Thanks. Some good ideas are coming out here.
You can probably see where my concern lies with such a small body as the soprano ukulele and the fragility of the wood.
Watching the video over and over again..... I don't think that I am going to have the luxury of pulling out the bottom slat first. Note that in the video the slat doesn't come out with a tug until the temporary clamp at the left is released. With the thin uke wood and the strength of the spring steel, that is going to break the wood.
The uke wood is only .070" thick, and about 2-3/8" wide. Fragile.
Lets look with photos at my particular problem....
First, the form:
Actually I have one lucky thing going for me here, as it isn't a standard soprano ukulele shape that I am building, but more like the shape of a dreadnought guitar, with a broad waist, and hardly any curve up to the upper bout from the waist. The whole thing is just 9-1/2" long though.
This by the way is John Hall's bender. You can see that the uke form is pretty tiny when it is in there.
And I am going to have to reposition the retainers for the ends of the springs for the two cauls. But that is easily done.
Rather than pull that lower slat out, I think that I am going to have to devise a way to retain it until after the upper slats, blanket and wood have been released. Two pieces of bent coat hanger wire bent into a tight U shape will do the trick here, as the ends can go through the form tubes. In other words, release the lower caul a little, hold the lower slat down, and insert the two "staples" to hold it down.
And the same at the upper bout end
The waist may be a little more problematic though. In this photo the waist caul has been lifted about 1/8". There's a heck of a lot of upward pressure on the steel already as it tries to unspring itself. Only trial and error will tell me how far it can be released before the spring steel rises enough to break the wood. But at this stage I don't even want to waste my test side pieces on what will probably be be a destruction test.
At the moment the only thing that I can think of doing is to drill holes in the uprights (which will fall just outside the waist caul), and find a way of holding down the lower slat (whilst raising the waist caul) in order to insert a couple of rods, or even nails would do it. But it would be awkward.
What I have thought of doing however, is to have the lower slat full width, but the upper slats narrower. A uke side is less than 2-1/2" wide! That way, the four retaining "nails" could be pushed in to hold the lower slat down even before releasing the waist caul.
Do you think that might work?
Rod