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Old 04-25-2014, 12:32 AM   #41
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Old 04-25-2014, 08:22 AM   #42
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I've been a fan of Hatterius LRCs for years but always thought they were SD not FD. I'm confused on the 42 LRC, the designer says full displacement but in the same discussion he says it will go 11 knots?
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Old 04-25-2014, 09:58 AM   #43
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I guess my 24' trawler is too small to make the list! The little guy gets no respect around here!
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Old 04-25-2014, 10:21 AM   #44
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Full displacement craft don't operate at a SLR of 1.75 and that is what this designer is suggesting as I read in the attachment.

IMO he's speaking from a marketing point of view. I haven't seem the stern of these boats though but think the afterplane must have a relatively flat and straight run or 11 knots cruising would not be practical or perhaps even attainable.

Some people do separate SD from FD buy the speed capabilities. As eyschulman has pointed out there is definitely a significant grey area in definition and there are boats that swim in the cusp of two different types. And I might add that a motorsailer isn't a "true" motorboat or sailboat. A bit of each but not a thoroughbred of either.

Many think that a "true" trawler should be a FD craft. The opposite is actually true IMO. Probably 90% of trawlers are SD so SD is actually most representative of the type. FD trawlers are actually just super slow trawlers.

I see dhmeissner's post now and that sums it up directly. The post is either directly saying or at least strongly implying that a FD craft should command a greater degree of "respect" and their owners as well. Many times I've called a boat owned by a person that was under the impression that it was a FD boat a SD boat. And the response was clearly that of offense. How dare you call my boat a SD. Noth'in semi about it ... it's the real thing .. ect.

Actually the design of a FD boat is quite easy to pull off compared to a good SD. So perhaps a good SD design should command more respect. But for a trawler a SD is best in that all those people w SD trawlers can't be wrong. SD is better as stated by the buyers of trawlers. The old and the new. Look at all the go fast trawlers like the Fathom 40.

Bottom line IMO is that FD boats should command no more respect than SD boats ... perhaps even less. SD boats are, all things considered, better trawlers than their heavier and slower family members.
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Old 04-25-2014, 11:19 AM   #45
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Well, a full displacement might be able to do 1.75 of the hull speed. The Eagle hull is tapered to the stern, so it does tend to rise out of the water. The original spec said cruise at 10 knts max speed 12 knts. 12/7= 1.71 However, we are pushing a lot of water and burning a lot of fuel for an extra 3 knots, but it can/could be done. I set the RPM at 1500 so the speed ranges from 7 to 9 depending a current and wind. The max rpm is about 1800.
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Old 04-25-2014, 11:25 AM   #46
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Willard 36, you could apply 1000hp and she would still only make 10k but she will make 6.5k using 13 of her 50hp.
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Old 04-25-2014, 11:33 AM   #47
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As Hargrave says it's a "bad place to be", and yes with enough horsepower and fuel you can push any displacement hull way above hull speed to get to that "bad place", very akin to that very bad place on a planing hull between hull speed and planing speed.

My main takeaway from Beebe's and Gerr's books was that the main advantages of a full displacement hull were the greater interior capacity for fuel, and to a lesser degree water, and stores, coupled with being a bit more fuel efficient at slow speed. I haven't seen any evidence to the contrary in real life.
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Old 04-25-2014, 12:05 PM   #48
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George wrote "with enough horsepower and fuel you can push any displacement hull way above hull speed". Not "way above". Just a little above. In the Willard Owners Group there's one fellow that has an 80hp engine is his Willard 30'. Max speed is (according to him) 8 knots. That's only one knot above HS by more than doubling the power. Boats that go "way above" HS just aren't FD.

If you actually called Hargrave up and asked him about it he'd probably say something like "calling something a semi something just would have complicated things" or "It's more in keeping w the essence of the boat and how we intended it to be used" ... like at FD speeds.
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Old 04-25-2014, 12:51 PM   #49
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What's in a name? I say again look at how the boat works and if its right for you forget the label. What does it matter if a marine architect can measure the buttock angle or whatever and proclaim the boat FD or SD. I think the OP should start out by determining how he wants to go through the water and find a boat that will do that and not worry about its classification.
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Old 04-25-2014, 01:17 PM   #50
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Brooksie and Manyboats--the more I view Willard hulls the more I am convinced my boat's designer was a huge Willard fan--almost identical. Anyway, I am probably 10HP overpowered (original engine was 18HP and I'm now powered with a 29HP Volvo). I generally see little gain (perhaps 1/2 knot) when I increase the throttle beyond 2800 RPM or so. I simply make more noise and a larger wake; the bow also begins to lift.

On a somewhat related note, I've been notably and uncomfortably above hull speed before... "surfing" is one way to do it! I went through some nasty weather outside the entrance channel near Albert Whitted airport in Tampa Bay. I was literally surfing on 4-6 foot following seas and achieved around 8-9 knots on occasion according to my GPS. It was a bizarre feeling--I could feel the boat being "lifted up" and I had little control. It was not fun!
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Old 04-25-2014, 01:22 PM   #51
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George wrote "with enough horsepower and fuel you can push any displacement hull way above hull speed". Not "way above". Just a little above. In the Willard Owners Group there's one fellow that has an 80hp engine is his Willard 30'. Max speed is (according to him) 8 knots. That's only one knot above HS by more than doubling the power. Boats that go "way above" HS just aren't FD.

If you actually called Hargrave up and asked him about it he'd probably say something like "calling something a semi something just would have complicated things" or "It's more in keeping w the essence of the boat and how we intended it to be used" ... like at FD speeds.
If you can get Hargrave on the line there is a future for you as a medium!

Put 300 horses on that Willard and see what happens. Or tow it with a big tug, what do you think happens then, stops the tug in it's tracks?

I guess it all depends on what you or I mean by "way". And Hargrave meant by "bad place".

A buddy had a 42LRC, at WOT maybe 10 knots and very very ugly, there in that "bad place".
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Old 04-25-2014, 01:28 PM   #52
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Put 300 horses on that Willard and see what happens. Or tow it with a big tug, what do you think happens then, stops the tug in it's tracks?
I'm guessing the Willard would be visiting King Neptune and exploring the ocean's depths.
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Old 04-25-2014, 01:30 PM   #53
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But eye all the stats are supposed to tell you. And the rules of thumb like a boat whose stern looks more like the bow than most boats will be (all other things considered) better equipped to deal w quartering stern seas. A FD boat w fuller ends will be (generally speaking) harder do drive but capable of a bit more speed than the boat w skinny ends.

Knowing boats is to understand as much as you can and exercise it as much as you can and apply it as much as you can ....... If you really want to know. You're right. You can enjoy boating immensely and know little or perhaps nothing about the difference between SD and FD. But this is a forum and forums are for learning and sharing knowledge in addition to experiences and a few jokes. But you are right no one should feel he needs to know this stuff. Those who don't care will be reading something else they do care about. Lots of threads I never look at at all. And there are many w such an undescriptive title I don't bother.
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Old 04-25-2014, 01:35 PM   #54
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And this discussion will help him discover "the way he want's to go through the water".
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Old 04-25-2014, 02:46 PM   #55
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I would think a FD may have a bit more room down low in some cases, but generally they have a much smaller interior due to the tapered beam in the aft, compared to squared off SD hulls.

In regards to surfing; I quite like it. When the waves are just the right size and angle, control can be maintained and its a lot of fun. I find that in 4-6 foot waves directly on the stern are perfect, if they are well spaced and not not breaking. But there are ugly 4-6 foot waves too, that I try to avoid.
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Old 04-25-2014, 03:48 PM   #56
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I would think a FD may have a bit more room down low in some cases, but generally they have a much smaller interior due to the tapered beam in the aft, compared to squared off SD hulls.
I am not sure I understand that comment. ?





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Old 04-25-2014, 04:27 PM   #57
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I'm not interested in a discussion of full vs. semi-displacement. I was looking for any information, based on fact/experience, as to what model/manufacturer are true full displacement. Using the search engine is like searching for a single screw on Yachtworld. You get a list and when you see the actual pictures you quickly find that half of them are twin screw. I'm looking for a true full displacement trawler, 1980 or better, under $150K. Who did or currently makes one?
Totally agree. Using "single screw" as a sole search term is problematic in Yachtworld and elsewhere on the internet can get you in a whole lot of trouble.
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Old 04-25-2014, 06:51 PM   #58
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George so kindly posted a picture of Windhorse, felt by many and numbers back it up, one of the better combination of economy and speed in the yacht business today. Tad Roberts has some similarly efficient designs, alas no pictures yet of that vessel's bottom.

The FPB Dashew design is approaching 15 builds with the largest around 97 feet and currently under construction in NZ.
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Old 04-25-2014, 07:44 PM   #59
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I can only guess why the OP wants a true FD hull. I am thinking he is looking for comfort safety and economy. If the OP has not figured it out yet from all the above posts and pictures of hulls not all FD hulls are created equal and some creep into the SD category by various standards. I should like to throw an other issue out for the OP to think about. Many of the prototype FD trawlers based on North Sea fish boat lines have a nasty tendency to roll underway and at anchor. These boats often with somewhat rounded bottoms and rounded buts with deep draft carry flopper stoppers and bilge keels for good reason. I owned a round bottom trawler back when I lived on the East coast and I would not do that (barf)again. Having a more modern hull form can deal with some of these faults. Marine architects have learned a thing or two over the last 100 years thus the large # of hull forms deviating from the prototype trawler. My last and present boats have hulls derived from lobster(Downeast)boats. This hull form is happy travelling below -at- and above hull speed depending on power applied. When I cross the open water straits in my cruising area I encounter many FD boats on the way. When it is snotty I change gears and pop out of my usual hull speed travel. I apply enough HP to get me up on top of the waves and I am across the straight in about an hour while the FD boat occupants are slowing down and being abused for three or more hours. Yes I have to burn some fuel to do that about 1.2 G/NM at 16-18K but it is worth it. I would also like to point out that a larger modern motor will only burn as much fuel as called for by the prop to power the boat at a given speed. 20 hp demand from a 30hp motor will burn about the same fuel as 20hp demand from a 300hp motor. Now the old school diesel people are going to jump all over me. You are going to carbon up your motor if you don't run it 80-90% load. That has been debunked especially with modern common rail motors-just run them at spec. temps and up to 80 load for 10 min. at the end of the day. A motor properly managed at 40-60% load will more than likely outlast a motor being run at 80-90% load. Just more stuff for the OP to think about.
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Old 04-25-2014, 09:54 PM   #60
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Eye,
If you think good SD hulls are a recent development you are probably mistaken. William Hand comes to mind. Hand created some brilliant SD hulls.

The early days of engines saw engines that could only drive a boat as fast as a sailboat (a FD) hull and in those days very narrow. As the engines became slowly (I repeat) slowly more powerful a hull type that probably never existed before was created out of the need to take advantage of the increased power of the newer engines. The semi-displacement hull. One that could run regularly at hull speed and above.

There was a long period of time where perhaps just about every conceivable SD hull shape was developed because of the lower amount of power available. Even as late as the 50s yachts were considerably narrower like the bull nosed Chris Craft. I remember the mid 50s the CC 62' yacht was powered by 3 flat head 6cyl engines.

So instead of now having newly developed SD hulls newer hulls are probably designed along the lines of old well established designs and design principals. And as power is less available because of limited fuel or whatever we will return to the well developed hulls of the past. I believe we are going back to the old designs much more than creating new ones.

Perhaps I'm wrong though and just aren't familiar with new developments. I am aware of some designs such as the Axe Bow and BulbousBow but the mainstream bread and butter shapes for SD hulls I think we're well established about 100 years ago.

If I'm wrong at least it will be an interesting door to open.
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