Weatherproofing plywood?


#1

Considering making garden small ornamental structures, cut and carved by the forge( think exotic birdhouses), out of 1/8" plywood.
Considering how it would de-laminate fairly rapidly, I am considering resin impregnation as a possible method to overcome this, as just painting the surface wont be good enough, long term.
Anyone with experience of this, or suggestions for alternatives ?
I would like to keep to natural materials, though combining wood with some synthetic components would be an acceptable compromise.
John


#2

Marine ply perhaps? Check these people out.http://www.clcboats.com/shop/products/boat-building-supplies-epoxy-fiberglass-plywood/marine-plywood-cedar-strips/okoume-marine-plywood.html

Harry


#3

I think you just have to be careful of the glues they use if you plan to laser. Most outdoor plywoods use phenolic glues that are not laser friendly.

I’ve used varathane outdoor finish to great success. Fairly easy to apply with reasonable results.


#4

I may be wrong about phenolics. Quick google search made them seem that they may be okay to cut. I hope anyone else weights in on that.

https://hobarts.com/sheet-materials/wood/laserply_124_15_56/

Has laser able exterior ply. That was a quick google search.


#5

I’ve read that marine plywood doesn’t cut well with a laser :cry:.


#6

Yacht varnish?


#7

Fine Woodworking did an article a while back on the best finish to use outdoors.

You could use any laser safe plywood, apply this finish and it looks like it should have a good chance of looking nice if left outside.

This finish is also what is used to protect cedar strip canoes. Fiberglass fabric is placed over a cedar strip shell, then held on by epoxy, but since the epoxy is not UV stable, a marine varnish is applied over everything to protect it.


#8

Why not solid wood? Warping concerns?


#9

Does cedar zap well? I have been thinking similarly, but also along the lines of using regular wood that could weather nicely. (One of my planned projects is a design-your-own template where the attachment tabs (for some value of tab) would be fixed but most things in between would be drawable by the user.)


#10

With a 40w epilog laser, I have experience cutting, or trying to cut, marine grade plywood. It is not that the glue cannot be lasercut or is toxic (it might be), it is that the glue takes more than ten times the number of passes to cut the same depth as “normal” plywood. I tried to cut 1/4" marine grade plywood and it took me more than 15 passes, and the edges were so charred that it was not worth it. The same thickness of plywood, for interior use (baltic birch in my case) cut be cut in one pass.

I think it has something to due with the glue not absorbing the laser light.


#11

Oh, I want you to try this so we all will know! I have just been contemplating getting into resin impregnation, probably with cactus juice. I wonder how the resin and the plywood glue will treat each other?

If you are going 1/8" why not just solid wood plies?

Another possibility would be aerospace epoxy, perhaps West system. You get every nook and cranny sealed with that and your bird house would be like a bug encased in amber!


#12

Most epoxies break down in UV light and should be painted to prevent breakdown. I have tested them and they only last 3 or 4 years without being painted. Here is one that is advertised to provide UV resistance. I have yet to test this one. Epoxy is a glue and not a finish so it is best to put it over fiberglass tape which will give it very good strength. It will finish clean and allow you to see the wood, or paint it for additional protection.

http://www.duckworksbbs.com/supplies/epoxy/dwx/index.htm


#13

Hi All, and thanks for all the thoughts.
I had wondered about going with solid wood, and possibly impregnating that with the type of acrylic(I think) that is used in the preservation treatment for prehistoric timber. Nothing like belt and braes IMHO !
I wanted to avoid any ‘surfacing’ be it tape or even just a painted/varnished layer if possible, as this inevitably seems to either peel in odd spots, or water gets under it, and it goes cloudy.

As a slight change of topic, but it is outdoors, take a look at what these guys are doing in their limited space, and take heart if you think space is going to be a problem for the forge.

Happy New Year all,
John


#14

I’ve used linseed oil on several personal projects. It’s not for everyone everywhere. I’ve used it for years between Utah and Nevada. I still use it on some trailer decks and animal enclosures to keep the wood lasting longer. It’s cheap, and less toxic for the animals when they chew on the wood than a paint or urethane.

I don’t know where you live. Mildew can get to it if it’s in a fairly humid environment.


#15

Currently Corinth, MS and Norfolk, UK, back and forth at the present.
My friends in both places start with “Oh, you’re back then. How long for this time ?”


#16

I like the fiberglass resin idea. UV will eat almost anything, but I can’t think of a material that will outlast the clear fiberglass for outdoor exposure. Same stuff they laminate stone slabs together with for a bullnose edge.


#17

Linseed oil is awesome. We have a brand up here called “tried and true”. They aren’t cheap but have a great version with beeswax in it. Gives a great sheen and protection for cutting boards.

I can’t comment on outdoor applications, but it’s great to hear you had success in a less humid environment.


#18

You think linseed would work well outdoors during winter in Wisconsin? Would like to make some outdoor Christmas decorations!


#19

Bear in mind that “linseed oil” and “boiled linseed oil” are very different - BLO has metallic driers and hardens like a lacquer, while “linseed oil” will harden much more slowly and never get as hard.


#20

Raw linseed oil is foodsafe and can be used on cutting boards or butcher block tables. Boiled is definitely not foods and should not be used on cutting boards.