cyma curves

Re: cyma curves

Gil

>Cyma Curves can be seen upside down in wood turning. A vase is most typically a cyma curve right? well a modified cyma curve. I don't know why we don't see more cymas in turning.

I have turned a few things which border on short Cyma Curves, and I personally don't like them that much.

However if one were to remove the bottom 1/8th of the cyma curve, where you typically see a ball and claw foot, the design would flow wonderfully. I'm not into hollow form turning, but when I do get into it I will be trying some designs around the cyma curve. If you took an S and removed the lower 1/3 it would be a brilliant form as well.

Interesting topic and wonderful to talk about form!!

-Gil

Re: cyma curves

Wally Dickerman at Green Valley, Az.

>Interesting subject Keith. Isn't the ogee form a shortened cyma curve? Wouldn't a pedestal bowl using an extended ogee form be a cyma curve? The ogee curve is used a lot in bowl turning, but a pedestal bowl has to be done perfectly to be accepted as good form to me. I have seen some that nailed it and were a beautiful form.

Wally

Re: cyma curves

Keith Tompkins

>Thanks Wally.....Your forms came to mind when I posted this. I wonder if you have done forms with the type of curve I describe. I agree, the form must be "nailed" to look right...Do you have any photos of your work which employ the cyma curve?

I have seen numerous pieces in critiques where the cyma curve was used. The advise was always the same...eliminate the reversed curve, and continue the same flow all the way to the foot. Is this just personal opinion, a fad, or something based on sound principles? Maybe it's just hard to get it right.

Re: cyma curves

Keith Tompkins

>HI Gil, I really enjoy studying various forms and styles....BEFORE I cut and twist them apart!LOL As you may suspect, I'm working on some things with the cyma curve as a design element.

Re: cyma curves

Ron in Drums PA

>Okay maybe I'm dense this morning. Besides I'm a visual type of person. Do you have an image of a cyma curved bowl?

Re: cyma curves

Keith Tompkins

>Hi Ron, here's a bowl I made several years ago....before I knew what a bowl gouge was!! The photo doesn't show it too well but you can see the reverse curve at the base....hope this helps.

Re: cyma curves

Jerome Laux

>OK. I like it. You see similar design elements in some of the extreme balusters and more on furniture pieces. Could you post a couple of pics of the Egyptian pieces so we could see their examples??

You mean something like this? 

Ron in Drums PA

>

Re: You mean something like this?

Keith Tompkins

>yep, that's it!

Making curves

Sam Simpson

>Hi Y'all,

Here is a small devise you can use to help with some of these curvature decisions.

Make a few paper cones.- A circle cut to it's center and then slipped together as a cone. Make note of the ratios. -The relationship between the base and height. Take a pencil and draw a line from top to bottom, as the cone is being turned. A second set of ratios is formed as the drop is related to the revolution. Good precision can be achieved with gearing, but freehand turning will yield educational results. Cut the cone open along the pencil line. The resulting curve will offer a lot in your furniture and bowl designs. Make several, of differing ratios, and use them to assist in your designs. Years ago the label "French curve" was attached.

Regards Sam Simpson.

Re: cyma curves

Pascal Oudet

>Keith,

good to see you open the debate here. the question on WoW didn't generate many answers, though I'm sure we have some pottery specialists on the forum.

It's just my feeling, but I think there is a general trend to take 'most of the time valid' things as universal truth (and use them as critiques).

Here is a profile shot of my piece (copy of an old Greek wine pitcher) before the finish was applied. If I had had to maintain the same curve to the bottom, while keeping the same height/width ratio (good balance between bottom part and neck/handle), I would have ended with a very narrow bottom. it doesn't work for a utilitarian item (the original piece).

btw, I found the golden number had been used in several ratios in this piece.

Pascal