Top/bass bar initially tuned

posted 16 Jan 2021, 04:27 by Peter Grankulla   [ updated 16 Jan 2021, 05:00 ]

It's quite difficult to tune high density tops. Tuning is about weight/stiffness distribution and it's easy to make mistakes because weight has to be reduced proportionally in the right places
(To achieve "common" graduation scheme where thickness is proportionally thinner to the wood's density)

Learned from previous high density top, density 0.49.
This one is ~0,50-0,51

1. cutting the f-holes does not lower M5 as much
2. installing the bassbar (equal density as top) only increased M5 to 367 Hz
3. "optimizing" the bass bar from straight 15 mm to shaped 12,5 mm only decreased M5 a few Hz
    - after this great care should be taken, it would be possible to optimize further without too much decrease in M5.
        => But then you get the Wolf at C, described here: Wolf tone at C (B1+)

4. Tuning is not about getting the "right" M5 it's about getting all the parameters "right
    - weight
    - thickness/graduation scheme according to the wood's density
    - bass bar weight and stiffness

5. The top is still quite stiff - feels stiffer than usually ~360 Hz M5 feels
   - feelings are not to trust too much though

Nodal lines M5/M0

posted 25 Aug 2020, 07:02 by Peter Grankulla   [ updated 25 Aug 2020, 07:03 ]

The back plate is of lesser performance wood and arch height is left 18 mm, this I think is why the nodal line of M5 is closer to the center, than usual.
By tapping, two frequencies are heard/visible on FFT spectrum analyzer. It's important not to follow the other one called M0, it's higher and will give a too low final M5, when hollowing out the inside.


Continued work on back plate

posted 19 Aug 2020, 04:00 by Peter Grankulla

Optimized for final shaping

Purfling work outside

posted 5 Aug 2020, 06:20 by Peter Grankulla

Exploring modes and arching

posted 23 Jul 2020, 05:29 by Peter Grankulla

For those who understands Kreit's system. I learn more every time. Because I'm not in a hurry I'm documenting this one thoroughly.
Removing wood from upper area 1/2/3/(4) carefully its possible to keep M0/M5 at the same frequency.
Removing wood from lower corresponding areas (which are the most reactive areas), you can lower either one of modes or both and thereby adjust there deltas.
Removing wood from the sides lowers both modes, but keeps Hz/cm3 steady.
But, it's really important to understand the "Italian arching" style and aim for the straight lines in upper and lower bouts.

Back in workshop after a looong pause

posted 22 Jul 2020, 09:32 by Peter Grankulla   [ updated 22 Jul 2020, 09:33 ]

Ribs, plates cut out and starting back extrados. Always interesting to take this first step to see how the back will turn out.

Really glad I have documented the last four so well in spread sheets with modes and notes for every 5-10 g removed. Also where removed, edge thickness etc..
This one's back follows the patterns of Soil #2

Varnish cooking time

posted 1 Aug 2019, 07:59 by Peter Grankulla   [ updated 7 Aug 2019, 10:52 ]

Still no time for making new violins, but varnish cooking every summer is a must! Same recipe as last year

Cooking colophony, as the colophony is reduced it gets more viscous and the temperature has to gradually be raised:

Cooking Colophony One Hour

Cooking Colophony Four Hours

Ribs with a Japanese saw

posted 21 Aug 2018, 09:31 by Peter Grankulla   [ updated 21 Aug 2018, 09:39 ]

After a long break it's time to continue The Soil project, working on the fifth 

Varnish cooking time

posted 16 Jun 2018, 03:42 by Peter Grankulla   [ updated 16 Jun 2018, 13:12 ]

Warming up, quite pale in the beginning, planning to cook the rosin for 10+ hours

=> 9,5 hours total cooking time. The weather was windy and reduction of colophony was faster than last year. Need to do some test later, I wonder if it can be too dark

Two hours:


posted 24 Dec 2017, 04:35 by Peter Grankulla

Perfect timing:

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