When a string is less than 60mm thick it becomes difficult to make it using horizontal laminates because the outer face veneers tend to pull it out of shape when being glued up.
For this reason for these stringers I use a more traditional laminate technique where I clamp the laminates to a form. This is also very useful if there are several curved parts of the same radius to make as the same form is used for all the parts.
The form is fairly quick to make, I just screw battens to some plywood shapes. The battens are drilled to receive threaded rods that will accept the same home made clamps that I use for clamping veneers to forms built with horizontal laminates.
Here are a couple of articles on how I set up this stair:
In the video below I go quickly through the main stages for building a curved laminated string for a 5 story stair.
The strings are made of laminated 7mm bendy ply and outer faces of 2mm oak veneers. The oak veneers have to be assembled with tape to get the total width of the string, note how the tape is pulled first across the joint to pull the joint tight and then all along the joint to hold it tightly together.
The laminates are glued up with ordinary white PVA glue easy to use and cheap the only problem being you have to move fast before it dries.
This is why the string is wrapped in plastic film to stop the glue drying too fast while being pulled into shape on the form.
The form is just made of battens onto which I screw the home made clamps I use for gluing laminates onto horizontal laminated forms.
All these standard parts make building different forms fairly quick and easy.
Here ‘are some photos that show how I make these clamps:
Here’s the video on building laminated strings:
Here are a few more photos that show some details on the way the strings are built:
Here are the photos of the finished stair:
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