Increasing Crown

[Overs Pianos]

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Dale and all,

The idea for adding crowned ribs to an existing=20
flat board was entirely the idea of David Kinney.

I must admit that when David mentioned that he=20
wanted to add auxiliary ribs, I thought it was so=20
much trouble, and difficult to get them in the=20
high treble, that I felt it would be easier to=20
rip the board out and build another one.

But I agreed that if he was prepared to endure=20
such an experiment, that it would certainly be=20
worth a try. He marked out the location areas for=20
the ribs and cleaned off the finish, then wedged=20
the board up using the back braces to=20
approximately match the crown of the machined=20
ribs. The auxiliary ribs were fitted to the board=20
by screwing them through the panel. After the=20
glue dried he removed the screws and doweled the=20
hole using hammer shank.

I haven't seen the piano yet. But everything=20
David does is executed to the highest standards.=20
So you can be sure that the work will look very=20
tidy.

I'll be travelling to his home workshop (1.5 hrs=20
west into the mountains from Sydney) to see the=20
piano as soon as the action is done. I'll forward=20
a report to the list once I've seen and heard it.

Best,
Ron O.

PS. A few responses to Dale's post below.

>   Great post. my cup o tea
>    I'm Interested in the Mechanics of how this=20
>was accomplished with the board still in the=20
>piano. Ie. How were these ribs  attached ?=20
>Removing the old finish neatly to get  a good=20
>glue bond ?how you determined the size & height=20
>of ribs & what consideration did you give to the=20
>effects of the old ribs that were flattened and=20
>pulling the crown down.

The height and width of the ribs was determined=20
by the physical space available regarding height.=20
The width of 15 mm was arrived at after=20
considering the two conflicting interests of=20
making them as thin as possible to reduce the=20
added weight, while providing sufficient gluing=20
area to ensure a successful joint. After some=20
discussion we arrived at 30 mm deep by 15 mm wide.

>  I assume this is a CC board to begin with.

It would largely have been CC, although I=20
understand that B=F6sendorfer do crown their ribs,=20
so it may well have been a combo CC part Rib=20
supported.

>Putting on new finish with beams and all in the way.

Yes I know, what a pain.

>Pictures would be facinating.

David's got a Canon 300D, so I'm sure he won't=20
mind taking a few images once its all done. I=20
could post them to our website for all to see.

>   Very interesting experiment. Resourceful & I might add clever thinking.
>   Dale
>
>Hello all (and Dale, who I've CC'd since he could be off list at present)
>
>A re-crowning exercise.
>
>A local colleague, David Kinney, is currently=20
>rebuilding a B=F6sendorfer (late-ish model 200,=20
>about 20 year old example I think). The sound=20
>board was collapsed but otherwise without any=20
>visible panel defects. As an exercise in sound=20
>board re-crowning, he commissioned us to build=20
>him a set of crowned sitka ribs for fitting in=20
>between the originals. We made them 30 mm high=20
>in the middle by 15 mm wide, so as to maximise=20
>the added stiffness without adding too much=20
>weight to the board.  We made them only long=20
>enough to match the un-feathered lengths of the=20
>adjacent original ribs
>
>I understand that the result is very successful.=20
>After doing the usual total internal refinish he=20
>has reset the down bearing throughout, which=20
>required a considerable packing height for most=20
>string sections. He says that about 50% of the=20
>unstrung downbearing angle sunk out once the=20
>piano was pulled to pitch, which is about on par=20
>with new factory boards. I haven't heard the=20
>piano yet as he is still doing the action. It'll=20
>be interesting to hear it once its up and=20
>running.
>
>Ron O.
>
>


-- 
OVERS PIANOS - SYDNEY
    Grand Piano Manufacturers
_______________________

Web http://overspianos.com.au
mailto:ron@overspianos.com.au
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