Side thickness for tight curve?

[StuartGold]

I have designed an “F” like mandolin design but with the scroll on the body reduced to a curved point (with an arc in the body side of 180 degrees and a diameter of 1 1/8). I realize that this might be a difficult curve to bend (see image). I am using highly figured red maple. I would like some feedback about two points (no pun intended)

1. With that kind of bend, is it correct that I should consider maybe thinning the side of the curve to .045 - .065 “ ?

2. I know that I will probably need a backing strap to help prevent cracking with bending (using ½” pipe with electric coal igniter). I thought that I read somewhere that although most people use metal, for a tight bend like that perhaps a leather belt might work better. Any ideas?

[sunburst]

It depends on the wood. Some pieces bend easily at .060" or more, I've had to go to .040" (about like violin ribs) for scroll bends with some wood. Keep thinning what you have until you can accomplish the bend, and if it won't work, try different wood.
Leather won't work. The reason for the metal strap is to keep the outside surface from stretching to the point of failure, and leather will stretch.

[HoGo]

0.065" should be plenty thin unless you have some very uncooperative piece of wood (some pieces just want to break at any attempt at bending). Backing strap will make it MUCH easier and if you will have problems you can bend two thinner pieces and laminate together...
I once managed to bend 2mm thick figured maple bindings for complete F5 including headstock. The tightest curves required some fancy techniques to prevent breaking but it worked.

[Marty Jacobson]

Why not put a mahogany block in there? Then your "side" can just be veneer, .030" or so, and you may not even need to bend it. Just glue it onto the block. That veneer will give the mahogany block some cross-grain support, so you can keep it pretty thin.. like Lawrence Smart does (and many other discriminating builders, no doubt).

[HoGo]

John was faster and accurate. He's right metal strap is good for bending. My trick at bending VERY tight curves was similar to what is used for bending thick pieces for furniture. The strap will take some of the stretching of the wood surface just by being pressed on hard but for thick pieces it needs to be fixed on both ends of bent piece so it takess ALL stretching. I did this by clamping the bent piece to the strap. I made tiny "clamp" out of two rectangular pieces of steel with two bolts. Sandwitch steel, belt, wood, steel held together with bolts. On one end I used the clamp as stop just pushing against the endgrain of piece. You need to clamp the wood close to the start and end of curve so it won't buckle in opposite direction when bent. In few cases the wood had tendency to get crushed too much by the pressure so I adjusted the clamps a bit loose for those bends. If you are careful enough you can bend 2mm thick maple around 1/4" dowel. JUst last thing, I've always wetted the wood before bending.