Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 23-09-2015, 11:08   #1
Registered User

Join Date: Sep 2015
Location: Portugal
Posts: 14
Boat Specs - Weight

Hello,
I'm new to boats, looking to figure out lots of stuff, but I have one doubt that I must clarify upfront.
When I look at specs for a boat, usually there is the indicated displacement and then the ballast weigth.
What is the actual total weigth of the boat, for trailering?
Do I have to add the two or is the ballast just fyi?
Or is that no usefull indication of trailerable weigth and I must check some other way?

I have a fairly limited towing weigth for my car, 1180kg or 2600lbs, and that will have to include the trailer along with outboard engine, etc... so I need to figure this out first...

Thanks for any help.
Pedro.
__________________

__________________
ptrailsail is offline   Reply With Quote
Old 23-09-2015, 11:23   #2
Registered User
 
goat's Avatar

Join Date: Apr 2013
Location: Everywhere (Sea of Cortez right now)
Boat: PSC Orion 27
Posts: 1,097
re: Boat Specs - Weight

Displacement is the weight you're looking for. It's actually the weight of the water that would be displaced when your boat is floating, but for your case it's close enough to the weight. Ballast is weight placed below the waterline to help right the boat and is already added to the displacement.

Be sure to add the weight of all the stuff you put on the boat to the total weight; water, fuel, batteries, dinghy, food etc.

This is a simplified explanation, you could get into all kinds of discussions on the intricacies of densities etc, and if I know this forum it probably will.

goat
__________________

__________________
goat is offline   Reply With Quote
Old 23-09-2015, 11:35   #3
Registered User
 
Steady Hand's Avatar

Join Date: Jul 2014
Location: Crewing All of 2017 Available Globally
Boat: OPB = Crewing in 2017
Posts: 4,851
re: Boat Specs - Weight

Quote:
Originally Posted by goat View Post
Displacement is the weight you're looking for. It's actually the weight of the water that would be displaced when your boat is floating, but for your case it's close enough to the weight. Ballast is weight placed below the waterline to help right the boat and is already added to the displacement.

Be sure to add the weight of all the stuff you put on the boat to the total weight; water, fuel, batteries, dinghy, food etc.

This is a simplified explanation, you could get into all kinds of discussions on the intricacies of densities etc, and if I know this forum it probably will.

goat
Good answer.

One small correction:

The ballast weight is INCLUDED in the determination or calculation of the displacement of the boat, not "added to" the weight of the boat.

For the OP: The ballast is considered a part of the boats designed total weight. It is listed separately so buyers can know how much of the total weight (displacement) is ballast. Two different boats of the same displacement could have very different amounts of ballast included to make them stabile when floating in the water.
__________________
Ahoy All Sailors! Need experienced crew for a passage or delivery in Atlantic, Pacific, Caribbean, Med, PNW, ICW, coastal or across an ocean anytime in 2017? I am available on 24hr notice. See my CF Profile "About Me" page for details. Happy to lend a hand!
Steady Hand is offline   Reply With Quote
Old 23-09-2015, 11:47   #4
Registered User

Join Date: May 2014
Location: USA
Boat: 41' yawl
Posts: 609
re: Boat Specs - Weight

Quote:
Originally Posted by goat View Post
It's actually the weight of the water that would be displaced when your boat is floating, but for your case it's close enough to the weight.
Displacement is _exactly_ the weight of the boat, and _exactly_ how much weight in water it would displace when floating.

Original poster, displacement = total weight of the boat, *including* the ballast.

Ballast is typically a specific bit of weight placed low on the boat for stability.

So you can tow a boat who's displacement is 2600 pounds (minus the weight of the trailer).
__________________
chris95040 is offline   Reply With Quote
Old 23-09-2015, 11:59   #5
Moderator
 
cabo_sailor's Avatar

Cruisers Forum Supporter

Join Date: Mar 2008
Location: Tarpon Springs FL
Boat: Cabo Rico 38
Posts: 1,905
re: Boat Specs - Weight

Don't forget tongue weight. Your vehicles towing capacity is limited by both. This will also dictate what class hitch you need.


Sent from my iPhone using Cruisers Sailing Forum
__________________
cabo_sailor is offline   Reply With Quote
Old 23-09-2015, 12:04   #6
Registered User
 
denverd0n's Avatar

Join Date: Jun 2008
Location: Tampa, FL
Posts: 3,949
Images: 6
re: Boat Specs - Weight

Quote:
Originally Posted by chris95040 View Post
Displacement is _exactly_ the weight of the boat, and _exactly_ how much weight in water it would displace when floating.
True, in actuality, for each boat. But a little misleading, I think, since we are talking about the published specifications here, and almost no boat ever weighs "exactly" the same as its designed displacement. There are always some differences, and sometimes they are significant.

What's more, the moment you add anything to the boat that the designer did not include in his calculations, then the boat weighs (and displaces) more than the published displacement specification. Which is why...

Quote:
Originally Posted by chris95040 View Post
So you can tow a boat who's displacement is 2600 pounds (minus the weight of the trailer).
This is only true if the boat has no additional kit, whatsoever, in it. Otherwise, as goat said: "Be sure to add the weight of all the stuff you put on the boat to the total weight; water, fuel, batteries, dinghy, food etc."
__________________
denverd0n is offline   Reply With Quote
Old 23-09-2015, 13:16   #7
Registered User

Join Date: May 2014
Location: USA
Boat: 41' yawl
Posts: 609
Re: Boat Specs - Weight

Quote:
Originally Posted by denverd0n View Post
True, in actuality, for each boat. But a little misleading, I think, since we are talking about the published specifications here, and almost no boat ever weighs "exactly" the same as its designed displacement. There are always some differences, and sometimes they are significant.

What's more, the moment you add anything to the boat that the designer did not include in his calculations, then the boat weighs (and displaces) more than the published displacement specification. Which is why...


This is only true if the boat has no additional kit, whatsoever, in it. Otherwise, as goat said: "Be sure to add the weight of all the stuff you put on the boat to the total weight; water, fuel, batteries, dinghy, food etc."
Really good, important points.
__________________
chris95040 is offline   Reply With Quote
Old 23-09-2015, 20:54   #8
Marine Service Provider

Join Date: May 2012
Location: New Orleans
Boat: We have a problem... A serious addiction issue.
Posts: 3,940
Re: Boat Specs - Weight

Don't forget to count the weight of the trailer. A twin axle steel trailer for a 20' boat can easily top 1,100 lbs.
__________________
Greg

- If animals weren't meant to be eaten then they wouldn't be made of food.
Stumble is offline   Reply With Quote
Old 24-09-2015, 00:31   #9
Senior Cruiser
 
newhaul's Avatar

Cruisers Forum Supporter

Join Date: Sep 2014
Location: puget sound washington
Boat: 1968 Islander bahama 24 hull 182, 1963 columbia 29 defender. hull # 60
Posts: 3,946
Re: Boat Specs - Weight

A web site that you will find valuable for all the info for most sailboats like weights layouts sail areas and the like is. WWW.sailboatdata.com
__________________
newhaul is online now   Reply With Quote
Old 24-09-2015, 03:46   #10
Registered User

Join Date: Sep 2015
Location: Portugal
Posts: 14
Re: Boat Specs - Weight

Well Thanks for all the great info everyone!

"A twin axle steel trailer for a 20' boat can easily top 1,100 lbs"

Well, I saw some trailers allready and the maximum I found was around 200kg or around 440lbs, maybe they were aluminium, but I'll be watching for that, thanks for the heads up.

As for the weigth of all the stuff that goes in the boat, maybe I'll start a new thread, not go off this topic.

Thanks again, you just helped me move forward in my quest
__________________
ptrailsail is offline   Reply With Quote
Old 24-09-2015, 10:30   #11
Registered User
 
Cadence's Avatar

Join Date: Dec 2008
Location: SC
Boat: None,build the one shown of glass, had many from 6' to 48'.
Posts: 6,057
Re: Boat Specs - Weight

I may be wrong. I was under the impression that displacement was the weight of the displaced water when loaded to the design waterline.
__________________
Cadence is offline   Reply With Quote
Old 24-09-2015, 10:43   #12
Registered User

Join Date: Jun 2012
Location: Port Aransas, Texas
Boat: 2002 Seawind 1000 (33 ft) Cat
Posts: 840
Re: Boat Specs - Weight

Probably need to tell us what boat you are considering. My BIL has a water ballasted Hunter. The water is drainned out as it comes up the ramp. You would not need to consider that weight for towing.
__________________
sailjumanji is offline   Reply With Quote
Old 24-09-2015, 10:46   #13
Registered User
 
Terra Nova's Avatar

Join Date: Apr 2007
Location: Marina del Rey, California
Boat: Freya 39 cutter- Terra Nova
Posts: 3,645
Re: Boat Specs - Weight

Quote:
Originally Posted by chris95040 View Post
Displacement is _exactly_ the weight of the boat...
Not exactly.

Cadence is correct. Displacement includes even fuel and water (50% full?).
__________________
1st rule of yachting: When a collision is unavoidable, aim for something cheap.
"whatever spare parts you bring, you'll never need"--goboatingnow
"Id rather drown than have computers take over my life."--d design
Terra Nova is offline   Reply With Quote
Old 24-09-2015, 11:47   #14
Registered User
 
Cadence's Avatar

Join Date: Dec 2008
Location: SC
Boat: None,build the one shown of glass, had many from 6' to 48'.
Posts: 6,057
Re: Boat Specs - Weight

Quote:
Originally Posted by ptrailsail View Post
Hello,
I'm new to boats, looking to figure out lots of stuff, but I have one doubt that I must clarify upfront.
When I look at specs for a boat, usually there is the indicated displacement and then the ballast weigth.
What is the actual total weigth of the boat, for trailering?
Do I have to add the two or is the ballast just fyi?
Or is that no usefull indication of trailerable weigth and I must check some other way?

I have a fairly limited towing weigth for my car, 1180kg or 2600lbs, and that will have to include the trailer along with outboard engine, etc... so I need to figure this out first...

Thanks for any help.
Pedro.
I wouldn't worry about it. Us common sense. And frankly, it is what you can pull up a ramp on it's grade. I don't think there is a magic number.

Best of luck.
__________________
Cadence is offline   Reply With Quote
Old 24-09-2015, 12:32   #15
Registered User

Join Date: Jun 2012
Location: Port Aransas, Texas
Boat: 2002 Seawind 1000 (33 ft) Cat
Posts: 840
Re: Boat Specs - Weight

I hate to tell you this, but relying on published weights is problematic. I have done ratings for multihulls - including many trailerable boats - for years. What we find for even manufacturer's that actually weigh their boats is that a particular model can vary 10% to sometimes 15%. Maybe it is uncalibrated load cells, or maybe even manufacturing variation. Plus there is no standard - do you include the mast, boom, sails, battery, motor? Weight is such a huge performance variable for the Corsair trimaran fleet, that we had specific rules for weighing the F-31's- what had to be on the boat, etc. Easiest way was usually to weight the boat and trailer, launch the boat, and weigh the trailer. Even then there would be a 200 lb difference on the same boat from one year to another, which was due to scale calibration. And these boats were in the 3,000 lb category. Other manufacturers were much larger variation. So if you are trying to guess at 10 lbs, 50 lbs, or a couple of hundred pounds only to play with before overloading your rig, I think it's not reliable.

PS. The trailerable tri's are a piece of cake compared to trying to understand what a Lagoon weighs, or a one-off build. We have a 39 ft cat that weighs less than 7000 lbs (TRT 1200) and some condo-cats the same length probably around 25000 lbs.
__________________

__________________
sailjumanji is offline   Reply With Quote
Reply

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Volvo MD2 weight vs Md6a weight. gjordan Engines and Propulsion Systems 2 06-07-2012 00:23
Converting from 'Charter Specs' to 'Owners Specs' - Practical ? simonmd Monohull Sailboats 14 09-11-2010 20:57
Spinnaker Specs for My Cat svcattales Multihull Sailboats 8 24-05-2009 16:09
V-berth specs Guy E. Crouch Meets & Greets 1 15-01-2008 16:55



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 12:51.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.