I hope to replace my patio roof using curved cross members – thats 4 x 6’s perpendicular to the house, curved cross members and then 2 x 2’s on top.
I plan to rip good straight grain 2 x 8’s into 3/4 inch strips. Then given a good form and lotsa clamps, laminate them in to 10 foot lengths. A 10 foot radius looks reasonable to me. I think I will try a scale model to settle on the radius.
I’m comfortable with building the MDF form and the other prep. My questions are (1) what is the best wood to use (outdoors in southern California) and (2) what is the best glue and finally, (3) is there a rule that says for a given radius, my laminations should be so thick. It’s possible that 3/4 inch is too thin for the radius.
Thanks
Gordon
Replies
For glue I would use a resorcinol(sp?) glue, usually you buy it in powder form and mix with water. This glue will not allow as much spring back as yellow glue. Water resistant enough for this application.
I'm not sure on the no. of laminates, the more the better, and how much longer would it take to cut them into 1/2" thick pieces, I cant say on the number of laminates to use with out looking at the thing as a whole but when I'm in doubt I opt for to many.
Doug
I have made a few laminations for trim work mostly, and going by how the thin strips behaved I would cut thinner to the point where easy flexing is possible. 3/8 or less comes to mind. Run the cut pieces through the planner and then light sand before gluing. I have used yellow glue with out problem, hyde or epoxy might be better. Scrape the excess glue and then run through the planer to clean up.
I think there are a lot of ways you could do what you're describing--either solid wood or plywood for the material, and resorcinol or epoxy for the adhesive. I've never heard or read anything about the creep factor in poly glues, but they might be a candidate also. Lengths of 1/2" thick fir baseboard with the profile ripped off would probably be ideal--dry, clear material. 1/2" plywood in 4x10 sheets would also probably work.
Gordon, I've done some curved work using PL polyurethane construction adhesive and it's worked well. Also used Resourcinol and Urea Resin; much more work and shorter working time. And more $.
The more plies the better. 3/4" might be fine, 1/2" or even 3/8" might be better. The ends tend to want to straighten out, so make your piece a couple of feet long on each end and cut to length after it's glued up.
in addition to all the competent advice so far..I'd add..
the greener th wood the more easily it will bend..the absence of knots is obviously in your favor..
I would second the PL adhesive..fantastic stuff.
you did not say what the finished dimension would be, so Iam assuming..something like a 2x6? remember to add plenty of length to the rough idea..it will saw tooth at the ends.
finally, a steel strap or belt and a comealong hitched to both ends saves a ton of clamps, while also compressing the outer layers grain..avoiding splitouts.
Spheramid Enterprises Architectural Woodworks
Repairs, Remodeling, Restorations.
We use a 100% poly glue, usually the PL one. Squegee it flat on both sides, lay it up on your form...and don't buy 100 clamps. Get 5 or 6" inch torx lag screws, and a bunch of 2x scraps longer than your form is wide. Screw one above and below the lamination into your burly form.
I hope this makes sense. It ensures awesome clamping pressure without buying dozens of clamps. We have used it on everything from arched doorjams to fascia.
jesse
Jesse,
I don't follow what you are saying - about using lag screws. Do you attach pieces of 2 by to the form and then hammer in wedges?
I appreciate your response..
Gordon
Instead of purchased clamps he uses home made clamps.. Strap of wood top and bottom and a bolt or lag bolt to tighten the whole asembly.
Much cheaper than clamps (basically all you buy are either bolts or screws if it's flimsey enough) and other than the scraps of wood it's made from can be reused later for other projects!
As to wood, Just about anuy wood will work.. I'm using cherry for my bent forms here in Minnesota. use whatever you'd like to see.
Have you considered a solid piece?
You could steam one yourself, pretty easy to do and if you build a nice strong form it will look a lot better than that plywood look you get from laminations..