Laminates and composite board in organ-building

[MusingMuso]

David Coram's mention of fibre-board being used as a material in the Compton organ at St Geroge's RC Cathedral, Southwark, sent me on a bit of a "google" concerning the materials now often used in organ-building.

 

In the process, I discovered things that I didn't know, including a few "thumbs down."

 

In fact, when I started to search, I wouldn't have known that there was a difference between hardboard and what we call MDF, but in fact, there is a huge difference in the make-up of the materials.

 

At the ouset, let's draw a veil over "chip-board," which is a fairly brittle and rather horrible material probe to the effects of even modest damp.

 

On the other hand, we must include the best marine quality ply, which has been used very successfully by many organ-builders.

 

It would seem that hardboard is a completely natural material: in effect disintegrating real wood, autoclaving it, deliberately venting the autocalve pressure suddenly and allowing the fibres of the wood to literally explode. The bonding resin of the original wood is effectively re-used, producing a grainless, very consistent material, which can then be accurately worked and machined. The effects of damp can be protected against by the use of various varnishes: not that hardboard is especially bulnerable to mildly damp conditions.

 

MDF (medium dense fibre), is a very different material, though broadly speaking, it is similar to hardboard, except that it uses formaldehyde as a chemical agent in the bonding resin. A couple of thumbs down seem to be given on the basis that it can easily be gouged and chipped, and screws do not hold well when undone and then re-tightened, which explains why MDF furniture manufactirers tend to use special fixings.

 

One of the more alarming things I have discovered about MDF when used for toe-boards, is a tendency for metal pipe-feet to corrode very rapidly, which may have a lot to do with the formadehyde in the bonding resin. (The jury is out on this at the moment).

 

What I find interesting, is the fact that there are a vast number of materials from which to choose, and a similar range of quality, just as there is with real, seasoned timber.

 

The intial question is simple. Why should natural wood be any better for organ-building than the best composite board, and if it isn't, is it just a matter of tradition and pride that it is used?

 

To put it another way, if you were a consultant engineer called into investigate organ windchests, which path would you choose; contemporary materials or traditional ones?

 

 

MM

[ajsphead]

MDF also blunts your tools very quickly. It does have its place, swell box construction for instance, but it is very heavy for its surface area. There is also something which is just "not very nice about it". Marine ply is stable, but it depends on the cut and the quality. I think we went through an experimental phase trying out new materials and it's hard to find an improvement over properly cut and seasoned timber for stability, lightness consistency and so on. You also have to be careful to be aware of materials that respond to climate in different ways, or not at all in the case of aluminium for example. The two often do not mix and can give unreliability. Often these days, the problem is getting properly seasoned timber. The argument is often biased towards inert versus 'natural' and which is preferable as both can be succesful if done properly. We tend to be more conservative now, but if done correctly then the argument for success becomes more debatable. The issues of the past were often hung on the material rather than the execution unfairly as it was easier to criticise being "different". There were however some howlers like wire trackers that were never going to work.We do live and learn but can have a natural tendency to go backwards rather than forwards and be rather insular although technology and cost are associated.

[MusingMuso]

MDF also blunts your tools very quickly. It does have its place, swell box construction for instance, but it is very heavy for its surface area. There is also something which is just "not very nice about it". Marine ply is stable, but it depends on the cut and the quality. I think we went through an experimental phase trying out new materials and it's hard to find an improvement over properly cut and seasoned timber for stability, lightness consistency and so on. You also have to be careful to be aware of materials that respond to climate in different ways, or not at all in the case of aluminium for example. The two often do not mix and can give unreliability. Often these days, the problem is getting properly seasoned timber. The argument is often biased towards inert versus 'natural' and which is preferable as both can be succesful if done properly. We tend to be more conservative now, but if done correctly then the argument for success becomes more debatable. The issues of the past were often hung on the material rather than the execution unfairly as it was easier to criticise being "different". There were however some howlers like wire trackers that were never going to work.We do live and learn but can have a natural tendency to go backwards rather than forwards and be rather insular although technology and cost are associated.

 

========================

 

 

Thank you for a thoughtful and thought-provoking reply, which must be based on a great deal of practical experience. The point about the blunting of tools is interesting. I shall have to test out some of my old Sheffield steel drill-bits on MDF, and see how quickly they blunt before I have to grind them sharp again.

 

I wonder if America organ-builders use proprtionally more inert materials than is used in Europe?

 

The reason I suggest this as a possibility stems back to my time in the US, when I visited the workshops; not of an organ-builder, but of a harpsichord maker of world renown.

 

In my rather green ignorance, I asked why the soundboard was bowed.

 

"It'll be just fine a month from now," came the reply.

 

That was the effect of seasonal humidity change at the start of the fall season; the likes of which we never experience over here.

 

I quite take the point about mixing aluminium with natural wood materials, which is just a basic engineering fact of differing absoprtion/warpage/ expansion/contraction characteristics, where two materials do different things. It's just the same in all metal engineering, as a bi-metal strip so beautifully illustrates.

 

It seems to me, that where non-slider windchests are employed, as with Pitman chests or the individual unit-chests of an organ-builder like Compton, all that is required is stability and strength, on which to screw or hang the various components. So in effect, good, well seasoned timber would seem to be a bit of a waste in such situations, when perfectly good alternatives exist.

 

I just get the feeling that many craftsman would, for no really valid reason, raise their arms in horror at some of the things done with theatre-organ re-installations.

 

I expressed surprise on entering a re-planted Wurlitzer, where the chamber-floor seemed to be full of plastic drainage pipes. These turned out to be the wind-trunking, and when I questioned it, I was asked, "It works doesn't it?"

 

It did indeed work, and had done for quite a long time, so the only possible grounds for objection were entirely aesthetic.

 

MM

[CTT]

Setting aside the issue of obtaining suitable timber - one point that is only mentioned in passing, is the context in which the materials are going to be used in. Obviously in a restoration, one isn't going to use modern materials (though I have seen it done - shudder!). However in a rebuild or addition the case isn't quite so clear cut.

Thinking of a pair of instruments that were installed in a rebuilt a couple of years ago - there was a three manual instrument installed in a west end gallery and a two manual chancel organ. Both had to be reconfigured to fit into the available space. With the two manual instrument, being more historically intact than the three manual, the decision taken was to continue using timber for the trunks and use traditional materials and techniques.

The gallery organ having a new layout and additions, the decision was made to retain all that was viable and useable of the existing instrument, but use new materials where required. That meant new timber building frames, but that zinc trunking was not used in the new layout. Rather marine plywood for all the main trunking and pvc trunking to the off note chests. For anyone that has tried to solder up old zinc trunking - especially 'dirty' zinc - using pvc is a blessing. It can be heated and curved, comes in a large variety of diameters and bends and wooden flanges can easily be made to fit any chest. (The pvc being screwed into the timber/ plywood flange and sealed with sealant.) - Not that I am advocating using pvc in any and every situation. Once again the instrument and context determines the material. (Obviously working on a 1920's HNB is going to involve a lot of zinc trunking and dark mutterings)

With the new chests inside the gallery organ, marine plywood as well as timber was employed. Rackboards and faceboards were made out of marine plywood and to fit in with the existing soundboards, timber rack pillars were used. With regards to using plywood for chests, or any part where there is wind passing through a hole in the ply - the hole still requires sizing out and sealing. Here is where I think that some issues with more modern materials has occurred. There has been this 'new' wonder material that has just come out ( be it chipboard, customwood, mdf, hardboard, etc...) and so it gets used, and used badly. For example, there were organs in New Zealand that were built or rebuilt using chipboard (or if the budget stretched that far customwood or plywood.) And every time a swell shutter or trunk is brushed as the tuner moves around the organ, another layer of chipboard falls down into the pipework. All because the chipboard was not sized with glue, but rather just painted. And yet there is a cathedral organ with chipboard used in the soundboards - but because it was sealed properly there is no problem with it and it is over 40 years old. With plywood faceboards I have had faults where there is running between chest magnets that can be put down to gaps in the laminate, and if the holes had been sized with glue in the first place it wouldn't have to be glued on site upside down while lying on bellows weights.

It may be what was alluded to with regard to the pipe feet and mdf topboards. If the mdf was properly sealed there should be no reaction between the pipe metal and the chest.

Or customwood chest that have no dowel plugs inserted across where the faceboard screws are located so that the screws are biting into timber rather than end grain mdf. Once again it is not so much the material rather the lack of consideration of the properties of the material, and how to best treat it.

 

Anyway - I had better rein in this hobby horse before it breaks into a gallop.

[MusingMuso]

Setting aside the issue of obtaining suitable timber - one point that is only mentioned in passing, is the context in which the materials are going to be used in. Obviously in a restoration, one isn't going to use modern materials (though I have seen it done - shudder!). However in a rebuild or addition the case isn't quite so clear cut.

Thinking of a pair of instruments that were installed in a rebuilt a couple of years ago - there was a three manual instrument installed in a west end gallery and a two manual chancel organ. Both had to be reconfigured to fit into the available space. With the two manual instrument, being more historically intact than the three manual, the decision taken was to continue using timber for the trunks and use traditional materials and techniques.

The gallery organ having a new layout and additions, the decision was made to retain all that was viable and useable of the existing instrument, but use new materials where required. That meant new timber building frames, but that zinc trunking was not used in the new layout. Rather marine plywood for all the main trunking and pvc trunking to the off note chests. For anyone that has tried to solder up old zinc trunking - especially 'dirty' zinc - using pvc is a blessing. It can be heated and curved, comes in a large variety of diameters and bends and wooden flanges can easily be made to fit any chest. (The pvc being screwed into the timber/ plywood flange and sealed with sealant.) - Not that I am advocating using pvc in any and every situation. Once again the instrument and context determines the material. (Obviously working on a 1920's HNB is going to involve a lot of zinc trunking and dark mutterings)

With the new chests inside the gallery organ, marine plywood as well as timber was employed. Rackboards and faceboards were made out of marine plywood and to fit in with the existing soundboards, timber rack pillars were used. With regards to using plywood for chests, or any part where there is wind passing through a hole in the ply - the hole still requires sizing out and sealing. Here is where I think that some issues with more modern materials has occurred. There has been this 'new' wonder material that has just come out ( be it chipboard, customwood, mdf, hardboard, etc...) and so it gets used, and used badly. For example, there were organs in New Zealand that were built or rebuilt using chipboard (or if the budget stretched that far customwood or plywood.) And every time a swell shutter or trunk is brushed as the tuner moves around the organ, another layer of chipboard falls down into the pipework. All because the chipboard was not sized with glue, but rather just painted. And yet there is a cathedral organ with chipboard used in the soundboards - but because it was sealed properly there is no problem with it and it is over 40 years old. With plywood faceboards I have had faults where there is running between chest magnets that can be put down to gaps in the laminate, and if the holes had been sized with glue in the first place it wouldn't have to be glued on site upside down while lying on bellows weights.

It may be what was alluded to with regard to the pipe feet and mdf topboards. If the mdf was properly sealed there should be no reaction between the pipe metal and the chest.

Or customwood chest that have no dowel plugs inserted across where the faceboard screws are located so that the screws are biting into timber rather than end grain mdf. Once again it is not so much the material rather the lack of consideration of the properties of the material, and how to best treat it.

 

Anyway - I had better rein in this hobby horse before it breaks into a gallop.

 

==========================

 

An excellent contribuition from CTT; thank you.

 

I think it demonstrates that all materials have a use, but knowing the material properties is paramount to longevity.

 

It reminds me of a racing-engine I had constant problems with, when the head gaskets kept failing. Having blamed half-a-dozen failures on the gasket material, (itself upgraded), and on the point of having Wills Rings machined into the head, an old, experienced engine-builder suggested that it may be an oil seal problem.

 

So it was, that I investigated the neoprene O-ring seal, which sat well away from the water-cooling ports. Getting too hot as compared to normal use, it was virtually melting, and the very hot, pressurised oil was destroying the gasket material. A change to a small fibre and brass seal solved the problem completely, and had I known, I would have been many hundreds of pounds better off!

 

I suppose that there is no substitute to the "school of hard knocks," where we learn by practical experience, and it seems to me, that many of the problems many associate with modern materials, might have been avoidable with the sort of care and attention to which CTT alludes.

 

I shall never be a convert to chip-board however!

 

MM

[CTT]

==========================

 

I shall never be a convert to chip-board however!

 

MM

 

No argument from this corner either. But if it has been sealed and is stable - let sleeping chipboard soundboards lie, that's what I say.

 

CTT

[Barry Oakley]

==========================

 

 

 

 

 

I shall never be a convert to chip-board however!

 

MM

 

 

And neither shall I, having once had a replacement flat roof made from the stuff that when the rain finally penetrated it turned to porridge.

 

 

But I have heard of MDF being used for chests and I suppose if it's properly glue flooded (and it is a stable material), it should be OK.

[Contrabombarde]

MDF is available both uncoated and coated in a thin veneer of hardwood, so I suppose if you were building swell shutters (where its density makes it a very effective material) but didn't want any risk of disintegrating you could use the veneered version (and veneer the cut faces too for overkill). They would stain up rather nicely too!

 

I was very impressed by the craftsmanship of a console I had the pleasure of viewing in the workshop of one of the regular contributors to this forum who pointed out that the climate of the place to which the organ was heading meant it was not actually built of solid oak but oak veneered marine-grade ply. If it's good enough for a boat, or a vintage British spoorts car (am I right in thinking that Morgans are still built around a wooden chassy) then it should be good enough for an organ.

[MikeK]

This topic was aired in February 2009. I can report that the MDF soundboard for the new Great mixture at Redland Park URC in 1990 is still in excellent condition. The tuning rarely moves & the whole unit has never needed any attention.

[MusingMuso]

MDF is available both uncoated and coated in a thin veneer of hardwood, so I suppose if you were building swell shutters (where its density makes it a very effective material) but didn't want any risk of disintegrating you could use the veneered version (and veneer the cut faces too for overkill). They would stain up rather nicely too!

 

I was very impressed by the craftsmanship of a console I had the pleasure of viewing in the workshop of one of the regular contributors to this forum who pointed out that the climate of the place to which the organ was heading meant it was not actually built of solid oak but oak veneered marine-grade ply. If it's good enough for a boat, or a vintage British spoorts car (am I right in thinking that Morgans are still built around a wooden chassy) then it should be good enough for an organ.

 

===============================

 

 

I can hear the groans already, but I know something about marine-ply for two reasons. I worked for Volvo-Penta marine for a while, and spent some time going around boat-building factories: not exactly slumming it, but going to Sunseeker International at Poole and Marine Projects in Plymouth etc. Those boats are mighty expensive, and worked out at about £30,000 per foot length of boat....God knows what they cost now!

 

It was interesting to see some of the materials being used, and considering what strains and stresses they have to withstand, I was quite impressed.

 

The second source of knowledge comes from practical involvement in motor-sport, and I can tell you that Morgan Cars never used marine plywood chassis, but the Marcos GT certainly did, and many have outlasted the later steel chassis versions. Morgan Cars use a steel chassis, with an ash body frame sitting on top of it. Marcos used fibre-glass for the bodywork

 

Water is always going to be the enemy of wood, but one only has to see it used in marine applications to realise that it is perfectly possible to seal it from the elements.

 

I suspect that the secret of longevity with Compton organs, when both wood or hardboard composite was used, is the fact that things were carefully varnished.

 

The big drawback with materials such as MDF is always going to be the way the material is joined. I assume that it can be glued, but screws and nails are not sufficient, because once a screw is removed from MDF, it will not tighten up properly again, unlike natural timber. So it will always need those special fastenings, which I believe expand as screws are inserted into them. It's one of those materials which is mid-point between wood and metal from an engineering point of view, but with the right approach, I would think that it should prove extremely durable.

 

MM

[CTT]

===============================

 

The big drawback with materials such as MDF is always going to be the way the material is joined. I assume that it can be glued, but screws and nails are not sufficient, because once a screw is removed from MDF, it will not tighten up properly again, unlike natural timber. So it will always need those special fastenings, which I believe expand as screws are inserted into them. It's one of those materials which is mid-point between wood and metal from an engineering point of view, but with the right approach, I would think that it should prove extremely durable.

 

MM

 

The method differs depending on which way the screw is going. If the screw is going through the face of the MDF it can usually withstand being removed and put back in quite a few times (So long as no one is using an electric screwdriver and those self-boring pozi-drive screws). However if the screw is going into the edge of the MDF it is a different story. The expandable fastenings over time split the board, so the most suitable method that I've used so far is to bore a 1/2" - 3/4" hole into the board (set back slightly from the edge) under where the screw will go and glue in a dowel plug. This means that the screw is actually gripping into timber - across the grain. The kitset MDF kitchens use the same idea but with metal cams and fittings that cost a lot more than 3/4" dowel and glue! And if you wanted to be extra cautious, a punching of perfection leather glued on the inside of the chest covering where the dowel is, to insure that there is no air leak. Although if it is glued in properly there shouldn't be any gap in the first place.

 

Christopher

[MusingMuso]

The method differs depending on which way the screw is going. If the screw is going through the face of the MDF it can usually withstand being removed and put back in quite a few times (So long as no one is using an electric screwdriver and those self-boring pozi-drive screws). However if the screw is going into the edge of the MDF it is a different story. The expandable fastenings over time split the board, so the most suitable method that I've used so far is to bore a 1/2" - 3/4" hole into the board (set back slightly from the edge) under where the screw will go and glue in a dowel plug. This means that the screw is actually gripping into timber - across the grain. The kitset MDF kitchens use the same idea but with metal cams and fittings that cost a lot more than 3/4" dowel and glue! And if you wanted to be extra cautious, a punching of perfection leather glued on the inside of the chest covering where the dowel is, to insure that there is no air leak. Although if it is glued in properly there shouldn't be any gap in the first place.

 

Christopher

 

=========================

 

 

That's a neat and resourceful little trick!

 

MM