Welding a steel hull

Why would you expect to have 100% when up to 30% of your strength has been lost?

"...when dragging doesn't even warm it up..."....fine, run the torch over your hand see if your hand warms up!

If you wish to ignore the significant data that clearly show the effects of arc strikes by such reputable bodies like TWI and the IIW, not to mention endless research papers documenting many different failures etc all caused by arc strikes resulting in the transformed martensite and also localised brittle fracture and that new codes have been developed world wide that categorize arc strikes as poor workmanship and sites of cracking etc, as also noted above, then that is your prerogative.

No one is forcing you to ignore the enormous body of evidence, against your...er...what...hmmm..doesn't feel warm ergo must be ok ,method of QA!

I think i'll go with the endless documented evidence, which you choose to ignore (much I've seen myself first hand too) of arc strikes and their detrimental effects, over your doesn't feel warm approach.

 

"If you can't dazzle them with brilliance, then baffle them with bull," seems to be your approach. You say a piece of 3/16th plate will break in the middle if it is used on a 36 foot hull and an arc is dragged over it? ********! If jesus , mohamed and budda were all to claim it would, it would still be ********.
The plate gets much warmer out in the sun. So do we waste many hours trying to keep the sun off it.
Drag a stinger lightly over the middle of a flatbar , the bend it back and forth to your hearts desire and see if it acts any different where the stinger was dragged. It won't , period. End of story.
I once did some work for a hotel complex in Abu Dhabi in the Persian gulf. They had to wear asbestos suits to work on it in the morning and evenings so it wouldn't burn them . Thats a lot hotter than a quick drag of a stinger over plate would ever get it. So did the hotel fall down. No.
The hundreds of thousands of miles steel boats have sailed without structural problems , the pounding of boats on reefs and lee shores with no more than minimal dammage, is an enormous body of evidence. I no of no boat builder or shipbuilder who would lose any sleep over a stinger being dragged over a plate , nor hesitate to do it. i know odf no incidence of ther area of a hull where the stinger was draged over it, acting any differently than the rest of the plate.
Seeking out more tedious, time consuming and expensive ways to make a boat project a lot longer and more expensive, is far more of a threat to ones cruising dreams than dragging a stinger over plate could ever be. That type of elitist , masochistic putitanism has cost far more people their cruising dreams that all other causes combined.
Brent

 

Brent
From your posting above, it is clear you have not looked at any of the references, not understood one word i have written, nor have you read the TWI guidance (attached previously) too. Clearly you either lack the comprehension to fully appreciate this subject (its ok, not everyone can understand metallurgy and fracture mechanics) or you just flatly refuse to accept anyone else's word other than your own. That's fine, no one is forcing you too. You just seem to be getting all hot and bothered because your understanding/method of fabricating is not endorsed by any major institution worldwide, quite the contrary. All you have done is exposed yourself in your own preferred practices, procedures and MO to anyone reading this posting.

Since the views I have expressed above are based upon my own experience of surveying boats, as well as endless mountains of work by many reputable institutions around the world which i have also gathered, to understand why such a simple thing as an arc strike can cause minor and major failures.

If you wish to continue to be ignorant of such well documented and now enshrined in codes of practice around the world, that is your prerogative. As such there is no point discussing this further with someone who refuses to accept internationally recognised methods of QA and the implications of not doing so.

PS...I take it you didn't drag the gun over your hand to see if it's warm then!

 

The main reason why arc strikes are a defect is because they leave behind spatter . In time the spatter will come of exposing bare steel to oxidisation which is why we grind and buff all arc strikes

 

"From your posting above, it is clear you have not looked at any of the references, not understood one word i have written, nor have you read the TWI guidance (attached previously) too. Clearly you either lack the comprehension to fully appreciate this subject (its ok, not everyone can understand metallurgy and fracture mechanics) or you just flatly refuse to accept anyone else's word other than your own."

Yup!

Arc strikes create hard spots, reducing ductility. This practice is admonished by every governing body that I know of, and is easily found within their codes. Why do they all mention arc strikes as a flaw in procedure? All part of the great global conspiracy, I suppose. Couldn't be that tests have been performed, often post-failure incident, results have been gathered & the governing bodies have shared the info. for our betterment, could it? That would be too logical!

 

Welding

That a boat could survive 16 days of pounding on a lee shore in 8 ft surf and be pulled off in 8 ft surf, pounding for 1/4 mile on every wave, could pound across 300 yards of coral in 8 ft surf, suvive a collison with a freighter, a collision with a steel barge at hull speed, or a collision with a log boom at 14 knots all without significant damage, is strong enough, is far too logical for many bureaucratically run institutions . What do institutions have to say about the ratio of pleasure to time and money? What do insitutions have to say about the way perfectionist nit picking, with no regard to cruising results, ends up trashing so many cruising dreams. They end up forcing the price in terms of time and money of building a good reliable steel boat, far beyond the means of many who belong out cruising. They are by their very nature , elitist. They completely ignor that which is a far bigger issue to most cruisers, something which I have drastically eased the pain of for hundreds of cruisers ( to the great chagrin of elitists.).
The same institutions approve of fibreglass boats built to their specs, which any of my origami boats could sail right thru without suffering any serious dammage. They state that such flimsey boats are OK to go to sea in, if they are built to spec, yet a boat that could sail right thru them is not strong enough. Find yourself a Lloyds approved wood or fibreglass boat and we will have a demolition derby . Dont have the balls? Then so much for your claimed belief in their infallibility, or your imagined problems with my boats.
Find a wood or fibreglass insitution approved boat with the track record of zero structural failures at sea of my boats. You won't.
Brent

 

This is a fascinating debate, and the points raised by both 'sides' have a lot of credibility to me.

I know Brent can get a bit um.. 'enthusiastic' on his preferred methods, but in this case I can totally understand his point.

While there is a lot of reference to 'all those incidents' reported on the effects of arc strikes, - I suspect they are very specialist examples, involving pressure and or vibration on system critical steel components where arc strikes have any effect. Critical failures being stressed supports, tanks and the like.

My thinking is that Arc strikes across the main area of a hull of your standard well engineered steel yacht couldnt have the slightest significance, considering what the properly welded areas go through, which is the point Brent is making. In fact I would be hard pressed to think of a single place on your average steel yacht where they would be a problem from a stray strike. eg. Engine mounts are usually so big that an arc strike couldnt affect them.

However, I would love to be enlightened on any well documented failure caused by something like random strike that wasnt on a highly stressed or highly vibrated component. (And I wouldnt be impressed by examples that included subsequent over-grinding that created the problem.)

Onwards with the debate hooooooooh....

 

It neither takes more time, nor costs more money, to follow correct fabrication & welding procedures when building a boat. So, why would you?

 

My point exactly. Boat building projects die the death of a thousand cuts , none of which is by itself is significant, but they add up over time ,and worrying about totally insignificant issues adds up to dithering time and money away, something boat builders have to be constantly on guard against. I've dealt with many a dither master, and if I didn't push a bit ,we'd be there forever.
Dithering creep becomes a habit which eventually makes a once affordable boat expensive. This is evident everywhere, in the time and money spent building otherwise simple boatbuilding projects..
What I'm saying is dont sweat the petty things and don't pet the sweaty things. Just build the friggin boat.
Brent

 

What has an accidental arc strike got to do with 'correctness' ???

Its like asking a carpenter to not make sawdust or wood splinters.

Still waiting on a applicable example ........

 

If I may chime in...

Many views and methods has been aired on this thread with many getting hot around the collar. However, this thread is all about welding a steel boat and although enlightening to read some "high tech" methods of welding, I believe it is not applicable on small boats. More so the arc strike issue - arc strikes are as part of welding a pig to a Russian sausage.

In general, smaller steel boats are much stronger than large steel boats and the strength of these boats much underrated, and on that tack I support BS views although not his methods. Bear in mind that many steel boats are being build by amateurs with basic or very little welding skills and this was the purpose of this thread to give some input what is good and bad, how to and not to to these people, although some of our professionals can gain some as well...

 

When you are doing awkward overhead welding and the flux is off the end of the rod , the only way top get started is to drag the rod and burn the steel back in the flux. Puting the work down every time and finding a piece of scrap to burn the steel back, then beginning again would add a huge amount of time and cost to a project, for no real gain. Is it worth the extra expense to make a boat 60 times overstrength instead of 45 times over strength, if it even does that much, which I seriuously doubt.
The institutional nitpickers who advocate the later , often have little experience being in the awkward overhead welding position, but simply do their calculations on workbench work, and have little comprehension of the realities of building a small boat on a budget, limited in both time and money.
My first boat was an example of the huge distance between insitutions and reality. She was a Pipe Dream Cruisiung sloop designed by Francis Kinney. She was tank tested at the Davidson INSITUTE, one of the top testing facilties in the world at the time.
If that horrendous abortion was the best such a reputable INSTITUTE could come up with, then so much for the credibility of INSTITUTES!
They tank tested her by pushing her thru a testing tank from a fixed point , which has little relevance to being pushed by sails.
She was hopelessly unbalanced, with zero directional stability. I managed to get her to New Zealand , where I made major improvements, which I had considered in building her, but didn't, due to my inexperience at the time. The changes were a huge improvement , altho the hull was still grossly unbalanced.
That someone with zero experience can see obvious faults and see major design improvements that the worlds top gurus can't see, completely blew my faith in gurus and their INSTITUTES.
Wynand , take some patterns off any hard chine boat you like, and pull one together using origami mehthods, and you will never go back to building frames. You always have the option of putting frames in afterwards, with a fraction the work, but the total redundance of frames becomes very self evident, once you have the shell together. What supports what also becomes entirely self evident.
Brent

 

The initial comments to which I referred included dragging an electrode across a plate. In deference to BS's assertion, no, the sun - from the perspective of one on the earth's surface - is not as hot as a welding arc, not even close, or we'd all be dead.

Arc strikes compromise the base material. The molecular structure at the surface of the material is transformed(see molecular states of steel - austenitic/martensitic/ferrites/pearlites). The result is a hard, brittle area at the strike site, where fatigue strength & ductility are reduced, possibility of cracking increased dramatically, due to an alteration of crystalline structure of molecules & resultant bonding challenges with un/less - affected molecular structure of surrounding material. What sort of example are you hoping for? This is something that is taught in the most basic of welding programs, if you do not wish to accept it, that is your issue, not mine, look it up yourself. I would think that there is a university with a decent engineering dept. in your area. Chances are good that they will have done studies.

In discussions centred on the welding of steel hulls, when considering the advice that one should give to a first-time builder whom is not formally trained to weld, I believe that encouraging sound fabrication procedures is a better example for one to set, than to slag convention, without reason.

Proper joint fit-up & edge dressing, appropriate penetration & fusion, absence of undercut & stray arc strikes, speed of travel, electrode manipulation, etc., should be encouraged, in my opinion. Suggesting that any, some, or all, of these considerations is not important is foolish & misleading. There is nothing "elitist" about building the best boat one can. There is nothing elitist about following sound practices & procedures.

By the same token, if you want to half-*** things, go to it, it doesn't affect the rest of us. When one suggests that others half-*** things, however, I believe that members of these forums should point out the folly of those ways.

Great stress concentrations are created during & post construction of metal boats. The size of the boat is not as important as the manner in which it is put together. It is laughable to think that some of those who promote metal boatbuilding would then compromise the value of building in these materials. Had these same people been responsible for pioneering the construction of welded metal ships, the result would have heralded both the birth & death of our industry.

 

Some thoughts on the arc strike issue.

Having been a tool and die maker for over 30 years and an airframe mechanic in the service and having seen and made my share of screw ups I long ago developed an appreciation of just how strong, durable and tolerant the metals we work with are.

On a project as large as a boat I would like to meet the person that could work to 100% quality.

If this were a major problem I would think the hue and cry would have been heard long ago.

While I can well believe the transformation steel would undergo with an arc strike, under normal circumstances the areas affected would be so minor an area as to be compensated by the sheer amount of material surrounding the affected area as to minimize the problem.

Even on the most demanding projects I have worked on there was an allowance allowed for less than perfect workmanship usually expressed in a percentage of some sort.

It seems to me that the conscientious worker would try to limit such incidents even if to reduce the amount of rework.

That said any increase in quality is going to take a much greater increase in the percentage of effort, so there has to be a realistic point at which one says good enough.

 

I agree. My point was not that "everything must be perfect", nor was it that "stray arc strikes won't happen". I thought that I had made my point clearly enough. Arc strikes will happen, but should be kept to a minimum.

As I have spent a lot of time twisted like a pretzel in the bowels of ships/barges/etc., dealing with the loss of a bit of flux off the end of a rod is second nature. It does not need to, nor should it, be dragged across the plate, though that is an easy solution to the no-flux problem. I suppose there could be a situation where one has no scrap metal, or a dog, at hand. Of course, one could drag the discussion out further by arguing about the amount of flux the rod is missing, but assuming that it is 1/4 to 1/2 inch, I'd recommend striking the arc & holding it off for a second or two. This being said, if someone new to welding were dealing with this problem, I'd suggest they use another rod & save the "offending rod" for a time when they can strike it on scrap.

As one moves from mild steel to alloy, stray strikes become even more of a concern. Just the other day, I saw a new welder trying to weld up the rope guard on a fishboat. He was at the top of the guard & his spatter was falling on the prop. A few minutes spent wrapping a couple of fire blankets around the prop would have saved about $75,000 . Sometimes, an ounce of prevention is worth a pound of cure.