Waterline paint question: How to factor in provisioning weight? - SailNet Community
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Waterline paint question: How to factor in provisioning weight?

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Last edited by chrisncate; 03-03-2015 at 01:57 AM.
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Old 01-12-2011
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What's the PPI for your boat??? What boat do you have?

The PPI tells you how much weight it takes to lower the boat in the water—pounds per inch... and if you have a rough idea of how much gear you'll be putting aboard, you'll have an idea of how many inches to raise the water line.

BTW, one figure I've heard of for cruising full time is to add 1500 lbs per person. IIRC, that is supposed to account for the person, their clothing and gear, and their food and water... but I don't know how accurate this is.

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Old 01-12-2011
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PPI or Pounds per Inch is what you should be looking for

PPI = pounds LOAD that will more deeply immerse the water line by 1 inch

Go to: Sail Calculator Pro v3.53 - 2000+ boats & find your boat in the left hand column of part #1 and 'click'; then go to Part #2 and find the parameters of your boat, including PPI
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Old 01-12-2011
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Quote:
Originally Posted by sailingdog View Post
BTW, one figure I've heard of for cruising full time is to add 1500 lbs per person. IIRC, that is supposed to account for the person, their clothing and gear, and their food and water... but I don't know how accurate this is.
Thats pretty close to actual for a long term cruising load - IMO
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Old 01-12-2011
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Quote:
Originally Posted by RichH View Post
Thats pretty close to actual for a long term cruising load - IMO
Given who I got the info from, I thought it was pretty close to right, but wasn't sure.

Obviously, for a shorter cruise, the load will be less, though more than what you'd have daysailing. I'd say any cruise four-weeks or longer in duration is going to probably be at the 1500 lbs. per person point as a rough guess, unless you're stopping in marinas every night...

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Old 01-13-2011
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Quote:
Originally Posted by chrisncate View Post
678 ppi
Just remember, the PPI generally increases as the boat gets lower in the water since the waterplane area generally increases, at least to a point... then the boat sinks... So, if you're going on a summer cruise with two people, you'd probably want to raise the waterline FOUR inches or so on your boat.

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—Cpt. Mal Reynolds, Serenity (edited)

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Old 01-13-2011
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BTW, if you do raise the water line prior to loading the boat, I'd use an ablative multi-season paint, so that the paint doesn't become inactive from exposure to air.

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—Cpt. Mal Reynolds, Serenity (edited)

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Old 01-13-2011
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Quote:
Originally Posted by chrisncate View Post
Good insight, thanks. I didn't know exposure to air could affect bottom paint.

She will probably be loaded at launch if all goes as planned, so I don't think it will be an issue.
IIRC, most bottom paints, other than multi-season ablatives, need to be submersed within 72 hours or so of being applied. This is especially true of hard bottom paints.

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You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.

—Cpt. Mal Reynolds, Serenity (edited)

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Old 01-13-2011

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Don't want to steal the thread, but what about the density of salt water vs fresh? If I'm sitting 1/2" below the water line in fresh water, what does this do when I bring it to salt water?

1989 Sabre 34II Targa
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Old 01-13-2011
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Salt water is denser so the boat will rise up in salt water

Gary H. Lucas
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