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Old 03-27-2016, 11:49 PM   #21
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Originally Posted by markpierce View Post
Dave, using a beam to lwl ratio, the Coot is 0.4.
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.
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Old 03-27-2016, 11:58 PM   #22
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0.35 for my Krogen 54. Not sure where that puts it - probably in the middle somewhere. Not super beamy but not super skinny.
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Old 03-28-2016, 12:05 AM   #23
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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.
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Old 03-28-2016, 12:55 AM   #24
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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...
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Old 03-28-2016, 02:58 AM   #25
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Quote:
Originally Posted by markpierce View Post
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.
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"!
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Old 03-28-2016, 07:13 AM   #26
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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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Old 03-28-2016, 07:19 AM   #27
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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.
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Old 03-28-2016, 08:12 AM   #28
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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/a...1&d=1459167101
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Old 03-28-2016, 08:19 AM   #29
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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.
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!
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Old 03-28-2016, 09:01 AM   #30
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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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Old 03-28-2016, 09:27 AM   #31
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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?
If not heeled....perpendicular to the points where the hull meets the water.

If heeled ....the same...but that would probably be a challenge...
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Old 03-28-2016, 10:26 AM   #32
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Xlantic, great info. That looks like a least squares fit line of that data?

I am continually impressed at the depth of knowledge and data that some of you guys have readily at hand.
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Old 03-28-2016, 10:42 AM   #33
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Originally Posted by FF View Post
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)
What is "L" and "b" in that formula?
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Old 03-28-2016, 11:08 AM   #34
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That looks like a least squares fit line of that data.
Yes, R2 of 76% which suggests a pretty good fit.

I suspect the larger boats in the sample are non-planing and hence relatively narrower for greater efficiency. For planing boats there may be a smaller or no efficiency penalty for being relatively wide?
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Old 03-28-2016, 11:29 AM   #35
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Spent a couple days aboard Iowa running from Norfolk to Ft. Lauderdale. Pic below shows firing the 16" guns. Most terrifyingly awe-inspiring thing I've ever seen.

BTW, Great Harbour GH37 and N37 have a 36' 2" LWL and 16' 0" beam.. Works out to .44
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Old 03-28-2016, 11:36 AM   #36
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KK42: 15' / 39.167' = 0.383


Jim
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Old 03-28-2016, 12:20 PM   #37
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An interesting comparison of the same perspective shot taken many years apart.
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Old 03-28-2016, 04:54 PM   #38
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Originally Posted by psneeld View Post
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.
Gosh darn it, Scott! You're right, I've never thought (or cared until this thread) about "waterline beam". I'm probably closer to 0.29 than my previous 0.33.

Art, I'll try your plumb bob thingy....man, you must have been bored!
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Old 03-28-2016, 07:46 PM   #39
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Regardless, the Iowa-class battle ships are skinny compared to our boats.
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Old 03-28-2016, 08:00 PM   #40
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Man she sure went on a diet.

Some day maybe Ill get to feel a big ole gun fire a round or two.
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