Rib crown, was ;Big, fat, wide, shallow rib mystery "solved" ???????

[Ric Brekne]

List

4 meter radius ??  Isnt that rather a lot ?  Your point about not being 
able to tell whether the other ribs were crowned or not brings me to ask 
the list how one can really tell for sure whether ribs have been pre 
crowned or not.  I assume you have to have them removed from the panel 
to have a good enough look ??  Up to now I have had basically 2 things 
to go on.  Dimensions are evidently a good hint.. tho not decisive.  
That is to say that it seems likely that shallow and wide ribs were used 
in non rib crowned applications... because they bend so easily.  
Secondly... I have this idea that  if you take a rib and press it so 
that its grain along the rib is all horisontally oriented... then if the 
rib is flat well... it was flat... if there is curvature to the glue 
surface then it was crowned... does this make sense ?

Cheers
RicB


Ron Nossaman writes:

I replaced the board in an old Knabe grand a few years back.
The top four treble ribs were not only crowned (about 4 meter
radius, at that), but laminated. I couldn't tell whether any
of the other ribs were crowned, but the board was concave
under bearing load.

There's a difference between rib crowned and rib supported.
These boards are still primarily panel supported, crowned ribs
or not.