Why is the LWL so much shorter than LOA

[Martin_J]

Not sure if it is the same for manufacturer measurements but IRC measurements for example state...
Note that on boats with skegs, stern overhang is measured to the intersection of the actual hull (the canoe body) with the water, ignoring the skeg.
If the upper end of the rudder is above the waterline, it is preferable to measure SO on both sides.

This would I expect bring your SO (Stern Overhang) to somewhere well forward of the aft end of your rudder blade.

 

[Keen_Ed]

If the LWL is from the designer, then he'll be working to his design weight. Very unlikely that the builders actually deliver a boat down to that weight. Shallow buttocks mean that as the boat is immersed, the stern overhang gets used up quickly.

 

[DJE]

Me too.

For example the difference between the LOA and the LWL of the J111 is about 4 feet, and it looks like this.

http://www.jboats.com/j111-tech-specs

Numbers look about right to me:-

 

[Buck Turgidson]

Line drawings of the type show the LWL to be at the intersection of rudder and hull at the stern so your painted lines are higher than the design LWL.

 

[Angele]

I'm with others who reckon the designed waterline is well forward of the stern.

I have a boat with a stem that is much more vertical than yours (as you can see from my avatar). I also have the hull length (according to the specs) in addition to the LOA and LWL. My measurements are as follows:

LOA 12.32m = 40'5"
Hull length 12.06m = 39'6"
LWL 10.74m = 35'3"

So, my stem fittings (anchor roller) account for 11" and the difference between hull length and LWL is an additional 4'3", making 5'2" in total. Given the bow of your boat has much more of a rake to it, I can quite believe an extra 2' difference.

Do you have the manufacturer's measurement of the hull length?

 

[silver-fox]

I'm with others who reckon the designed waterline is well forward of the stern.

I have a boat with a stem that is much more vertical than yours (as you can see from my avatar). I also have the hull length (according to the specs) in addition to the LOA and LWL. My measurements are as follows:

LOA 12.32m = 40'5"
Hull length 12.06m = 39'6"
LWL 10.74m = 35'3"

So, my stem fittings (anchor roller) account for 11" and the difference between hull length and LWL is an additional 4'3", making 5'2" in total. Given the bow of your boat has much more of a rake to it, I can quite believe an extra 2' difference.

Do you have the manufacturer's measurement of the hull length?

No I just have the LOA and LWL quoted by the manufacturer.

I am beginning to think the answer is that the one offered by a few earlier posters which is that the design water length is totally different from the "real life" water length as painted on the hull.

Whilst my OP was about my own boat it was also meant to be a general question because I had noticed the significant difference between LWL and LOA in several straight stemmed and straight transomed boats -which is the more fashionable design these days, where you would expect the difference to be minimal.

 

[prv]

I'm with others who reckon the designed waterline is well forward of the stern.

I am too now, having seen the drawing posted above. I was assuming the OP's painted waterline was more or less accurate.

Pete

 

[silver-fox]

I am too now, having seen the drawing posted above. I was assuming the OP's painted waterline was more or less accurate.

Pete

It is accurate - in the sense that it shows where the WL actually is when the boat is unladen. But it sounds to me like the designers LWL is the result of a theoretical calculation based on the design weight of the boat and, if that is the case, then this is the reason for the discrepancy between published figures and real life - maybe!!

 

[Romeo]

Here are 2 photos of my boat out of the water. A quick look at the stern shows that the waterline extends to within a few inches of the sugar-scoop stern of the boat and whilst the stem is raked, a handily placed piece of scaffolding helps guess that the difference at the bow between waterline and LOA is around the 3 ft mark. Yet the specs for the boat say LOA is 41ft 8 ins and LWL is 34ft 3ins a difference of 7ft 5ins. How can that be? Can anybody explain this?

You have forgotten to fit your bowsprit.

 

[Tranona]

No I just have the LOA and LWL quoted by the manufacturer.

I am beginning to think the answer is that the one offered by a few earlier posters which is that the design water length is totally different from the "real life" water length as painted on the hull.

Whilst my OP was about my own boat it was also meant to be a general question because I had noticed the significant difference between LWL and LOA in several straight stemmed and straight transomed boats -which is the more fashionable design these days, where you would expect the difference to be minimal.

The designer of your boat, Bill Dixon, is still very much alive and kicking. Why not give him a call and ask him how he arrived at the figures?

 

[Martin_J]

oooh.. I wondered why Tranona suggested that she's a Bill Dixon design but after looking at your blog I realise why. No wonder I thought the shape was similar to my s38.

Just checking out the photo on the blog that shows her from ahead. She looks low in the water.. Strange.. Do you have any photos from astern whilst she is in the water showing true waterline?

I would still expect the top of the rudder to be visible.