I am seeing a customer on Tuesday who wants me to make him a sign to go up outside the gate of his property. ( It’s kind of a retreat with camping spots and what not.)
So, the design for the top part of the signs is a tree with leaves and it also shows the roots. Something like this:
So Im thinking the easiest way to do this would be to use a thick sheet of Marine Plywood and do a V-carve on it and then paint it.
My question then is, how or what would you seal it with, and would you seal over the paint as well at the same time? Im always thinking the “weakest point” on such signs would be the edge between the sealed surface and the paint in the V-carve when it (eventually) lifts or peels), if that makes sense?
It also needs to hold up to a lot of humidity and full sun where I live. I have used marine grade varnish on similar signs before, but it turn white paint yellow. No good!
Anyway, Im hoping someone with a lot more experience than me can guide me in the right directing here!
I wouldn’t recommend plywood, firstly. Use SignFoam, it is NEVER going to rot, or deform. There are a couple of different manufacturers and they have products specific to sealing and painting, doesn’t need varnish!
There are some youtube videos on using it. It is not cheap, but your above process is not either.
Last spring a made a Vcarve road sign (used a ball nose rather than a V bit) using marine plywood. I used primer and paint I had on hand. I think it was killz primer and an enamel paint. 4 months later the paint was peeling off from the sign edges and some of the carved edges. I sanded it off and could see water stains at all right angles, every letter, edge, etc.
If you are set on wood, then some marine grade epoxy that won’t yellow might work. Eventually the water will penetrate regardless of what you use, so starting with a durable rot resistant wood is good choice. Maybe even pressure treated?
I think the customer is set on using wood. I will have to check with him tomorrow about what exactly he is after then. If it is for showing the grain of the wood or just because he wants something that is not printed on a flat surface…
I have mentioned pretty much all the drawbacks of using wood for such a sign and that it will cost 3x or more than just having it printed on sheet metal like the roadsigns or something, but he still wants to go down this track.
I have looked at the penetrating epoxy option. More or less the stuff they use for shipbuilding. Just afraid Im opening a can of work for myself as I have not worked with this before. You will have to seal over the painted artwork as well else that is the point where moisture will eventually get in. Like the one posted above by Atroz…
The drawback of that is that you probably wont be able to touch it up later if needed because you have effectively sealed the surface of the paint. Unless you paint over the engraved and sealed areas…?
We do not have access to any HDU here, unfortunately. Have searched far and wide but nobody is making it and very expensive to import.
As a newbie and in awe of the body of knowledge .about cnc here, I have experience with painting and epoxy that may help.
If you use thin epoxy glue (West Marine) and paint the whole surface including the edges you will have a lifetime board. You may lose a little detail so try a sample first Not sure about your process but will tell of painting the bottom of my steel yacht in 1978. Got the hull sandblasted below the waterline, and sealed the surface with epoxy g]ue, while the glue was just slightly tacky applied a layer of paint. The paint was glued to the hull and the last time I saw the boat the bottom paint was still adhered perfectly.
Epoxy will not cut most paint, You could paint the board then seal it, or you could seal the board then paint it after a light sanding and even seal it again over the paint.
You can make wood water-tight by sealing it with epoxy resin. You can even fiberglass over wood and layer with resin. They do it with hot tubs and campers.
I have made some Adirondack chairs on my CNC using cheap box store pine lumber, sealed with Total Boat penetrating epoxy, and sprayed on a few coats of their Halcyon finish. At almost a year out, they look the same way they did as when I made them. They live on a pool deck in the Florida sun. I know that white oak is supposed to be bullet proof to the outdoors, but I never played with it on a CNC. Also, there is a new MDF product engineered for outdoor use that is looking promising. I cannot think of the name of it, but they ship free samples. I carved a few up, painted them and put outside to test them out. I am impressed so far. I will try to find out who makes it and report back.
I managed to swing the customer to using a hardwood slab instead which I know there are plenty of where I live. Some of them have been here for the past 12 years and still look exactly like they did the first time I saw them…
Anyway, the Epoxy Resin is something I looked into as well and will definitely be trying that on some projects.
Epoxy is not U.V. proof. It ALWAYS needs to be coated with a u.v. resistant paint or varnish of some kind. And then every one to two years it will need re-coating.
I have used epoxy building boats for years and I know of what I speak. Marine plywood will last pretty long even uncoated, but everything has its life time. The sun always wins!
