If you're framing out a full circular moon gate or a big curved opening into a simulator bay, double-layer your OSB or plywood for the radius templates. Cut identical ribs using a trammel arm on your router, sandwich them, and stitch them togehter with 2x4 blocking spaced every six to eight inches. Skimping on blocking here is a massive mistake. Flexible arch bead needs continuous, rock-solid backing or your circle will look wavy the second drywall mud dries. When you're tying a low pony wall into the curve for a bar top or counter, anchor that half-wall directly to the concrete slab before skinning the curve. That junction takes a ton of lateral torque from people leaning on the counter, and you don't want vibration cracking your taped arch seams later on. Also, plan your paint transitions early. If you're doing a bright white arch against moody, dark walls in the sim room, use plastic tear-away L-bead right at the color break. Taping a clean, sharp line on an inside radius by hand is pure misery without a mechanical edge to cut against.
Tips for framing large moon gate arches that nobody talks about
Sep 28, 2026
Last reply: 6 hours ago
4 Replies
I framed a seven-foot radius moon gate for my basement sim bay last winter using the trammel setup with a half-inch spiral bit. Double 3/4-inch CDX was plenty stiff, but I ran into an issue with the 2x4 blocking spacing. Even at six inches on center, pulling standard 1/4-inch drywall around the inside barrel created slight flat facets between the blocks. I ended up wrapping the inside circumference with a layer of 3/8-inch bending ply first to create a true continuous sweep, then glued the sheetrock to that. You're dead on about bolting that return pony wall down. I shot four Ramset pins into the 4-inch slab and tied the top plate directly into the OSB rib with Simpson SDS screws. People treat those drink rails like bar stools when they're watching someone tee off, so if there's any play at the base, that drywall joint will hairline crack in a month. Also, big second on the Trim-Tex tear-away bead. I had Sherwin Williams Iron Ore on the sim side and pure white out in the hall. Trying to run tape smoothly on an overhead inside radius is a nightmare, but the plastic tear-off strip gave me a laser-sharp cut line.
Man this makes me want to start ripping into my basement studs tonight!!
Quick question on the sim side of things though—did you guys plan for any low-voltage LED channel along that curved barrel, or does any ambient glow completley mess with your launch monitor cameras? I’m drawing up plans for my own bay right now and dying to know if overhead accent lighting ruins the ball tracking!
Before guys were running routers on trammel arms, we just swung a strip of strapping with a finish nail and a pencil, rough-cut the arc with a compass saw, and cleaned the edge with a spokeshave.
On tight barrels, the trick we used before bending ply was everywhere was hitting the back paper of 1/4-inch rock with a damp sponge twenty minutes before hanging. Let the gypsum take a little moisture and it'll drape right over that radius like a wet blanket without faceting or snapping. Did dozens of barrel ceilings that way back in the 80s.
I'm pretty green with framing and routers—mostly just done basic shelving so far. For that trammel setup, is that just a strip of scrap plywood screwed directly to the router base with a pivot screw at the center, or do I need to buy an actual jig for it? Also, how much extra room do you have to leave in the square rough opening so the circular rib assembly actualy fits inside? I'm terrified I'd frame the opening too tight and not leave enugh clearance for the blocking.
Join the Discussion
Have something to add? Share your thoughts — no account required.
Didn't find your answer?
Ask the community — no account required