natural edged bowls

[hawkeyefxr]

I was watching a video of a natural edged bowl being turned on youtube, i have done a couple myself though only small ones say 6in diameter. This video showed a bigger one, about 10in diameter i should think, the thing is it appeared oval. My brain says this this cannot be as there is a fixed centre.
So why does it appear oval when it is in fact round?

 

[rayf6604]

It has to be an optical illusion but I have thought the same thing. The only conclusion I came to was that the scalloped shape makes it look like it's oval


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[Phil Dart]

It depends on whether to bowl is cut with the grain parallel to the bed bars (as in spindle turning) or across the bed bars (as in traditional bowl turning).

If it's parallel, it won't be oval. If its across, it may well look oval, either depending of the size of the bowl relative to the width of the log it's turned from (theoretically, your bowl diameter could be as big as the length of the log, but if the width of the log is less than it's length, then yes, it will be oval). - or secondly, because the more you form the shape. both inside and out, the more you cut away the "sides" of the log, so again, it will be oval.

 

[Dalboy]

If turning a natural edged bowl across the grain then if you measure along the grain it will be longer because when turning what appears to be the narrow parts is where this section is lower down the bowl making it oval in shape

 

[Penpal]

All surmise ,no picture to confirm or deny.

Peter.

 

[Dalboy]

All surmise ,no picture to confirm or deny.

Peter.

From experience don't have any pictures at the moment

 

[AllenN]

It is not surmise it is cylindrical geometry, Phil is quite right. The fact that the edges are receeding in view to a point will make it look oval if it has been turned with the grain at an angle to the bed.

 

[Phil Dart]

All surmise ,no picture to confirm or deny.

Peter.

No surmise Peter - just basic geometry and physics. No photos to demonstrate the principle, but that does not make it any less valid. You must have turned the occasional natural edged bowl yourself in your time , surely.

 

[Penpal]

Apologies one and all my statement was not to debunk all of the theories being expounded by Hawkeye that the appearance was involved a picture from someone would aid in how it does appear.

Of course eyeing,measuring and showing confirm the anomoly detailed. Yes I have made and seen so many edged turnings. We had a guy in our Wood Guild who made literally hundreds for sale each year for many years,the original maker of Ugg Boots over here used to sell them from his business premises.

Peter.

 

[bigbob]

Agree with Phil but I think another optical illusion is a lot of folk use wide angle lenses or the wide end of a zoom lens as it is convenient to fit the object of interest in the shot. When I first started getting interested in all things wood when two bits of wood were being joined together and the 90 deg upright bit looked curved or squint remember thinking to myself I would not put a utube video out with such a warped piece of wood (apart from not having the skill to do so) until the dawning realization that the poor presenter was using a wide-angle lens. Now it’s annoying as I notice it all the time when wide angle is used instead of soaking up the information hope I have not spoiled others enjoyment of utube by mentioning this.

 

[Bill Mooney]

Derek has itridht that the lower parts of the bowl have to be narrower because of the curved shape of the bowl. The bowl is actually turned as a circle. It is not an illusion & it's not the camera lense playing tricks it is simple geometry.