Dale Erwins----/Rib Crowning Jig pic's

[Farrell]

Dale responded to a question I had about his rib crowning jig. Here it is.

Terry Farrell

> > Subj:Re: Dale Erwins----/Rib Crowning Jig pic's 
> > Date:2/11/2002 4:42:02 AM Pacific Standard Time
> > From:<A HREF="mailto:mfarrel2@tampabay.rr.com">mfarrel2@tampabay.rr.com</A>
> > To:<A HREF="mailto:Erwinspiano@aol.com">Erwinspiano@aol.com</A>
> > Sent from the Internet 
> > 
> > 
> >        You wrote
> > Hello Dale Erwin. Thank you for the rib crowning jig pics. I have a 
> > question. From the picture I can easily see how you make your first cut on 
> > the rib. After this first cut and you let the rib relax, you are left with 
> > a rib that has a straight edge on the uncut side and a convex curve on the 
> > other. Obviously, the convex curve will be glued to the soundboard back. 
> > How do you then cut the other side of the rib so that you end up with a 
> > constant-thickness rib?
> > 
> >   Terry
> 
>         Your very welcome
> 
> >    I was wondering if any body saw the pictures as this is the first 
> > question I've fielded.
> 
>          All the rib crowning rebuilders I know do not care that more beef 
> falls in the 
> > middle the rib or under the bridge. This idea is in line with the 
> > diaphramatic concept in that the majority of the soundboard mass is in the 
> > middle of the board.
> >   I frequently add 1mm to the overal depth at the thickest part of the 
> > longer ribs because the rib ends are losing some mass due to the 
> > aysemtrical thickness. Does that make sense?
> >    If you wish to have a constant thickness rib you can. After the crown is 
> > cut the next step is to run the backside of the rib thru a large radius 
> > router bit  This puts the usual half moonish radii on it. Use a fence and 
> > feather board.if you value your fingers.  The rib is still thicker in the 
> > middle at this point. After the ribs are glued on to the board use Dana 
> > Mazzaglias rib radius plane which has a radius blade. It is a simple matter 
> > to plane out the extra mass in the middle if this is what you decide you 
> > wish.
> >   A question you didn't ask. With this jig it is easy to put the highest 
> > part of the crown under the bridge. Make a  mark indicating the bridge 
> > location on the rib. Install the rib on the jig where the C clamp is. This 
> > will become the highest part of the crown on the rib. This has limitations. 
> > The high treble ribs for example are too short but wherever the bridge 
> > travels thru a wider part of the board it is feasible.
> >   
> >     If you wish post this to the list as others may have the same question. 
> > Hope all is well with you. By the way I just recieved the Roseland Sitka 
> > soundboard panels and they are really beautiful. Seamless joints, great 
> > color match. They are a higher quality board than most I've tried
> >     >>>>>>>>Best--Dale Erwin>>>>>>>>>...
> 
>