Patching and Plastering - mounting fireplace mantle on wall

please redirect me if I'm in the wrong forum;
I'm hanging a wooden mantle over the gas fireplace; I'm drilling holes into the back of the 3"thick mantle, and using epoxy to fasten the pipes into those holes and the pipe will be screwed into flanges. I am using lag bolts to hang the pipe flanges on the wall & have 2 studs behind the drywall to lag into, but I'd like a center pipe/flange as well, but there's no stud there to lag into. Is there any equivalent of a drywall anchor, expansion or or molly bolts that I can use to attach that center flange to the drywall?

Are you imbedding the flanges below the sheetrock plane? That will give the mantel a flushness to the wall. Is there a stud offset between the two end ones? You may have to just offset one flange, or install two additional ones to make it equal. Your technique is pretty right on. Just a note to be sure to attach the flanges and pipes to the studs first, before you pour the epoxy in the holes and lift it up. I know it was elementary, but I had to mention it because you stated it in that order.

Larry

thanks Larry- elementary or not, please mention any tips to help out. I will be mounting the flanges first, and tilting them ever-so-slightly (shims) upwards first, then pouring the epoxy & mounting the mantle onto the pipes. I wasn't going to recess the flanges in the drywall. Instead I was planning on making cuts in the wall-facing side of the mantel so that it mounts flush to the wall. I thought that would be easier to chisel/ sawcut out a small concave area of wood for the flange to sit in.
There is no stud offset between the 2 ends ones because the gas fireplace now sits between those studs. (& the fireplace frame is mounted to the same studs)

but I still have the same original question= are there any kind of fasteners, molly bolts, anchors, etc. that I could use to secure a center flange to the sheetrock?

same original question= are there any kind of fasteners, molly bolts, anchors, etc. that I could use to secure a center flange to the sheetrock?

It's not the fasteners that come to question, but the ability of the sheetrock to hold it, so the answer is "no".
Cutting the profile in the mantle will serve the same purpose. I just didn't want you to have the epoxy poured, lift it up and not be able to have it flush to the wall.
Do you not think the two flanges will be sufficient?

Well we'll never place anything other than small picture frames or (lightweight) knick-knacks on the mantle, so I'm only hoping that two flanges would be sufficient but also don't want it to sag a few years down the road....do you have any other suggestions?

PS: I did find one product from Wingit Innovations LLC: they appear to be akin to very heavy-duty toggle bolts. They claim to be rated to hold up to 300lbs! (Wingits Innovations - Patented fasteners, fastening systems, grab bars, shower seats, master racks, anchors, crescent shower rods. (http://www.wingits.com))
If you check them out, could you please let me know if you think I could use one at the center of the mantle to secure a flange + pipe there.?

I use similar items to hang mirrors, or other objects not subject to more weight than the item itself exerts. Your mantle will be "laid hands upon" at sometime and the fasteners will work excellently! The sheetrock won't, so, basically if you feel warm and fuzzy putting the anchors in the sheetrock, by all means do it, but please understand the sheetrock will give before the fastener will. Take care.

Thanks for the all the advice, I truly appreciate the insight!