Coroplast for really big frames?

[katman]

First, thanks to Ron and Hugh for privately taking the time to share their thoughts on one of my current projects. Ron suggested we open the discussion up to all because many of us are sort of circling around coroplast, gatorfoam (or gatorplast) and other materials as we try to balance conservation, weight, structural stability, etc.Oh, you coroplast converts--i've never used it but will be doing so soon so be patient and please help the ruest of us understand this product.

Here's the project: two pieces of "poster art" beautifully printed (looks like screen printing) on to canvas. Size: approximately 55" x 80" total for each. Client does not want them stretched. They will be hinged at the top and floated so various printer and merchant markings in the borders can be seen. Acrylic glazing, with spacers. I know, the glazing is gonna want to bow.

Because of the size I am playing with the mix of materials to try to keep the weight down while minimizing bowing in the package. The art will be mounted to cresent rag museum board, which I will splice together to achieve the size I need. My original plan was to affix the mounting board to a rigid backing board. I planned to use gatorfoam, which I am familiar with but unfortunately is (1) fairly heavy and (2) not available to me in sheets larger than 4 feet wide. I planned to splice the gator to the size I need, butting and joining with hot glue and perhaps running mylar strips over both sides of the glue seam (of course, I haven't found a mylar source so if anyone has a good source, please let me know. My backup is to make up and use strips of plastic laminate, probably about 6 mil.)

While working through this plan I thought about gatorplast, which is similar to gator foam but with plastic instead of wood facing. Gatorplast is lighter. However, same 4 foot wide limit. That's were the coroplast came in. I can get it in 5 foot wide sheets.

I gather from Ron that this stuff is light enough so if I used two sheets(dougle layer) in a criss-cross arrangement (biasing the ribs) it would be very rigid and light. Because these guys are going to be big, I thought about the same approach with gator but rules it out because of weight.

So, what do you Grumblers think? Will coroplast work or is there something better, like gator, out there? How should I affix my mounting board to the coroplast backing board, and what adhesive should I use to stick my two layers of coroplast together? Oh, what thickness of coroplast do you think I should get?

 

[wpfay]

8mm polyflute (Trade name "Coroplast") is available from Small Corp in 60" x 120" panels. It is archival grade (no additives). They also have oversized polypropylene honeycomb support panels, though they are not in their catalog at present.
They also will manufacture to spec aluminum honeycomb support panels. They may even be able to provide the panel with a seamless 4-ply rag face since they have 4-ply in 60" x 104".
Call them at 800-392-9500 or visit web site (www.smallcorp.com).
They are in Greenfield, Ma.

I'm not awere of any of the Gator Brand foam board products that are c/p.
I used 3/16" acrylic on a similar sized piece and had minimal bowing.
A subframe with cross bracing (strainer) will probably be necessary, and can be used to help reinforce the support panel.

Best of luck.

 

[Jim Miller]

Sounds like Wally's been there & done that.

I planned to splice the gator to the size I need, butting and joining with hot glue and perhaps running mylar strips over both sides of the glue seam (of course, I haven't found a mylar source so if anyone has a good source, please let me know. My backup is to make up and use strips of plastic laminate, probably about 6 mil.)

Mylar & most smooth plastics will not stick to any hot glue I've seen, including 3M's Mini-Weld.

But to answer your question, United Mfrs Supplies is a stocking distributor of Mylar-D or a currently-available equal, such as Melinex 516 or Hostaphan 43-SM.

 

[Framing Goddess]

Katman, check out Small Corp. first for their oversize board. Any time I have had large boards shipped in, I add the freight charges right on the top of my customer's invoice.
I would use atg or maybe SupaStickee! atg to bond two sheets of coroplast together. I might also use a bit of it to stick the coro to the strainer behind. Maybe a touch of pva glue, too.
I would use pva glua to bond the 4 ply rag to the coro, maybe a line or four of ss atg to hold it in place until the glue dries.
I would use two thickness of the thinner coro, then the rag on top.
The coroplast-er, polyflute- will work beautifully.
Good luck!
edie the hopeyouhavelongarms goddess

 

[Rebecca]

You might try Tycore, a honeycomb paperboard, in 1/2" or 3/4" thickness.

http://www.archivart.com/artcat.html#p10


It is very lightweight and rigid. More so than Coroplast. Unfortunately you would still have to splice. Perhaps wood-glueing the reverse to a lightweight wooden strainer, and then covering the assembly with washed fabric?

And also unfortunately, one has to buy a whole box. Perhaps you could convince a local distributor to carry it? Or, you could call Archivart's customer service and see if they've sold any to someone in your general geographic location, and buy a couple of sheets from them.

Despite these drawbacks, for some jobs it is just the thing.

Rebecca

 

[JudyN]

Our supplier of polyflute has a product called "Alumalite"
Aluminum on both sides and the polyflute inside. It is used in the sign industry. I have not used it yet but plan to order some with my next polyflute order. It should be very rigid for our large frame projects.

 

[katman]

Thanks fellow Grumblers for the guidance and new products and suppliers to add to my list. Now if I could only get the client to go with a liner instead of plain spacer I'll be happier looking at this job when it's completed.

 

[Framerguy]

Katman,

I sure wish you lived closer to my area. I have wanted to try Tycore and would be glad to split a box with you but I don't think the drive to Annapolis would give me an edge on my profit margin for the board. (Would you like to see the Heartland of America ............... like, soon??)

If you go with choroplast, why would you need oversize boards? If you are going to cross laminate 2 boards with the flutes running at right angles, you won't have a big issue with seams weakening your board, would you? If you thoroughly glue the boards together at right angles, the seams of one board would be at right angles to the other board and would be supported one direction to the other.

(Now, THAT really makes alot of sense!! But, you may know what I mean.)

Framerguy

 

[katman]

Okay, SmallCorp is bookmarked. They have some nice products. Harbor Sales on the other side of the Chesapeake has coroplast, honeycomb board and some other items so it's time to go shopping. Framerguy...Annapolis ain't that far and, well, the blues and rockfish will be running soon in the bay. Light line with a 20 pound fish attached to the end is almost as good as (is this a family channel?) grillin and eatin it later with a cold beer.

 

[preservator]

The Alumalite that Judy mentioned looks like a
very stable support source. The baked enamel paint
on its surface might be a cause for concern, but
one can order Econolite which has one side that
has not been painted and that side can be painted
with artists' acrylic as a sealing coat. This
alternative is also less expensive than the Alumalite sheet. This sort of product could be
very useful where the framed item is both large
and heavy.

Hugh

 

[Genuine525]

You can try GE Polymershapes in MD. They sell Gatorboard, Coraplast, Plexi, Gatorplast etc. Check out thier web site URL=http://www.gepolymershapes.com
GE Polymershapes
Jessup, MD
301-604-3623

 

[DGBuck]

Katman,

This is not as difficult a project as it may seem.
The key to these over-oversized projects is building a sub-frame(like Wally said)out of strainer stock(or like material)with several cross braces(I would use 3 in this case, across the 55" width) and cover this with your spliced AF foam. You can even use 2 standard 40x60 sheets for this size.(cut both sheets at 55" then splice; 40+40=80"!!!)

Here' how you do it:
-Build strainer with outside dimension of 55x80
-add cross braces(3), one dead center, then split the difference with the other two.
-cover strainer with 3" aluminum HVAC tape on the "flat" side of bars (to keep the nasties in the wood strainer at bay!).
-cut your 2 sheets of AF foam at 55"
-apply double rows(double thick) of AF atg and a bead of pva to the strainer on the taped side.
-tape your two 40x55" boards together, front and back, with Lineco aluminum barrier tape(you could even run a bead of pva in the seam for extra strength).
-apply spliced board to your atg'd strainer, making sure the splice centers on the middle cross brace, and apply pressure.
-cover this with a spliced four ply board (use 1 sheet 48x72 and one 40x60 so the seam doesn't line up with the splice in the foam).

Now you have a very rigid mounting surface, using materials you probably already have in your shop!

Clear as Mud?!!!

P.S. The strainer should'nt add much more weight than a sheet of coroplast, but it will add some depth. Also, you are adding a non-pc component(the wood strainer) to the framing package. It would be, in this case, fairly well isolated.

[ 03-28-2003, 12:43 AM: Message edited by: DGBuck ]

 

[DGBuck]

Okay. Last night after I got home I started thinking about this project and I came up with some possible drawbacks. So before I'm flayed, I'll try to correct myself.

In laminated systems of dissimilar materials there is always going to be differing rates of expansion and contraction. This may pose a problem long term with the technique that I posted above. As the wood strainer and the rigidly held foam expand and contract at different rates, the foam could over time, start to buckle and bow in the voids where it does'nt touch the strainer. This may be noticeable or maybe not, alot would depend on the environment. The boards I have made in this fashion (probably 3-4 over the last several years) are holding up, as far as I know. We do, however, have a very dry climate here.

A better long term solution, that would eliminate the problem of dissimilar materials, and would probably be adequate for a project of this size, may be to do just a laminated board using 3/16" AF foam with 3 thicknesses. It would be lighter weight and very rigid:

-cut four pieces of AF foam (as above) at 40x55"
-cut two pieces at 10x55"
-cut two pieces at 27.5x60"
-tape the 40x55" pieces together to make two boards 55x80". Tape only one side of board to eliminate the build up of the tape thicknesses. Note which way the boards bow.
-lay one 55x80 board on the table, tape side down.
-apply AF atg and pva to one side of the two 10x55" pieces and the two 27.5x60" pieces.
-stick the 10x55" pieces on the ends of the 55x80" piece on the table, and stick the 27.5x60" pieces between them running the length of the board. You should now have a two ply 55x80" board.
-apply AF atg and pva to the laminated board and place the other 55x80" taped piece on top of it, orienting the bow in the board opposite to the other taped 55x80" board.
-Apply pressure and let dry

This should give you lighter weight board than a coroplast sandwich, and more rigid.

Hopefully I didn't miss anything this time

P.S. One of the great things about forums like the Grumble is it makes us re-think some of the things we're currently doing. When your working in your own shop you are relatively unaccountable and mistakes are just your own. But when you start recommending ways to do things to other people, especially on a public forum like the Grumble, you better make good recommendations or your own mistakes may multiply. I realize what's said here is not gospel and everyone is responsible for their own framing, but I do pride myself in doing things the right way. It's great to have this resource that forces us to continually re-think our techniques and is propelling the professionalism of the framing industry forward at a much faster rate than it has ever known.

Still learning....