Latest Lightweight, Rot Free Panels for Projects

[jimbunyard]

Noticed that you seem to be planning to use epoxy to fasten the Formica to the foam. While this will probably work, epoxy is probably not the best choice for this application.


Properly done, the old style, solvent-based Weldwood contact cement is likely the best choice in terms of cost, efficiency and permanence.



'Proper' in this case would be at least two thin coats applied to each surface (three on the porous core might be better), fully dried between each coat (about 15 minutes). Bonding technique for full sheets takes some planning and prep; what I do is take multiple 1/4" thick strips of whatever, space them evenly on the coated core panel, position the coated Formica panel on the strips, and then strategically remove the strips so that no air pockets are formed as the bond is made between the panels. After the strips are removed, the bond should be 'reinforced' with a hammer and block of wood...

Almost takes longer to write it down than do it. While wet, clean up with paint thinner, once it dries; acetone, xylene, toluene, etc...

[Chotu]

Perfect, Jim. I was looking at using this stuff actually. I did not want to use epoxy. I'm have severe asthma attacks around epoxy. I guess that’s another part of my search for the right materials here. I need to avoid avoid epoxy. I wasn’t sure if this contact cement would hold up or not, but it seems like this is what most people use to bond Formica to everything. I’m glad you are giving it a recommendation.

As luck would have it, I actually have complete vacuum bagging capability Left over from building the boat itself.

My plan is to put all the panels under vacuum to create a perfect bond line. Should go very quickly this way. Slap that stuff on and all over the place, get the Formica in place, and put it under vacuum for like half an hour or whatever. Should go up very quickly.

[Amapola]

We had good results with Coosa. We replaced our rub rails with it and are currently replacing our built in dock boxes on the bow.

[Mexican Hat]

I have made a few boxes and cabinets for a camper van from foam/formica composite. Hinges and joints are the only issue as the core won't support them but easily solved with inserts of wood in the foam where you need fasteners. This would be before you laminate the formica... Joins can be done with wood cleats and screws but most joints can just be glued.
If you can bag the foam so much the better. Edging is easy with laminate trim strips. It's stiff, light and while not structural is surprisingly tough. I think this would be a good material for your door.

[Chotu]

Originally Posted by Mexican Hat

I have made a few boxes and cabinets for a camper van from foam/formica composite. Hinges and joints are the only issue as the core won't support them but easily solved with inserts of wood in the foam where you need fasteners. This would be before you laminate the formica... Joins can be done with wood cleats and screws but most joints can just be glued.
If you can bag the foam so much the better. Edging is easy with laminate trim strips. It's stiff, light and while not structural is surprisingly tough. I think this would be a good material for your door.

Thanks! Got some scraps to make a test panel today.

The foam (XPS) feels almost strong enough to use for cabinetry even before I start adding a skin. Pretty strong stuff. Should be rock solid after a skin of Formica

Thanks for the tip on the wood inserts for hardware. That's exactly what I'm planning to do. Should make hinges and everything a breeze.

What did you use to glue your joins?

I'm attaching everything to a rough epoxy surface (the hull). And haven't reasoned out how to do the corner joins yet or the attachment to the hull with this material.

[Buzzman]

Another option might be to use melamine-coated plywood. Link below is an Oz supplier, but there must surely be similar elsewhere...??

Melamine Birch Plywood | Richwise Australia

Has that fine, white "kitchen cabinet" smooth finish that resists water, yet has the structural strength and light weight of plywood.

Cut it with a router rather than a saw for a dead straight, splinter-free edge.

You can get 50mm long 12mm diam cutters for most handyman-grade routers, whihc ought to be able to cut up to 12mm thick ply sheets in a single (slow) pass.

[Mexican Hat]

Chotu, I used thickened epoxy but more because I had a lot of it around than because it was ideal. I did filet some of the inside joints also but I decided after a few that it wasn't really needed. There's enough surface area for overlap joints and once its all assembled it's pretty strong. Not sure if they'll damage the foam or not but the one-part polyurethane glues might be a lot easier.

[jimbunyard]

If 'XPS' means expanded polystyrene, I don't think that that is compatible with either contact cement or polyester resin. It is, however, I believe, with epoxy. Not sure about Gorilla Glue (polyurethane) or methylmethacrylate.

[Chotu]

Originally Posted by jimbunyard

If 'XPS' means expanded polystyrene, I don't think that that is compatible with either contact cement or polyester resin. It is, however, I believe, with epoxy. Not sure about Gorilla Glue (polyurethane) or methylmethacrylate.

Hmmm. I guess I'll see soon when I do the test panel. I'll let you know.

[Chotu]

Originally Posted by Mexican Hat

Chotu, I used thickened epoxy but more because I had a lot of it around than because it was ideal. I did filet some of the inside joints also but I decided after a few that it wasn't really needed. There's enough surface area for overlap joints and once its all assembled it's pretty strong. Not sure if they'll damage the foam or not but the one-part polyurethane glues might be a lot easier.

Thanks for the input. I'll give those a try if the contact cement is no good. Looking for an adhesive that is dry/set up in 15 minutes max.

[smj]

Originally Posted by Chotu

Thanks! Got some scraps to make a test panel today.

The foam (XPS) feels almost strong enough to use for cabinetry even before I start adding a skin. Pretty strong stuff. Should be rock solid after a skin of Formica

Thanks for the tip on the wood inserts for hardware. That's exactly what I'm planning to do. Should make hinges and everything a breeze.

What did you use to glue your joins?

I'm attaching everything to a rough epoxy surface (the hull). And haven't reasoned out how to do the corner joins yet or the attachment to the hull with this material.

How would you treat the cut edges of the XPS, in example the openings for the cabinet doors and the raw edges etc.? Sounds like it would have the same problems as the pre glassed Nida Core panels. This may not be a worry for you, but do you think cabinets made out of XPS would devalue your Schionning?

[Chotu]

Originally Posted by smj

How would you treat the cut edges of the XPS, in example the openings for the cabinet doors and the raw edges etc.? Sounds like it would have the same problems as the pre glassed Nida Core panels. This may not be a worry for you, but do you think cabinets made out of XPS would devalue your Schionning?

I'm using the fold over technique suggested by Wilsonart. It'll work with any core. Finally figured that part out.

It's a lot lighter than glassing nidacore, so it's looking to be the best way to go.

I don't think extremely lightweight cabinetry made of foam adequate for the purposes of holding dishes in place will devalue the boat.

[Breaking Waves]

I don't know if my experience will help at all, but .....20 years ago I made a complete cored interior - made it up in modular components in my shop over a winter while a yard was building the hull.

It seemed like a 'well-solved problem' even back then already.

You could buy pre-made panels, but I made mine just copying what I thought were the best practices from the higher quality guys. I used a 4x8 'press' rather than a vacuum set-up, seemed both simpler and faster for making a bunch of panels.

I used foam (urethane) and honeycomb cores, and ply and glass and formica skins. Interior 'design' was varnished to about waist level and then white above that - so varnished nice plywood skins for lower cabinetry, and generally semi-gloss white painted fiberglass skins above. Formica where esthetic was less important.

I generally used 'peg and glue' for the joins, with some nice solid shaped mahogany corner pieces in a few places for esthetics.

Looking around today for best practice examples, I am a bit surprised at how little the cored panel world has changed. I would consider Dragon Plate who are very technical/high stiffness to weight oriented (and ofc very expensive), as someone who has likely got the good core options sorted out given their skins are quite expensive.

[jimbunyard]

I hope you're using destructive testing in your evaluation, because extruded polystyrene is not a good core for this application, at least not in densities commonly available. While it has reasonably good compression characteristics, it has very poor tensile strength, which will likely lead to lamination issues in the long run.

[Chotu]

Originally Posted by jimbunyard

I hope you're using destructive testing in your evaluation, because extruded polystyrene is not a good core for this application, at least not in densities commonly available. While it has reasonably good compression characteristics, it has very poor tensile strength, which will likely lead to lamination issues in the long run.

It's a shelf to hold dishes. Ha ha. It doesn't matter AT ALL what it's made out of as long as it holds the dishes and weighs nothing.

It doesn't need any tensile strength. That comes from what I'm laminating to the outside of it. It needs compressive and shear strength. And it's got lots of it. The one I'm using as a test panel approaches divinycell in compressive strength. Sheer feels pretty good too, but the Numbers would be better.

But you had it right on the contact cement. Doesn't work at all.

Note:. I ALWAYS use destructive testing when testing out a panel.