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Old 10-30-2009
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True displacement

I'm looking at a used 27 foot cruiser with a listed displacement of 7300 lbs. The boat is now 30 years old and I'm wondering how much it might weigh now given that it has probably absorbed some water, and of course, been modified during restorations etc. over the years. Anyone have personal accounts of how the displacement of their older boat varied from the listed displacement when moderately equipped? I know there is no set answer to this question, I'm just hoping to learn a bit of the ballpark ranges from people with much more experience than myself.
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Old 10-30-2009
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I'm 6000 heavier then spec....water absorption is negligible really..its not like your a sponge or anything like that...some plywood maybe wet here and there and overly heavy but 200 lbs of water would be a lot in a 27 'boat..I would not concern myself with absorbed water unless it is obviously a compromised hull and is showing signs of delamination or sevear blisters ( deep big ones) ...Any weight difference will be 98% more to do with what amenities have been installed on the boat or original construction differences.

Older boats varied quit a bit in weight per build and per interior configuration...Have your yard lift it in their travel lift..it will be within 500 lbs or so as far as accuracy.
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Last edited by Stillraining; 10-30-2009 at 10:25 PM.
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So with a listed displacement of 25k for your ketch you were 6000 lbs, or 24% heavier.
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29,700...ok I was off 1300#...shoot me


OH ya now I remember...thats less BEER!...
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Old 10-31-2009
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Thanks. That helps. 19% seems reasonable.
Anyone else have weights to share?
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Old 10-31-2009
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In 1974 Catalina listed the 27's displacement at 6550 lbs (I've seen a few other numbers as well) but at her last haul-out, Essorant weighed in at almost 8000 lbs, a gain of nearly 23%. At the time she had all of our gear, the furniture, eight sails, two full gas tanks, bunch of crap in storage, etc. The stuff does add up.

Other displacements I've seen:
At 6240 listed, the gain would be 28%.
At 6850 listed, the gain would be 17%.

I understand that manufacturers often listed the displacement of the hull, internal structure, ballast, and rig with just about nothing else inside the boat (no motor for example), for racing ratings purposes.
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Old 10-31-2009
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It also very probable that the boat never weighed that lower number to begin with. Catalina didn't put a finished boat on a scale. The displacement was calculated, with a certain amount of estimation involved. I've also read similar things about C27s from people who were trailering them, that they rarely weighed less than about 7500 lbs. All that stuff inside, which as you say wasn't included in the published number, (batteries, fuel, junk) adds a lot, too.
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Adam I think your numbers need attention. ( Oh wait maybe your referenceing listed manufactured weights to your 8000..never mind)

Navel architects have to estimate the displacement ...there is no practical way to weigh a ship..so for the most part is is the same for yacht designers as well... A theoretical water line drawn and a displacement calculation based on that line...If they were off say one inch on my boat the effect is roughly 2000#

Jeff will hopefully chime in here.
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Last edited by Stillraining; 10-31-2009 at 01:47 PM.
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Old 10-31-2009
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Some newer travel-lifts will tell you your actual weight. I carry a ton of fuel and water. I was told once at a yard not to come in with my tanks full for a haul-out.
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Old 10-31-2009
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Boats don't gain a lot of weight simply because they're older. If the boat you're looking at floats on or near her waterline, she displaces what she's supposed to. Others above have already suggested that the displacement listed in the brochure may include lightening tweaks made by the marketing department: no water, fuel, sails, stores, lines, anchor, or crew. Adding weight with joinery changes, equipment, stores and other "stuff" may or may not affect how the boat behaves, however, and may or may not make any difference to you. It depends upon the boat. We sailed a 27' Soling for a long time. Adding 100 pounds of extra weight to that boat would have made it totally uncompetitive. We did everything we could to minimize weight aboard. Adding 100 pounds of soup cans in the lockers on a 27' Bristol Channel Cutter might not even lower her 1/4" on her lines: you'd be hard pressed to notice any difference. So... if the boat's floating and has gear you like, don't worry about her displacement. If the scale the yard uses may be off by 500# (according to the posts above), it isn't going to be of any use anyway.

Last edited by paulk; 10-31-2009 at 09:26 PM.
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