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@Uwek, I decided to hold off on the wales until I see how the lower outer planking goes. I laid out the first strip and a question immediately came to mind. Do you see it yet?
A hint...
You guessed it. The aft part of the frame sits above the surface of the sternpost. Normally in a carvel planked ship, this would be flush. I have no idea of what is proper for this ship so I started looking at the photos provided by Boudriot. No definite clues there but it appears that the lowest plank sits flush with the stern post, while the ones above seem to have a sharper line indicating that they may be partially clinkered... yet even they appear to be flush where they meet the sternpost.
I sanded down the planks aft and lower edges to sit closer to the keel and sternpost.
Meanwhile, I finished the lower plank. I had a little bit of trouble getting it to align perfectly with the rabbet near the center point of the ship, but close enough for now.
As you can see, I clamped on plank 24c to see how it would fit. Some of these planks are a bit tricky because they have a twist to them and do not want to sit flush. A good soaking and several clamps will be needed.
It appears to me that a gradual transition from clinkered to carvel is called for on these lower stern planks. How to achieve this is obliquely described in the Ancre monograph:
As it turns out, the Boudriot plans seem to confirm that there is indeed a very slight clinker (almost but not quite flush) where the planks reach the sternpost. If you don't have the Ancre monograph, you should get it. It's quite good!
So I propose that we will need to sand an angle where planks 24 and 25 meet, so that they gradually transition from figure 1 to 3 in the figure above.