Re: fg butt, is dishing necessary
Wade,
Are you using 1/2 inch ply? If so, I would vote to dish the joint and
use multiple layers of 9oz. bias woven tape. The result will be much
stronger. Dishing the joint is not hard or especially time consuming. I
used a 4" angle grinder with a a course (#30) grit flap disk. I dished
both ends/both sides of 30 sheets of 1/2" MDO before changing flap
disks. On each side of the joint I used three layers of 9oz. bias woven
tape split into 2", 3" and 4" widths. I use a tungsten blade roller
cutter to split the tapes. I dished the ends of each sheet 1/2 the
width of my widest tape and the thickness of the three layers. I used
peel-ply next to the splice to get a smoother joint. Polyethylene works
also, but sometimes you get wrinkles which leave a dent to be filled.
Once I switched to peel-ply, the joints came out very smooth with no
sanding needed except a few spots where excess epoxy oozed out at the
edge. I used a paint scraper while the epoxy was still green to remove
this ridge at the edge.
The trick with the angle grinder is to practice on some scrap until you
figure out how to control it by rocking it with the back hand on the
fulcrum of the front hand. It is like a floor buffer if you have ever
used one. If you hold it at the proper angle, and move against the
rotation, it is easy to get smooth, accurate dishing.
One compromise would be to dish the exterior side for three layers, and
use one or two layers on the undished interior side which is in
compression when bent to shape. Be sure to butter the end grain of the
joint with thickened epoxy whatever you decide about dishing.
I have some scans of a joint in the Dakota folder in the "files"
section, They also show the curved clamping boards I use to spread the
pressure evenly across the 4 ft. joint. I worked on a long bench of
planks on saw horses. (The knees object to working on the floor). The
pressure boards allowed me to glue both sides of the joint at the same time.
http://groups.yahoo.com/group/bolger/files/Dakota/
Vince Chew
Are you using 1/2 inch ply? If so, I would vote to dish the joint and
use multiple layers of 9oz. bias woven tape. The result will be much
stronger. Dishing the joint is not hard or especially time consuming. I
used a 4" angle grinder with a a course (#30) grit flap disk. I dished
both ends/both sides of 30 sheets of 1/2" MDO before changing flap
disks. On each side of the joint I used three layers of 9oz. bias woven
tape split into 2", 3" and 4" widths. I use a tungsten blade roller
cutter to split the tapes. I dished the ends of each sheet 1/2 the
width of my widest tape and the thickness of the three layers. I used
peel-ply next to the splice to get a smoother joint. Polyethylene works
also, but sometimes you get wrinkles which leave a dent to be filled.
Once I switched to peel-ply, the joints came out very smooth with no
sanding needed except a few spots where excess epoxy oozed out at the
edge. I used a paint scraper while the epoxy was still green to remove
this ridge at the edge.
The trick with the angle grinder is to practice on some scrap until you
figure out how to control it by rocking it with the back hand on the
fulcrum of the front hand. It is like a floor buffer if you have ever
used one. If you hold it at the proper angle, and move against the
rotation, it is easy to get smooth, accurate dishing.
One compromise would be to dish the exterior side for three layers, and
use one or two layers on the undished interior side which is in
compression when bent to shape. Be sure to butter the end grain of the
joint with thickened epoxy whatever you decide about dishing.
I have some scans of a joint in the Dakota folder in the "files"
section, They also show the curved clamping boards I use to spread the
pressure evenly across the 4 ft. joint. I worked on a long bench of
planks on saw horses. (The knees object to working on the floor). The
pressure boards allowed me to glue both sides of the joint at the same time.
http://groups.yahoo.com/group/bolger/files/Dakota/
Vince Chew