I figure the order of magnitude of the FW/SW waterline change should be a little more than an inch for 30-ish foot Ericsons. As Doc Brown says, "
If my calculations are correct..."
One long winter night, I set up a spreadsheet for my boat, to calculate the various performance ratios, as a function of cargo. It was tied to a speculative manifest spreadsheet with the weight (known or guessed) of various additions, cruising gear & consumables. And some rule-of-thumb I found for the prismatic coefficient. Anyhow, I figured that it takes about 700 lbs to raise my waterline an inch. Empirical evidence suggests that this is within the realm of reality. I decided to ignore the freshwater/saltwater thing, but hypothetically, it means that the 700 lbs would raise the waterline 11/16 inch instead, in temperate sea water.
Put another way, the boat (empty) should float 32 mm (1 1/4") higher in sea water, which would put the (original) boot stripe high and dry all around, despite the resting list. Or 42 mm (1 5/8") higher with the maximum amount of cruising and diving stuff and provisions that I can imagine (but still 2" down). Which would be about the place where I attempted to re-draw the boot stripe.
Doesn't seem to make a difference as far as waterline
trim, that I can see, however. The list disappears if I sit on the starboard settee. Or fill the water tank and hang the kayak on the starboard rail.
Oops. Beat me to it. Interesting that we come up with similar numbers. Great minds think alike?
edit again: rule of thumb from Wikipedia article on Plimsol lines: The freshwater line should be (D/4T)mm above the temperate seawater line, where D is displacement in metric tons and T is the immersion in cm/ton at that draft.