I’m building a stand alone table that will sit inside a bay window. My plan is for the top to be two 1” plies (2” think) of solid white oak that angle 20 degrees to mimic the window (see sketch). I want the angles of the top ply to join end-to-end, using dominos, at the crease (see sketch) which is at a 70 degree angle. Questions: Will I have wood movement issues with the top joining at a 70 degree angle instead of straight on or am I overthinking it? If I’m good to go should the bottom ply layout be the same as the top layer? And if there are concerns—I’m bracing myself!— what are my options? I could convert my top pieces into shop sawn veneer over MDF or make three segments and use connector bolts, but I don’t like either of those compromises. Any advice?
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There is a theoretical change in angle on a wide miter that can cause frames to fail. I don't think that is an issue when the ends are free like your 3-leg table. Rather than a full thickness bottom ply, think about building with a doubled edge and a "hollowed" interior. Make all of the joins in the same plane. Dominoes would be my chioce, and with the cavity below you have space toadd stiffeners across the seams underneath.
Just to add a bit .... the issue of mitre-gapping is more likely to occur if there's a significant change in surrounding moisture levels - and/or in the wood itself. The location you're intending to put this item might be more subject to such changes because it may be near a heating source such as a radiator; and may get regularly sun-dappled because of being in a bay window. If the window causes condensation, that too can change the local humidity.
Its can also cause a significant change in the wood moisture level if the atmosphere in the making-place is very different from the atmosphere in the intended location. Many woodworking sheds can be colder and damper than inside a house, especially in a bay window. Make sure the wood used is acclimatised to the final location of the piece, as far as possible, during the making. Mitre joints are notorious "canaries" indicating humidity-caused wood movements.
All solid wood "moves" with surrounding humidity changes. The least likely to move in a demanding location would be high quality plywood or blockboard covered with high quality veneer.
Thanks to both of you. The suggestion to "hollow" out the bottom ply was just the nudge I needed and saves both work and weight (white oak is heavy). And I'm going to take my chances on wood movement and trust that the top sections are glued and joined at a small enough angle that they'll move enough in unison to not be an issue. Besides our house has pretty stable humidity. Merry Christmas!