A well-built new carvel hull has seams in which the plank edges are together (touching) along the inner two-thirds of their thickness.
***This is referred to as "outguage".
The outside third of the seam has a slight bevel to accommodate the caulk (cotton or oakum) and the seam compound.
***Bevel depends upon the planking thickness and the wood species used.
***Softer woods need less outguage harder woods need more.
When caulking a new hull an experienced caulker will go pretty easy with the mallet and iron, hitting just hard enough to get the stuff into the seam, but not enough to force the caulk hard.
***This is where the experience and 'touch' come into play. A real heavy hitter can destroy a new build just by not listening/feeling the tightness of the corking material as he/she/it, drives it tight.
With paint (preferably red lead)
***Best to pay the seam as soon as you can after corking.
***I was taught to cork a few seams on one side and then cork the matching seams on the other side.
***When done corking for the day, out comes either the red lead or the 'yard paint' and the seam brush to pay the corking and prevent it from creeping.
***Also, you just don't grab a hank of Mohawk corking cotton and stuff it in the seams.
It must be twisted and 'thinned' before use.
and seam compound to hold the caulking stuff in, the wood-to-wood part of the seam will close tight, the outer third will also close a bit, but not enough so the wood edge is damaged by caulk that is forced too much. The seam compound will squeeze out somethat, which is why you don't put a nice finish coat of enamel on a new hull. Use semi-gloss or flat the first year.
***Then the vessel is hauled out and the seams are 'set back'.
Wood has swelled from a years immersion in the water and the seams can now take a bit harder blow with the mallet.
***NOTE: this once again is a judgement call based on the wood, the tightness of the seam and the skill of the corker.
The above describes the pretty ideal situation. In caulking an older hull that has aready exerienced some shrinking and swelling, a good caulker reads the situation and pounds accordingly. Some factors he takes into account are how long the hull has been drying out; the kind of wood; the width and thickness of the planking; the condition of the seams; the condition of the fastenings; how the iron acts when hit; and how the iron and mallet sound when the caulk is hit.
Good caulking is an art that takes quite a while to learn. There's a lot more to it than just pounding stuff into the seams. It's easy to wreck a hull if it's not done right.