downside is the cost of the ceramic strips - which is probably why it has not caught on with the boat-building fraternity!

 

Chris G

 

Twenty years ago in the shipyards in Holland, were using ceramic inserts on modular builds, where sections were built in separate sheds and then brought to the slip. Deck sections were welded with a baby submerged arc welder, the head of which ran on a track. I guess a big wide beam keel could be welded in half a day

[emkay]

Load of Bollocks!

 

Get them to sort it!

Thanks Gary, first rain and the seams leaked! Notified and being rewelded on 4th Jan.

[Paul Evans]

And repainted in a covered dock?

[the grinch]

we only welded one side of the 10mm baseplates at Clubline when i was there and the boats then got tested to destruction by the hirers, none that i know of ever sprung a leak.

[Timleech]

we only welded one side of the 10mm baseplates at Clubline when i was there and the boats then got tested to destruction by the hirers, none that i know of ever sprung a leak.

 

I don't see any logical reason why properly prepped and welded bottom plates should need to be welded from both sides, but logic doesn't always come into these things

Most modern nbs usually have bottom plates thicker than the structure requires, from that point of view 100% penetration wouldn't be essential anyway, but you certainly wouldn't want a substantially weak line which could flex in preference to the rest of the bottom.

Welding the cabin top from below and leaving the top of the seam exposed doesn't seem a good plan, though I've seen boats like that. I think if determined to build a cabin that way, PU sealant (Sikaflex etc) would be a better, longer lasting filler than car body filler.

 

Tim

[emkay]

And repainted in a covered dock?

Just primed at present, the boatfitters who first notified this as a potential problem are supervising the work and yes it is on dry land. No harm done and thanks to all