Back bending

So...I have sourced a tame cabinet maker who will make me some jigs to an accurate tolerance which will be a good start.
My question is this..would it be acceptable to bend or shape a unidirectional curve on the back (heel to end of body) as opposed to a two way rad? (or is it a hang-able offence).
Cheers
Sheepy

I've seen some builders do it that way. Some quite extreme with very little to no bend from side to side. I don't like the look of it, but I can't think of any over riding reason why you shouldn't try it.

My personal preference is for a radius on the entire back with the sides either a uniform depth or deeper at the tail block than at the heel.

I have done this on some ukes.. but i had a problem with the waist area... the thin back was dishing on the waist central brace area..I suggest a more robust arched central brace than I used if you do it this way..it might work try it

Ok, interesting stuff.
I was thinking of getting aforementioned joiner to make me two jigs, an external jig to assemble the sides, blocks and back kerfing with the radius shaped into the top of the jig (so i can sand the rad onto the sides of the Uke in the jig) and then another sort of radiused bending block to shape the back to the same curve.
What foxes me is how on earth you shape the side profile to accept a 2 directional rad accurately??
Cheers
Sheepy

Uncle Sheepy said:

What foxes me is how on earth you shape the side profile to accept a 2 directional rad accurately??
Cheers
Sheepy

Click to expand...

Its called "Development work"...this example is of a cylinder cut off at 45 degrees showing what it looks like opened up..Uke's are a bit more complicated shape than a cylinder,..but it can be done..Tyneside Shipbuilders/Platers are great at this sort of stuff.

I find it easiest to estimate the first side shape in a series of an instrument designs, bend the sides, assemble them with end block and neck block, secure them well in the outside mold with an inch or so of the top or back of the sides exposed, drop that onto a radius dish, and then scribe a pencil line around the sides and hand plane to the line, finally using sandpaper on the radius dish to clean it up. Then put in the kerfing, resand, and glue on the back or top. When you've gotten both the back and top on, then wrap some heavy paper around the instrument, mark with pencil, and cut the contours. Shrink that by the thickness of top and back, and then make a plastic template. Make a working router template from the plastic one, and you'll be able to get the sides shaped very accurately...as long as you can reference at the butt joint when bending. Worst case this will get you in the ballpark.

Right, I'm going to the North East next week so I will be scouring the bar's for a geordie ship builder

So Rick what your saying there is that I need to clamp the sides etc into an external jig with some showing above the top and profile the sides with a rad dish whilst in the jig and then use said dish to rad the back plate? That makes sense if I have got you right and seems a straightforward method.
This part of the process will be my nemesis I can see