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Rivetted Construction In The Modern Day


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Thanks for taking the time to explain this in so much detail Steve.

I can't speak for anybody else, but I for one am always fascinated to hear exactly what the potential issues are with these kinds of projects.

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Thanks Steve.

 

While Yarwoods and Harland &Wolff had all the resources of a shipyard available, boatbuilders like Harris Brothers were presumably 2-3 man outfits with limited resources. That might explain the relatively crude lines of their boats!

 

I can't imagine that 100 degree angle was ever an off the shelf product, let alone a curved and varying angle section as needed for the chine angle at bows and stern. So these must have been specially made. I had always assumed (without any knowledge) that chine angles were formed by taking a standard 90 degree angle section and opening it out in a press a short length at a time - a somewhat lengthy and tedious process I would imagine. Not sure whether you would curve the angle before or after opening it out though. 

 

Some Harris boats had rounded chines. Is this simply because it was easier to fold a plate to the required curve than to form a chine angle?

Edited by David Mack
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I think that you are right, I don’t think such things were available off the shelf, perhaps the yards sorted it theirselves or perhaps smaller, local rolling mills were more prepared to produce small batches of non standard items. It wasn’t exclusively boatyards that had a need for such sections, any company involved in fabrication and riveting would have similar requirements. Whatever the answer is, the boatyards found such items readily available and it wasn’t a problem to them.

 

When I was looking for angle I did consider having 90 degree opened out, but the problem with that is that the heel of the angle, where it is strongest, will remain at 90 degrees and the flanges will curve outwards. Therefore, along the centreline of the flange, which is also the rivet line, there will be a gap between the plate and the angle. A significant portion of the strength of a riveted joint is provided by the friction between the two surfaces, from the tension of the rivet contracting as it cools, so it is important that the two surfaces are bolted together tightly before being riveted. Such an angle could be ground flat but frankly, I’d rather fabricate it.

 

I had never thought of it before but it is strange, isn’t it, that to consider undertaking a riveted job you might end up fabricating the necessary sections by welding, it is the skills to do otherwise that we are in danger of loosing

 

Having said that the cost of a new riveted boat would be astronomical, it is interesting to look at the costs of Grand Union boats when they were built. Big Northwich and Woolwich motors were £900 each, I understand about the cost of two suburban semis. I know property prices don’t reflect true inflation over that time, but even so they were far from cheap

 

 

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4 hours ago, Rose Narrowboats said:

That's about £61k in today's money.

 

Nah, two suburban London semi's is closer to £900k (depending on the suburb) ?

Edited by cuthound
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I would imagine (and I really have no particular knowledge here) that the rolled sections are just about impossible nowadays, knees etc. but it might just be worth dropping a line to the Ironbridge Gorge museum, a few times a year they fire up the iron rolling mill there and roll iron strips and flat sections for demonstrations. I was told that blacksmiths are a market for this stuff, who knows, amongst the piles of rollers and lord knows what there might be something useful

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On 02/05/2018 at 22:35, Steve Priest said:

The major issue in building a new riveted boat is that the sections required are no longer readily available, as they have been rendered obsolete by welding. I remember Ian Kemp saying to me several years ago that he believed that most people regarded wooden boatbuilding as a dying skill, but wooden boats are still built in large numbers all around the world, and whilst each type of boat has it’s own idiosyncrasies the principles remain the same. In his opinion, iron boat building, as he called it, was the skill that we were really in danger of loosing. I hadn’t thought of it that way before, but found that I agreed with him entirely.

 

In terms of sections, what I mean is the angles, knee sections etc that you need for a riveted boat but not a welded one. Some years ago I had to replace, by riveting, the chine angle on a Josher over the length of the straight sides. This angle is not a right angle, but comes out at about 100 degrees, and I needed somewhere in the region of 90 feet of it. I spoke to railway locomotive restorers, traction engine restorers, boilermakers, and heavy section benders, but pretty much drew a blank, in the end I had to fabricate it myself. There was as much fabrication and welding to achieve this as there would be to fit and weld the side to the bottom on a welded boat, and that is before we started punching it out, fitting the footings and riveting. I was lucky that I did not need to replace the angle at either end, where it curves in and the angle opens out at the same time. The same thing would apply to the gunwhale angle, normally an unequal angle again of about 100 degrees, curving in, and up, and flaring out at the same time as it reaches the fore end. Plating wise, the straight sides may present few problems, but the plates at the fore and stern ends may require a plate forge to shape them. When we build the fore ends of welded josher copies most of us fabricate and weld a series of horizontal strips to form the shape, fabricating the same shape by riveting would mean using substantially larger individual plates and would require a plate forge to shape them, and of course, the skill to use it. It would also require a higher standard of fitting, welding plates together can be much more forgiving in terms of gaps. There are also the forged items to consider, the stempost, with hoodings to accept the fore end plates, and the sternpost and skeg.

 

I think another thing to consider is that those of us who do this sort of work are small concerns of one, two, or three people trying to replicate work that was done by shipyards, namely Yarwoods and H&W, and all the resources that they had to hand. It is a big ask.

 

That is not to say that we are not able to replace significant portions of boats, Ian Kemp has replaced the straight sides and knees on several boats, and substantial rebuilds on fore and stern ends, we at Brinklow have lengthened three boats between us by riveting ( Antlia, Sextans, and my Dutch barge Trijntje), replaced side plates, swims and counters, chine angles, areas of gunwhale angle, swims etc. But perhaps a new riveted hull is a step too far. Possible, of course, everything is possible, but the cost would be astronomical.

 

In terms of riveting work on new built boats, I have riveted an engine room and back cabin on a new little Northwich copy, but, having noticed discussion on another thread I can say that there was no real riveting on our little Woolwich copy Astraea, we did fit a portion of knee in the well deck area, along with a butt strap, gunwhale angle etc but these were with rivet heads fitted from the inside as a late addition to the job. It took me ages!

 

 

Steve

Very interesting to gain some insight into the construction of components that i've given little thought to. 

Something that came up earlier in this thread was the jointing of the plates where the straps are. I have looked at these before and the weld resembles those used to join railway line, a process that I saw many years ago which involved surrounding the joined area with a pot containing an intense, magnesium like fire which when removed gave a similar looking smooth weld. It's hard to imagine how this could be achieved on such a long joint, can you throw any light on the actual method used?

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On 07/05/2018 at 10:05, BWM said:

Very interesting to gain some insight into the construction of components that i've given little thought to. 

Something that came up earlier in this thread was the jointing of the plates where the straps are. I have looked at these before and the weld resembles those used to join railway line, a process that I saw many years ago which involved surrounding the joined area with a pot containing an intense, magnesium like fire which when removed gave a similar looking smooth weld. It's hard to imagine how this could be achieved on such a long joint, can you throw any light on the actual method used?

 

Thermit (or thermite) welding. I doubt it would have been used in boatbuilding.

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Where the plates meet on the outside of the butt straps the detail that you have noticed is caulking, not welding.Have a look at post 18, BEngo has described this process, but basically the plates are burred together with an airchisel with a slightly v or u shaped head. When BW did a lot of platework on the ex GU boats, either themselves at Bull’s Bridge or farmed out to others, they did tend to weld over the joints between the plates rather than caulk them, but more often than not these welds were not particularly neat.

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9 hours ago, Steve Priest said:

Where the plates meet on the outside of the butt straps the detail that you have noticed is caulking, not welding.Have a look at post 18, BEngo has described this process, but basically the plates are burred together with an airchisel with a slightly v or u shaped head. When BW did a lot of platework on the ex GU boats, either themselves at Bull’s Bridge or farmed out to others, they did tend to weld over the joints between the plates rather than caulk them, but more often than not these welds were not particularly neat.

This is fairly typical of the joins on Hawkesbury, I assume done during original construction. Which method was used to create these? 

20180511_073920.jpg

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11 minutes ago, Steve Priest said:

That is a caulked seam

So the inner piece is covered in caulk, the two outer plates are riveted to it, squashing the caulk, then the caulk is smoothed down in the gap between the plates?

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No, the two plates are riveted to the butt strap with the edges of the plates butted together, the caulking is done by burring the edges together with an air chisel with a vee shaped or slightly rounded head. If you look carefully you can still see a faint line which is the edges of the plates. There is no separate caulking material, although I have occasionally come across a small fillet of steel let into fill the gap when they have made a mess of fitting the plates together. On a seam like this you would rarely find anything between the plates, sometimes tar paper or boilermakers felt might be used, but nothing substantial as a gasket because it would compromise the tension formed between the pates as the rivets cool, and hence the strength of the joint itself. 

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36 minutes ago, Steve Priest said:

No, the two plates are riveted to the butt strap with the edges of the plates butted together, the caulking is done by burring the edges together with an air chisel with a vee shaped or slightly rounded head. If you look carefully you can still see a faint line which is the edges of the plates. There is no separate caulking material, although I have occasionally come across a small fillet of steel let into fill the gap when they have made a mess of fitting the plates together. On a seam like this you would rarely find anything between the plates, sometimes tar paper or boilermakers felt might be used, but nothing substantial as a gasket because it would compromise the tension formed between the pates as the rivets cool, and hence the strength of the joint itself. 

Ahh, okay thanks, understood. So the caulking is effectively a cold weld between the two plates?

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40 minutes ago, Steve Priest said:

No, the two plates are riveted to the butt strap with the edges of the plates butted together, the caulking is done by burring the edges together with an air chisel with a vee shaped or slightly rounded head. If you look carefully you can still see a faint line which is the edges of the plates. There is no separate caulking material, although I have occasionally come across a small fillet of steel let into fill the gap when they have made a mess of fitting the plates together. On a seam like this you would rarely find anything between the plates, sometimes tar paper or boilermakers felt might be used, but nothing substantial as a gasket because it would compromise the tension formed between the pates as the rivets cool, and hence the strength of the joint itself. 

But why did they do this? Wouldn't a double row of rivets each side pull the butt strap tight to each plate to give a waterproof joint anyway? And if there was any seepage wouldn't the joint very soon rust up and become watertight?

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There is no real place for rivetting a modern narrowboat, just to be authentic in appearance. Even during the 80's, 'rivetted' boats or boats sold as such, were usually dummy rivets. I've seen many very well known builders doing the process, talked to many too. Its a very easy process to make rivets 'look real'..

 

Its a little like.. glorious straight plate work along a cabinside and 'bog' or body filler, same with welds etc. Many boats aren't that 'honest'.

Edited by 70liveaboard
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24 minutes ago, 70liveaboard said:

Its a very easy process to make rivets 'look real'..

I strongly disagree - very few builders can apply fake rivets that look vaguely like real ones.

 

IMO only the specialist yards produce anything that can be considered reasonably convincing.

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4 hours ago, alan_fincher said:

This is how you do convincing..................

 


 

 

 

 

 

 

 

Disagreeing is good, we live in a democracy. That doesn't mean to say either of us is right, I believe I am right, you believe you are. Nothing wrong with that.

 

Edit: this post is in answer to the one above the one below, that I pointed too. ?

Edited by 70liveaboard
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