MDF as screen 'frame'.

[Gary Lightfoot]

I built my screen over 3 years ago using timber which I glued and screwed together to make a fram with center brace, then stretched blackout cloth over it.

MDF is now very cheap for 8 x 4, so I wondered what it would be like if it was cut to the correct 16:9 ratio (or even 4:3), then had 'windows' cut out so that it resembled my frame. You'd be left with two table tops and a long strip which could be used for something, but the cost would only be £4 or so.

Then you could stretch your screen material or blackout cloth over it, and not worry about it warping etc. Wood can warp a little, but it's never been a problem I've noticed.

It just struck me as being a simpler way to make a screen frame, and all you need is a drill and a jig saw. You'll have to make sure you can get a straight cut for the edge(s) you remove though.

Gary.

[ReTrO]

Probably useful for other people, but I'd stiuck with your frame if it's doing the job well.

Only thing you'd have to mind would be to make sure the MDF didn't warp/move/wobble forward or backward and make the surface un-flat. So it'd need some back bracing still. to the tiop MDF for going anywhere.

[Gary Lightfoot]

Actualy I didn't intend on changing my screen, I just thought it might be useful to those who are considering making their first screen.

I currently hang mine on two small pices of wood which are screwed to the wall, and that gives the screen a little left/right movement to help with lining up the picture (if necessary). The same could be done with the MDF. I would think the 12 or 18mm would be better, as the 6mm would be more likely to bend.

Gary.

[theritz]

Gary,

I reckon it would be prone to warping - there would be no torsional rigidity - might be a runner to stretch the material over a correctly proportioned piece of MDF, but I reckon it has the disadvantage of being heavy (and needing some sort of mounting bracket or frame at the back anyway) - then there's also the "How do I get it home" issue - Tempest style even !!


I had thought of trying it as a base for a painted screen........ but I'm too lazy and enjoying the PJ I'm "minding" too much to start dis-asembling my setup.................

Seasons Greetings, btw......


Sean.

[Gary Lightfoot]

I was thinking that an 18mm thick piece of MDF cut as described would be less prone to warping/twisting than the 5 pieces of 69mm x 18mm wood that I use for my frame.

Instead of having to glue and screw the pieces together, you just cut out the the two oblong bits you don't need, so that you end up with exactly the same size and shape as my frame. The only difference being that it's one piece and not 5.

That doesn't take into acount the differences between MDF and timber, but MDF is less prone to the effects of heat and moisture isn't it?

What do you think?

Gary.

We use mdf at work, and up to 18mm will be warped to some extent. 25mm is pretty flat, and I bought in some 38mm which was great - weighed a ton though! I reckon you could still do what you plan, and use some small angle iron to brace the edges to make flat.

Cheers

Rob

[theritz]

Gary,

but MDF is less prone to the effects of heat and moisture isn't it?

................. I don't think so...... ............... I've seen stuff in the likes of B&Q bent like an S-hook., stuff stored in the house go the same way (heat) and stuff in my shed take on Dali-esque characteristics from moisture..........

Effectively, this issue of whether a sheet with cut-outs would be suitable as a screen frame will only be answered by someone trying it - I still figure that the rigidity of the sheet will be dramatically reduced by removing the bits that need to be removed..................... I guess a lot depends on how much material is removed from the sheet - cutting out circles would probably retain more rigidity than cutting out rectangles.

For me. at least, the convenience of making a frame from 2x1 outweigh the biz of transporting and working on an 8x4 sheet.


All the best,

Sean G.

[Gary Lightfoot]

LOL.

Well, seems like MDF may not be a good idea after all...

How was the 2 x 1 frame then Sean? I used 69mm x 18mm which seems to work OK, but 2 x 1 is easier to screw together You don't need to countersing the screw an inch like I did). I only chose the wider timber so it wouldn't bow under the stress of the stretched screen material. How has yours faire in that respect?

Gary.

[theritz]

Gary,

I mitre cut the corners, glued the facing edges, and cut triangular bracing pieces from 6mm MDF, glued and screwed over the mitred corners. This yielded the basic rectangular frame which had little torsional rigidity (quite "wobbly"...). I then attached two bracing pieces, in the same direction as the short side of the recangle, each about a third of the way in from the side, glued and screwed to the top and bottom pieces of the rectangle..... still not completely rigid (as you would expect..) but a lot better. About 15 mins later with a staple gun and the job's oxo....... The two bracing pieces mean no chance of bowing along the long sides of the rectangle when pulling the screen material taut, and the two short sides of the rectangle are too short to bow in any case. Before and after diagonal measurements confirmed no change............Also the two bracing pieces allowed me to attach the screen to the wall using hangers on the top of the bracing pieces, leaving the screen "float" about .75" out from the surface of the wall.

It sounds very "around the houses" when written out but you know yourself, its abc when you're used to this kinda stuff.

It's still fine................. attracted the odd grubby mark when I was building the screen wall and masking so I intend to recover it during the New Year....... gotta choose whether to go for DRH or try something acoustically transparent - I'd really like to get L C & R behind the screen....... don't want to go perf because of LCD, micro perf from HH quite expensive... and couldn't be sure of avoiding unwanted "moire" effects............ considered the Dazian Celtic Cloth route, but a bit of a pain to import from US....... some more exploring at the fabric wholesalers, methinks....


All the best,


Sean.

[Gary Lightfoot]

Sounds like a nice job. Apparently the most expensive part of the screen is the frame, so I think DIY a good way to save some cost.

I'm not sure if the benefits of a perf screen outweigh the compromise - have you heard both, and what did you think?

Gary.

[theritz]

Gary,

The desire for a perf or acoustically transparent screen has more to do with wanting to re-arrange my screen wall than anything else. At the moment i'm losing a little over a foot of viewing distance, because the screen is actually located a foot away from the back wall - my hcpc and receiver, as well as L C & R speakers are all behind the false black screen-wall.

Ideally. I'd like to "bury" the speakers in the back wall and relocate the pc and receiver - Mrs Ritz is cool with having the wall (a partition wall) butchered, as well as having any equipmen located in cabinet(s) in the adjoining room (a downstairs loo.....).

This way I'd regain viewing distance (critical with the AE100) while keeping the "stealth" appearance of the movie room - a big factor for me. I hated having speakers etc. on view - from looking at others picture posted here and there, I understand that this doesn't bother lots of folk, but it drove me nuts. Now when I'm looking at a movie, there's just a jet black wall, no equipment on view (although the display of the receiver glows through the screen-wall material - that doesn't bother me, a bit cool imo). I'd also be an advantage to locate the equipment elsewhere - noise from PC gone..... only slight issue is having to use a different room to load dvds etc.......

It's a reasonable weekends work to sort it all out, and work and family have the happy knack of getting in the way (as well as my own inability to make my mind up.... and stick to it !) I also need to sort out some dvd storage............


All the best,

Sean.

[cosmic023]

Hi All,

I used Dazian Coated Celtic Cloth as a screen covering with my DIY LCD PJ till it died in the summer, the picture quality was very good when fed via the HTPC. It's a 1.0 gain fabric, it's a good fabric but i think it needs a backing because it's a bit thin and light shows through easily.

Looking into building a new screen using the same material after the new year, i'm glad i found this thread because i was gonna go down the route that Gary had talked about. I did think about bowing and the weight problem, as it's gonna be hanging from the ceiling via chain, instead of fixed to a wall.

I'll go back to the 2x1 timber frame idea with bracing to build a 72x55.5 4:3 screen. I'd like to build a dedicated 16:9 screen, but i'm afraid of burning a 16:9 image on my CRT PJ, I'd go 4:3 ratio and get a 74x42 16:9 screen into the bargain as well, dual format screen makes it easier and i can maximise the phosphour / light output of the PJ.

I hope this makes sense ??

Cheers

Cosmic023

[Gary Lightfoot]

Sounds like you both have some good project work to be getting on with next year - looking forward to seeing pics of the results etc.

Gary.