<!doctype html public "-//w3c//dtd html 4.0 transitional//en"> <html> David Skolnik wrote: <blockquote TYPE=CITE>Ron N's clarification is worth repeating here   <blockquote type=cite class=cite cite>String downbearing is the product of tension and bearing angles. The board is, under all circumstances, exactly resisting the string downbearing force - exactly. The measured crown of the board, compared to the downbearing angles, is an indication of how successfully the board is resisting the string downbearing force.</blockquote> I think it may have been Bob Hohf who used the term 'residual downbearing", to, as I understood it, refer to the measurable deflection after the string has compressed the board as much as it was going to.  On a healthy (ie. crowned board), that 'residual' downbearing could theoretically be anything from zero + .0001 (?) and up. But if it were zero, you have none, and if you show a negative  deflection, you enter a different world of forces.  From the point of view of measuring this deflection when there is not much to be seen, how accurately can it be measured?</blockquote> Thats exactly my point... Downbearing in pianos per say can not be directly measured.. It can only be calculated. Re-read Rons very concise and correct (to my mind) summation. You origionally asked ".., are you saying that it is not possible to take measurements with a gauge (and string under the 'panel')and make some conclusion about the downbearing present in the piano?" And I agree in my answer with what Ron has written.... that yes... taken together, a measument of positive crown and a measurement of postive down bearing indicates exactly that there is indeed positive downbearing and crown...(grin) and as such says the board has at least some spring in it and that the string plane is not too high relative to the panel.... but thats pretty much all I think you can discern from those facts...valuable tho that information in itself may be in some cirmcumstances. But you do not know how much down bearing there is because in our strung and up to tension example because you simply cant measure it and the soundboard deflection of the strings prevents you from knowing what the real string deflection angles are.   <blockquote TYPE=CITE>Again, in a strung piano, is a test string, run next to, or even in the place of, an existing string, going to be able to account for the effects of cap indentation?  The problem is a bit quantum...in order to truly duplicate the piano string with the test string you must recreate the offset created by the bridge pins, and yet, as soon as you do, you are potentially distorting the vertical direction  of the test string travel.</blockquote> Grin... well... I wonder if it gets a bit beyond whats practical and needed in this regard to put so accurate a number on downbearing per se as to take into consideration string offsets and the angles of bridge pins....or what ? <blockquote TYPE=CITE>  So, are all the methods of measuring termination angles equally accurate?  </blockquote> Probably not... but there are some good ones out there. <blockquote TYPE=CITE>David Skolnik</blockquote> -- Richard Brekne RPT, N.P.T.F. Bergen, Norway <A HREF="mailto:rbrekne@broadpark.no">mailto:rbrekne@broadpark.no</A> <A HREF="http://home.broadpark.no/~rbrekne/ricmain.html">http://home.broadpark.no/~rbrekne/ricmain.html</A>  </html>