Best way to deal with seams on multiple face panels across large lighted cabinet?

why not just order a 4'x50' piece of polycarbonate?

Although I would suggest looking into a flex face for this light box.

 

I agree that a flex face insert would probably be a better option. Though, I was going through some old post a few weeks ago and I believe it was signbrad that talked about putting a strip of thin clear poly to overlap the seams. It'd be bonded to one panel which braced the other panel and kept them in line. Maybe the extrusion is capable of using a hanger bar as well.

 

We have done the the overlap strip, not great but it works

 

If you insist on doing 4 panels then you can cut 2"x48" inch strips of polycarbonate (clear would be best) then bond them together with weld-on in the back of each panel 1" exposed to give you a retainer strip to hold the panels together so they don't bow at the seams. I would also screw the poly to the aluminum box once everything is in place so it doesn't move.

EDIT- I forgot to mention. You actually want to cut them 2" x 44" or what ever the inside space is so the poly retainer strip doesn't get in the way of the aluminum retainer where you slide it in.

 

I would design the sign not to hide the breaks and then you can fasten them how you see fit. trying to hide them isn't going to work, so make them part of the sign...

 

Did you happen to mention the old sign had vacuum faces for a reason ??

Going with something which the original design was not intended to do can easily come back to bite you, should something go wrong. Connecting them all together could easily result in a good stiff wind get in there and blow a solid 4' x 50' face out of a sign cabinet. That's 200 sq ft of solid sail coming at ya on a windy day. Could demolish vehicles, decapitate people and hurt little dogs, if it ever got loose. That much weight and resistance could very easily knock an end lip off.

If the budget doesn't warrant doing it correctly..... regardless of profit or non-profit..... I'd walk. Yes, someone will do it, but that is tooooo big to tackle the ways being suggested.

Many many years ago, I was helping another sign shop who decided to join 2 pieces which were I believe 6' x 20' each. We had both pieces fitted into the cabinet. He already had a clear 3" clear glued to the back side of one and we were in the process of tying them together. Guess what ?? A wind came along, tour the end off the sign.... almost knocking us off the roof and that thing sailed across the whole parking lot and took out two parked cars. Luckily, no one was in the area walking in the parking lot. This was a huge sign on top of one of the biggest day care centers in the area at the time.

 

I understand you are trying to "help" a non profit, been there done that. Instead of you racking your brain price them on a custom pan face and price them on printed banners stretched over this sign. Till they can get funds. its quick, easy and you will probably make more money off banner install than going thru the whole pan face ordeal

 

I reread your posts but did not see where you mentioned the thickness of the polycarb you are using, 1/8", 3/16", 1/4"? You can "break" (put a bend in polycarb) with heat but you need a good heat strip to do a good job, and 48" is a big heat strip. You would have to get straight bends for the panels to butt up good so the clear strips would be a better way to seam. I would also hope you had a wide retainer to hold that long piece in good. That is why pan faces work well on those because it gives extra strenght to hold them in place.

 

Another point. If it is a single face sign that originally had a pan form face, it may have been engineered for a pan face because the distance from the lamps to the sign face is a factor. If it used a minimum depth cabinet, you may get lamps showing uneven lighting ("hot spots") because they are too close to the new sign face.

 

I like this idea, but chances are they'll never have enough money for proper faces.

 

I always try to remember that just because I am doing work for a Non-profit Organization doesn't make my company a Non-Profit Business.

 

I've never done it. I worked for a short time in a shop and they would rabbit and glue two panels together. This was on a large donut shaped sign but didn't have a lot of surface area.

 

Price out replacement pans. If you want to make a charitable donation to the non-profit, go ahead, but don't compromise your professional standards.

 

depth of the cabinet is critical, as stated. flat faces will show hot spots if cabinet is not deep enough. one reason for the use of pan faces it does place the face aprox. 3-4" more, away from the lamps.

 

I've seen faces far smaller than this expand and contract almost an inch depending on how big the temperature range is. When working in electric sign shops, the rule of thumb we were always told to follow was to expect anywhere from 1/2"-1" expansion and contraction.

A 4'x50' is a monster sized cabinet in terms of surface area to account for on wind load and expansion and contraction.

If you screw them into the frame and restrict the faces ability to naturally expand and contract, something has to eventually give. Plus, it binds everything together and in the event of a heavy wind load, changes the entire engineering of the sign and face. Pan formed faces have a deflective property and added rigidity to aid in buffeting heavy winds. Flat faces have only two directions to go, inward or outward. Both are undesirable from a safety standpoint.

The seam strips are a valid option and one I've used most often over the decades, but I wouldn't fasten the pieces together for the same reason I just mentioned.

I'm curious to see how the sign looks right now and wish folks would share a photo of such unique conditions so we all could better assess the situation.

 

Stick with pans. If they can't afford it and you don't feel the need to make them a sweetheart deal so you can do it right and sleep at night, walk.

 

Is this some old mall where a supermarket moved out and is being taken over by the non profit. Can you clean the old pan faces off or is that too much labor cost and new flat faces would be cheaper?

 

You dislike my post because I suggest the best wrong way to do this sign. I suggested all the correct ways to make the sign. OP doesn't want to nor does the client have the budget. I suggested the best way for him to do it incorrectly. When I say screw the sign panels in I should of mentioned only one screw at the top center of each panel. This still allows for expanding and contracting.

I would strongly suggest screwing them in to the top. I'd rather have a bit of insurance that these are going to stay in place especially the middle three panels blowing out because of some huge gust of wind.

Please also tell me how the heck are you supposed to allow for a 1" expansion from a polycarbonate sign panel when it hast to fit very close to snug inside of the retainers so it holds the sign panels in. Expecially larger panels that tend to sag and bow in the middle. If you allow for a 1" expansion that would be even less of the retainer holding it in on the center of the panel. Just the weight of some larger panels cause the panels to sag in the middle. That is why I like to put a screw at the top center to hold it up in place.

EDIT: If anything you would have to allow for contracting only. Expanding would make the panel fit tighter and just bulge in the middle when it gets hot. Contracting would make the sign panel shrink a little pulling it away from the retainers especially the top retainer allowing it to be blown out. So I wouldn't cut sign panels smaller to allow for this. I would just do the 1/8 - 1/4" shorter on the height side of it so it slides in properly.