Welcome to the forum. Everyone steals ideas around here ... it is considered a complement! 17'6" wide is a nice width. I would have loved a couple of extra feet.
I found my receipt of the screen material: 98" x 13' Center Stage XD ; I cut on an approximately 10-15 degree tilt. The tilt is necessary to prevent the possibility of moire patterns with some projectors.
No problem with the screen frame being MDF. My horizontal pieces are exactly that. The vertical sections where made from some 2" finger jointed pine I had around the shop, but the horizontals are made from two strips of skirting board (baseboard for the Americans ;-) laminated together with wood glue AFTER being partially routed. The reason why I performed most of the routing prior to glue up was because the frame is curved. I glued the two strips using the frame as a curve profile to make the pre-bent piece. Routing the curve section would have been unwieldy. In retrospect I might have been able to make a straight frame and then bend as it was clamped into place, but I think the pre-bent approach made for a much cleaner and risk free fit.
I'll see if I can put together a sketch of the frame profile (horizontal sides) and the frame mounting a little bit later but I'll try and describe the build process:
1. the aluminium (British spelling just for you) flat was clamped onto the bend steel frame so that is was flush to the inside edge and overhung the outside edge by about 3/4" (this is important). Holes were drilled and regular intervals (6" I think) sized for future tapping.
2. The aluminum was removed and the holes in the steel were tapped. The aluminum was drilled oversize and countersunk so that it could be later fixed with countersunk head machine screws for a flush surface.
3. In a clean
workshop the screen material was layed on the frame and the rubber O-rings were fitted (obviously I has screwed in self tapping screws with a nylon sleeve on the back side to match where I had fitted grommets around the edge of the screen) so that it was wrinkle free. The location of the tapped holes were marked in the screen material.
4. The screen cloth was removed and the marked holes were punched with a home made punch to about 5/8" or so. The reason for this will aid understanding of how it all then fits together...
5. After painting of the frame, the screen fabric was fitted for the final time. I let it sit overnight so it was correctly stretched and tensioned. Then the aluminum flats were re-attached to the steel frame with countersunk machine screws. These screws passed through the holes in the screen material and essentially clamped the screen material in place. I did think of adding small washers so the aluminum stood above the steel and would allow the screen material to retain tensioning from the O-rings. This probably would be an improvement, but my clamped approach has worked perfectly so I don't think it is necessary. I also believe the aluminum flat stiffened the steel so I did not get any additional sag once the screen was hoisted vertically.
6. Ok, so now the frame is placed on the aluminum and squared up and set so that the masking edge rods run free (equal separation across length of . It is attached through some holes drilled in the part of the aluminum flat that overhangs the steel ... you can screw through the overlap and into the wood frame.
7. Note that I did find that the 1/8" aluminum flat was not sufficient to prevent the masking from binding. Either shim out with washers as described in step 5 or do what I did which was to stick a strip of approx. 1/8" think plastic tape on top of the aluminum before the frame thus lifting it an additional 1/8". Edit: Or use 1/4" aluminum flats instead
Here is the hastily drawn visual:
- Paul.Edited by Moggie - 6/12/13 at 12:35pm