Crown without soundboards

[Michiel van Loon]

Ron,
Here is the story of how I get crown.
The first thing I had to know, was how much curve I had to give. From a
colleague I learned that for Steinway pianos it had to be 25 mm to 1 meter.
That is a part of a circle with a radius of 4478,052 mm.
I used Mr.. Gates’ MS Excel to calculate this for me.
I ordered 11 pieces of special "Resonanzbodenrippen Holz" at the company
Strunz in Pocking Germany.
I took a piece of 18 mm board sized 1250 mm x 120 mm , marked the curve in
the center and sawed it in two pieces along the curved line. Each half I
attached to a beam 60 x 160 mm 1800 mm long. This I repeated 11 times. So I
used 22 beams I bought at a demolition firm for $40.
Each rib I planed to the width of the original ribs. The height comes later.
These ribs are straight, not curved
After repairing, sanding, bleaching and drying of the soundboard, I pressed
the ribs (one at a time) to the soundboard. See photos 7, 8 and 9 at
http://www.xs4all.nl/~mvanloon/steinway%20fotos.htm .
First I did this without glue to put masking tape on the board on both sides
of the rib and to stick small nails a little bit into the board to prevent
the rib to swim away in the glue. Only just then did I fix the rib in his
final position. The masking tape was removed when the glue was dry enough
not to drip on the board. If you try to remove it when the glue is hardened,
you are in deep trouble.
I also needed 30 clamps , those cost a bit more, $40 a piece. But I got
them with a high discount.

BTW. I agree with Tim Keenan.
The panel is NOT the ONLY thing supporting the crown.
1. The panel takes care of the pressing forces in the whole construction
perpendicular to the wood fibres.
2. And the ribs take care of the stretching forces parallel to their fibres.
3. The gluejoint keeps both opposite forces in balance.
Take one the three away and you have a problem.
Please correct me if I'm wrong.

Michiel van Loon
Meppel
Nederland
http://www.xs4all.nl/~mvanloon
tel/fax ++31 522 255160