Posted by Cam Bortz on March 07, 2002
Kent SmithIn the past month I've had two failures with signs made of HDU, on of them repairable, the other not.
In the first case, I'd made a SF carved sign and backed it up with MDO. We've done this lots of times, using West System as the adhesive, but in this case, on the advice of someone who will remain nameless, we used a type of flooring adhesive, specifically Liquid Nails, as a cost-saving measure. The adhesive bond failed after only a month outdoors; fortunately the client saw the sign delaminating and I was able to bring it in and do repairs without damage to the face. I removed the backup MDO, and re-glued it with a semi-liquid mix of West System thickened with HDU sawdust. A bit of fresh paint on the edges and the sign will go back up after about three days.
I'm not as lucky with the other sign. This one was solid 1.5" HDU, DF, hanging from a scroll bracket. High winds literally flipped the sign over the bracket, snapping it in half; the half that fell shattered into several pieces. It will have to be replaced; the client is currently seeking an insurance claim, as the damage was weather-related, but the lesson to ME is clear enough - no more solid HDU signs! All our HDU will, from now on, have a backing and/or a core laminate of another material - I've used MDO and 1/8" aluminum in the past, and may consider Dibond for this in the future, all using West System as adhesive. Sometimes it just doesn't pay to experiment - and I still have another sign out there with Liquid Nails that I have to keep an eye on. Ouch.
Rick SacksA few thoughts about the second application. I would be concerned about the hanging method. Sounds like the sign was allowed to swing which is a method I typically avoid. I have a number of similar signs up, just HDU, rigid hung with all-thread into the brackets. Epoxy around the all-thread helps to keep it from ovalling out the HDU. It is also a good idea to engineer the bracket for rigid wind load. We have 60 mph winds plus in March and have not had problems.
D. BernhardtWe tried a couple of the alternate brands of eurethane glues and made some samples. Ace hardware's brand was the weakest. Some expand more than others. Some have a less dense foam when dried, and turn powdery when you trim the excess off with an exacto knife. The Gorilla brand was the toughest.
Cam BortzYup....feel for ya mate. I've never had that particular problem although after the first time I used HDU I always used a core of plywood/MDO. However...I gotta add that although the jury is still out I'm sure the best adhesive for foam to wood combo's will be the poly urethanes. Gorilla glue is what it's called down your way I think. I also have tried all sorts of adhesives too. Ther should also someday be a larger discussion about the methods of use for west systems. There are a ton of ways to mis-use it.
properly mixed WS has never failed me, which is testimony enough.I've tried Gorilla Glue and it seems to work fine. My objection to it is the foaming/expanding action as it cures, wich leaves me with wads of hardened foam to trim off the sign - its particularly annoying when it's an applique on the sign face. Perhaps someone has developed a better way to cope with this.
What I like about West System is that the viscosity can be adjusted by adding fillers, either theirs, or better, HDU sawdust (which I always have in vast quantities!) I've mixed it to the consistency of a stiff spackle to fill gaps and voids, which is ... handy when you've got an old sign to restore and there are decay cavities to fill. That, and
D. Bernhardt
Mike JacksonThe way I deal with the foaming (which I think is a good thing) is slice it off the edges with an old chisel turned over. It is so easy to sand and when using appliques of wood on wood the unwanted areas are real easy to clean up. WS with the appropriate fillers, will always remain my tried and true for bonding planks but when it comes to lamination....POW the poly-urethanes win out on every turn! My reservation re; west system for foam is that is so ... hard and for that reason I get suspicious.
Hi Cam,
Ouch! Sorry to hear about these problems, but we have all had to deal with them along the way. Right? I never really felt good about relying only on a glue with the exception of laminating redwood panels. When glueing HDU to another material, we always nailed in at least a half dozen aluminum brads in the least conspicuous areas...then touch up the heads. The other way was to nail in the brads to the MDO prior to glueing, but leaving about 3/8" of the brad sticking up. Using a pair of nippers, we clipped the head of the brads. Once the glue was applied, we were able to press the HDU down and through the brads. I never used Liquid Nails, but we did use clear silicone and other similar "paintable" clear caulks. West Systems Epoxy would be a good choice, as you mention, but you would need to make sure it had set up before leaning the sign up out of the way and off the sawhorses or table.
Good luck on the insurance claim!
Mike Jackson
Denver Chapter of the Letterheads