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RickyB 05-03-2016 08:18 PM

What is boat length measured?
 
In searching for a new boat I'll see "boat length" or "nominal length." Since most boats that interest me have a bow pulpit or over hanging anchor at bow & swim platform at stern, are these figured into advertised length of a boat? I like to see LWL (length at water line).

MYTraveler 05-03-2016 08:45 PM

There are at least 4 different ways to quantify boat length:
1) Documented length -- I don't know the formula, but I believe it excludes swim steps and bow pulpits.
2) Length overall (LOA) -- this is what most marinas (at least on west coast of US, Canada and mexico) base their slip fees on, and is often used by owners to describe the size of their boat;
3) Length at water line (LWL) -- probably most useful, but least used,
and
4) manufacturer's "designation" (like a 550, implying 55 feet) -- practices are wildly inconsistent between manufacturers with many "stretching" (even beyond LOA), but a few, inexplicably, understating.

For an apples to apples comparison, I would suggest documented length or LWL

Britannia 05-03-2016 08:48 PM

Quote:

Originally Posted by MYTraveler (Post 439199)
There are at least 4 different ways to quantify boat length:
1) Documented length -- I don't know the formula, but I believe it excludes swim steps and bow pulpits.
2) Length overall -- this is what most marinas (at least on west coast of US, Canada and mexico) base their slip fees on;
3) Length at water line -- probably most useful, but least used,
and
4) manufacturers "designation" -- practices are wildly inconsistent between manufacturers with many "stretching" but a few, inexplicably, understating.

I have heard your definition of 1) described as Length on Deck (LOD).

boatpoker 05-03-2016 09:09 PM

Documented length (Register length in Canada) is measured from the inner part of the stem to the foremost edge of the rudder stock. I'm a Transport Canada Appointed Tonnage Measurer.

Ted 05-03-2016 09:19 PM

Quote:

Originally Posted by boatpoker (Post 439206)
Documented length (Register length in Canada) is measured from the inner part of the stem to the foremost edge of the rudder stock. I'm a Transport Canada Appointed Tonnage Measurer.

Unless they have changed since the '70s, if you had a sternpost they
measured to it.

Still valid?

Ted

Hawgwash 05-03-2016 09:27 PM

Quote:

Originally Posted by Britannia (Post 439201)
I have heard your definition of 1) described as Length on Deck (LOD).

And centre line length.

Ted 05-03-2016 09:29 PM

When referring to smaller (runabout size etc.) boats there was a
difference between Canadian or American measurements.
Canadian used the centerline length, American measured from
the bowstem to the transom around the gun'ell.

Ted

Hawgwash 05-03-2016 09:37 PM

Quote:

Originally Posted by Ted;
American measured from
the bowstem to the transom around the gun'ell.

Ah yes, the old take the long way from A to B and use a rubber tape.

If I'm not mistaken Bayliner started that one.

Ted 05-03-2016 09:42 PM

I don't know who started it, but it was in use in a book of
plans by Mechanics Illustrated from mid 1950s.

Ted

bogranjac1 05-03-2016 09:43 PM

So many different methods.
You would have to think that C.L.(centreline) from the actual bow to stern of the hull - disregarding bow spit, duck board , pulpit and pushpit etc. would be the only true indication of the vessels length.

Hawgwash 05-03-2016 09:47 PM

Quote:

Originally Posted by Ted (Post 439222)
I don't know who started it, but it was in use in a book of plans by Mechanics Illustrated from mid 1950s.

That leaves me hangin' on by a thread then. Bayliner started production in 1957.

kthoennes 05-03-2016 09:49 PM

My Mainship 37 is 41' 4" if I measure from the aftmost bumper molding on the swimstep to the forwardmost edge of the forward-angled bow pulpit rail. If I'm checking into a marina that charges by the foot I'm a 37. If I'm boasting, I'm a 41 or 42.

Britannia 05-03-2016 09:58 PM

It's all a question of why you want to measure the boat. If it's to fit in a slip then you need to include pulpit and swim step. If you want to show off to friends that's a good number too, rounded up of course! If you want an idea of the speed then waterline length is the most interesting. In fact, the LOD or CL is the least interesting in some ways. It gives you an idea of how big the boat is from a livability perspective, but to be of any use you really need to include beam and cabin height (and double decking if any).

THD 05-03-2016 11:31 PM

I just wish there was not only some consistency from builder to builder, but that builders would also share how they denominate their boats. I have seen boats listed as a "34" or "52" but when looking at the measurements, LOD, LOA, LWL, whatever, not a single one of them will be 52! With Krogen, they clearly list their models by LOD and make it plain that is what they have done. I wish more builders did the same.

drb1025 05-04-2016 12:09 AM

The state of WA limits the use of their mooring buoys to boats 45' in length. My boat is a DeFever 46' but the length at the waterline is 43 and change, so how the boat is measured is important. I emailed the parks and rec dept for an answer and they stated that they go by whatever length is on the registration, so I am SOL for using state mooring buoys.

boatpoker 05-04-2016 01:02 AM

Quote:

Originally Posted by Ted (Post 439210)
Unless they have changed since the '70s, if you had a sternpost they
measured to it.

Still valid?

Ted

I received my training in 1999. Don't know about the seventies.

boatpoker 05-04-2016 01:04 AM

Quote:

Originally Posted by drb1025 (Post 439248)
The state of WA limits the use of their mooring buoys to boats 45' in length. My boat is a DeFever 46' but the length at the waterline is 43 and change, so how the boat is measured is important. I emailed the parks and rec dept for an answer and they stated that they go by whatever length is on the registration, so I am SOL for using state mooring buoys.

Get it documented, it'll come up a few feet shorter.

boatpoker 05-04-2016 01:05 AM

Quote:

Originally Posted by THD (Post 439245)
I just wish there was not only some consistency from builder to builder, but that builders would also share how they denominate their boats. I have seen boats listed as a "34" or "52" but when looking at the measurements, LOD, LOA, LWL, whatever, not a single one of them will be 52! With Krogen, they clearly list their models by LOD and make it plain that is what they have done. I wish more builders did the same.

These are the same builders that started calling planing and semi-planing boats ...."trawlers"

Hawgwash 05-04-2016 07:05 AM

Quote:

Originally Posted by boatpoker (Post 439256)
These are the same builders that started calling planing and semi-planing boats ...."trawlers"

They were probably ex audio peddlers from the 70s as well. No 2 audio equipment manufacturers of components used the same standard for their specs. It was a jungle out there.

Larry M 05-04-2016 07:14 AM

Our Krogen 42 is documented at 43'. We're 46' overall from the tip of the bow pulpit to the edge of the swim platform. The swim platforms 3' as is the bow pulpit.

rwidman 05-04-2016 08:06 AM

I use two measurements. 31' (the LOA) if I'm bragging and 28' (the documented length) if I am paying for a slip.


Sometime between when my boat was manufactured and the end of production, the manufacturer changed the designation without any change in the boat.

drb1025 05-04-2016 09:23 AM

Quote:

Originally Posted by boatpoker (Post 439255)
Get it documented, it'll come up a few feet shorter.


It is documented and it says the length is 46', which doesn't include the swim step. The DF 49 Euro version is the same as the DF 46, except it has an integrated swim step that extends the hull, thus it is labeled a 49. I don't understand your comment.

Britannia 05-04-2016 10:08 AM

Quote:

Originally Posted by Larry M (Post 439280)
Our Krogen 42 is documented at 43'. We're 46' overall from the tip of the bow pulpit to the edge of the swim platform. The swim platforms 3' as is the bow pulpit.

My Krogen 54 is documented as 54.4 and the original brochure lists "Length Overall" as 54'5". Just for fun (and because I was home from work sick) I measured the length on deck and got to 54'9". I measured along the surface of the raked deck and it's likely that Krogen measured a horizontal straight line distance from stem to stern. That could easily account for the extra few inches I measured. The bow pulpit is 32" meaning that the boat is just over 57'. There is also an aftermarket swim step that a PO installed - it's about 2.5'. I'm in a 60' slip though I could manage a shorter slip given my bow pulpit is 10' off the waterline and can overlap the dock without being a hazard.

Richard

porman 05-04-2016 11:25 AM

Quote:

Originally Posted by drb1025 (Post 439248)
The state of WA limits the use of their mooring buoys to boats 45' in length. My boat is a DeFever 46' but the length at the waterline is 43 and change, so how the boat is measured is important. I emailed the parks and rec dept for an answer and they stated that they go by whatever length is on the registration, so I am SOL for using state mooring buoys.

I had the same discussion with Wa state at the boat show. Our Mainship 430 is 43' on deck, 48' overall, and documented at 41.1'. They told me they would go with the documented length. However, I worry about the ability of their mooring buoys to hold my 40,000 lbs if the wind really starts blowing.

HeadMistress 05-04-2016 11:42 AM

Quote:

Originally Posted by RickyB (Post 439192)
In searching for a new boat I'll see "boat length" or "nominal length." Since most boats that interest me have a bow pulpit or over hanging anchor at bow & swim platform at stern, are these figured into advertised length of a boat? I like to see LWL (length at water line).

46 CFR 170.055 (k) defines vessel length as:

(2) Length overall (LOA) means the horizontal distance between the forward-most and after-most points on the hull.
(3) Length on the waterline (LWL) means the horizontal distance between the forward-most and after-most points on a vessel's waterline.
(4) Length on deck (LOD) means the length between the forward-most and after-most points on a specified deck measured along the deck, excluding sheer.

You can read the whole "Definitions Concerning a Vessel" section here:
https://www.law.cornell.edu/cfr/text/46/170.055

Boat builders are required to use those definitions in any model name or number. However, harbormasters only want to know how much dock length the boat will occupy (and therefore how much they can charge you), so they include bow pulpits and anything hanging off the stern on davits.

MYTraveler 05-04-2016 12:06 PM

I had arranged a slip based on my assurance that my boat was not longer than 70' -- it needed to fit in the slip with no more than 5' protruding beyond the slip, and the slip itself was 65'. I felt comfortable with that because the boat was documented at 64', and other marinas, which charged based on their measurement of LOA, had always come up with 68' or 69', based on the horizontal distance overall. I hired a delivery captain to move the boat about 100 nm to the new (temporary) slip, and got an urgent phone call when he arrived. It seems the dock master had measured the boat at something in excess of 70'. I assured my captain that it had been miss-measured and asked him to watch and verify the measurement process. An hour later he reported back that my boat was, in fact, substantially over 70'. Turns out the dock master was running a tape along the outside of the hull, from the stern to the tip of the bull pulpit, and my licensed captain thought that was the right way to measure. Never mind that the boat did not extend more than 5' beyond the slip.

rwidman 05-04-2016 02:46 PM

It's not easy to get an exact LOA measurement of a boat unless you measure it when it's out of the water and drop a plumb line from the two extreme ends.


What's really a shame though is when someone bottom painting the boat wants to include the swim platform and anchor in the calculations. I had a quote recently that did that. Only the waterline length is being painted so that's all they should use to calculate if they are honest.

No Mast 05-04-2016 03:45 PM

Catching up on this thread... I owned boats in which the manufacturer added an inch or two to the model number so their 50 Ft model really wasn't. I understood their perceived marketing value in doing so. What I don't understand is why Selene goes the opposite way, and by quite a bit. Our Selene "53" is actually 60ft LOA. Why would you do that??

HeadMistress 05-04-2016 04:41 PM

What's really a shame though is when someone bottom painting the boat wants to include the swim platform and anchor in the calculations.

The USCG definition of LOA used be (my wording from memory may not be exact, but it's very close) "the length over the centerline from the furthermost point on the hull, exclusive of any pulpit or bumkins to the aftmost point on the stern, exclusive of any motor mounts or other attachments."

And when bow/anchor pulpits and swim platforms were usually teak or mahogany bolted onto the boat, that definition made it clear that they were not to be included. But around 1980, boat builders began integrating swim platforms into the hull mold and and pulpits into the deck mold. Although the pulpits can't be included in the LOA because they're part of the deck, not the hull, swim platforms that are part of the hull can be...thus allowing builders redesignate a boat that was still 28' from bow to transom as a 30' or even longer, depending on the size of the "back porch" and increase the prices accordingly.

I remember a long weekend raftup of 5 or 6 boats...my 1979 32' Trojan F32 was tied to a friend's brand new 36' Carver....our transoms were lined up exactly even. When I took a garbage bag to the bow to get it out of the way, I looked over at his bow...it stuck out only a few inches beyond mine. The remainder of his additional 4' of LOA was all a two level "back porch" molded into his hull...from the transom forward his was boat was the same length as my F32, which also had a swim platform, but it was teak and bolted on...so not included in the LOA.

HeadMistress 05-04-2016 04:56 PM

Quote:

Originally Posted by No Mast (Post 439376)
What I don't understand is why Selene goes the opposite way, and by quite a bit. Our Selene "53" is actually 60ft LOA. Why would you do that??

You're prob'ly including a pulpit that's part of the DECK mold, not the hull mold, in your measurement...the builder can't count that in the LOA. If there's a swim platform that isn't integral to the hull mold, they can't count that either. But a dock master can, and will!

BandB 05-04-2016 05:22 PM

The most common measurements I see are:

1. LOA without platform or pulpit

2. LOA with platform or pulpit.

Both of those are centerline lengths. #1 is the documented length and #2 comes into play in determining slip size needed and charged for. The only time this becomes complicated to me is when the platform is an integral part of the hull. That's where LOD (length on deck) excludes it and hull length includes it.

LOA for documentation purposes does include any integral swim platform and excludes one that isn't integral to the hull.

LOA also called centerline length or documented length.

Fortunately, except as shown by the one marina in this thread, I haven't heard of anyone measuring along the outside of a boat in decades. However, before regulations there were some builders calling that LOA.

LWL is critical to knowing your displacement or hull speed. It's also important for bottom painting. You'd think it would be also for hull cleaning, but I don't know a single diver who uses it. The ones I know go by LOA.

Then there's the nominal length. Many say, the builder called it 62'. Well, look carefully. While some like KK do label it Krogen 52', more use model numbers which can represent anything they want. Don't assume a 550 is 55' or a 44 is 44'. We have a Sunseeker Manhattan 65. Same hull as a Manhattan 63. Look on their brochure or web site and the length is 69'1". Well, that's LOA with platform and pulpit. Nowhere on the brochure or website will you see the LOA without platform and pulpit. It is, and the documented length is 63'. You will also not see the LWL anywhere. Among other things you won't see, you won't see the air draft anywhere. And if you look at the water draft on their brochure it won't mention what engines. It's actually with IPS. With traditional drives it's 3" less.

Beneteau is a good example too. On the Swift Trawler 50, they never refer to it as 50'. It's just a model number. They are actually closest to their LOA including pulpit and platform which is 49'2". The hull length and documented length is only 43'9". Notice how Sunseeker and Beneteau took opposite approaches to numbering. Sunseeker numbers close to the hull length. Beneteau numbers close to their LOA with pulpit and platform. So model designations are generally useless.

Someone mentioned difficulty in determining centerline length or LOA for slips. Actually very easy. Pull it in and measure how much shorter or longer than a known slip length, or just dock it on a side tie anywhere. Mark on the dock the furthermost points of the boat. Measure. I have encountered marinas that measured for transient. That's exactly how they do it. Actually saw a bit of a dispute. They accepted my number without measuring because I gave them length including pulpit and platform, not documented length. They were trying to explain to another boat that they didn't care what his document said. They cared about how much space it took and if he didn't want to pay for the platform and bow pulpit, he should just remove them then.

RT Firefly 05-04-2016 05:32 PM

Greetings,
Re: post #29...She said bumkins...
http://www.reactiongifs.com/wp-conte...09/tee-hee.gif

dhays 05-04-2016 05:34 PM

Peggy has a good point. My NP43 is 42' from the tip of the hull at the bow to aft of the cockpit. LOA is 45.6 because of the integral swim step.


For purposes of WA State Mooring bouys and my WA State Marine pass my NP43 is 43' long (and I'm sticking to it).

No Mast 05-04-2016 05:44 PM

You know, I just complained about it, never stopped to think it through. Thanks Peggy!

markpierce 05-04-2016 06:50 PM

My builder, Seahorse Marine, has described the 35'8" deck length of the Coot as both a 35-foot or 36-foot boat, depending on mood. If one includes the bow pulpit and the up-folded swim platform, it's about 38'. ... Never had a marina measure-tape my boat. Nevertheless, not all suitable-length berths can accommodate the boat's 13' beam. Desire 16' feet and more! Fortunately, my home berth is over-sized.

http://www.trawlerforum.com/attachme...d2e98f3874.jpg

BandB 05-04-2016 06:59 PM

Quote:

Originally Posted by HeadMistress (Post 439399)
You're prob'ly including a pulpit that's part of the DECK mold, not the hull mold, in your measurement...the builder can't count that in the LOA. If there's a swim platform that isn't integral to the hull mold, they can't count that either. But a dock master can, and will!

Makes even more difference in a small boat. All the leading runabout builders started going that way. Look at Sea Ray. A 230 is 23' in the mind of the buyer, with the integral platform. In my mind it's still a 21' boat. Their 19' is 17' to me. The trickiest is their 19 SPX outboard. How did they call it 19'? Well, they have integral platforms that extend on both sides out beside the outboard.

JDCAVE 05-04-2016 07:01 PM

Quote:

Originally Posted by Larry M (Post 439280)
Our Krogen 42 is documented at 43'. We're 46' overall from the tip of the bow pulpit to the edge of the swim platform. The swim platforms 3' as is the bow pulpit.


Prior to sale, I had my surveyor measure the length of my KK42. While the boat was on the hard, we used plumb bobs to measure "Length on Deck" from the bow (not including the pulpit) to the transom of the hull, just below the caprail. It came out to 42'3" which is what most kk42's are listed at in brokerage listings. I needed that measurement surveyed for a specific requirement of a "license" that was transferred to my vessel at purchase. It just so happens that this vessel length and the identified length of the license were identical, which was a good thing.

Larry, I roughly figured out our length overall at 45'. That's what I tell marinas I visit. My swim platform sure doesn't extend 3 feet beyond the transom that overhangs the forward part of the swim step. The swim step maybe adds 18".


Jim
Sent from my iPad using Trawler Forum

Pura Vida 05-04-2016 08:50 PM

A friend had a 2004 Sea Ray 380 Sundancer, next to him at the dock was a 2007 Sea Ray 38 Sundancer which had the integrated swim platform the 2007 was 2 feet shorter overall.

BandB 05-04-2016 09:27 PM

Quote:

Originally Posted by Pura Vida (Post 439450)
A friend had a 2004 Sea Ray 380 Sundancer, next to him at the dock was a 2007 Sea Ray 38 Sundancer which had the integrated swim platform the 2007 was 2 feet shorter overall.

Interesting way to moderate the pricing increases too.

78puget-trawler 05-04-2016 11:15 PM

This is from an old 1964 copy of Merchant Vessels of the United States, includes yachts.


"Register length". "is the length of a vessel measured on the top of the tonnage deck from the fore part of the outer planking or plating at the bow to the after part of the sternpost of screw steamers and to the after part of the rudderpost of other vessels. The register length is not usually the same as the over-all length nor the load water line length." This is old and may have changed, I don't know.


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