OT: outdoor wood sculpture

[Steve Hoffman]

This is a bit off topic but I need some advice about constructing a wooden sculpture that will be outside for at least a year. It will have to survive rain, direct sun, freezing in winter and baking in summer. It'll be in the middle of Kansas. I thought boat builders might have some insight about adhesives for this project.

The piece is a figure about 6' tall, standing on one leg and taking a step with the other (raised) leg. I will make this by laminating 2x12 lumber, using glue and dowels. Then I'll refine the contours using a belt sander and rasps. The mating surfaces will not be machined flat and square so there may be some gaps in the glue film. The lumber is untreated pine.

After the figure is shaped, I'll prime the hell out of it with an oil primer, then give it two coats of paint for the final color.

I'm concerned about what type of glue to use. A lumber store suggested floor mastic as a waterproof material but I worry this would be too flixible and allow the laminations to creep apart. What would you suggest as an appropriate adhesive for this project? Also, would the type of paint I use have any effect on the selection of glue?

[Jim Creech]

Either Epoxy or Resourcinol would be good choices as the sculpture is to be painted. Both can be thickened with milled cotton fibers to help with gaps in the joints and will not be affected by paint.

[russell lusthaus]

Jim is correct - Either will work - epoxy with fillers IMHO is a lot easier to work with.

While you are not asking for suggestions, I would still point out that using pine for such an application, even with good paint, is asking for trouble - not with the adhesive, but with rot.

There is an old boating expression which goes something like "White pine in a boat starts to rot just by thinking about putting White Pine in a boat."

If you want to fiberglass the whole shebang when complete - that would be a different story.

What are you building? Where will it go in a year? Indoors?

[Steve Hoffman]

Jim is correct - Either will work - epoxy with fillers IMHO is a lot easier to work with.

While you are not asking for suggestions, I would still point out that using pine for such an application, even with good paint, is asking for trouble - not with the adhesive, but with rot.

There is an old boating expression which goes something like "White pine in a boat starts to rot just by thinking about putting White Pine in a boat."

If you want to fiberglass the whole shebang when complete - that would be a different story.

What are you building? Where will it go in a year? Indoors?

You are right, Russell. Pine isn't the best material for this application but this is an experiment for me. I've never worked this large before and I'm not sure if my construction methods will be adequate for the weight. This is an entry into a sculpture competition. The winning works will be displayed in a downtown area, right on the street, for a year, then replaced with new works. Assuming my project is selected, it'll only have to survive one year in fairly good condition. By then, I'll know more about working at this scale. I do plan on making another version for indoor display only.

Encapsulating it in fiberglass is an interesting idea. Do you mean with resin only? The local Lowe's had 3 gallons of resin on the discount table. If I painted the piece with resin, would I have problems with moisture in the wood?

By the way, thank you for your help.

[Jim Creech]

Encapsulating the entire project in epoxy or polyester resin will certainly help protect it from the elements, however, epoxy resin will develop a wax film when cured which will require removal prior to painting. Also, not all paints are compatible with resins which will limit the type of paint you can use. An additional drawback is disposal of the sculpture. For what you are doing I would recommend some good exterior primer and all weather paint.
Good Luck on the competition and post some pics as it comes together!

[Steve Hoffman]

Would one of the common wood glues available in hardware stores work here? The project won't be submerged but it's inevitable that water will work its way into the wood.

[Steve Schoene]

The problem with using the ordinary carpenter's glues is that they have ZERO gap filling capacity, so that any gap will dramatically reduce the strength of the bond. The other advantage of using filled epoxy, which does fill gaps with strength, is that is also fills those gaps that would be avenues for water and rot. Also use epoxy to saturate the end grain of the wood, especially any surfaces that will see ground contact.

By the way, construction lumber isn't necessarily pine. And, for only slightly more, if you specify douglas fir 2x12's you will get a much more durable outdoor wood--not ideal but much better that white pine.

[russell lusthaus]

What I suggested was to use the resin and fiberglass cloth - when applied the cloth weave will disappear. This may be very hard to do depending on whether or not you have many nooks and crannies, so to speak.

As someone else mentioned, you could also use just resin - and encapsulate the entire sculpture. Two things about this - the resin will seal the piece, but not 100% - although probably enough to hold up for one year. Resin and top coated with varnish combo would be even better. However, the cost to encapsulate this sculpture would be quite high - with a product like CPES (best for this application, IMHO) - very expensive - but maybe something like RAKA (cheaper) epoxy would work. You will have to look them up and price them out. Not sure I would even know how to calculate the amount you would need. You could also use West Systems Epoxy (my favorite - but also pricey for this kind of application) and they have great tech support - so call them and ask. They will talk to you.

Good Luck

Also -someone mentioned that you get a white substance (amine blush) on the epoxy after it cures - and to be careful when applying a top finish. This is true of most epoxies - but some are now advertised as amine blush free (I never used of of these). To me, this would not matter - as I would wash the sculpture after the epoxy has cured anyway - and if you get an epoxy with blush - you just wash it off with a scotch brite pad and water.

[Earl Kelly]

Steve, have you thought about using Cypress instead of pine. I don't know what part of the country your in, but in the South, cypress is not that much more than pine and will hold up outdoors much longer.

I agree with the epoxy or resorcinol glues for laminating. Of course both are expensive.