Laminated Bridge Cap Construction

[Ron Nossaman]

>That is pretty much how I am making this bridge cap. I just cut the width 
>oversize a few millimeters. I slopped on the epoxy just a few minutes ago, 
>laid them up, and ever-so-gently set a big pinblock on top of it and then 
>a couple of 50 lb. buckets on top of that. I just gotta hope and pray that 
>I didn't knock anything sideways and made any of the laminations slide out 
>of position. If that happened, I'll go to just laminating up a block and 
>cut a cap out of that like you described.
>
>Terry Farrell


With that horizontally laminated bridge root, I started with one layer of 
end-glued pieces clamped to a 1x10, so I had a minimal number of pieces in 
wet glue to deal with at any one time. A bit later, I added the second 
layer. Then, after the glue dried some, I ran it through the planer to 
level the surface, and glued and clamped on another layer of butt jointed 
pieces. I could plane and add another layer every hour or so, so I did it 
in a day, while I spent most of the day doing something else.

Another thing. cross laminating a vertically laminated bridge root should 
make it both a whole lot easier to bend to any old dog leg you want, and 
limit vertical dimensional changes with humidity swings to 20% of the 
change a regular vertically laminated root will experience. I haven't made 
an entire bridge this way (just short test samples), so I don't know quite 
how much it would affect stiffness. That's a lot of edge gluing for the 
cross ply laminations unless you have wide veneer sheets to cut them from.

Ron N