Rocker with plywood?

[Satan]

Is there an easy way to put rocker into a piece of plywood?

If so what is the easiest way?

[devin]

are you using a solid chunk of plywood or laminating two+ sheets of thinner plywood together?

the boards i make are made using 3 layers of 3mm baltic birch. we put marine glue on both faces which whill stick to eachother, then vacuum bag the whole board. to put the rocker in we weight the board down with a few dozen bricks with the ends propped up with about 50% more rocker than we actually want, as the board springs back and doesn't hold it all too well.

.devin

[Satan]

I just got a single piece of plywood. I'm not in the US so I don't have access to fancy stuff like vacume bags.

I could do three layers of 3mm plywood. What is marine glue?

[kitezilla]

If you are using one half inch plywood, like most people, just soak the board in water or cover it with wet rags for an hour, and then take the board and suspend it by the ends on two chairs, and then place a 5 gallon bucket in the middle of the board .......fill the bucket with a hose until the board really bends a lot....the bucket will be almost full......then let the board dry in the sun with the weight in place. You will get about 2 cm rocker in the final board........seal the bent board with varnish and this will preserve the rocker.

[devin]

marine glue is simply glue that's meant to seal boats and the such, so it's waterproof and won't delaminate in water. the stuff that we have comes as a powder and you have to mix the correct ratio of water and glue to get the consistency you want.
i agree with kitezilla if you're just going to use a single sheet of plywood. i'd say the best way to get the rocker to stay would probably be to get the board damp, then place your weights on it in early morning, then leave it ouside in the heat of the day. the water would evaporate faster than it would if you were to leave it over night and hopefully cause the rocker to stay better. but always remember when using plywood to put more rocker in than you want.
the rocker i put on my boards is 3 stage. this is just done by propping up the tips, then placing all the weight on the board at about the foot straps, while the rest of the board (between the foot straps) is laying flat on the ground.

.devin

[bay surfer]

For laminating 3 pieces of ply, Screw them together on a table when gluing, drywall screws work good for this. A jig table is a heavy piece of ply, with a strip of wood at both ends for rocker. Just screw the pieces of ply to the table and let the glue set, remove the screws fill the 1/16 in holes, shape and your done.
This method works better than vacuum bagging for shaping ply, no bricks, pressure constant and you can adjust the rocker shape when laminating.

SATAN
What size of board are you making? Most larger ply boards do not need rocker, and rocker actually decreases performance of the larger ply boards. With 9 or 10 mm ply the ply flexes when riding, dynamic rocker.

[Satan]

Thanks for the responses. I made a 128cm board. I can ride it but it definitely would benefit from some rocker.

The next windless day, I'll give one of these methods a try.