The MA thread - AKA Everyday Fan Vault Construction for Beginners.

[J-G]

Essentially the conic sections have been known since about 350BC - so the answer to the first question I suggest is Yes.

The second answer I suspect is 'probably'

 

[Adam W.]

I think you're right, as the huge masonry fan vaults have a thickness of 200mm or even less in some cases.

 

[Trainee neophyte]

I have seen something on YouTube about traditional spanish thin brick rooves using this technique. Extraordinarily shallow pitch - almost horizontal, and very thin.

Found it! A timbrel roof, apparently:



(Apologies for any intimation that I know what I am talking about - this stuff is way above my pay grade.)

And on a completely separate note: when did the plural of roof become roofs? Was there a memo?

 

[Adam W.]

Interesting day today.

I found out that Hyperbolic functions were introduced in the 1760s by Vincenzo Riccati and Johann Heinrich Lambert. But that's in Wikipedia, so I'll have to check the source properly.

I also managed to plot 1:3 scale drawing of the vault as a very tidy hyperbolic cosine using Hooke in about an hour. It was easily done with a piece of rope and a pencil. Which has got me thinking about how it was done in the 14th. century.

I think I have a credible answer, but I'll try it out on a full size drawing of the vault I'm planning first and use it to make a plywood template to cut the principal rib from.

 

[paulrbarnard]

Interesting day today.

I found out that Hyperbolic functions were introduced in the 1760s by Vincenzo Riccati and Johann Heinrich Lambert. But that's in Wikipedia, so I'll have to check the source properly.

I also managed to plot 1:3 scale drawing of the vault as a very tidy hyperbolic cosine using Hooke in about an hour. It was easily done with a piece of rope and a pencil. Which has got me thinking about how it was done in the 14th. century.

I think I have a credible answer, but I'll try it out on a full size drawing of the vault I'm planning first and use it to make a plywood template to cut the principal rib from.

I would guess they substituted charcoal for the pencil but probably stuck with the road.

 

[Adam W.]

After drawing a full size vault and plotting a rib on a 12" board, I'm beginning to wonder if they used bent timber like a cruck frame. Crucks were common in the south west and perhaps fan vaults were initially a variant which became more elaborate over time.

I'm also thinking that there was a joint in the rib of the larger vaults and they were designed as a suspended decorative ceiling instead of a structural element.

Loads of working out to do before I touch any timber, as I want to be certain that I'm going along the right tracks.

 

[Dee J]

Agree on the naturally curved timber. Cruck frames in houses certainly, but especially the long tradition of grown frames and knees in shipbuilding. Current forestry, industrial building and manufacturing is obsessed with volume handling of straight regular commodity material - but historically (I believe - need source) specialists would scout woodlands to identify potential useful forms for selective felling.

Boat Design Net

Also referred to as 'compass timber' in some shipbuilding glossaries.

 

[Adam W.]

The chances of me getting bent timber here are virtually nil. If I was at home things would be easier, as I'd be able to mill my own from the local woods. I'm not going to mill it in Denmark and try and freight it over, so I'm stuck with boards.

I'm looking at southern yellow pine as I can get it in 12" wide boards and the price is bearable, oak of any kind is out of the question as prices around London are silly and it's going to be painted and then chopped up at the end of the day anyway.

I've been reading Cecil Hewetts books on cathedral carpentry and he shows exploded views of some vaulting such as the lantern at Ely cathedral. His drawings show that the vault is suspended from a much larger hidden frame and I'm beginning to go down the suspended decorative ceiling route, as it makes most sense. Plus there's always a timber roof structure in cathedrals to hang it from and I can scarf the long rib sections together to save on timber.

Also timber doesn't react under load like masonry, as there's grain and defects to think of, and a curved section cut from a straight board will have areas at the ends where the grain will likely fail under loading.

I'll scan and post some of Hewetts drawings of Ely later.

 

[MARK.B.]

All interesting stuff Adam , most beyond my understanding although i may have had a hyperbolic function once after a dodgy curry

 

[Inspector]

Adam would the woodworkers have been consulted during the planning stages of a roof build or would they have been tasked with decorating after the masons were done? I realize there would have been an overall drawing of the building and detail drawing of sections but have the feeling they would have had to match the wood to the building to fit. I'll sit corrected if off but I doubt they were calculating curves etc to any extent, just fitting and adapting to make the work match the designers vision. Different in a building where the timber was the main load bearing structure, basically what you are working on, then the math fell on their laps.

Pete

 

[Tris]

Would it be worth contacting one of the coppice associations in Hampshire or Sussex? There's a lot of overstood sweet chestnut with swept butts that might suit your needs in that part of the country.

 

[Adam W.]

Adam would the woodworkers have been consulted during the planning stages of a roof build or would they have been tasked with decorating after the masons were done? I realize there would have been an overall drawing of the building and detail drawing of sections but have the feeling they would have had to match the wood to the building to fit. I'll sit corrected if off but I doubt they were calculating curves etc to any extent, just fitting and adapting to make the work match the designers vision. Different in a building where the timber was the main load bearing structure, basically what you are working on, then the math fell on their laps.

Pete

In England, master carpenters and master masons acted as both architect/designer and builder up until the 17th century, when architects with no practical training or trade began to appear on the scene.

Buildings such as the 14th. century timber lantern at Ely cathedral would have been the responsibility of a master carpenter working in conjunction with a master mason to produce the whole cathedral.

I doubt very much that something like this is just made to fit and plonked on top of a load of masonry and must have been designed at the same time as the stone tower by people with a deep understanding of material properties.

To produce something like the lantern at Ely, which is vast, would have required a certain amount of working out by someone with knowledge of practical geometry and structural mechanics. I doubt very much if it was just built to fit, as it's a complex piece of timber engineering consisting of many layers all acting as one, and I would imagine that modern engineers and architects would struggle to design a timber structure like it today and sign it off.

In the east of England we have a tradition for building enormous timber structures, such as the barns at Cressing Temple, built in the 13th. century. These stand on a brick plinth, as there is no natural source of stone and a carpenter has had to do the maths to make it stand up. There may have been even larger timber structures at the time which have been lost due to decay or fire. So the knowledge possessed by carpenters at the time was equivalent to that of a master mason, and they both acted as designer working to the clients specification.

The vault which I'm planning is inspired by a later insertion into a Norman stone tower at Winchester and is suspended from a hidden timber structure, much like the decorative vault at Ely. The real load bearing engineering is in the hidden parts, which consist of massive timber structures, much like the barn above, resting on masonry designed to support them and then clad in fancy timber vaulting by highly skilled carpenters.

It may even be the point at where carpentry and joinery began to be viewed as slightly different disciplines, as the vaults were scaled down to produce decorative rood screens in west country parish churches, such as the 15th. century one at Long Sutton in Somerset.

Is it joinery or carpentry when it becomes that size ?

The curves may have been based on the rope catenary, which is why I'm messing about with it, as it's the easiest way to produce an arch, which isn't just a segment of a circle and avoids the use of complex maths.

My rib layout without the use of maths (below) which is also the precise description of the load path for a vault of that size. I'm beginning to think that fan vaults without maths are easily laid out, even though they look very complicated at first glance.

So I think the short answer to your question is yes and no.

 

[Adam W.]

I feel a change of mind coming on......

From Canterbury, Henry IV chapel vault.

I should be able to get unlimited access to that one and I think it'll make a lovely timber vault, as it's quite slender.

 

[kmcleod]

Is it worth looking at Roslin chapel in Scotland - its largely stone, but decoratively etc it may be an option ?

 

[Adam W.]

Went and had a look at the Chapel of Edward the Confessor, built on the request of Henry IV in 1440, at Canterbury Cathedral. Very nice it was too.

It would make a good exercise in cusps and piercing and would make a lovely polychromed ceiling for a canopy.

 

[Jacob]

In England, master carpenters and master masons acted as both architect/designer and builder up until the 17th century, when architects with no practical training or trade began to appear on the scene.

Buildings such as the 14th. century timber lantern at Ely cathedral would have been the responsibility of a master carpenter working in conjunction with a master mason to produce the whole cathedral.

I doubt very much that something like this is just made to fit and plonked on top of a load of masonry and must have been designed at the same time as the stone tower by people with a deep understanding of material properties.

View attachment 117103

To produce something like the lantern at Ely, which is vast, would have required a certain amount of working out by someone with knowledge of practical geometry and structural mechanics. I doubt very much if it was just built to fit, as it's a complex piece of timber engineering consisting of many layers all acting as one, and I would imagine that modern engineers and architects would struggle to design a timber structure like it today and sign it off.

In the east of England we have a tradition for building enormous timber structures, such as the barns at Cressing Temple, built in the 13th. century. These stand on a brick plinth, as there is no natural source of stone and a carpenter has had to do the maths to make it stand up. There may have been even larger timber structures at the time which have been lost due to decay or fire. So the knowledge possessed by carpenters at the time was equivalent to that of a master mason, and they both acted as designer working to the clients specification.

View attachment 117104

The vault which I'm planning is inspired by a later insertion into a Norman stone tower at Winchester and is suspended from a hidden timber structure, much like the decorative vault at Ely. The real load bearing engineering is in the hidden parts, which consist of massive timber structures, much like the barn above, resting on masonry designed to support them and then clad in fancy timber vaulting by highly skilled carpenters.

It may even be the point at where carpentry and joinery began to be viewed as slightly different disciplines, as the vaults were scaled down to produce decorative rood screens in west country parish churches, such as the 15th. century one at Long Sutton in Somerset.

Is it joinery or carpentry when it becomes that size ?

View attachment 117105

The curves may have been based on the rope catenary, which is why I'm messing about with it, as it's the easiest way to produce an arch, which isn't just a segment of a circle and avoids the use of complex maths.

My rib layout without the use of maths (below) which is also the precise description of the load path for a vault of that size. I'm beginning to think that fan vaults without maths are easily laid out, even though they look very complicated at first glance.

View attachment 117108

So I think the short answer to your question is yes and no.

I read (somewhere) that full size layout drawings have been found scratched on floors of churches and temples. It'd make sense as complicated curved shapes were ancient technology in ship building and "lofting" must be as old as ship building itself. Lofting - Wikipedia
Still in use until very recently, also for large constructions chalk-lined in steelyards etc until computers took over.
I imagine builders would shape stone and timber to match drawings on a horizontal surface before lifting it on to form work etc. much like the simple "rod" as used for normal joinery

 

[Adam W.]

@Jacob That's interesting, I had the very same conversation yesterday with the resident geometry master.

His father worked at British Aerospace and he said that they laid out all their stuff on massive steel sheets in a huge loft. He also reckons that there's a framing floor in York Minster and I'll see if I can track it down.

I'm now starting on laying out the drawing for the vault and I've decided to make it as a tester, which is a canopy over a tomb. So it's going to be scaled down to about 5'6"x 3'3".

I'll post some photos once the full size drawing is under way, and I plan to show the drawing at the MA show in October along with the graduating MA's before starting on the joinery.

It's getting pretty exciting and attracting a lot of attention, so I hope I don't screw it up.

 

[Jacob]

@Jacob That's interesting, I had the very same conversation yesterday with the resident geometry master.

His father worked at British Aerospace and he said that they laid out all their stuff on massive steel sheets in a huge loft. He also reckons that there's a framing floor in York Minster and I'll see if I can track it down.

I'm now starting on laying out the drawing for the vault and I've decided to make it as a tester, which is a canopy over a tomb. So it's going to be scaled down to about 5'6"x 3'3".

I'll post some photos once the full size drawing is under way, and I plan to show the drawing at the MA show in October along with the graduating MA's before starting on the joinery.

It's getting pretty exciting and attracting a lot of attention, so I hope I don't screw it up.

Sounds exciting!
I imagine their elaborate curved architecture exists because it follows the technology - they did it because it was possible - they knew how to do it with graphical and geometric methods involving very little maths calculation and much less trial and error than popularly rumoured - though there are lots of tales of retrospectively added buttresses etc which sound true!

 

[Adam W.]

I'm trying to do it without resorting to calculations and plan to set it out without using a square or protractor, which can introduce errors. My tool kit is a rope, a pencil, a pair of dividers/compasses, a straight edge and a large piece of paper.

I made three measurements, length, width and the rise of the three centered arch at the wall. So far things seem to be falling into place quite nicely and I'm being sent stuff like this late at night.

How to inscribe a circle with eight contiguous circles around its circumference, without resorting to maths or guessing.

Beautiful !

 

[AJB Temple]

Not sure if you are aware of this, but it may be of interest to others. Most aspects of church architecture and decoration have a meaning or symbolism. It is thought that pillars and decorative arches may in some instances symbolise arms thrown up in praise of God and the apex of an arch the hands clasped in prayer. Couples are often wed beneath the Chancel arch. Michelangelo was said to make a philosophical point that two arches meet at their weakest point to make a stronger whole ie symbolic of marriage (which may be couples as we know it, or indeed marriage of the priesthood, clergy and nuns to Jesus.)

The cover pieces where arches meet are also often symbolic. Perhaps for a tomb canopy you could incorporate some relevant symbolism in the design, such as Jacob's ladder with carvings of angles rising and falling (see the excellent and well known example on the west front of Bath Abbey).

I am not religious, but I do enjoy the skill and complexity of church architecture. There are many learned texts on the subject (including ecclesiastical furniture). A good starting point is "How to read a church" by Richard Taylor.

Good luck with your MA project. I don't visit this forum often any more, or originate threads here any longer, but will drop in now and again to see how you are getting on.