I have a bridge that sets on 3” foam abutments that is actually carved into a larger sheet of foam for the layout. There isn’t any wood to screw the bridge into and I was thinking of drilling a ½” or maybe a ¾” hole down through the foam and cementing a wood dowel in the holes. I just don’t know what to use for the glue. It is high density foam and I once tried to glue a couple of pieces together only to discover that the glue never dried past the first inch of the edge even after 2 years and I want the entire surface of the dowel bonded to the foam. Ok I just read the sticky on how to use this forum and I have no idea if this is supposed to be here or not. I don't think I understand it. Postings are just getting so complicated.
First off, this is better for the Inspection Pit, so it has been moved there. In a number of ways, I have had good experience using latex construction adhesive (like Liquid Nails) for gluing to foam. Just be real careful when you pick some up, as any kind of petroleum based product will eat at the foam.
LOL, Oh well kind a figured I might be in the wrong place. Thanks The thing I'm worried about is that I was thinking about drilling the hole the same diameter as the dowel and pushing it into the hole. So when I do that most of the glue will slide up to the top and cause a seal which would prevent it from drying inside the hole. I need something that will dry no mater what like epoxy, but I think epoxy will dissolve the foam.
Epoxy should not melt foam. Use 30 minute or two hour epoxy, not 5 minute. I would use 3/4 dowel, roughen it up with 100 grit. I would also bend a small piece of music wire into a 90 degree bend, use it to poke some holes in the sidewall of the 3/4" hole. The epoxy will flow into the small holes and increase grip. Coat the hole with epoxy and press in the dowel. Let it harden overnite and you have mounting points
Use the large white plastic wall anchors. I used them successfully in extruded foam so that I could use screws to secure a small backdrop to a diorama whose base was extruded foam. I would first pre-drill a smaller hole to the correct depth, nip off the pointed extension to the wall anchors, and then drive them into the foam. (Edit - just reread your question, and I believe I misunderstood. Gorilla glue works, but so does PL300, or even DAP Alex Plus caulking.)
Wow I thought for sure it would melt the foam, but I guess I could do a test. I really hope you are correct because that would solve a lot of problems. I used some epoxy to make a river in foam once, but I had sealed it with paint first. So I took a look around and found a two bottle of stuff to mix so I'll give that a try. Thanks for replying.
Thanks for replying. I don"t know about Gorilla glue, but I know the DAP will not dry all the way through if it seals itself airtight at the opening.
The "How To" Forum is not for Q&A. Only approved tutorials. The Inspection Pit is for all non-scale specific inquiries: Paint, trees, hydrocal, glues, foam cutting, how to make decals, etc, etc.
There are adhesives made specifically fro foam board. Should be available at any hardware store. You'll find them in the same section as the tubes of caulk, etc. Try embedding a (glued) small block of wood. It can't twist loose if attaching with a screw. That's what I have done in the past, using Gorilla glue or yellow glue.
There are dowel pins with spiral grooves to allow space for the glue. There is also some made of the same composite as the biscuits that swell up from the moisture in the glue to fill in any voids.
I did think of that and I do have some but the largest I've ever seen was 3/8" and not sure how large they actually come. Anyway I was just on the Gorilla Glue web site and went through their application questionnaire. I had to go through every application before ending up with the regular Gorilla Glue and also the Epoxy. I'm going try the regular Gorilla Glue on a test piece because I have some already, and them buy the epoxy if I'm not happy with it. I wish now that I would have planed ahead and made the abutments out of wood to begin with, but its too late to start over at this point because its all painted with foliage already installed.
With gorilla glue you want to dampen the wood dowel with water, water sets the process off and many forget the water part. If it were me, I'd dip the entire dowel in water then just lightly take the water off, and excess will combine with the gorilla glue. Gorilla glue expands, it really expands so less is better than more; I've used the glue a lot but have moved over to using the 5 minute epoxy. Why not go to Dollaram (dollar store) and purchase their 5 minute epoxy - $1.25 - and do a test on some scrap foam, if nothing melts you're good to go.
Thanks Rick, as it turned out I had the gorilla wood glue and not the other stuff, but while I was looking for it I came across a small bottle of “Elmer's Glue-All Max” in my assortment of glues. I don’t remember what I bought it for or how old it was and once I broke through the stuff that hardened on top it looked pretty good so I gave it a try. I couldn’t read the directions on the bottle and there wasn’t any information at their web site, but I did find something on YouTube and it appears that both brands use water to activate the hardening. I also saw a small blurb of information about avoiding soaking wood when gluing wood to foam so I only wet the foam in my test piece. I didn’t have time last night to actually drill a hole and glue the dowel into the hole so I just glued a piece of wood to a piece of foam and its holding pretty well. Later today I’m going to try the dowel in the foam hole and cut it in half tomorrow to see what it looks like inside. I’ll post a photo of the results tomorrow. Anyway the YouTube video below is what I saw before trying it. To be warned it is a Elmer’s Video, but its all I could find. [video=youtube;X82UXAaEqJ4]https://www.youtube.com/watch?v=X82UXAaEqJ4[/video]
Just to update, I used a hole saw which tore up the foam pretty bad inside the hole so it looks like epoxy is the only way to go for complete surface fill in. I’ll have to wait until I go to a store that sells it.
I use these plastic sheetrock screw inserts. They have a huge, very coarse thread. I thread them into the foam. Back them out and remove. Spritz some water in the hole. Put Gorrilla Glue on the outside of plastic insert and thread back into hole. Once dry I put a screw in.
