Elliptical/Bell gable end roof

[Bill_Emery]

Here is the construction. The book shows it for isometric construction; but you can use any angle. We are bisecting the mid points of the lines.

A good tip is to start with Chief's oval, as your initial starting point. It shows you the centers, and tangent points; although you can't snap to them. Chief could make ellipse construction very easy if we could snap to the oval.

The ellipse tool does not show the focus points of the ellipse.

4 center ellipse08242015_0001.pdf

[yusuf-333]

OK nice mark, actually I wasn't around PC but exactly that was was what I meant. And one important thing to know here is, the ridge angle of the wings must be equal to the eave angle of the middle one. Also included the same roof done by 4 roof planes. The only difference is the pitched of the two roof planes in the middle will have a pitch equal to 1/2 x thier eave angle( the ridge angle of the wings). The cross check is also included in the plan for the formula.

Bill, may be you didn't read carefully this post, yours is a graphical approximation of this concept.here I put one step and exact relation ship between the two (left and right )ones and the two (middle roofs). Read carefully how one's ridge angle is related to the other's eave angle. Open the plan and see the two options one(Four roof planes on the right side)

Or some one who understands my broken English can interpret it. No need for trial and error, if you really get my point. So you see..... I won, but that isn't really why I am back tracking. It is very important to understand that concept.

[Bill_Emery]

Hi Yusuf,

You and I differ a little in our approach to the problem. I think both are good solutions. 

 

I do understand what your saying about creating a point of tangency for the two arcs.

 

That said, using Chief's tools for roofs and walls we can only approximate an ellipse by combining arcs. 

 

I use a standard (but old) method of approximating an ellipse that produces a fairly smooth curve.  The geometric construction gives me all the information I need to produce a roof in an easy predictable way, and all I need to do is to enter the information from the construction into the DBX.  This has some advantages.

 

You'll notice that my roof planes come quite close to the point of tangency that you describe without a lot of manipulation.

[yusuf-333]

Hi Yusuf,

You and I differ a little in our approach to the problem. I think both are good solutions. 

 

I do understand what your saying about creating a point of tangency for the two arcs.

 

That said, using Chief's tools for roofs and walls we can only approximate an ellipse by combining arcs. 

 

I use a standard (but old) method of approximating an ellipse that produces a fairly smooth curve.  The geometric construction gives me all the information I need to produce a roof in an easy predictable way, and all I need to do is to enter the information from the construction into the DBX.  This has some advantages.

 

You'll notice that my roof planes come quite close to the point of tangency that you describe without a lot of manipulation.

Thanks bill, I am cureous the two methods are good as you say and complement each other. To get the initial startup boundaries one should use your method to predict the arrangements and limits of the drawing, but then since you can't snap it as you said you should use finally my method to get the tangency point smooth. I mean, after setting up the drawing limits you should just copy the ridge angle of the lower roof and paste it in the eave angle of the upper roof and again put half of the same number in to the roof pitch dbx and click OK ...done it. So the 2 of us are necessary to get a predictable roofs and smooth connections at the same time.

thanks bill.