Richard mijn jongen Thanks for the compliment and blowing my cover (you already know that I don't like you that much :)) I can see that it is somewhat confusing but I am only referring to the fact that the name K isn't mentioned as such in Fenner 's book. Steingraeber and Fenner employ different crowning methods at least in the way of the total amount of crown and where to put the highest point of the soundboard. The both use the cc method for their boards. When you talk to Udo Steingraeber he will emphasize that his company is not constructing the board the Fenner-way but uses a different approach. How that approach is in detail I don't know but I know they achieved good results. Now about the Fenner approach, at least as I perceive the method he describes is his book. Fenner is (was) an advocate for using stress in the board as an effective possibility to change the different frequencies in the various areas of the board to get a better match with the string frequencies. The goal is to achieve an uneven stress in the board more towards the treble and less towards the bas. He is also talking about the bending stress along the grain which is a effective way to raise the frequency analogous to a singing saw. Fenner constructs his boards following this principle and doesn't want a uniform crown but an uneven crown with more stress with a highest point shifted to the treble. In his book he explains how to do achieve this and calculate the radii for the ribs etc. which are used for the board and the mould. To help achieving a shift in frequency bending the board along the grain will not help that much so he is compressing the board in that direction. One possibility is (before gluing)to lift he board at the highest point with a block temporary fixed to the braces about max. 2 times the expected crown and then fix the board to the rim. After gluing the block is removed and the board will have some extra compression. Or you can combine it with pressing the board into the cavity of the outer rim which is more easily done before fixing the bridge to the board. Extra compression along the grain can also be achieved by gluing the long bridge (straight not curved) after the board is glued in. Yet another approach is to glue a heavily dried (cooked) bridge on the board first, before gluing the ribs to achieve a crown and add some extra stress. So much for now This time a friendly salute Arnold ----- Original Message ----- From: "Richard Brekne" <Richard.Brekne@grieg.uib.no> To: "Newtonburg" <pianotech@ptg.org> Sent: Sunday, February 13, 2005 12:26 AM Subject: Killer Octave & Pitch Raise > Arnold my friend !! > For those of you who dont know, Arnold is the > fellow who works together with André. Arnold > works alot with soundboard rebuilding projects > and is IMHO an all around great guy. > > Thanks for chirping in, but I am afraid you lost > me a bit... first you say there is no K point, > then you say there is. Then you say Klaus and > Udo use different crowning methods, and then you > say they use the compression method. Begins to > sound like the strawman in the Wizard of Oz just > after the goons raided them in the haunted > forest and flew off with Dorothy ! :) > > Seriously tho... would you mind going into a > little more detail. I'd loveto have this whole K > point thing clarified for me. I've been a bit > curious ever since I first heard about it, and > havent seen the subject pop up here before at > all. Also... I remember distinctly Udo talking > about crown and compression along the grain > being << essential >>... so if you know more > about what he meant there I'd love to hear that > as well. > > And for what its worth, your use of the word > Tension should (I believe) be interepreted as > general Stress by readers. Correct me if I am > wrong Arnold.. but you didnt mean actually > stretching something... just applying different > stresses.. yes ? > > Thanks for the post ! > > RicB > > > > > _______________________________________________ > pianotech list info: > https://www.moypiano.com/resources/#archives > >
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