Self-tensioning frame for a DIY canvas screen - AVS Forum
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post #1 of 60 Old 01-25-2006, 07:27 AM - Thread Starter
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Self-tensioning frame for a DIY canvas screen

In looking for ways to build very large screens with commercially available materials I was finding I was limited to a very few methods. Painted walls were one and fabric stretched over a frame was another. Most cloths suitable for stretching and painting become hard to find when widths exceed 60 inches. And I found artist canvas readily available in widths up to 144 inches and of very high quality, sold from rolls full width, priced very reasonable and made to accept paints. They come in three weights and the texture is very smooth and becomes smoother with each coat of paint. The canvas in of itself seemed to produce a surface that dispersed light evenly back to the viewer and combined with low luster paints gave a 180 degree viewing field.

I built several test frames of smaller size to experiment on and it became apparent that as the frame became larger stretching the canvas very tight became harder. That was when I started designing a self-tensioning frame. The idea being if I could first apply the canvas to the frame as tight as I can and then have a means behind the screen to stretch it tighter and then leave a pre stressed adjustment when any temperature or humidity changes happened the frame would compensate. So that's what I did. Instead of explaining more I have attached a link to a page that contains pictures of the whole process and will be happy to provide drawings or more information if someone wants to make another.

The frame system could be modified to any size or aspect ratio. And the fabric wouldn't have to be canvas BOC would work fine also I think.

My screen is 72high X 96wide 4:3 and is coated with two coats of a light grey mix I found thru doing comparative tests. The screen shots are not the best as I'm still trying to figure out the best way to show what I'm really viewing. I will be adding more pictures to the album as I get them rather than reposting new links all the time.

See link below:

http://community.webshots.com/album/546725411dBQqjb

I hope this information helps someone out.
Bud

Edit May 4, 2007
I realized I never posted any thumbs to this thread so I thought I would edit some in at this point of the build. I will post some at the end of the thread of the finished images.








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post #2 of 60 Old 04-01-2006, 05:44 PM - Thread Starter
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I posted a few new screen shots to the link in my signature some have been asking to see. It shows the increases in gain I'm getting with the addition of the polyurethane and paint mix. All the newer pictures are labeled as having the topcoat.

Edit May 4, 2007
I realized I never posted any thumbs to this thread so I thought I would edit some in at this point of the build.

Painting






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post #3 of 60 Old 04-02-2006, 01:08 PM
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Hi Bud

I'm trying to build a frame for BO cloth. Your design looks good but I can't quite figure out the construction details from your photo's. Is the outer frame that the canvas is attached to "floating" enabling the tension to be changed as required?

thanks

Tim
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post #4 of 60 Old 04-02-2006, 07:26 PM - Thread Starter
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Quote:
Originally Posted by tstruth View Post

Hi Bud

I'm trying to build a frame for BO cloth. Your design looks good but I can't quite figure out the construction details from your photo's. Is the outer frame that the canvas is attached to "floating" enabling the tension to be changed as required?

thanks

Tim

Tim that's exactly right. Each of the four sides is not attached to the others they are guided and held square by the others but are free to all move outward. Turning the nuts will expand the frames tightening the canvas cover. I then took it a step further and had the nuts compress the springs. And the springs push the frame out all the time. So in theory if my cover got a little loose the frame would retighten all on its own. That part might be over kill but I just wanted to see how it would work. If you didn't want to get into the springs you could just have the nuts to stretch the canvas. I have played around a little with BOC and unless you are wanting to just project to the white cloth I like canvas better for painting. It's a material that as the paint dries shrinks a little. I also like the slight texture as you can see from the close up picture I took. I think a little texture helps with smoothly diffusing the light and also hides the SDE better. I'll see if I can get a close up shot like the one I took comparing the painted canvas and BOC with the projector turned on and post it along with the rest.


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post #5 of 60 Old 04-02-2006, 08:04 PM
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Excellent. I think I will build a variation on this theme. Its not patented is it?

Signature.
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post #6 of 60 Old 04-02-2006, 08:13 PM
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Hi Bud

So the outer frame corners have a "through mortise and tenon joint" that is not glued or fastened - is this right?

Also, does the canvas/cloth at the corners have to be wrapped in any special way so it doesn't tear if adjustments are needed later?

thanks

Tim
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post #7 of 60 Old 04-02-2006, 10:00 PM - Thread Starter
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DnoyeB
Not yet

Tim that's right. What I did was by making the outer frame from strips of plywood glued together in strips, did two things it made a very ridged beam and it also let me stager the ends to make those mortise and tenon joints without cutting. I also left short openings to make the holes for the threaded rods.
As for the corners you kind of fold it like wrapping a Christmas gift. Same idea. Its not like you get a lot of movement as you tighten more its just tension and stretching of the canvas. I had a few wrinkles after stapling and when I tightened they all came right out. After a day without paint I retightened and painted. One thing to note I did put a screw in each corner to hold it square and to size while I stapled it up. When I got to the corner I took those out and finished the stapling. Its still a good idea to work from the center out all four sides at the same time and get it as tight as you can by hand first.

There is another thread about using frame stretchers at 45 degree angles at the corners floating around here someplace. Those would work nice with this design also. If you cant find that post pm me and I'll dig it up.


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post #8 of 60 Old 04-11-2006, 01:11 PM
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Can I ask why you put the extra blocks that hold the tensioners flush with the fabric side of the frame . All those blocks touching the screen like that will make noticeable flat spots when the screen under tension twists .

I think screens of that size will have a tendency to twist rather bow in the centres .

Bruce
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post #9 of 60 Old 04-12-2006, 04:21 AM - Thread Starter
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Bruce
The reason for the blocks was to avoid doing just what you said. You may have been looking at the picture that shows the back of the frame. Around the whole perimeter of the screen is a .75 x .25 strip of molding that has a round edge. They call it screen door striping or something like that. That gives a nice round edge for the fabric to wrap around and holds it out from the frame just as you said. Then the blocking holds the inner spreader frame back another .25 inches. So at any point the fabric is .5 away from touching anything except that outside edge. As for warping the beams that form the outer frame being laminated out of 3 strips of 5 ply plywood became very stiff to resist warping. The way the corners interlock each supports the other from warping and the studs passing thru the holes in the outer frame give support to the outer frame to prevent warping along with pushing outward constantly. It has been in use now for several months and still drum skin tight and perfectly flat. The test screen I made on the other hand suffered major warping. I made that the old method with just 2x3 frame and triangle corner braces and stretched the material around it


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post #10 of 60 Old 04-12-2006, 06:40 AM
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I see so you did trim the face, that's good I didn't see it on there as a detail .

Bruce
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post #11 of 60 Old 04-13-2006, 08:09 AM
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Bud,

Is that a DIY mount (with a Sharp sticker) you're using for the projector? I don't recall seeing you mention anything about that in previous posts, but it looks to be an interesting alternative to the MonkeyMan based mounts. If it is DIY, I'd be interested in some more detailed shots.

Slightly off topic: remembering your (justifiable) frustration at the lack of attention this concept was getting, I'm glad to see your thread picking up steam. I'm also glad to see you persevered in your DIY efforts despite the amount of garbage one sometimes has to put up with on this forum. Well done.

-dave
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post #12 of 60 Old 04-13-2006, 11:04 AM - Thread Starter
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Quote:
Originally Posted by ORPhD View Post

Bud,

Is that a DIY mount (with a Sharp sticker) you're using for the projector? I don't recall seeing you mention anything about that in previous posts, but it looks to be an interesting alternative to the MonkeyMan based mounts. If it is DIY, I'd be interested in some more detailed shots.

Slightly off topic: remembering your (justifiable) frustration at the lack of attention this concept was getting, I'm glad to see your thread picking up steam. I'm also glad to see you persevered in your DIY efforts despite the amount of garbage one sometimes has to put up with on this forum. Well done.

-dave


Dave
With the fear of going way off topic but why not I started the thread.
Your observations are only partly right. A lot of attention has been paid to a few things I have posted about but mostly thru PM's. I think a lot of people view this site on a fairly regular basis but are afraid to jump in and post in the open forums. That's the sad part. I have received so many well written questions and ideas that people are afraid to put out there. And I can only assume its because they don't want to get on some side of a debate that should never be more than a discussion. From the number of PM's and like I posted the other day the photos have been getting well over 5000 views a week. There are a lot of people out in the world wanting basic information on DIY.
But thanks for taking the time to view the photos and read the posts and also the complements.

You did catch me on the homemade projector mount. I thought putting the Sharp sticker that was laying in the box would throw you off.
I thought about making a standard old pipe mount aka monkey man but I would have needed to get into the ceiling to anchor it to something. There are a lot of people with plastered ceilings that could do something like I did and just secure the mount up with 4 molly bolts. I could also envision a wire track type race way that could hold cables and deliver power to the projector that could be surface mounted to go along with it.
It's always amazing to me that some of these products haven't been made yet. One question I have seen a lot in the front projection forums deal with how to hide wires and homeowners wanting a neat looking job but don't want to rip their ceiling down to run wires. Maybe I should start up a cottage industry and build some of these things.

My mount is pretty basic its just 4 bent aluminum legs (L's) the front two slotted to allow up and down angle adjustment. The center projector support is the same material bent into a (U) with cutouts in it in the areas of air intakes and access to the bulb without taking the projector down. Just remove the front two bolts and the projector swings down and you can change the bulb. The rotational adjustment is allowed by the slots that mount the projector to the center support. Picture curved slots and 4mm bolts and washers. The drop height was a given from the information provided by the Sharp web site so I didn't allow any adjustment there. The throw distance was ample to use the zoom for in and out. that only left side to side. And brings this post back on topic. If you look at the photo showing the stapling on the back you will see a screw at the top. That screw and one on the other side is how I hang the screen to a (L) hook from the ceiling. At the screen I'm able to slide the screen right to left a few inches to fine tune it in that direction. I didn't give that mount much thought really until now but it did work out pretty well and is very sturdy also. As has been noted before I tend to design stuff to really last.

If I take the projector down again I'll try and take a few more pictures but I think from my description someone could make something similar to work with their projector.

A lot of the work I have done with my setup has been a little outside the box and done so intentionally to try and advance or at least show another approach when I can to what everyone else is doing. I just today had a discussion with a coworker over lunch that is just now building a home theater. His projector will be located mid room on the ceiling and we both thought wouldn't it be nice if say Sharp made a snap on back cover that had the projector finish and smooth molded lines that would hide all the plugs and wires going out the back. I have looked at a lot of photos of very high end high $$$ home theaters and in the shot of the screen there is this big water pipe hanging down and wires coming out of the back of the projector. There are some cleaver ones also where it's tucked up into a drop feature in the ceiling.


Bud

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post #13 of 60 Old 05-26-2006, 06:34 AM
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bud,
what kind of canvas did you end up purchasing? Linen or Cotton? also Primed or Unprimed?
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post #14 of 60 Old 05-26-2006, 07:57 AM - Thread Starter
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Quote:
Originally Posted by gwyden View Post

bud,
what kind of canvas did you end up purchasing? Linen or Cotton? also Primed or Unprimed?

The Canvas I bought was unbleached cotton. I believe you could use linen also I haven't tried it. The things I liked about the canvas is I knew it has been used for painting for a hundred or more years, I knew it was a very tough material that would hold its tightness over time, I knew it came in widths up to 12 feet and I didn't see many people needing to go higher than that with a screen, the cost is very low with shipping mine was under $40 and I also found and liked that when it dried with the paint it shrunk and became tighter on the frame.

The things I liked about it that others may dispute was the texture. I personally believe with a high lumen projector and trying to obtain a very wide viewing angle and with a uniform texture that is in the sub-pixel size is a good thing. I believe and tested with only my eyes that the screen door effect is somewhat minimized with this type of texture without any loss in picture quality because at the distances we view from the texture is non discernable. Texture that is unevenly distributed is very discernable when viewing the image as a whole.

Lastly what I liked about canvas was the ease of DIY painting I brush painted it without taking any real caution about brush marks etc. and with the flat gray latex paint it came out perfect with a couple coats. When I added a slightly higher gain topcoat it was a little less forgiving with a brush but was still quite easy for a first time DIYer to do


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post #15 of 60 Old 05-26-2006, 11:59 AM
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the cost is very low with shipping mine was under $40
=======
Bud,

Did you buy it from Dick Blick?

John
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post #16 of 60 Old 05-27-2006, 07:22 PM - Thread Starter
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Originally Posted by craftech View Post

Did you buy it from Dick Blick?

John

John

Actually I don't really know where the canvas I purchased came from other than the supplier was in the Cleveland Ohio area. When doing searches I found a number of suppliers selling it around the country and was about to place a internet order when I was talking to a furniture refinisher and he said he had a source for it and could get me a discount of a few bucks plus combine the shipping with his bulk shipments so I just let him order it. At that time I was still evaluating if canvas was a good choice of material so I didn't worry too much about how or where it came from. I have had a number of pm's though about the best place to source it and would welcome anyone to post here that has a good company name or internet source for the canvas. I know a couple sources I found on line seemed to be charging close to double what I paid.

Once again it comes bleached and un-bleached and in at least 3 weights and widths run all the way up to 12 feet. So with a frame system like I built I would see no problem building a 10 foot high screen using this method.


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post #17 of 60 Old 05-29-2006, 10:28 AM
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Bud,
I built my first screen out of the Parkland Plastic sheeting with a painted silver back (rough side). I project against the smooth side of the sheet.

Have you ever compared the images from your canvas screen to the Parkland screen? If so, how do they compare? I really like the image on the Parkland plastic. Vivid.

JOhn
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post #18 of 60 Old 05-29-2006, 11:48 AM - Thread Starter
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Quote:
Originally Posted by craftech View Post

Bud,
I built my first screen out of the Parkland Plastic sheeting with a painted silver back (rough side). I project against the smooth side of the sheet.

Have you ever compared the images from your canvas screen to the Parkland screen? If so, how do they compare? I really like the image on the Parkland plastic. Vivid.

JOhn

John
I have not tried the Parkland material. But I have heard some good reports on it much like yours. One reason I didn't experiment with too many of the sheet goods is around here 4x8 is what most stuff comes in and sometimes you might find some 5x10 material but very limited. I needed 6 foot height. The second reason is my theater was much like building a ship in a bottle. The stairs leading down to 150 year old basement make getting large sheets down difficult.

Like all that get hooked on DIY I wish I had time to one by one go thru all the different materials and paints suggested on here and then compare them against a bank of different projectors with varied specs. But I haven't yet found the time or the funding to do so. We have to collectively take each other at their word when we hear a success story. And people that make an attempt at least at posting screen shots sometimes help us judge even though we know a still cam cant capture what it is we see. But sometimes like in the case of ambient light issues the rest of the picture gives us clues as to how the screen is working with a given projector. That's what I tried to do in some of the images I posted.

My advice to a lot of people is if say in your case Parkland is working good and you are happy then post just what you did and the type of projector and what the room lighting issues are and then if you can a couple pictures of what you have both with some lights on and then none. I also personally think its nice if you can reference something we all have played with and know what its like to project on. And I find that is BOC buy a yard and tack it to the corner of your screen and people can kind of reference from that what might work for them. Lastly if it takes your breath away forget it's a screen and sit back and enjoy it.

Its all about paying it forward to me.


Bud

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post #19 of 60 Old 05-31-2006, 01:07 PM
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As far as canvas is concerned. DickBlick is awesome for damn near anything art related. Wife went to art school and blick was the only place that had a better deal then the local art store (even with the school discount, when purchased as a large order)


If you are looking for large format canvas here is a good place to start

*this is the one I purchased*
http://www.dickblick.com/zz073/09/
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If you are looking for large format canvas here is a good place to start

*this is the one I purchased*
http://www.dickblick.com/zz073/09/
========
Did you use the "primed" or "unprimed"?

John
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Quote:
Originally Posted by craftech View Post

If you are looking for large format canvas here is a good place to start

*this is the one I purchased*
http://www.dickblick.com/zz073/09/
========
Did you use the "primed" or "unprimed"?

John

primed always. It gives you a nice thick WHITE coat to work with. I have not tested getting unprimed and priming it myself but according to the wife it is more trouble the n it is worth.,
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post #22 of 60 Old 06-01-2006, 05:51 AM - Thread Starter
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Quote:
Originally Posted by gwyden View Post

As far as canvas is concerned. DickBlick is awesome for damn near anything art related. Wife went to art school and blick was the only place that had a better deal then the local art store (even with the school discount, when purchased as a large order)


If you are looking for large format canvas here is a good place to start

*this is the one I purchased*
http://www.dickblick.com/zz073/09/


When clicking on the dickblick.com link above it looks like pretty good pricing. I didn't spend a lot of time searching the site but it looks like the canvas comes 63 inch wide rolls that should be pretty good for most building a 16:9 screen for home use. The weight canvas they sell is a little lighter than what I used but that also should be fine, as it will have a finer thread count and a smoother surface. Keep in mind canvas does come in rolls up to 144 inch width.

As for primed or unprimed. I had no problem going straight to latex over the raw canvas I know artist need the primed surface for color bleeding etc but in my tests the paint held fine to the canvas with the added benefit of the canvas shrinking as the paint dried. Ether method should work though.

Thanks for listing a good source for canvas.


Bud

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post #23 of 60 Old 06-01-2006, 06:01 AM
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Quote:
Originally Posted by bud16415 View Post

When clicking on the dickblick.com link above it looks like pretty good pricing. I didn't spend a lot of time searching the site but it looks like the canvas comes 63 inch wide rolls that should be pretty good for most building a 16:9 screen for home use. The weight canvas they sell is a little lighter than what I used but that also should be fine, as it will have a finer thread count and a smoother surface. Keep in mind canvas does come in rolls up to 144 inch width.

As for primed or unprimed. I had no problem going straight to latex over the raw canvas I know artist need the primed surface for color bleeding etc but in my tests the paint held fine to the canvas with the added benefit of the canvas shrinking as the paint dried. Ether method should work though.

Thanks for listing a good source for canvas.

yeah I was talking with a buddy here @ work and he was going to help me make the wide screen but you re right. If anyone is looking for the the large format canvas here is the one I would go with

http://www.dickblick.com/zz073/22/

Folded Blanket Canvas 144" × 6 yd $89.98

As for my needs I would need 75" x 3yd

Folded Blanket Canvas 84" × 6 yd $56.68


leaving me with enough to do a second screen if I really wanted to. =-)
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post #24 of 60 Old 06-01-2006, 06:07 AM
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one more thing worth noting

I called the local Art Supply store and they have a 75" x 3yrd roll for $20

This is not a half bad price but again it is personal preference.
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post #25 of 60 Old 09-08-2006, 01:33 PM
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maybe Im being silly but why not just put some eyelets on the edges of your chosen fabric and attach bungie chords? In other words, the frame stays constant but behind the screen these "bungie's" (or big elastics if unfamiliar, the kind one uses to secure items onto your car or trailer for trips) will keep tension.
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post #26 of 60 Old 09-11-2006, 04:05 AM - Thread Starter
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Quote:
Originally Posted by MikeAttwood View Post

maybe Im being silly but why not just put some eyelets on the edges of your chosen fabric and attach bungie chords? In other words, the frame stays constant but behind the screen these "bungie's" (or big elastics if unfamiliar, the kind one uses to secure items onto your car or trailer for trips) will keep tension.


Mike

I have seen that done and seen it work. Many people build outdoor screens like that, but you need a lot of eyelets and cords. Each point you put one makes a stress point and a small ripple will happen half way between eyelets. My goal was to make it perfectly smooth. The other problem with the cords is getting them to all pull equal. If you count the rows of staples on my screen it would be like using 400 bungee cords.


Bud

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post #27 of 60 Old 01-04-2007, 07:55 AM - Thread Starter
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I haven't posted to this thread in a long time and over the last few weeks a couple topics keep coming up that this thread might shed some light on.

The first being using wide fabric stretched over a frame.

And the second being problems with applying poly or poly blends as a topcoat.

It's been my experience that the two go hand in hand in some ways. When I applied the poly mix over my painted screen I experienced some of the same problems some are seeing today with trying to get the coating on thin and even without painting into a tacky edge. Even though the canvas (I know now) is much easier to paint than a smooth hard surface. I still by not knowing what I was doing caused a couple spots in the finished screen where fresh poly was painted into tacky poly.

What I did was paint my screen with a 3 inch brush during the final topcoat and painted from the top down in maybe 4 to 5 inch strips starting at the left side and going to the right. Similar to how you would spray paint. By doing these narrow strips I was able to always be brushing into a wet edge of the strip above. It is virtually imposable to leave a brush mark when painting the poly mix over the canvas texture in this method. Using the brush lays the paint on in a different manner than a roller and this avoided any bubbles etc.

I don't know of anyone else brush painting a screen but I had great results doing a 6 foot x 8 foot area with this method.


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post #28 of 60 Old 01-19-2007, 07:57 AM - Thread Starter
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Self tensioning canvas screen update.

Last week the screen took a very hard hit. A to remain unnamed person who may have been slightly judgmentally impaired went to sit in a chair who's base was caster wheels. The aiming of the landing was not the best and in half missing the seat the chair went across the room at a high rate of speed until contacting the screen.

At this point I had to make a judgment call save the screen or the person who also took a very hard landing against the floor. Doing the proper thing I gave assistance to the screen(JK) after all the ruckus cleared I noticed two very large dents into the canvas but no puncture. I cleaned the surface with some windex and a soft cloth and thought oh well I needed a new project so here we go again. These dents were about 2 inches across and were very easy to spot on the screen and the image.

To my amazement the next day they were half gone. I took the screen down and misted the back side (raw canvas) with some water and gave all the tension screws a turn. This is the first adjustment I had made in a year of use. The next morning the dents had 95% healed themselves. And after a week I cant see the spots.

So not only did the canvas stretch and shrink back so did the latex / poly paint.


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post #29 of 60 Old 01-19-2007, 10:02 AM
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Hey Bud,

Just out of curiosity, how heavy would you say this thing is? If one had a mind to move it semi-frequently,would they be asking for more trouble than it's worth?
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post #30 of 60 Old 01-19-2007, 07:20 PM - Thread Starter
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Quote:
Originally Posted by ORPhD View Post

Hey Bud,

Just out of curiosity, how heavy would you say this thing is? If one had a mind to move it semi-frequently,would they be asking for more trouble than it's worth?

Weight was only a secondary concern when I built the screen. I intended it to be a permanent setup and the whole reason I built all the workings into the inside of it was so I didn't have to get it down and mess with it from time to time. My guess is it in the 60 pound range and its not a screen that you keep in the back room and bring out for movie night and if hung from a wall I would want to make sure I was into a couple studs. Mine is ceiling hung with two of those rubber coated hooks you hang your bike from the garage ceiling with.

My big effort in the design was to stretch a piece of cloth as flat as a pool table and as tight as a drum skin and have it maintain those two things over a long period of time.

It could be weight reduced a lot I think. Thinner material etc and in a 16:9 AR at say a 120 inch screen could be lighter than mine for sure.

I'm putting in (2) 12 inch subs shortly and hopefully its heavy enough to not sway when they hit.


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