We are making a 4x8 (cut out borders) sandblasted 15# HDU (SignFoam). In previous postings we read that we should glue a piece of MDO on the back to make the sign stronger.
Any suggestions on what to use to attach the MDO to the SignFoam. Prefered methods? Type of glue?
Should we attach the MDO to the HDU before we paint and sandblast? Or should we do that before installing?
Should the "face" side of the MDO be glued to the HDU or should the "back" side of the MDO be glued to the HDU?
Thanks for your help! HDU is new to us. Our previous projects were smaller ones.
------------------ Mark & Stevie Naeyaert Deaf Signpainter Sign Language Interpreter Trainer Signs by Naeyaert Swartz Creek, Michigan
Posts: 36 | From: Swartz Creek, MI | Registered: Jul 1999
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When doing a job with HDU that is backed with MDO, I use double-faced MDO and glue it with a two-part epoxy. With a big 4x8 piece, don't skimp; place the MDO on the floor, spread glue, lay down the HDU, get it lined up (I use a couple of sheetrock screws which will be removed later.) Put another piece of plywood or MDO on top of the HDU to protect the surface. Use plenty of weight to press them together (I park the motorcycle on it!) and leave it overnight. When you are all glued up, Coat the edge of the sign with more epoxy, which will keep water from delaminating the MDO, paint your background, mask, blast, paint/finish. Be sure to wash and abrade the epoxy on the edges, and paint thoroughly. A sign built like this is at least as strong as one and a half inch redwood, and will last longer. Best of luck.
------------------ "A wise man concerns himself with the truth, not with what people believe." - Aristotle
When the going gets weird, the weird turn pro. - Raoul Duke (Hunter S. Thompson)
Cam Finest Kind Signs 256 S. Broad St. Pawcatuck, Ct. 06379 "Award winning Signs since 1988"
Posts: 3051 | From: Pawcatuck,Connecticut USA | Registered: Nov 1998
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Hi, Cam's method works just great - as long as it is a really cool motorcycle like his Triumph.
Oh, one more thing, BARE SURFACES!! (On the panels as well as the motorcycle.) We had a near disaster once epoxying painted HDU to Painted MDO - The paint ripped right off the primer and the faces nearly fell off - not the hot setup.
For two-sided signs we commonly use 3/4" HDU with a 3/4" d/f MDO core making a substantial 2.25" thick composite panel - beefy. We finish all panels as separate pieces leaving the backs of the HDU bare and only finishing the outside inch or so of the MDO peremeter. That lets us work on both faces simultaneously, face-up on the work bench. Final assembly is our last step.
For the final assembly we've had very good results tapping a couple very short nipped-off brads into the MDO and applying West Systems Epoxee in "blobs" a hand-width apart across the contact surface with a bead of either silicone or polyurethane adhesive caulk around the outer edge to seal out moisture. The brads keep the HDU from slipping sideways when we put the weight on it for drying.
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