It's been a few months since
I introduced myself and the two Klepper kayaks I intend to make sea seaworthy again after many years on land. They are both old, one Aerius I from early 1980:s and one Arius 20 from 1976 (or so). Not only are they old but they have also been stored assembled outside for many years exposed to cold, humidity and pressure from the weight of snow. A result is that some parts have deformed or broken. Not only that but also wasps had build a nest on the Aerius 20 and used the cotton for material.
So I started with the Aerius I which still have a deck and hull in fair condition.

Some of the ribs had been deformed and had to be replaced.

Klepper has its own fittings in even its own copper aluminum alloy and some of them are
available online and some are harder to find. There were some on this rib that I couldn't find but I learned that aluminum can be soldered rather easily. It turns out that aluminum melts at 660 °C while zinc has a melting point of 420 °C which means you can melt zinc and not melt the aluminum part. I used a heat gun (should reach about 500 °C) an a cheap butane gas burner to melt the zinc (gas burner should be able to reach temperatures around 1000 °C).
It turns out that zinc is available to buy at marine store as a galvanic anode at a reasonable price. I don't know the strength of this seam but it will have to do for now. I suspect salt water won't be the best for the zinc.

The fittings are of course riveted to the ribs and the rivets had to be drilled out.

After stripping the ribs of fittings they could be used as templates for new ribs. Since they are bilateral, one good side was enough. I put the rib in warm water and let it soak before I put it under pressure to make it flat enough to serve as a template.

Turns out the dimensions of last century's German plywood is not the same as this year's Swedish ones. Also birch plywood has to be ordered and in the process I learned that B is the best surface quality while XX is so so and BB is somewhere in between. Managed to buy B/BB which means one good side and one ok side. To get close to the original just above 13 mm thickness of the original I glued two 7 mm pieces together with polyurethane glue. It foams so the boards had to be pressed together tight.

Then finally I was able to cut the new ribs from my birch plywood.

I mounted the fittings on my new rib to make sure they were put in the right place for the rest of the frame. I know the fittings originally are riveted but I have no riveting experience and I also had a hard time finding rivets at the right dimension. It's probably not right but 4 mm stainless steel bolts and nuts had to do.
Reached a maximum length for one post. To be continued.