help me understand the loa & beam dimension

it makes sense to me that the beam should be measured at the waterline & the loa should be measured as if you did it with a giant set of calipers , or as if you were to fit the boat in a box sitting level to the water....whats the proper way to measure ..is the beam just the absoloute widest point of the boat?...I ask because I usually look at the beam for stabilitys sake & it the part measured is out of the water I have a hard time seeing it affect too much ..unless its a rash case ....say a cargo ship with a deck wider than the widest point of the boat at the water line...is there a standard or right answer to this guestion or are we able to pick the point that suits us best to point out...i.e.,....we all want a bigger boat , so one man would count the swim platform in his loa measurement...is he wrong ???

 

Beam is usually the maximum beam unless qualified by "waterline". LOA is subjective... for some it includes the Bowsprit and Bumpkin and for others it is the same as the LOD or length on deck without the extras. For me it includes the entire length of space the boat takes up, with whatever sticks out front and back included.

 

thanks bud...that's about what I figured ..I guess its gonna vary a little from builder to builder

 

There is some dispersion in how each views these terms. Hence each regulation generally defined in its first pages how they consider the dimensions of the boat. Many agree, but not all.
LOA: length over all, for me is the overall length. The length to be measured to put the ship in a box.
Here attached the definition of dimensions that ISO standard sets for small (up to 24 m in length) boats

 

good example ..I like that its ISO

 

LOA length over all includes everything because it is primarily used by the marina to charge you for the dock, slip or mooring. It's about operating cost not performance. LWL and WLB are what you need to design.

 

Sorry to disagree with this statement because most of the design calculations, and regulations applicable to the project, are not based on LWL but on a length which is usually the ship's hull length or, in other cases, the length of a waterline at 85% of her depth.

 

To regurgitate what another member said years ago. LOA is what your slip fee is based on. The rate/foot isn't negotiable, but the LOA sure is; so be nice to the guy who determines it, especially if you are planning on keeping the slip for a few years.

 

My take on it all is : LOA -- total length of the vessel including all appendages attached to the bow and stern increasing length. Example the bow sprit adds length to the vessel so it's length extending beyond the stem head is included in the LOA .
LOD -- is the length from the outside of the planking at the stern to the outside of the stem head at deck level.
LW -- Waterline Length Length of the hull as measured from the outside of the planking at the stern to the outside of the stem at the waterline.
Beam -- measured from the outside of the planking at the wides part of the hull generally at deck level.
Max. Beam -- Same as above but not necessary at deck level. An example would be where the hull has rubbing strakes or tumble home. The Max beam would then be measured to the outside of the rubbing strakes where they add to the max. beam width beyond the planking. Or In the case of tumblehome , max beam will be somewhere below the deck level and the water line depending where the hulls tumble home starts it's inward curve.
Waterline beam -- The hulls max. beam at the the waterline

A sliding bow sprit is often incorporated in the design to reduce LOA and thus save on docking (slip fee) charges.

 

so there is a distinction ...loa, lod, lw ...I guess its a no brainer ...length over ALL, is just that....length over ALLLLLLL ,,& I guess its safe to say as far as the general publics concerned we`ll use the no brainer method of measuring the loa &let the designers & architechts post specifics that`ll be used for specific purposes...& meantime im gonna run down the dock & point my outriggers back up to the sky before somebody comes along & tries chargin me any more for my slip on account of em`hangin over the transom....all good info

 

I've rarely seen the distance outboards or sterndrives extend past the transom included in claimed LOA. My understanding is the USCG does not include outboards or sterndrive length in determining if a boat is less than 20' in length and therefore falls under the small craft floatation and capacity regulations.

 

It is not normal regulatory bodies are governed by the LOA. In general, when it comes to boats larger or smaller than 24 m in length, for example, they refer to the length of the hull or a waterline at 85% of the depth of the boat.

 

Keep in mind that EU and US regulations and definitions differ, and experience with one system is not always applicable to the other.

 

So I said in a previous post, each agency, in the first pages of their rules, clearly defines how to take the dimensions of the boat. The approach not only changes between EU and US but between the various standards. But do not change much.

 

Obviously I did not consider ships with bow bulbs in my comment.

While we are still griping about slip fees, remember LOA includes davits and half the width of the dingy hanging on them according to harbormasters or more accurately the 'giant calipers'.