Beam to Waterline Ratio

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Since most folks on TF appreciate spending time aboard their boats and recognize how important space (interior and exterior) is, I thought it would be interesting to see if we can identify the trawler (under 75') with largest beam to waterline or beam to LOA ratio.

If nothing else, this fun little exercise may help someone tweak his/his next boat search when looking for a live aboard.

John T.
 
Obviously, that would be a Catamaran, probably something like a Africat 42 with a beam of 22' or so, Lagoon 43 with nearly the same, and PDQ 34 with a 16 ft. beam. If you mean Mono-hulls, it would likely be the Great Harbor GH or N-37 with 15' 10" I think. The Manatee 36 is pretty fat with 13'8". There must be other fat ladies out there. Interesting question though.
 
Largest? I think these NS boats win....roughly 50' x 27'.

NSboat.JPG

Scotiastar.JPG

Thankfultoo.JPG

Grizzhull.JPG
 
Beam Size

Tad Roberts said:
Largest? I think these NS boats win....roughly 50' x 27'.

Wow, these are something else. Who is the builder and where are they built? I would be curious to understand how they handle and under different sea conditions and how efficient they are to operate. Thanks

John
Click to expand...
 
John T,
A wide beam to length ratio will automatically give low efficiency. Frequently fish boats are wide for carring capacity. But sometimes they are short and wide to accomodate max length rules or laws.

The American Tugs are much wider than the Nordic Tugs. Also much taller w presumably much more space inside. I'm moored right next to where they are built so see a lot of them. In years past I didn't like them because they threw big wakes and seemed very inefficient but now I like them. If I could afford one and the fuel I could see myself buying one. I like the style even if a little chubby .. especially the FB. The FB is steeply sloped in front.
 
Beam

manyboats said:
John T,
A wide beam to length ratio will automatically give low efficiency. Frequently fish boats are wide for carring capacity. But sometimes they are short and wide to accomodate max length rules or laws.

I totally agree on the efficiency factor and when I think of designers aiming for the "most" efficient mono hull design I think of Set Sail in Australia with there "cross an ocean quickly aluminum narrow hulls". I also recognize the FD hulls can go a little wider than SD without hurting performance. It is a bit of a balancing act and interesting to see how different designers manage expectations.

It will be interesting to see what everyone comes up with for both recreational FD and SD hull ratios.

John
Click to expand...
 
My boat I am told gets one mile/gallon at 13 knots. It's 65' long by 22' wide.
 
I went the other way. 38x11.5.
 
My boat qualifies as a "fat boy. 35'8" by 13': 2.6 to 1.

Edit: waterline length is 31'3", making for a 2.4 to 1 ratio.
 
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My current boat (anyone want to buy it?) has a beam/LWL ratio of 0.37, fatter than even your Coot. Very fat for a sailboat. Pretty efficient though.

The boat I have an offer on has a beam/LWL ratio of 0.33, so a bit skinnier.
 
Dave, using a beam to lwl ratio, the Coot is 0.4. :eek:
 
108'6" beam. Designed to fit through the Panama canal with a 110 ft limit. Happened to spend a few years of my relative youth on a sister ship.

Nothing like the ride storming through heavy seas or bombing up the SoCal coast at 25Kt's plus....
 
Forgot to add this photo of Iowa while she was in our backyard near San Francisco. She is on the lower right (obviously!). Length to beam is very "fast"!

The structure on the upper left is the covered dry dock which was used by the US Navy and CIA to covertly salvage the Soviet Union's submarine (K-129) northwest of Hawaii in 1974 (sunk in 1968). Today the structure is used by a local ship yard near San Francisco (Bay Ship and Yacht). The dry dock was originally built by Howard Hughes for marine mining operations.
 

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Wasn't "mining" the cover story, like the GSF Explorer which recovered part of the submarine?:

https://en.wikipedia.org/wiki/GSF_Explorer

Recall seeing the Explorer when passing near the reserve fleet in the 1980s.
 
Beam to LWL on the Defever 44 is about .38
38.5' LWL, 14.75' beam
Pretty chubby.

Bill
 
markpierce said:
Dave, using a beam to lwl ratio, the Coot is 0.4. :eek:
Click to expand...

ah, I see. Yup, less waterline than I had figured. That is a beamy boat, and it looks like the Coot carries it for more of its length than my plastic bottle sailor.
 
0.35 for my Krogen 54. Not sure where that puts it - probably in the middle somewhere. Not super beamy but not super skinny.
 
Someone should keep a running tally (not volunteering). My guess is that the majority of TF boats will be in the .33 to .35 range.
 
1977 Tollycraft: 34' loa with 12'6" beam, tri cabin, having big sundeck and good sized fly bridge makes us very happy!

2.5 nmpg at 6 knots (that's 1.5 knots below 7.58 knott hull speed) and 1 to 1 mpg at 17 knot cruise make us smile - alot.

Nuff said... :D
 
markpierce said:
Wasn't "mining" the cover story, like the GSF Explorer which recovered part of the submarine?:

https://en.wikipedia.org/wiki/GSF_Explorer

Recall seeing the Explorer when passing near the reserve fleet in the 1980s.
Click to expand...

I think you're right, Mark. I worked a lot offshore in the '70s on Glomar drill ships. Mostly the Glomar Atlantic and CUSS-1. Best food in the "patch"!
 
Like the meaning of "is" , efficiency must be defined.

At low speeds surface area is most of the resistance , not wave making ,so a beach ball would be most efficient.

For many folks that love boating in a slip a boat wide enough to fill the slip , with no extra charges, a 2-1 LB ratio would be fine , esp if the vessel were 2-3 stories high with an oxygen tent on top.

Huge volume , low slip costs.

long and Skinny does raise the speed the boat can go, IF one is willing to pay the fuel bill for the speed..

The added wetted surface of a say 6-1 or 8-1 LB ratio would be less efficient doing the Trawler Crawl , although a higher percentage of hull speed would lower the bill at fast cruise.

Fat or skinny the desired motion in the ocean should be considered , not just mere volume, if the boat will leave the slip.

Years ago the AYRS came up with a simple method of figuring "hull" speed for a variety of boats.

The old formula was created by looking at fat boats of the time , and doesn't work well for skinny fast boats.

S = L/3b X SQRT of (LWL)
 
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Be careful comparing apples to oranges.....if using beam to lwl...make sure you use beam at the waterline to get a usable figure...


I have no idea what my waterline beam even is.
 
My Grand Banks 50 has a LWL of 48' and a beam of 16' giving an "aspect ratio" of 0.33.

Ten years ago I worked on a consulting assignment for a European yacht builder and one of the things we looked at was the beam to length ratio of competing boats at the time. We examined the beam-to-LOA (not LWL) ratio of around a hundred models of leading brands, mostly planning boats (we did not examine "trawlers").

This is graph of the ratio. Each circle is a boat model. As one can see boats tend to become relatively narrower as their length increases. Also there is a great variations at a given length.
http://www.trawlerforum.com/forums/attachment.php?attachmentid=50149&stc=1&d=1459167101
 

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psneeld said:
Be careful comparing apples to oranges.....if using beam to lwl...make sure you use beam at the waterline to get a usable figure...


I have no idea what my waterline beam even is.
Click to expand...

I wondered the same. So, I took plumb bob and with boat as close to perfect centered vertical, at widest deck beam location, I calced beam difference at wl. Our Tolly's wl beam is 10' compared to deck beam of 12'6". Also measured wll in similar manner... it's 32' compared to deck length of 34'

Tolly has: hard chine 32' x 10 water line foot print with approx 2'9" draft to keel bottom.

I use the 32' wll to mathematically calc hull speed of 7.5 +/- knots. With both engines running 6 to 6.5 knots is the sweet spot for getting 2 + nmpg. With one engine running 4.5 to 5 knots gets upper end of 2 nmpg. 16 to 17 knot cruise on full plane gets 1 nmpg. WOT 22 to 23 knots gets OMG nmpg... probably about 1/2 nmpg?? which would equal 44 to 46 gph... or put another way, at let's say $5 per gallon = WOT would amount to approx $225 per hour. I do not go that speed, often at all! :lol:
 
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My ratio is somewhere around 0.30, depending on how I measure my Water Line Length.


What is the proper way to measure WLL on a boat with a canoe stern? Is it tip to tip in a straight line at water level, or the curved length along the waterline?
 
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