Joining Plywood floors Revisited

[zapj]

I have read posts on different methods such as lap joints and scarf joints for plywood. Has anyone considered or tried this method? On the two edges to be joined first install a 1x glued and screwed to the edge of each sheet. Step two would be to put glue on the facing 1x's and the end grain of the plywood. Step three would clamp the 1x's together thus pulling the edges of the plywood together and secure with screws. This method would seem to add your backing under the plywood joint and also apply pressure fo a glued butt joint. Just looking for input for a wacky idea.

[Arne]

What is the benefit over just having a 1x3 overlapping the 2 ply edges.?

Once you have glue inbetween, I'm not sure just being able to pull them together in this way has any particular benefit....

Another thing, are you talking for the floor?

On my upcoming tear, I'm considering gluing 2 1/4" thick ply together to get 1/2"... the joints would overlap and I'd get additional plies and greater strength...... plus, no unsupported seam...

The design of the tear would have a V shaped tongue running under a goodly portion of the floor from back mid section to the ball mount for support, but no x-members (less aero drag)...

[Gaston]

my floor is 1/2"plywood. I glued the edges and covered the seams with 3/4x2 strips. I used thickened epoxy for the glue and the seans match up with supports on the frame. The tear i'm building is a 5x10 so the ply runs across the floor. (the floor is upside down in the photo) There is no advanage to "squeezing" the joint . with epoxy you will have a "starved " joint and it will be weak. I just line everything up, epoxy it then hold it with nails while to drys

[zapj]

What is the benefit? I'm not sure and that is why the search for input. Why do you clamp and not just lay end grain wood together when building thickness? Why is the 1"x3" screwed to the plywood and not just layed on top until the glue dries? I think you would have a stronger joint if the fibers where glued to themselves rather than a thickness of glue between. When the wood expands and contracts will it create a gap to be filled if the ends are simply touching but the back is bonded tight? I was just looking for a simpiler way than having to use a router or table saw to make a rabbit or worring about an matching angle cut the full lenght without a jig. If it would make a tight joint then yes it could be used on the skin side where you may be using a form of paint instead of aluminum.

[Joanne]

Hey Zap,

I lap jointed mine. Not so much for strength but to learn how to use a router. I think a butt joint with a backing strip would have worked just as well and been easier for me to make.

The only place I can see a problem with using a butt joint with a backing strip might be when insulating. In the case of my walls, I would have had to cut a groove in the insulation for the backing strip or it would have bowed out.

Joanne

I have read posts on different methods such as lap joints and scarf joints for plywood. Has anyone considered or tried this method? On the two edges to be joined first install a 1x glued and screwed to the edge of each sheet. Step two would be to put glue on the facing 1x's and the end grain of the plywood. Step three would clamp the 1x's together thus pulling the edges of the plywood together and secure with screws. This method would seem to add your backing under the plywood joint and also apply pressure fo a glued butt joint. Just looking for input for a wacky idea.

[Arne]

The screws hold the pieces in place while the glue dries. If you have a flat surface, and put some weight on the 1x3, the screws, I'm guessing, only add about 15% additional strength.... but, the glue only has purchase where applied, the screws go through the entire piece.... if you used a penetrating epoxy, the screws are almost unnecessary if the application is done right.

Same with a house. 50% of the nails are only necessary to hold pieces in place until assembly is finished.... after that, they don't do much additional work.

[zapj]

Thanks again for the answers and ideas. I'm mentally constructing while waiting for the frame to be completed.

[bledsoe3]

Make it simple. Buy 5' wide plywood. No joints. Mine is overkill 5' X 8' X 1". But I got it for $58 and I just bolted it to the frame. 5' wide ply is more expensive, but it's a lot easier than making joints and there is no waste.