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02-17-2019, 03:38 PM
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#321
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Guru
City: Concrete Washington State
Vessel Name: Willy
Vessel Model: Willard Nomad 30'
Join Date: Oct 2007
Posts: 18,743
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Quote:
Originally Posted by sunchaser
If I saw an M30 sitting at the dock, looking at its stern would suggest an FD vessel. 43 knots out of this beauty.
http://www.mooresyachts.com
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Chaser,
It probably has a stern very much like the Bartender.
Both planing hulls.
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Eric
North Western Washington State USA
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02-17-2019, 03:58 PM
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#322
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Guru
City: Concrete Washington State
Vessel Name: Willy
Vessel Model: Willard Nomad 30'
Join Date: Oct 2007
Posts: 18,743
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Quote:
Originally Posted by Fish53
Almost every dragger I ever worked on had an immersed transom, including my own but it's important to remember that these vessels are designed to take on a considerable amount of load, far more than a pleasure boat of similar size. In practice minus ice and fish that may or may not be immersed. Oh boy this thread isn't dead after all.
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Not dead HaHa ....
you mean this FD hard chine vessel?
Nothing to talk about. FD
But perhaps the partially submersed transom. I can’t think of a boat w it’s transom fully above the water as being anything but FD. But there are some, quite a few actually, that have partially submerged transoms. The design element that is decisive on these boats is the angle (fore and aft) that comprises most of the bottom well aft of amidships. These boats have a quite steep angle aft that identifies them 100% as being FD. If the bottom was straight and about horizontal they could be even planing hulls.
This angle that is called Quarter Beam Buttock Line by naval architects has in the past been assigned numbers such that a shallower # than “X” indicates a SD hull and steeper than “X” = FD.
But whenever one assigns a specific number to something that number fails to hold up under all circumstances. But the QBBL is probably the best decisive road to separting FD from SD.
One other way to separate FD/SD is to evaluate the area and it’s percentage of boat submerged to the deepest point and how much area is submerged of the transom. But I know of no hard numbers to attach to that.
__________________
Eric
North Western Washington State USA
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02-17-2019, 04:12 PM
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#323
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Guru
City: Queensland
Vessel Model: Milkraft 60 converted timber prawn trawler
Join Date: Jul 2016
Posts: 5,482
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Quote:
Originally Posted by bgillroy
simple no flat sections aft. P and SD have flat sections aft.
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I guess the FD prawn trawler guys never got your memo
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02-17-2019, 04:27 PM
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#324
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Guru
City: Rockport
Vessel Name: Ana
Join Date: Jul 2015
Posts: 1,047
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I thought I tried to be a bit ambiguous with that reply by making the loading observation.
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02-17-2019, 07:11 PM
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#325
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Grand Vizier
Join Date: Jan 2010
Posts: 3,816
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Quote:
Originally Posted by Simi 60
I guess the FD prawn trawler guys never got your memo
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A SD hull that lacks the power to get on top of its bow wave of still a SD hull. With enough power, this boat could plane, because the flat sections aft will provide the lift to keep the stern from going under. It's a lot cheaper to build this shape hull, even if you never expect or want to go faster than displacement speeds.
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02-17-2019, 07:17 PM
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#326
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Guru
City: Concrete Washington State
Vessel Name: Willy
Vessel Model: Willard Nomad 30'
Join Date: Oct 2007
Posts: 18,743
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Why is it cheaper Delfin?
To build this shape of hull?
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Eric
North Western Washington State USA
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02-17-2019, 07:17 PM
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#327
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Guru
City: Rockport
Vessel Name: Ana
Join Date: Jul 2015
Posts: 1,047
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Quote:
Originally Posted by Delfin
A SD hull that lacks the power to get on top of its bow wave of still a SD hull. With enough power, this boat could plane, because the flat sections aft will provide the lift to keep the stern from going under. It's a lot cheaper to build this shape hull, even if you never expect or want to go faster than displacement speeds.
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yeah
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02-17-2019, 07:41 PM
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#328
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Grand Vizier
Join Date: Jan 2010
Posts: 3,816
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Quote:
Originally Posted by Nomad Willy
Why is it cheaper Delfin?
To build this shape of hull?
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Flat steel not requiring shaping, less steel.
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02-17-2019, 09:03 PM
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#329
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Guru
City: Concrete Washington State
Vessel Name: Willy
Vessel Model: Willard Nomad 30'
Join Date: Oct 2007
Posts: 18,743
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Delfin,
Don’t think bending is a problem on boats like this. I could be wrong as I’m no expert on steel building but I’ve seen a few come together w not very sophisticated equipment that had bends about the same as the bottom on these boats. It’s a bigger boat and takes more material but that shouldn’t be that much either. Bigger that a flatter boat bottom w/o such a big “underbelly”.
__________________
Eric
North Western Washington State USA
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02-17-2019, 09:38 PM
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#330
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Guru
City: Rockport
Vessel Name: Ana
Join Date: Jul 2015
Posts: 1,047
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Quote:
Originally Posted by Nomad Willy
Delfin,
Don’t think bending is a problem on boats like this. I could be wrong as I’m no expert on steel building but I’ve seen a few come together w not very sophisticated equipment that had bends about the same as the bottom on these boats. It’s a bigger boat and takes more material but that shouldn’t be that much either. Bigger that a flatter boat bottom w/o such a big “underbelly”.
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All you need is an English wheel and a couple of guys that know how to use it. The vessel in question may have been intended for a significant load in shallow water such as carrying a load of pots, but curved steel would be stronger for the weight if the design would allow it. A large "underbelly" gives an offshore boat better carrying and seakeeping properties.
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02-17-2019, 11:00 PM
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#331
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Grand Vizier
Join Date: Jan 2010
Posts: 3,816
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Quote:
Originally Posted by Nomad Willy
Delfin,
Don’t think bending is a problem on boats like this. I could be wrong as I’m no expert on steel building but I’ve seen a few come together w not very sophisticated equipment that had bends about the same as the bottom on these boats. It’s a bigger boat and takes more material but that shouldn’t be that much either. Bigger that a flatter boat bottom w/o such a big “underbelly”.
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Which stern do you think would be easier and cheaper to build - the above or the below?
__________________
"Dad always thought laughter was the best medicine, which I guess is why several of us died of tuberculosis." - Jack Handey
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02-18-2019, 12:28 AM
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#332
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Master and Commander
City: Vallejo CA
Vessel Name: Carquinez Coot
Vessel Model: penultimate Seahorse Marine Coot hull #6
Join Date: Sep 2010
Posts: 12,559
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The Coot has a similar crescent-shaped bottom.
__________________
Kar-KEEN-ez Koot
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02-18-2019, 02:57 AM
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#333
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Guru
City: Concrete Washington State
Vessel Name: Willy
Vessel Model: Willard Nomad 30'
Join Date: Oct 2007
Posts: 18,743
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Delfin,
My opinion would be the above by far. Lots of compound cirves on the “below” hull. The “above” hull is much more like a simple plywood rowing skiff but lots and lots of rocker. The panels or plates curve in only one direction like flat panels tend/want to do. The “below” boat has much more developed and complicated curved in many planes and in more directions. Rocker being the inverted curve of the bottom running fore and aft. Like the “rocker” on a rocking chair. Kinda like Marks boat on steroids. Marks boat has the same kind of rocker but to a far less degree. The “above” fishing boats are huge and very heavy. Marks QBBL would be much more shallow or put another way a lower angle than the big fishing boats. But the same type of hull basically. Most trawlers have fairly shallow QBB Lines. The IG’s for example have such a shallow angle it’s more like a planing hull. But none the less a SD hull due to her fairly heavy weight, big keel, and prop and gears suited more to heavy craft. Other trawlers like the GB are inbetween. More like a FD hull but still a SD.
All of this that I say is an opinion. And if you heard it from a NA it would likely be far more complicated.
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02-18-2019, 03:05 AM
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#334
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Guru
City: Concrete Washington State
Vessel Name: Willy
Vessel Model: Willard Nomad 30'
Join Date: Oct 2007
Posts: 18,743
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Mark 99.9 % of this question pretains to the stern, not the bow.
And your Coot has the simple plywood shapes of the “above” boats.
But your Coot has the “bone in her teeth” bow wave of a heavy boat having a fairly wide angle of entry. Unlike a “slicer” as you say.
But your hull is very much related to the “above” very heavy fishing boat hulls.
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02-18-2019, 06:31 AM
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#335
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Guru
City: North Carolina for now
Join Date: Aug 2011
Posts: 6,348
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__________________
George
"There's the Right Way, the Wrong Way, and what some guy says he's gotten away with"
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02-18-2019, 09:04 AM
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#336
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Guru
City: Carefree, Arizona
Vessel Name: sunchaser V
Vessel Model: DeFever 48 (sold)
Join Date: Apr 2008
Posts: 10,185
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George
Hull extensions or running gear forward can prove interesting.
Often with the rudder, keel and prop well forward from the stern, a vessel wanders a lot. The after market vertical wavelets on the stern sides are possibly an attempt to force the vessel to stay in a straight line.
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02-18-2019, 09:12 AM
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#337
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Guru
City: Concrete Washington State
Vessel Name: Willy
Vessel Model: Willard Nomad 30'
Join Date: Oct 2007
Posts: 18,743
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caltex I assume you’re looking for comment.
Looks like someone extended a FD hull.
This is a “head swim” example. Has a shallow buttock line angle suggesting a SD hull. She has more than most FD hulls have in submerged transom. Knee jerk reaction is “wow she looks really fast”. But that would assume a FD. Another thing I can say is that she looks like a boat designed to break the rules.
OK,
I’ll pigeon hole this boat as SD.
Why?
Buttock line is very long and almost flat. Transom submerged is significant for a FD and not much for a SD ... not a decisive element w this boat.
This boat is not at all like a FD ... well it is in several ways. She’s oviously built for speed and FD boats are not. She’s SD
But something I should bring into the discussion .... she’s VERY round and would be almost (if not dangerously so) scary in roll and perhaps lacks directional stability. See those little finns at the corners of the stern? I’m think’in they are add on’s because she may not come back out of a turn ... or at least be ruluctant to. Could even be a “bad design” but I may be over thinking it.
Can honestly say I’ve never seen a boat even closly resembling this one. I wanted badly to call her on the fence and so close to uncallable but the QBBL dosn’t lie. She’s SD
sunhaser I’m glad you agree to even some extent.
__________________
Eric
North Western Washington State USA
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02-18-2019, 11:42 AM
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#338
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Guru
City: North Carolina for now
Join Date: Aug 2011
Posts: 6,348
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The last pictured boat is a Nordhavn 62.
__________________
George
"There's the Right Way, the Wrong Way, and what some guy says he's gotten away with"
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02-18-2019, 12:16 PM
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#339
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Guru
City: Rockport
Vessel Name: Ana
Join Date: Jul 2015
Posts: 1,047
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02-18-2019, 12:41 PM
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#340
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Guru
City: North Carolina for now
Join Date: Aug 2011
Posts: 6,348
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The little aft outboard fins are aftermarket, but otherwise it is a stock hull.
https://photos.app.goo.gl/zBX7pigkggSEHBr78
And to Sunchaser's comment yes, typically boats with the prop and rudders well forward have issues in following seas. You see that on some old Hatteras motoryachts where an aftermarket cockpit was put on and the props and rudders left in their original position.
__________________
George
"There's the Right Way, the Wrong Way, and what some guy says he's gotten away with"
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