At 7:08 am -0700 28/5/07, David Love wrote: >I'm not sure I understand the problem with the 33/66 ratio. Why does that >create an interference? By interference I mean that the lengthwise line drawn through the tops of the copper coils is wavy and not straight, giving the string a very queer look. It would be interesting to be able to describe exactly what happens, but since I know it does happen I simply avoid the ratio. Here's a guess : the frequency with which the peak of the top-cover coincides with the troughs in the under-cover causes a crushing or squeezing sideways of the inside coils so that the top coil forces itself closer to the core. You might well say that they coincide fairly frequently with a 40/60 ratio, but the fact is that with this ratio the line of the string is acceptably smooth. >Also, during the wrapping process, is there some elongation and therefore >slight thinning of the copper wrapping such that you should build into your >target outer diameter calculations some factor for that shrinkage, as it >were. Absolutely. Say 10%. It will vary according to the stringmaker and to a small degree, according to the copper gauge. I made tables years ago for my odd string work and for sets I have a factor built in to the programme to allow for the stretch. Thus I specify a "target tension" and the programme gives me the actual theoretical tension after factoring in the actual copper sizes available and the reduction in diameter due to stretch. If I go on like this, I'll have the boys from the cabal round :-) JD
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