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how much does she weigh ?

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jm
Captain

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Canada
290 Posts

Initially Posted - 09/23/2002 : 10:07:08

In the specs page, the Catalina 25 fin keel states
a ballast of 1900 lbs and displacement of 4550 lbs.

Does the displacement value include the 1900 lbs of ballast
or does she have a total weight of 4550 + 1900 = 6450 lbs !

Yikes ! can't be..

Edited by - on

Spain
1st Mate

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USA
35 Posts

Response Posted - 09/23/2002 : 10:34:21

By the definition of displacement, it has to include the ballast.

Lee Spain
"Margareta"
'78 FK/SR #0931

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Bill Holcomb
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USA
769 Posts

Response Posted - 09/23/2002 : 12:54:01

Remember that the 4,550 lbs is the "design" weight in the late '70s. Over the years, redesign and options have probably added weight (pop-top for example). Then, you need to consider all of the other gear that the "design" weight does not include like: extra sails; motor & bracket; tools; water; fuel; stove & cooking gear + dishes etc.; radio & other electronics; and so on. A C25 can easily get up to 5,500 to 6,000 lbs. And, that without an inboard diesel, hot/cold pressure water, inverter, refrigerator, and other 'heavy' stuff.

Bill Holcomb - C25 Snickerdoodle #4839

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oldsalt
Admiral

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Response Posted - 09/23/2002 : 22:40:58

I don't believe that the actual weight of the vessel is the same as its displacement.

In order for an object to float, it needs to displace a greater weight of water than it, itself, weighs.

It has to do with density and volume. IE: a one ton block of steel will sink, well, like a block of steel. Fashion it into a hull with the adequate volume so that it displaces more than a ton, and it floats.
I think this is known as Archimdedes Principle.

As for what a C 25 weighs; I don't have the slightest idea.

So I have been no real help at all.

Regards, Oldsalt

Edited by - on

MattL
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Response Posted - 09/24/2002 : 03:47:26

Ballast is what is added to a bare hull to provide stability. Displacement is the weight of water that is pushed asside. The boat will not push any more, or less than it acutally weighs. Soooo if you want to make this difficult figure out the volume of the hull that is underwater and multiply it by the density of the given fluid and you should get the displacement weight. Volume will change as the boat goes deeper or rises up. also density of water will vary depending on salt content if in the ocean or the great salt lake or in fresh water.
An easier way would be to go to a public scale and weigh the empty traiier and then go back and weigh the trailer boat combination and subtract the difference. You know I have to take the boat off this week end, perhaps I can drop by the local land fill and get a couple of weights. Will let you know if I remember to do it.

Matt/Brigitte Loeffler
E.C. Rider
Cat 25 86'
FK/SR _/)

Edited by - on

mqp
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Response Posted - 09/24/2002 : 10:14:54

<BLOCKQUOTE id=quote>quote:<hr height=1 noshade id=quote> In order for an object to float, it needs to displace a greater weight of water than it, itself, weighs.<hr height=1 noshade id=quote></BLOCKQUOTE id=quote>

An object displaces the same weight of water, e.g. if the boat weighs 5000 lbs then it will diplace 5000 lbs of water. For an object to float, the volume of water displaced must be less than the volume of the object.

--Minh

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oldsalt
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Response Posted - 09/24/2002 : 19:16:20

<BLOCKQUOTE id=quote>quote:<hr height=1 noshade id=quote>

An object displaces the same weight of water, e.g. if the boat weighs 5000 lbs then it will diplace 5000 lbs of water. For an object to float, the volume of water displaced must be less than the volume of the object.

--Minh

<hr height=1 noshade id=quote></BLOCKQUOTE id=quote>

I don't believe so, which is why your anchor, which clearly displaces less volume than itself, sinks like an anchor.

The bouyant force on an object is equal to the weight of the fluid that is displaced by that object. If there is sufficient bouyancy, the object floats. If not it sinks.

It all has to do with relative density. If an object is 50% as dense as the fluid in which it is floating, then 50% of that object will be submerged. If it is 90% as dense then 90% will be submerged.

Lets say that all the materials that make up our boats were crumpled up and placed in a sack. It would still weigh exactly the same as it did before, but it would sink like a rock, since it displaces less water than before.

Displacement has to do with relative density as dictated by the design volume, more than it has to do with the gross weight of the materials that make up the vessel.

As for the keel, it may weigh 1900 lbs., but it displaces far less. The hull has to be designed with extra displacement, to take this into account.

I still have no idea what a Catalina 25 weighs.

So I still have been of no help at all.

Regards, Oldsalt

Edited by - on

Mark Rials
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39 Posts

Response Posted - 09/24/2002 : 21:23:53

Mine indicated 6000 lbs on the lift's scale
at the boat yard the last time she was hauled.

Mark & Pat Rials
C25 # 5450 "Garget"
Homeport Tampa, Fl.

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Dave Bristle
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Djibouti
10005 Posts

Response Posted - 09/24/2002 : 22:36:08

<BLOCKQUOTE id=quote>quote:<hr height=1 noshade id=quote>
I don't believe so, which is why your anchor, which clearly displaces less volume than itself, sinks like an anchor...
<hr height=1 noshade id=quote></BLOCKQUOTE id=quote>
Old Salt--you and Minh are saying the same thing. A basic physics text will tell you that a boat settles into the water until it has displaced an amount of water precisely equal to the weight of the boat, at which point it floats. Assuming the hull is large enough to do that before the gunwales reach the surface, it will float and even ward off some waves. Thus, the "displacement" is just the nautical term for the weight.

The anchor sinks because its density is greater than water--it cannot displace its own weight. A water balloon with no air in it will hang virtually weightlessly below the surface of the water because it displaces its own weight only after it has become fully submerged.

But I don't know what our C-25 weighs, either--I just know it's a handfull to move around by hand in our slip!

Your faithful amateur marine physicist...

Dave Bristle - 1985 C-25 #5032 SR-FK-Dinette-Honda "Passage" in SW CT

Edited by - dave bristle on 09/25/2002 10:08:18

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MattL
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Response Posted - 09/25/2002 : 03:27:56

Here is you science question for the day. If you have a glass of water and ice that is full to the brim, with ice sticking up over the surface of the water what will happen as the ice melts? A) water spills B) water level gets lower C) level stays the same

Density = weight / volume

OK water has a density of 1 gram/mL if and object has more weight / mL it will have a bigger density eg. 2/1 =2 this will sink. if you get a larger volume the density of the object goes down and therefore floats. eg. 1/2 = .25 smaller than 1 and will float.

take the weight of the boat and devide it by the volume of the boat to get its density. Unless you got a hole the density will be less than 1 g/mL or kg/L what ever units you use. If you measure the volume of the same weight of water you will find that the water has a smaller volume than the boat. The difference in volume is how much of the boat sticks out of the water. Ice has a density not much smaller than liquid water and thats why most of it is below the surface.

Here is you science answer for the day. C nothing happens

Matt/Brigitte Loeffler
E.C. Rider
Cat 25 86'
FK/SR _/)

Edited by - on

Dave Bristle
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Djibouti
10005 Posts

Response Posted - 09/25/2002 : 10:15:03

<BLOCKQUOTE id=quote>quote:<hr height=1 noshade id=quote>
Here is you science answer for the day. C nothing happens
<hr height=1 noshade id=quote></BLOCKQUOTE id=quote>
...unless the ice was sticking up because cubes were resting on the bottom of the glass--in which case, A. Right Teach??

Dave Bristle - 1985 C-25 #5032 SR-FK-Dinette-Honda "Passage" in SW CT

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dlucier
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Virgin Islands (United Kingdom)
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Response Posted - 09/25/2002 : 10:48:05

"If you have a glass of water and ice that is full to the brim, with ice sticking up over the surface of the water what will happen as the ice melts? A) water spills B) water level gets lower C) level stays the same"

"C nothing happens" - Matt

Matt,

I'm not a rocket scientist, but the more correct answer would be "B water level gets lower"? Isn't it true that frozen water(ice) floats because it takes up more volume and has less density than liquid water? As we are all vividly aware of here in Michigan, if you want to ruin something, leave water in it over winter and you will have a mess on your hands(broken pipes, sprinkler systems, outdrives,...etc) come spring because as the water freezes it expands(takes up more volume) and could destroy whatever it is expanding. If this is true, then as the ice melts and turns to a liquid it will take up less volume. And if indeed it takes up less volume, then the water level in the glass will go down as the ice melts.

So wouldn't the correct answer be "B the water level gets lower"?

Don Lucier, North Star
C25 SR/FK

Edited by - dlucier on 09/25/2002 10:50:31

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Dave Bristle
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Djibouti
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Response Posted - 09/25/2002 : 14:26:54

<BLOCKQUOTE id=quote>quote:<hr height=1 noshade id=quote>
So wouldn't the correct answer be "B the water level gets lower"?
<hr height=1 noshade id=quote></BLOCKQUOTE id=quote>
Isn't this fun? <img src=icon_smile_cool.gif border=0 align=middle> Don, I think Matt's right. His ice is floating so that the portion above the surface (and the rim of the glass) has the volume of water (when melted) that would take up the reduced volume as the ice below the surface melts. Since the ice is less dense, the water pushes exactly that amount of the ice above the surface. When it melts and its density becomes that of the water around it, the part above the surface lowers to the surface level.

Aaagh--this is hard!! It would be easier to conduct an experiment--but remember, if alcohol is involved, then the densities are thrown off. <img src=icon_smile_wink.gif border=0 align=middle>

Dave Bristle - 1985 C-25 #5032 SR-FK-Dinette-Honda "Passage" in SW CT

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Dave Seely
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Response Posted - 09/25/2002 : 23:32:11

Lets restate Matts question im a form that everyone can relate to. If you have a glass of BEER and ice that is full to the brim, with ice sticking up over the surface of the BEER, what will happen when the ice melts. In this case B is the correct answer because you always want to drink the beer before the ice melts and waters it down.

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MattL
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Response Posted - 09/26/2002 : 03:37:16

Don, I have to give Dave B the extra credit points for his answer. But Dave S. will get the A if he provides the beer.<img src=icon_smile_big.gif border=0 align=middle>

Matt/Brigitte Loeffler
E.C. Rider
Cat 25 86'
FK/SR _/)

Edited by - on

jm
Captain

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Canada
290 Posts

Response Posted - 09/26/2002 : 09:44:32

You guys are alot of help.. I'm calling Frank..

But I am going to perform that ice cube in the beer experiment until I prove or disprove all of this buoyancy/displacement theory you guys are posting - even if it takes me a dozen or more to do so.

And I will need lab assistants to assist with this experiment.

Oh, given the alcohol content of my Canadian beer may be greater than your US beer, the density/SG will be different, which may force us to re-do the experiment several weekends in a row, just so we can 'synchronize' beers.

Gotta go, the Beer Store opens at 10am..

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MattL
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Response Posted - 09/26/2002 : 11:13:13

Beer Store? Here in California we can just go to the local stop and rob for our supplies.

Matt/Brigitte Loeffler
E.C. Rider
Cat 25 86'
FK/SR _/)

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mqp
1st Mate

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Response Posted - 09/26/2002 : 11:28:16

Since this has been so fun, here's another puzzle that illustrates the displacement/boyancy priciple:

Immagine you're in a boat floating in a pool with your anchor at the bottom. You then proceed to pull the anchor up and put it in the boat. Will the pool level go A) up, B) down, or C) remain the same (assuming the boat doesn't sink with the anchor in it)?

--Minh

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Dave Bristle
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Djibouti
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Response Posted - 09/26/2002 : 23:29:09

Hmmm... I think it's A, (the level goes up) because when the anchor is lying on the bottom, it displaces only it's volume, but when it is being raised and when it rests in the boat, it becomes part of the boat's overall density, and therefore displaces it's weight in water, which is equal to more water. Thus, the increase in the boat's displacement is greater than the original displacement of the anchor alone. <img src=icon_smile_blush.gif border=0 align=middle>

Dave Bristle - 1985 C-25 #5032 SR-FK-Dinette-Honda "Passage" in SW CT

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MattL
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Response Posted - 09/27/2002 : 03:15:31

OK, lets think this through please.
We are on the bottom of the pool and we are displacing a set volume. now we are lifted up and our weight is on the boat. Our weight will push the boat down a tiny bit. Now in relation to the boat the anchor has a small volume and the boat goes down a small amount. My guess is that the small volume change is equal to the volume of the anchor. Now does this work just as well if the pool is full of beer. Probably not, because all your friends will be there drinking as they do the testing.

Matt/Brigitte Loeffler
E.C. Rider
Cat 25 86'
FK/SR _/)

Edited by - on

Mike Vaccaro
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Response Posted - 09/27/2002 : 03:45:03

Seems to me that if the pool is full of beer, concerns of bouyancy are over-rated. And if Archimedes lets you down (so-to-speak), you could probably still fight off the rescuers for some time.

Cheers,

Mike Vaccaro on the "Swoose"

Edited by - Mike Vaccaro on 09/27/2002 03:47:27

Edited by - Mike Vaccaro on 09/27/2002 03:49:34

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Dave Bristle
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Djibouti
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Response Posted - 09/27/2002 : 10:02:32

WATER, boys... Water! You can't do physics experiments with beer! The answer is always "B-down"! (Unless somebody in the pool, uh... <img src=icon_smile_shock.gif border=0 align=middle> )

Dave Bristle - 1985 C-25 #5032 SR-FK-Dinette-Honda "Passage" in SW CT

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Derek Crawford
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Response Posted - 09/27/2002 : 12:20:25

Dave - you do your experiments with water and let the rest of the boys have fun with their beer!
Matt - in Canada all liquor (including beer) is a government monopoly and you have to go to the government owned liquor store to buy it! And the taxes on it are about 95% of the price...<img src=icon_smile_dissapprove.gif border=0 align=middle>
Derek (just back from ducking Isidore!)

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RichardG
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Response Posted - 09/27/2002 : 12:33:14

How much wood could a wood chuck chuck if a wood chuck could chuck wood.

Sorry -- I couldn't resist.

RichardG 81 C25 SR/FK "Sanity"

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Lowell
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Response Posted - 09/28/2002 : 17:12:29

My '87 wing keel weighs about 5,800 lbs fully loaded. That includes the motor, fuel, full fresh water tank, empty holding tank, dishes, food, clothes, etc...

Lowell

Dreamer 5655

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MattL
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Response Posted - 09/29/2002 : 04:33:12

Derek,
I've been out of the business for about 15 years but the last time I worked the stills I think the price was about $30 or 40 per gallon of high proof. Could be mistaken, but it is high. Down here the tax depends on the proof beer and wine is the lowest, then fortified wines ie. port, then the hi test stuff. The Govt. keeps such a tight scedule that we had to get recepts for the samples we would analyse and then dump all un used stuff to be redistilled.<img src=icon_smile_dissapprove.gif border=0 align=middle>

Matt/Brigitte Loeffler
E.C. Rider
Cat 25 86'
FK/SR _/)

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