My wife and I are in the process of building an arbor for the back yard. One of the design elements she hit on is a circular “window” in the middle of the arbor. After spending many hours searching for an easy solution, I have come back to the place I should have started in the beginning. Here are the details: 4′ ID, 4′ 8″ OD, 4″ Frame width, made from 2x or 5/4 pressure treated stock. Imagine a wagon wheel without spokes and you are getting close. It will not be a structural element, but I do want it to stand up to the weather and the occasional vine.
I know there are a lot of ways to do this. Just need some suggestions to get the creative juices going. A promary concern is that the arbors will be stained so I am looking for attractive joints. Waisting the least amount of wood (aka money) is an important secondary concern.
Any ideas?
CJ
Replies
CJ, why pressure treated? I'm all for unconventional materials, but for what you're contemplating, won't that be kinda limiting? Unless you've got different P.T. where you're from, it's going to be A. green or reddish (but only on the uncut facets) B.perforated ("" "") and C. butt-ugly. the curved faces would no longer be "treated",so you'd have to brush on some thing nasty, and the only stain you could use would be a solid, or opaque stain- you might as well paint. If you're worried about rot, just use redwood or cedar, and treat it with an oil every couple of years. Now. To make a 4' diameter window, 4" "rails", You'd get the least waste by cutting it from a mitered 2"x6" octagon. But I would try to keep it simple, and start with a square of mitred 2x12's if I could. This will make for the simplest joinery. You'll waste more wood, but hey, you can always use the cut offs to make two rocking chairs and some "chocks" for your car tires. Once you figure out the best dimensions (least waste, etc.) from which to cut your circle (use cardboard for the layout), figure out where you can put a biscuit in each joint so it wont be exposed by your cuts. Glue, clamp. Now all you have to do is make a compass from a yardstick, center it, and draw your cuts. If you're using a jigsaw, attatch it to the compass and cut away. If you want it extra tight, cut it a little big, then set up a router on a compass base (just make a "necktie" out of plywood), and clean it up with a straight cutting bit - I wouldn't bother with this unless the window needs glass, though. You can smooth the curves pretty good with a belt sander if you're careful and keep it moving.
Thanks Saul and others for the comments. The choice of material (PT) was an effort to match some existing construction, but I am starting to think differently about this project. If it all comes together as we envision, redwood or cedar will make a huge difference.
CJR
The wider the stock that you use the less sides to the rough shape and the least number of joints to make. The trade off to this of course is more waste. I would use 2x10 for the cost effectiveness. I would spline the end grain edges after I mitered the corners and use polyurethane glue on everything.
I agree with Peter to use splines on the miter joints. I would suggest a 2-1/2 or 3" wide splines with contrasting double pegs on each side of the joint. Dadoing the open mortise with a tenoning jig is quick and easy. The pegs announce the joint and the end grain of the spline attest to the joinery. I would use apoxy for this purpose.
Doug
When I made an arched arbor for the north entrance of the shop property
http://www.superwoodworks.com/Projects/ArchedArbor.htm
I drew the inside and outside radius' on a sheet of plywood which was aproximately 3 3/4 inches wide and thick. Then used the layout on the plywood to find the best length for the pieces to be mitered. I used 4"x 6" white cedar. The joints were splined and glued with Gorilla glue.
After the pieces arches were sawn out with the bandsaw there was just enough waste left over to saw out a thin arch which worked well for a trellis that I made this spring for in front of the shop. http://www.superwoodworks.com/Projects/ArchedTrellis.htm
View Image
I did something similar four years ago when built my deck and arbor. This picture shows the arched "knee braces" I made and the pdf file is the Autocad drawing used to make them.
I printed the drawing at full scale and used it to make a template from 1/4" luan. Then, I made the arch segments from 2x8 redwood joined with biscuits and Gorilla Glue. Before cutting the biscuit slots, I laid everything out and used my template to make sure that the biscuits would be completely within the final arch. After the glueup, I cleaned up the joints, used the template to mark the arches and cut them on the bandsaw.
The arches were made a little longer than needed and were fitted by clamping them in place and scribing the ends. After they were cut to final size, they were sanded and the edges rounded over.
I've been very happy with them so far. After four winters, there's no sign of any separation of any of the joints.
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