Continuing wrestplank discussion from another topic.
Re MOE of wrestplank timber etc, I have never seen a wrestplank push backward to crush the register gap, but rather the much weaker belly rail collapse frontwards. Unless the mounting of the wrestplank is a complete disaster, but I personally have never seen that. The wrestplank slab is big, heavy, and immense. But I guess anything is possible. No doubt Carey who services huge numbers of instruments has seen such a thing.
RE North American wrestplanks: Both Red and White Oak are readily available in the USA, as is Maple (hard and soft) and Beech. Red and White Oak are fairly similar, with differences being around whether the pores are open (Red) or closed (White), color (not always though), and that White is generally (but not always) harder. My guess is that ZHI favors Red Oak because it is very stable in use, cheap, and readily available in quality and quantity. White Oak is a bit more expensive (not compared to the cost of a harpsichord though), and it can be a little more unpredictable in use. It also seems to have a higher tannin content and sometimes doesn’t play nice with iron.
North American Hard Maple and Beech tend to be rather unstable, both in drying and use. Beech is a little less common, and tends to be used more for small machined things like clothes pins rather than furniture sized items as it is quite unstable. Hubbard may have used Hard Maple due to its use in piano wrestplanks where it is cross laminated to counteract its instability. Beech may have been used to match European practice; however, North American climatic swings tend to highlight the disadvantages of Beech.
I’d say of the four woods, Red Oak is the most stable, holds tuning pins well, and has the added advantage of being cheapest and easily available in high quality.
In a series of experimental prototypes I’ve used laminated maple and beech (leftover piano pinblock material) and recently made a wrest plank of red oak, a piece of 3/4" oak from the local home supply store, laminated to be 1 1/2" thick. This is now my preference. Inexpensive, easy to work, resilient without being “sticky.”
Multilaminates are much harder, because of the large amounts of glue. Thus they are very unforgiving of any tiny irregularities in drilling or pin diameter. The Baldwin Piano Co. never really accomplished the level of quality control needed with 30+ layer multilaminate pinblocks, thus earning the eternal distaste of piano technicians who had to struggle with their miserable-to-tune pinblocks.
Quality 5 layer maple pinblock material can be purchased at a premium, but since the grain direction is rotated, it is less strong, as an unsupported beam, than straight, unlaminated oak, beech or maple. In the piano, it is supported by the iron plate, so does not need strength across the instrument. The point of the laminations is to reduce the chances of splitting from the many, large tuning pins which must have high torque to hold the piano strings under high tension. Not a problem with harpsichords.
Hi! Wolfgang: I can see that the term ‘unstable’ is far too vague, and generally defines a particular change -over time- in a material’s state of being. For wrestplanks I also hope to have chosen a slab of wood that, anecdotal evidence aside and guidebooks on timber notwithstanding, seems not to display signs of being liable to warp or twist all by itself over time. Already not warped or split. So: straight grain, no big knots, cut as far as possible on the slab or quarter, and then as old as possible, so drying has taken place. Luckily I have a rather cumbersome stock of beams from houses here in southern france: all oak, unidentified species, there are various varieties here, white probably, but they are ancient. The pins tend to be darn tight so careful drilling is required. Testing on offcuts, I often just run a 4 mm (new) bit over the grindstone to thin it down. I hope not be around should they show signs of instabilty over time, a very long time! I’m still looking for a defining photo of a beech wrestplank pulled into the gap. TWM
Stability in timber can also mean that the moisture content has stabilised to a constant level, whether by natural or kiln drying - precisely so the above mentioned movements are minimised or eliminated.
Here’s a thing. Good jacks made from fruit wood or our Tasmanian Myrtle and stable and never twist or bend to any functional degree. There are jacks that have been stable for hundreds of years. I’d call Delrin an unstable material - look how many jacks bend and twist after only 20 years.
Here’s a wood that is unstable: boxwood. There are so many traversos from 18C that are now quite banana shaped, and elliptical.
Unstable, as defined by a physicist, surely has some caveats according to the material being discussed. So the moisture content in old boxwood is the variable that causes them to banana ? Due to playing and the inside being wetted, perhaps. If one were to make a traverso from tasmanian myrtle it might just bend a little too, what do you think?
Delrin is odd, it doesn’t dry out moisutre wise, so some internal process of uneven polymerization is at work. Unlikely to be the UV effect that makes so many plastics crack as the jacks are safely under the jackraille.
Let’s not start a new topic here…I’m bowing out!
We are not talking about physics. [I have a background in physics.] Woodworking.
I have an interest in historical flutes. Cocus became available from the Indies in the early 19C. I’s dead stable, never moves, negligible ellipticity and has a glorious tone. The same is true of African Blackwood and other timbers such as mopane. These are all subject to the same wetness but do not move. I have never looked into what makes boxwood a bad choice. It’s a pity because boxwood flutes and recorders make a glorious sound.
I have an English D’Almaine cocuswood flute. It’s dead straight and the bore is perfect as the day it was finished, in 1827. I’d call that stable. The only thing you do to them is lightly oil the bore once a year or so.
Haven’t read the entire discussion, but I’ll put in my two cents’ worth. I would like to add two excellent choices, with which I have extensive long-term experience, viz.: walnut, which gets used a lot un-veneered on Italian harpsichords and works absolutely wonderfully, and steamed Euro beech, which has in recent years flooded the American market, is of exquisite quality and behavior, and is comparatively inexpensive. I’ve also used American white oak without any issues with the tannins against the iron pins, but don’t use red oak.
My not using red oak is not because I think there is anything particularly wrong with it, but I don’t like the smell of it, or the look of it, or, if I remember correctly from my encounters of many decades ago, the way it seems to cut and handle with tools. But I certainly would not go so far as to advise against it.
I would warn against warning me that walnut is not hard enough for the purpose; I’ve made far too many instruments using it successfully over too many decades for this to be an issue.