Good Morning Gentelmen , This is my first time on your message board so please excuse any errors. I am trying to complete a pair of round back corner cabinets w/curved bonnet tops. I have bent the back’s out of 1/4″ birch plywood on a 14 5/8″ radius My therory is to cut pie shaped wedges out of the laminations to form the compound curves needed to make the top’s , but either my math or the idea itself is flawed as the wedges are fitting at the toe and at the heel but are gaped open in the middel.There is a globe secretary pictured in the August 97′ issue of Fine Woodworking that will more clearly show what I am looking for. Any thoughts or sugestions would be a godsend!!!
Thank’s for your time , Buck
Replies
Buck,
This is a common problem in planking on boat hulls. I can not tell you how to do it but I know the subject is covered in books on building and planking wooden hulls. If my memory serves me correctly, you put the first piece in place and then scribe the matching contour to each successive piece. It does involve a lot af hand planing. I'm sure others may be able to give you more precise references.
Doug
Edited 1/13/2005 12:12 pm ET by Doug
I think Doug is right; hand scribing yields solid results. For doing it by the math, there is a book, Pocket Ref, that describes complex math formulas.
I borrowed "Circular Work in Carpentry and Joinery" by George Collings from a neighbor once and was amazed at the amount of info in there. I'm pretty sure I remember it addressing your problem (probably in more than one way). Might be worth looking at.
I love the smell of sawdust in the morning.
Buck, your problem is rather simple to understand, but not easy to cut. You are trying to cut a straight line to mate to a spherical shape. Consider the lines of longitude on a globe. They are not "straight." When mapmakers make flat maps, the longitude lines are quited bowed.
Of course, there are formulas for spherical geometry that will give you the three-dimentional angles, but the best way to do it is to make a form that you can trace onto your lamination.
Good luck!!!
Bert
Goodevening , I just wanted to say how much I appreciated the response concerning the bonnet top corner cabinet's by everyone. This was my first time on this web site and I am convinced it is the best use of the internet a dusty stair maker could ever pray for. I found the same book on curved joinery at Wood Craft in Norfolk VA, and as Jackplane said, it show's two or three different methods.
Thank's to all !!! Buck
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