posted
Epoxy. I use the same epoxy that I use on the letters. It IS a bonding epoxy and about the same cost as West System... so I figure why buy both.
If the sign is big, sometimes I'll drill pockets (flat bottom 1" dia. 1/2 inch deep holes with a forsner bit)in the back, drop in a stainless steel lag, then fill the pocket with epoxy. I have spacers laid out on the sign. Right after the epoxy is poured into the pockets, I lower the aluminum bracket so the lags go through the holes in the aluminum. The lags are now lined up, and the spacers keep the aluminum from bonding to the epoxy in the pockets. Or you can epoxy the aluminum to the back at the same time then add the self locking hex nuts after the epoxy is cured.
posted
Ahh.. different application than I thought. I was describing a way to attach an aluminum tube bracket on the back of a sign.
OK.. first, good idea to use aluminum. If you want to put HDU around a wood post, its best to make framed panels to box in the post, attaching the HDU box to only one side of the pole. Wood posts can swell enough from moisture to break open corner seams of HDU attached directly to the post
The epoxy I use is Dura Finish from SignFoam, the same stuff we use on HDU letters, mixing in paint for color. Another excellent brand is from Precision Board called PB Resin. Both are bonding epoxies.
At 3" x 3" by what ever length you have, with my experience of spreading epoxy, you'll need some decent working time. Either of the above mentioned epoxies should work as they are formulated for a slower set and thus a much longer working time and pot life. West System epoxy mixed in a large batch needs to applied VERY quickly or the pot will kick incredibly fast and you'll lose the batch. I know this from experience.
I'm wrapping posts with fluted signfoam. Plan to use SMA brand. 2 part epoxy since the Mfgr. is nearby and it does not expand like gorilla glue and similar products.
I have a mounting system of aluminum extrusions that groove through the signs, back to back (faces) flush and bolt to the posts. Exposed bolt heads and washers are primed and painted nicely. The SMA epoxy one can roll with a foam roller...medium setup/drying time. It comes in fast, medium and slow mixtures. I didn't want to buy 6 x 6 clear cedar posts and chance a foul when routing, so the signfoam is being done on the router table. Posts in cedar could have been done there too. I wonder if PVC posts would have been just as effective as the aluminum substrate post using epoxy? Trouble is finding 3-1/2" square material to laminate to in aluminum or PVC to achieve 6x thickness. I'm using excess signfoam, so cost for this approach really doesn't matter versus more traditional applications. I'm only going above ground height with the signfoam. Below grade is aluminum, probably with concrete fill.
Thanks again.
-------------------- Fran Maholland Pro Sign NJ Posts: 169 | From: Voorhees, New Jersey | Registered: Feb 2003
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posted
Sounds like you have it covered. I would try to stick with a slow hardner. The larger the batch you mix, the faster it will kick. Mix up a full quart of any epoxy, leave it in the quart container and it could harden completly in less than 15 minutes. Once it starts to kick it gets hotter & hotter and hardens faster & faster. I've melted down a few plastic containers before.
I would test epoxy on PVC before trusting it. Certain plastics is one of the things epoxy won't stick to. The plastic squeeze bottles we use to dispense the epoxy is easily cleaned out for re-use just by squeezing the bottle the next day when its hard. It just pops away from the inside of the bottle and we pull an epoxy replica of the inside of the bottle right out and intact with a needle nose pliers.
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