: I've been on with posts about my saggy aluminium keel.

I tried to run a tight wire along the bottom of the keel and it sort of stiffened it. Maybe it was the daylight too, but I did catch sight of a noticeable wiggle at the joints - as Jim and Bill points out - . The discrepancy between the inner and outer tube-diameters is 1 and not 2 mm, so I used the scrapped PC tin-cover (~ 0,5 mm) in between, and it probably won't be any better than it is now .. it has a much better response to the touch. And I feel the wiring all together is withering out of the equation. It's loosing it's function and it's a practical nuisance.
Maybe I could tighten up the gunwale stringers with a thin wire inside .. not as much to prevent the flexing, but to keep the 1m tubes stringed properly together.

Carsten