[inovermyheadagain]

HI,
Brand new to forums here, but everyone seems really helpful. I'm trying to create a single solid sheet of MDF 6.5 feet wide. (hanging artwork on it) I chose MDF because it's straight and dead smooth - great texture for a backdrop and should hold up over time. I couldn't get sheets wider than 4 feet, so cut it down to two sheets and now need to join together to make one large sheet. I thought I could butt them up to each other and screw on reinforcing boards on the back side to strengthen.

When I tried that strategy with scrap (don't want to pay for my materials twice) I can't get a good clean joint - screws don't seem to pull the reinforcing boards and MDF all the way together tightly. (I was counting on the screws to create tight glue bond, and counting on the glue to do the long-term work.) The one time I tried pocket holes with MDF previously I was very unsuccessful, so haven't considered that option this time. Does anyone have any suggestions for creating a tight(ish) joint between the narrow edges of this material and get a reasonably precise edge? It doesn't have to be load-bearing or strong - just has to stand there and stay still.

I have never done biscuit joinery, but I do have access to a biscuit joiner - would that be a good approach for MDF? Is that a skill I can pick up quickly?

Finally, I don't have any clamps that would hold 6.5 feet together. Was thinking of using tow-straps (like tie downs for my truck) to create lateral pressure to hold the boards together while the glue dries. Has anyone done that? Or taken other non-traditional clamping approaches to long spans?

 

[inovermyheadagain]

Thanks! I like the clamping strategy - that sounds like it should be a lot easier than messing with strapping all the way around the work.


I hadn't planned to paint the board itself, but going to hang a wall mural onto it. It's going into my office, but the walls are concrete block and nowhere near smooth, so can't hang the mural directly on it. The painting is on a heavy leather-textured vinyl, so it should be forgiving of a bit of irregularity in the surface, but don't want a visible vertical line running up the whole thing if I can help it.



I did pre-drill the holes, and used coarse-threaded #10 screws, but just couldn't get the material to tighten down like I wanted. have been looking more into biscuit joints - I think they may do the trick if combined with your block-and-clamp technique. Can add blocks to back side of the material where holes shouldn't be a concern. Does MDF respond acceptably to biscuit joints?

 

[inovermyheadagain]

If I could get a 78 inch square out of a 4x8 sheet I would do it. But the geometry doesn't work out. I have to join 2 pieces to get that size unless I can find something at least 78 inches on the shortest side. (a 4x8 sheet is 30 inches too narrow.)