Boat Design Forums  |  Boat Design Directory  |  Boat Design Gallery  |  Boat Design Book Store  |  Thanks to Our Site Sponsors

Go Back   Boat Design Forums > Design > Boat Design
Register FAQ Members List Calendar Search Today's Posts Mark Forums Read Most Recent Posts Gallery Images Search

Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old 07-07-2007, 09:21 PM
Newboatman Newboatman is offline
 
Join Date: Jul 2007
Rep: 10 Posts: 2
Location: Tennessee
How do I calculate the weight limit of a pontoon boat?

Can anyone help me find out the weight limit of a pontoon boat I recently purchased? It is a 1990 model, 24ft Riveria Cruiser and the tag that show the weight limit and capacity in number of passengers is old and unreadable.

I think it has 18" pontoons.

I know there must be an engineering formula for calculating the weight support capacities of pontoons but I cannot find one on the internet by using search engines.

Thanks,
Reply With Quote


  #2  
Old 07-07-2007, 10:28 PM
marshmat's Avatar
marshmat marshmat is offline
Senior Member
 
Join Date: Apr 2005
Rep: 2008 Posts: 4,132
Location: Ontario
Firstly, welcome aboard boatdesign.net

A pontoon boat is, for the purposes of load rating, considered a multihull vessel. In Canada, the relevant standard is TP1332 (1999) section 4, paragraphs 61-72 at http://www.tc.gc.ca/marinesafety/TP/...htm#multi-hull American standards are closely harmonized with Canadian ones. There should be an equivalent American standard but it will probably be harder to read and will produce virtually identical results.
You will find the Canadian standard to be quite readable and the calculations easy to do by hand.
Some will undoubtedly say in response here "just take the volume of the pontoons, multiply by the density of water, there you go". That's essentially how the standard works, with some added criteria. It is better to follow the accepted government standard, because (a) it is what the Coast Guard will hold you to if you're stopped by them, (b) the authors of the standard have already computed appropriate safety factors and outlined how to perform and evaluate the stability tests, which makes your job a lot easier and safer, and (c) they give you the formulae and definitions, and outline exactly how to do it so that it's nearly impossible to screw up if you passed grade 8 math.
Reply With Quote
  #3  
Old 07-07-2007, 10:35 PM
alan white's Avatar
alan white alan white is offline
Senior Member
 
Join Date: Mar 2007
Rep: 1400 Posts: 3,687
Location: maine
Also, any pontoon boat with the same length and pipe diameter should be the same capacity. Visiting a showroom you could either find one the same length, or calculate based on what lengths/diameters you do see.

Alan
Reply With Quote
  #4  
Old 07-07-2007, 10:41 PM
marshmat's Avatar
marshmat marshmat is offline
Senior Member
 
Join Date: Apr 2005
Rep: 2008 Posts: 4,132
Location: Ontario
Quote:
Also, any pontoon boat with the same length and pipe diameter should be the same capacity
If it also has the same dry weight and the same size engine, that is. Doing the actual calculations takes less than ten minutes if you know how much the boat weighs when it's out of the water.
Reply With Quote
  #5  
Old 07-07-2007, 11:05 PM
alan white's Avatar
alan white alan white is offline
Senior Member
 
Join Date: Mar 2007
Rep: 1400 Posts: 3,687
Location: maine
True---- though I think a ballpark is what's wanted, for practical reasons. Recycling yards and dumps have scales--- takes two trips, but very accurate. I plan to weigh my boat that way.
You are correct, that the dry weight will vary somewhat.

Alan
Reply With Quote
  #6  
Old 07-08-2007, 09:03 AM
lewisboats's Avatar
lewisboats lewisboats is online now
Obsessed Member
 
Join Date: Oct 2002
Rep: 1600 Posts: 2,269
Location: Iowa
surface area of a (virtual) slice of the pontoon (Pi x 9 (sqd) = 1.76625 sq ft x the length of the pontoon... 24 ft = 42.39 cu ft x 2 = 84.78 x 62.4 lbs/ cu.ft (water weight displaced) = 5290 lbs /2 (half the pontoons submerged) = 2645 lbs total all up weight. You will have to subtract the dry weight from that and I would also subtract another 10 % or 265 lbs just to be on the safe side. According to the CG, people weight 145 lbs so divide the remaining by that for # of people...then use common sense... 4 200+ lb "Bubbas" equals 5 to 6 CG people. And don't forget the Beer wt...gotta account for that...(just don't over do and drive).

Steve

Edited to add: Measure your pontoons...I checked on Riviera pontoon boats and all of them had 23-25" pontoons...which would significantly add to the capacity. Measure the circumference and divide by 3.14...should be close enough. Then plug half the remaining # into the spot where the 9 is in the above calculations and continue from there.
Reply With Quote


  #7  
Old 07-15-2007, 09:40 PM
Newboatman Newboatman is offline
 
Join Date: Jul 2007
Rep: 10 Posts: 2
Location: Tennessee
Thanks!

Thanks very much everyone who replied to my question. Amazing how helpful this site is!
Reply With Quote
Reply



Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes


Similar Threads
Thread Thread Starter Forum Replies Last Post
How do I calculate displacement from weight? Valk Stability 15 07-08-2007 09:24 AM
wet weight vs dry weight of Diesels... spank Boat Design 3 10-20-2006 04:16 AM
Average Human Weight, Safe Excess Weight, &c. Free Pirate Boat Design 12 03-14-2005 02:40 AM
Need to calculate the draft of a boat tibett Boat Design 1 11-09-2004 05:07 AM
No Limit reached limit Dutch Peter Boat Design 16 09-09-2004 08:20 AM


All times are GMT -5. The time now is 05:45 PM.


Powered by: vBulletin Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Web Site Design and Content Copyright ©1999 - 2014 Boat Design Net