Not sure of "displacement" & "ballast"

[Dean5735]

I've wondered awhile about this, I would like to know the true weight of my 85 C30TR for a trailer purchase. The manual says it has (approx) 10,300 lb. displacement and 4500 lb. ballast. I wonder if the boat less the ballast is 5800 lbs.? I've thought the displacement is the amount of water that is displaced by the boat.
Anyone know the actual weight of the boat for the proper trailer?
At the moment I use an old equipment trailer with 3 house trailer axles under it, no lights or brakes though, so we may get a new one that can be legalized.
Thanks Dean

 

[Stu Jackson]

Displacement is the weight of the boat. Ballast is the weight of the material in the keel. In general, almost all Catalinas are actually heavier than the published data from the manufacturer.

 

[Stephen K]

Be sure to add the weight of your personal stuff aboard (tools, supplis,food, the extra anchor...etc.) to the boats listed displacement for a better measure of total weight.

Stu, do you think the listed displacement per the brochure's considers any fuel or water in the tanks?....if not, that should also be considered.

 

[bffatcat]

displacement

Technically Displacement means: when a keel boat is dropped into the water the weight of the actual water the boat displaces until it reaches a point where it floats on its lines. Fortunately the actual weight of the hull, keel, plus the combined weight of gear weights the same as the total amount of water it displaces. This is why some heavily loaded cruising boats sit lower in the water. So Displacement and Hull weight are the same. the terms are interchangeble

 

[packman]

neutral bouyancy

wouldn't equal numbers in actual weight and displacement give you neutral bouyancy?

 

[bffatcat]

Buoyancy???

You cannot have what you call neutral buoyancy in a displacement hull. Again: A ballasted
boat will sink until displaces water equal to its weight, at that point it will float. Example:
Take any keel boat at rest on its lines. Remove a plug from the bottom. The boat will start taking on water. The more water the boat takes the heavier it becomes and the more water it displaces the lower it will sit. Until it sinks.

 

[Stu Jackson]

Real weighty...heh, heh, heh

Stu, do you think the listed displacement per the brochure's considers any fuel or water in the tanks?....if not, that should also be considered.

Stephen,

Every year on this board someone gets his boat on a trailer and rolls through a truck stop. Every year folks on other boards get new-to-them boats and ask how much they weigh.

I can't figure out why anyone cares, but they seem to.

Historically, every single discussion I've seen about Catalinas on the different one-design association message boards, results in at least about a 10% difference in boat displacement, actual being higher than spec'd. Our 12,000 # C34s are 14 to 16, same bump for C36s.

No one has bothered to ask the factory and if they have the answer is lost in the mists of time. If I were doing it, I'd include full tanks, why the hell not. Who know, who cares. It just doesn't matter.

 

[Ross]

Re: Real weighty...heh, heh, heh

Almost every warehouse district, feed store, quary, and grain elevator has a set of truck scales. When is somebody going to simply weigh a boat and be done with the question.

 

[Stu Jackson]

That's what they do do, Ross, and they they write in to complain it's way more than the published specs! Heck, what are WE gonna do about it!

 

[packman]

Okay, I stand, (sit), (sprawl), corrected, The reason I'm interested in actual weight and how to figure it is: A. shopping for a trailer; B. Is my old truck going to pull this beast without gearing/brake upgrades?; C. Where do I park said beast without risking large holes where the tires were? Did I misspell bouyancy? I hate that

 

[Stu Jackson]

OK, with the info provided here, take the DISPLACEMENT specs and add 10% -- it's really that easy.

 

[Dean5735]

Thank You! That is what I thought!

This is what I was hoping for, to find out my thinking was correct. So if my boat spec. says it weighs 10,300lbs. I should be looking for a trailer with a GVW capacity (gross vehicle weight) of 12K min. and 14,000 would be better. I tow it with a 3/4 ton chevy truck and have no problems towing it 9 miles from home to the marina. If I had brakes and lights I could go further (cheaper marina) and easier/safer and legal too.
Naturally I would have a bigger vehicle tow it further, like to New York or twords florida.

Thanks All, Dean

 

[BarryL]

Hey,

When the manufacturer lists a weight, that is usually without any fluids in the boat. When you add 50 gallons of water, 20 gallons of fuel, pot and pans, safety gear, an anchor and rode, and all that other gear, the weight goes up. Plus, boats that spend time in water tend to absorb some of that water. All this means that the boat will be heavier than you expect. So, as written, add a 10% fudge factor and you'll be OK.

BArry