Hello Philip and others, Reading your post again brought to mind that I had completely forgotten to suggest a significant advantage of the inside-out bag. With the seam inside the neck, the neck is very much less liable to constriction with all the consequent advantages of strangulation.
I have such a bag here which is very much like old examples I have seen in museums. Turned inside out with the additional folded strip of leather sewn into the seam. It could only have been reversed through the drone stock hole which is a smallish one to accommodate a 3 drone stock. Incidentally, whatever it was originally dressed with has preserved it beautifully and it remains supple and robust. The thickness of leather is variably 1.3mm to 1.5. Pretty much like your average bag from Jackie Boyce whose work I have always found excellent. Once one has conquered the thought of it, reversing a bag is not difficult. A bit like the current joke's punchline: Did I jump? Yes I did at first, but then got to quite like it. The rest is not suitable for this polite forum. Francis On 28 Jan 2010, at 10:57, Philip Gruar wrote: > I've found this thread fascinating, as I have also experienced strain on the > wrists - strain generally in fact - when playing a set where the bag neck is > too short, and consequently have started to use bags (from Jackie Boyce) > with long necks when making my pipes. This keeps the chanter well forward, > and leads to a much more relaxed playing position. However, I'm aware that > there can be problems with the neck kinking and restricting the airflow if > it is too long and narrow. John's post about Helmholtz resonators seems to > suggest that a long narrow neck would cause more (or at least different) > resonance problems than a bag where the neck opens out broadly from the > narrowest point at the stock, "broadening smoothly into the main cavity" as > he says. If a narrow long neck makes MORE problems, then obviously we makers > should avoid that shape - if the gradually broadening shape makes DIFFERENT > resonance, then how different? Are the resonating frequencies going to be > higher or lower; more or less likely to coincide with chanter notes? I'm > afraid my maths isn't up to the calculation, and anyway - on looking at the > Wikipaedia article, I don't see anything about a cavity with pressurised air > inside, where there is a constant flow (i.e. from bellows inlet through to > chanter), let alone flexible resonators like pipe bags. No doubt the science > has been done, and it would be interesting to have some ideas, even though > there must be so many variables that it will be extremely difficult to come > up anything better than vague generalistions. > > On the historical bag-shape question, the tear-drop shape of early bagpipes > certainly seems more suited to mouth-blown pipes, with the bag held well up > and in front of the body. Incidentally, I wonder if this shape is a natural > development from using an animal's bladder, stomach, or whatever rather than > making the bag from sewn leather? The swan-neck shape going into the chanter > would also make for ease of playing and no kinking of the neck (see > resonance discussion!). Adapted to the musette, and other early bellows > blown pipes e.g. illustrated by Praetorius there was the need for a long > flexible tube from the bellows. However, I would guess that both bag and > bag-cover are much more difficult and time-consuming to make than the simple > folded-over shape. Turning bags inside-out is surely only possible if the > leather is soft, and the early bags seem to be mostly made from quite thin > sheep or goat-skin. I wonder if the modern style of NSP bag - including the > excessively stiff leather sometimes used - is an influence from the Highland > pipe makers? What are the bags of the early sets in the Morpeth museum like? > I examined them all myself years ago and recall a variety of small, dried-up > bags and possibly early 20th-century replacements, but can't remember details > just now. Generally speaking though, I think most early small-pipes, and also > Irish pipes and Scottish lowland/border pipes which I have examined tend to > have small, squarish bags, shorter front-to-back and slightly deeper top to > bottom than what we use now. I don't recall the tear-drop shape used in any > late 18th/19th century British pipes. > However, several Reid sets I have seen had the most beautifully sewn and > turned (inside-out) bellows outlet tube. Now that's another whole thread to > become obsessed with! > > Philip > > > > > > ----- Original Message ----- From: <gibbonssoi...@aol.com> > To: <nsp@cs.dartmouth.edu> > Sent: Wednesday, January 27, 2010 11:44 PM > Subject: [NSP] Re: bag shape > > >> I always understood the point of the open-cell foam in the neck is to >> remove the neck resonance problem referred to earlier. The frequency of >> this resonance depends critically on the shape - if you model the bag >> as a big cavity with a narrow tubular neck,like a bottle, the formula >> for a Helmholtz resonator applies - see wikipedia for this. >> >> The formula will be quantitatively off as the shape doesn't really fit >> the 'bottle' model well, the neck broadening smoothly into the main >> cavity. But the order of magnitude should be fairly good. >> >> >> >> If this frequency falls in the range of the chanter, the chanter notes >> near this pitch will couple strongly to it and the pitch will be well >> away from what you would get with the same chanter in a different bag. >> Killing the bag/neck resonance means the chanter pitches will be truer. >> As air can flow easily through the foam at low frequencies but not at >> higher, the rapid oscillation of the bag/neck resonance is damped out, >> without badly affecting the supply of air to the chanter. >> >> >> >> >> >> I dread to think what clagging the open-cell foam with seasoning would >> do to the airflow, though... >> >> >> >> John >> >> -- >> >> >> To get on or off this list see list information at >> http://www.cs.dartmouth.edu/~wbc/lute-admin/index.html > > > -------------------------------------------------------------------------------- > > > > No virus found in this incoming message. > Checked by AVG - www.avg.com > Version: 9.0.733 / Virus Database: 271.1.1/2650 - Release Date: 01/27/10 > 19:36:00 > >
