I have noticed that with every boat I have owned that the factory waterline is always too low and that the waterline scum is above the line to the point that I must raise the waterline. Just for verification I sail on an inland freshwater lake so I do not have a large quantity of stuff on board. Anyone else notice this problem? I even heard somebody explain away the problem as being a result of freshwaater not being as bouyant as salt which meant the boat sat lower in the water. Just curious.
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displacement
i believe salt water weighs more per gallon ,therefore your hull displaces less salt water than fresh water. so that is why it sits lower in the water when it's in fresh water
i believe salt water weighs more per gallon ,therefore your hull displaces less salt water than fresh water. so that is why it sits lower in the water when it's in fresh water
Me Too
I have the same situation with my boat on freshwater. I always wondered why - so it's a water density thing, huh! I should have paid more attention in science class.
I have the same situation with my boat on freshwater. I always wondered why - so it's a water density thing, huh! I should have paid more attention in science class.
fresh vs salt
Really salty water might have a density of 1.03 So if a boat has a displacement of 12000 pounds, this would be about the same as adding three or four hundred pounds. Not enough to change the water line much. Here is a link.
Really salty water might have a density of 1.03 So if a boat has a displacement of 12000 pounds, this would be about the same as adding three or four hundred pounds. Not enough to change the water line much. Here is a link.
My new Jeanneau has a waterline about 6 inches above the water in Lake Michigan. Maybe the builder has learned about the scum level beinging higher.
Salt vs fresh water.
For the interested: Salt water weighs about 62.4 lbs per cubic foot. Fresh water weighs 64 lbs per cubic foot. The effect is that a boat designed for salt water will float lower in fresh water (displace more weight of water) than the other way round. That said, ALL responsible designers calculate displacement for FRESH water. This means they will float as designed in fresh water and a little higher in salt water. They will also be sufficiently stable in both. I won't vouch for it but I don't think the perceived increase in buoyancy can be THAT noticeable-- maybe an inch or so more of bottom paint showing on a 30-footer. (I could check the maths but I'm being lazy.) My dad would be present for the initial launching of each new Hunter model and the staff would have this running bet. Everyone wagered five bucks on where the boat would float-- an inch high in front, an inch low in back, whatever. My dad always bet on his designed waterline (DWL). 'If that line is where I said it should be, that's my five bucks.' He never lost. [wink] JC II
For the interested: Salt water weighs about 62.4 lbs per cubic foot. Fresh water weighs 64 lbs per cubic foot. The effect is that a boat designed for salt water will float lower in fresh water (displace more weight of water) than the other way round. That said, ALL responsible designers calculate displacement for FRESH water. This means they will float as designed in fresh water and a little higher in salt water. They will also be sufficiently stable in both. I won't vouch for it but I don't think the perceived increase in buoyancy can be THAT noticeable-- maybe an inch or so more of bottom paint showing on a 30-footer. (I could check the maths but I'm being lazy.) My dad would be present for the initial launching of each new Hunter model and the staff would have this running bet. Everyone wagered five bucks on where the boat would float-- an inch high in front, an inch low in back, whatever. My dad always bet on his designed waterline (DWL). 'If that line is where I said it should be, that's my five bucks.' He never lost. [wink] JC II
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