"How To" question for curved half lap

[Andrew W. Thomas]

I've attached photos of a laundry rack for hanging hangers I plan to build out of 4/4 maple.

I am fairly set on the design but only so long as I can figure out a way to accurately "dado?" one piece into the other. I plan to have lower support remain whole while removing half the material width out of the upper support.

Any suggestions as to how to go about accurately removing half the material from one curved piece and making them seamlessly fit together?

After they're glued up I'll complete the though tenon.

Thanks for the help.

laundry rack 01.jpglaundry rack 02.jpglaundry rack 03.jpg

[Sam Murdoch]

I think you will just need to clamp your pieces together in the proper orientation, mark them out, then dado to fit, with hand tools or an tricky router template. You might be able to get an accurate cut template from your modeling program.

Quite an "organic" design. i like it. Please do round over the tenons of your horizontal ends.

[Steve Baumgartner]

I'd make a negative pattern of the lower arm (i.e. a board with a hole in it the shape of the arm) and use it to rout the slot into the upper arm. To make the negative pattern, you first make the lower arm and then use it as a pattern to rout out a hole in a second board. You can use that pattern board directly if you use a template bushing that corrects for the fact that the hole is larger than the lower arm by the diameter of the bit. Since the hole is larger than the arm, you have to be somewhat careful to position it correctly on the upper arm. If that's an issue, you could make a smaller negative pattern to the exact size of the lower arm by using the same offset bushing and cutting a hole all the way through a second pattern board (the same action as cutting the dado with the first pattern, just cutting all the way through). With an exact match, you can use a bearing-guided bit for the final cuts.

Steve

[Dave Richards]

Since you've got the SketchUp model, why not just make full size patterns from the model to use as templates for the routing? They'd be easy to make.

[Brian Tymchak]

Andrew, that's a really unique design. I like it a lot.

After they're glued up I'll complete the though tenon.

I'm not sure how you are thinking about cutting that through mortise after glue up, but I'm thinking it might be easier to cut the mortise in the top bracket before gluing. Then, with the tenon in place (dryfit), mark the lower bracket to pare out the notch for the tenon. Just thinking out loud.

[Andrew W. Thomas]

Thanks for all the suggestions. I figured out how to make full scale prints in sketchup so I'll likely print the patterns and use those for cutting out the initial pieces then also for making a template for routing one shape into the other.

Also, good suggestion Brian. I might do a little of both too by cutting the main through tennon, gluing up the pieces, then paring out the bit of material from the other piece.

[Pat Barry]

Seems like for a couple joints like this it would be far simpler to clamp the two pieces together, scribe the curves on each, then use a router to cut the 1/2 lap joints up to the scribe lines. The template approach would be great for mass production purposes.