LumberJocks Woodworking Forum banner

Arched pergola beams - how to make them?

50K views 13 replies 8 participants last post by  a1Jim  
#1 · (Edited by Moderator)
A client wants me to build a pergola with arched beams.

The sample pics I've seen of the sort of thing they want are
glue-laminated out of shaped curved parts, lotta waste and
a lot of clamping to make just 4 or whatever.

So I've got a question of whether: (a) can I outsource these
glue-lams at any kind of reasonable cost?

and (b) would I be real stupid to glue up perhaps 2"x18"
blanks from 2Ă—6s (for example) and just saw them out?

Weight load is not going to be more than a few hundred
pounds on all the posts but I'm looking at spanning about 14
feet between posts with the curved beams.
 
#8 ·
Image


I made these with redwood 2Ă—8's.

First, I made a full size pattern from 1/4" ply, then determined the number of pieces of redwood I needed and the angles to cut the ends to cover the pattern

I laid the pieces out and traced the pattern onto the pieces and marked for biscuits - making sure that no biscuits would be exposed on the edge of a joint.

I cut my biscuit slots, tacked cleats at each joint, and assembled the whole thing using the cleats to clamp the joints.

When it was dry, I cut the arches on my bandsae, sanded everything and rounded the edges.

That was 10 years ago and - except for turning grey with age and exposure - the arbor is rock solid.
 

Attachments

#10 ·
I considered splines Jim, but didn't want anything peeking thru the edged of my joints which might provide a path for water.

I forgot to mention it earlier, but I used gorilla glue.
 
#11 ·
I question the need for splines when you've got a flat grain to flat grain glue joint.

Kindly,

Lee
 
#12 ·
Sawkerf
My job was paint grade so I just used bondo in the little bit of kerf that showed primer and painted. I like the splines because they had more glue surface(I made them 1/2" deep on each side of the joint ,I used resin glue for the spline joinery and construction adhesive to join the two layers together.
 
#13 ·
I've been mulling about my comment regarding splines, and I'm thinking they are a sensible addition to this project structurally.

The representative from Oregon changes his vote to Yea for splines.

Kindly,

Lee