Elliptical Frame Construction Advice please

[monkeybiter]

I'm about to embark on the construction of a decorative mirror frame. The mirror is elliptical; 430mm x 290mm on it's axes. I haven't quite decided the wood yet, current candidates are Lime or maybe ABW.
My question is, should I cut out in one from a wide [jointed] board or assemble from shorter overlapped& glued pieces keeping the grain running around the perimeter.
I reckon for strength and stability it would probably be wisest to add a thin ply back too.

Any help/advice gratefully received.

 

[Brentingby]

For both strength and stability, you would be best to make it out of multiple pieces joined with mitres. Cutting it out of a panel will result in cross-grain sections that will be weak. gluing it down to a piece of plywood will encourage it to split or warp or both.

eta: The first image I found of an elliptical mirror frame: http://s12.photobucket.com/user/tmsnoaa ... 0.jpg.html

 

[transatlantic]

Surely the answer is to steam bend it. Best of both worlds!

On a serious note though, the commerical ones tend to be segmented for strength, and I suppose because its also cheaper to manufacturer. I'd personally go with the first option. Cut it from one piece (in two parts), and at that point decide if its too flimsy and will need more rigidity with a rebated backer board. Could you not also rely on the mirror itself for rigidity? .. when it's all put togeather, and assuming the mirror is a good fit, then I think that would be rigid enough as a whole. After all, it's only going to be hanging on the wall. Perhaps that's a little naive.

Edit : Good point. I hadn't thought about movement on a single piece.

 

[Brentingby]

Edit : Good point. I hadn't thought about movement on a single piece.

Yes. When (not if) the walnut or lime moves with humidity changes, it will, at the very least cause the frame to warp. Over time it would likely split and crack. Depending on how the mirror is attached into the frame, it could even break the glass.

 

[woodbrains]

Hello,

Does it have to be made from solid timber? I would cut the ellipse from plywood and veneer. It opens up all sorts of decorative possibilities with fancy veneer that is not practical in solid, and ply will not move or break at the joins.

Of course if you are doing something like carving into the frame, then ply is out. But then so is the best technique for making it from solid, which would be layering and offsetting segments. Unless the carving is reasonably shallow, that is.

Mike.

 

[monkeybiter]

Mike, the idea is to construct a frame then rout a profile into it. There will be some carving, but the current plan is to make a couple of art nouveaux onlays in the same wood type and fix them to the frame.

 

[Hornbeam]

An approach could be to cut the ring in segments and stach laminate them with the segment joints offset. This would be easier than mitres and much stronger. Robert Ingham did this with a number of cabinets featured in one of teh wood working magasines
ian