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Old 08-10-2013, 10:55 AM   #41
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Originally Posted by manyboats View Post

Experience has it's place but there are many elements of the GH design that totally defy traditional marine architecture.

Boats and ships are shaped the way they are from centuries of designing, building and running boats at sea and on the water.
Just about every modern ship has a flat bottom. How does that defy traditional marine architecture?
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Old 08-10-2013, 11:50 AM   #42
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Traditional for a ship is mostly NOT traditional for a 40' pleasure boat.

Traditional for a 40' seaworthy offshore blue water boat will bring forth an image. And generally speaking that image will be the product of centuries of "traditional" seaworthy boats. That image will not look anything like a GH. There are many accepted standards of design for a good sea boat. For example it's often said that a good seaworthy design will have a stern that resembles the bow much more than typical boats of otherwise the same type. A low center of gravity and rather low windage also are elements of a seaworthy design.

I did mention the flat bottomed ships in my post. They do not have hard chines and they seldom (if ever) see the light of day. But I know little of ship design.
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Old 08-10-2013, 01:29 PM   #43
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NOT a bluewater boat:

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Old 08-10-2013, 02:43 PM   #44
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Take a look at the wake on that scow Mark and notice that he's going less that 1/2 hull speed. At hull speed that first wave after the bow wave would be at the stern. The wave from the bow goes out and comes back at a given rate and he would need to be going a bit more than twice as fast to have the first returning wave (the largest) come right up under the stern. The returning wave under the stern pushes the boat fwd to some degree regaining some of the energy lost making the bow wave.

That's one of the reasons our full disp hulls are so efficient. The upslope of the bottom at the stern is shaped a bit like (and significantly fits the wave) to help push the boat fwd. So in the vicinity of hull speed the FD hull is actually surfing. The square stern boats w the straight flat bottom just sinks the transom deeper in the water (actually the water comes up) creating more drag and turbulence.

But we pay the price of not being able to go faster at times.
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Old 08-10-2013, 04:14 PM   #45
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At hull speed that first wave after the bow wave would be at the stern. The wave from the bow goes out and comes back at a given rate and he would need to be going a bit more than twice as fast to have the first returning wave (the largest) come right up under the stern.
I guess I don't completely understand your explanation. In the photo below, my boat is going 8.4 knots, (No tide, calm water & a water line length of 29.7. Hull speed?

Please analyze the photo.
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Old 08-10-2013, 05:13 PM   #46
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If I were to redesign the Pilgrim 40 to be a steel hull below the deckline, what hull shape might be the best compromise? That's what I am researching.
Naval architecture is a complex undertaking; if you really want to get a good idea of the answer to this question, it would be worth paying a competent designer for a few hours of their time. I'd highly recommend Tad Roberts, who you can find on here or at Tad Roberts Yacht Design. You might also have a look at Michael Kasten's designs, Kasten Marine Design, Inc. - Custom sailing and motor yacht design..

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Old 08-10-2013, 05:20 PM   #47
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Michael Kasten Has some cool designs and great web sight.There are a couple on Yachtworld now.
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Old 08-10-2013, 06:56 PM   #48
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He could always consult with this guy too...


http://www.runningtideyachts.com/home/

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Old 08-10-2013, 07:52 PM   #49
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Or this guy. www.loucodegana.com

You guys crack me up. A naval architect and Professional engineer with a bachelors from Webb Institute (Do you even know what Webb is, and how hard it is to get in? I do, I went to NY Maritime. Those guys are freakin' brainiacs) and a masters from MIT doesn't know anything about hull form, stability or seaworthiness. Got it.
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Old 08-10-2013, 10:51 PM   #50
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Originally Posted by SeaHorse II View Post
I guess I don't completely understand your explanation. In the photo below, my boat is going 8.4 knots, (No tide, calm water & a water line length of 29.7. Hull speed?

Please analyze the photo.
Walt remember a long time ago I said you must be going about 8.5 knots and you said dead nuts but how did you know that? The wake tells the speed and something about displacement and hull design as well.

When a wave hits a wall like structure it decelerates and rises up. Gravity arrests the rise and the wave water stops momentarily but gravity abruptly pulls the water back down creating a new wave going in the opposite direction. Basically it bounces off the wall.

Your bow wave is created in the obvious way pushing the water aside as the boat progresses. A large wide entry angle pushes the water abruptly (quickly) up. How much boat is in the water, how blunt the bow is and how fast it's going determine the size of the bow wave. Over a long period of time you can see something about the bow shape from the bow wave given enough experience.

5.4X5.4=29.16. 1.34X5.4=7.236. Less than I would have guessed. That's your hull speed. My HS is 6.968 knots. So your HS is 1/4 of a knot faster. But you have a semi disp hull so you can go faster so your speeds are much greater but our HS is very similar.

But the secret to analyzing the wake is mostly in the stern wave. How big it is has to do w speed and displacement. At HS the crest of the stern wave is right at the transom. So the stern looks a little swamped. The water rises up to meet the stern and w a SD boat the stern is lifted but little push is created because of the high drag of the trailing edge of the transom that's creating lots of turbulence. The bottom of the SD stern is not curved like a FD hull so the stern wave holds up the stern but there is little tendency to surf so being at HS in a SD boat does not have the advantage the FD hull does. BUT .. a bit faster w the stern wave several feet aft of the transom the SD hull starts (in a big way) to shed the full disp drag at HS and starts to behave somewhat like a planing hull. At this point the FD hull has MUCH more drag. The stern of a FD boat above HS (or even at HS) has to "pull" the water up from below whereas going a bit slower the water rose up and back to the surface aided by the stern wave.

Back to the bow wave. Water is accelerated outward and it (to some degree) runs into a brick wall. No brick wall at all but the sea that acts like and takes the place of the brick wall. Re a hull at HS the bow wave stops it's rush outward, meets the sea and the sea pushes the wave back. So the bow wave "bounces" off the sea and returns back to the boat but at the stern. That's why you see a boat at HS w a little mountain of water at both ends.

Usually I get ready to duck tomatoes or experience silence when I go analytical but it's a pleasure Walt. Don't know if this helps or explains it but I tried. Hope I didn't tell any untruths but I may have taking liberty to make the hull speed thing more clear.
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Old 08-10-2013, 11:21 PM   #51
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Originally Posted by Northern Spy View Post
Or this guy. www.loucodegana.com

You guys crack me up. A naval architect and Professional engineer with a bachelors from Webb Institute (Do you even know what Webb is, and how hard it is to get in? I do, I went to NY Maritime. Those guys are freakin' brainiacs) and a masters from MIT doesn't know anything about hull form, stability or seaworthiness. Got it.
It looks to me like you're say'in I don't have the knowledge to criticize this guy. Fair enough. I couldn't even spell criticize (there I go again). I'm say'in what I think and what I may know. Regarding my comments on the GH boats I don't think I said anything wrong or untruthful. Flat bottomed boats pound and deep sharp chines trip boats into capsizing. I'll retract anything that was incorrect or out of line in any other way.

I'm not writing a doctorate here on TF. This is just opinions and discussion and of course fact when it appears. Have you ever criticized the president?

And notice that I didn't criticize the designer ... just the boat.
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Old 08-10-2013, 11:21 PM   #52
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Or this guy. www.loucodegana.com

You guys crack me up. A naval architect and Professional engineer with a bachelors from Webb Institute (Do you even know what Webb is, and how hard it is to get in? I do, I went to NY Maritime. Those guys are freakin' brainiacs) and a masters from MIT doesn't know anything about hull form, stability or seaworthiness. Got it.
Finally a smart post in this thread.

I have spent a few hundred hours cruising behind Joe Pica, beside Joe Pica, and rarely, in front of Joe Pica, and his GN 37.

If something (God forbid) should ever happen to the little DeFever Iíll replace it with a GN 37 (although Iíll have them leave out the house sized appliances - sorry Joe) and with a flybridge.

Who you gonna believe? A few posters with no credentials or a Webb and MIT trained NA?

There are posters here at TF who think they can determine the CG of a boat by looking at it. As one who has spent thousands of hours doing weight studies I have a message for you - youíre wrong.

There is a poster here who thinks the performance of a boat is based almost entirely on the stern. He never shows any evidence that he knows anything about block, or prismatic coefficients.

He offers no credentials.

Hey Joe, keep on cruising.

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Old 08-11-2013, 07:09 AM   #53
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..As far as redesigning a Pilgrim 40 below the waterline...why? What are you going to do with it? What's wrong with the original hull? All hulls are a compromise as said in the GH marketing mumbo jumbo...so what's your list of performance charachteristics? Why steel?

Most of all why in this thread? Why don't you start a thread on just what you have in mind so it's easier to follow?
Okay, started a new thread



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Naval architecture is a complex undertaking; if you really want to get a good idea of the answer to this question, it would be worth paying a competent designer for a few hours of their time. I'd highly recommend Tad Roberts, who you can find on here or at Tad Roberts Yacht Design. You might also have a look at Michael Kasten's designs, Kasten Marine Design, Inc. - Custom sailing and motor yacht design..

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Yes Scott. I answered some of your concerns on that new thread. Ill add more as you see what I am looking at material wise.

New subject thread HERE
http://www.trawlerforum.com/forums/s...oat-11212.html
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Old 08-11-2013, 10:17 AM   #54
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Sepec/Mike,
I think I remember you and some of your acidic posts of the past. You had a lines dwg for your avatar.. right? psneeld thinks the same way you do and I finally exercised the ignore button on him.

I know the principals and effects of both PC and BC but who else here does?

I'm trying to give the average guy just a bit of understanding about the physics and hydraulics of what the water is doing around his boat ... WO giving out information I know he dosn't understand. People do that in conversation to attempt to make themselves look or seem smart. Frequently people use acronyms that are so isolated the listener is very unlikely to know what the guy is talking about. Makes them look smart? Depends who the listener is.

If you think conversation on TF requires credentials you're wrong and 98% of the people here know that. You said my post was wrong and about one aspect of it wour'e right. A lot of engineering went into it. If the GH had ben built by a welder down the street AND designed by him it wouldn't be much of a boat. Some boats are probably designed by welders that have about 1/10th as much design knowledge as I do. I'm on BoatDesign.net too and my credentials there are "amature" as they are here re design.

The GH is probably a better boat than I think but flat bottoms and slab sides do have their limitations indeed. There are fish buyer scows in Alaska that are essentially powered barges and they negotiate some terrible water in the Bering Sea, Aleutian Islands and the Gulf of Alaska. I'm aware that barge like craft can be seaworthy but ther'e built for a different set of priorities ... comfort and grace not among them. But if I was to be foolish enough to cross the Gulf of Alaska I'd rather do it in a passagemaker. And a passagemaker the GH is not.

I can make a functional displacement hull out of a planing hull by modifying the stern. But I can't make a functional disp hull out of a planing hull by modifying the bow.
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Old 08-11-2013, 10:35 AM   #55
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Take a look at the wake on that scow Mark ...
I often leave it to the reader to make the connection, so I'll supplement my last post (#43), which had only a photo of a sailing scow, with this quote from an encyclopedia:

"Sailing scows have significant advantages over the traditional deep keel sailing vessels that were common at the time the sailing scow was popular. Keelboats, while very stable and capable in open water, were incapable of sailing into shallow bays and rivers, which meant that to ship cargo on a keelboat required a suitable harbor and docking facilities, else the cargo had to be loaded and unloaded with smaller boats. Flat bottomed scows, on the other hand, could navigate shallow waters, and could even be beached for loading and unloading; this made them very useful for moving cargo from inland regions unreachable by keelboat to deeper waters where keelboats could reach. The cost of this shallow water advantage was the loss of the seaworthiness of flat bottomed scow boats in open water and bad weather. ..."


Makes sense to me that different hull shapes can have different advantages and disadvantages.
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Old 08-11-2013, 10:54 AM   #56
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I'm trying to give the average guy just a bit of understanding about the physics and hydraulics of what the water is doing around his boat ......

........Frequently people use acronyms that are so isolated the listener is very unlikely to know what the guy is talking about.

If you think conversation on TF requires credentials you're wrong and 98% of the people here know that......

The GH is probably a better boat than I think but flat bottoms and slab sides do have their limitations indeed. .....

But if I was to be foolish enough to cross the Gulf of Alaska I'd rather do it in a passagemaker. And a passagemaker the GH is not......

I can make a functional displacement hull out of a planing hull by modifying the stern. But I can't make a functional disp hull out of a planing hull by modifying the bow.
Most TFers that read all the posts know that I don't always agree with manyboats. In fact, there are many posts by me that really take him to task. The above, however, in my opinion, are right on the mark.
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Old 08-11-2013, 12:00 PM   #57
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Call it what you may....conjecture or opinion, but I each time there are discussions such as this (save the occasional pissing contest), I gain usable points of reference as to what one might expect in the "behavior" of any particular hull type. I probably wouldn't even know what questions to ask a Webb or MIT NA. Meanwhile, thanks to the less technical smorgasbord here, I've gained a clear understanding of which hull designs are less likely to chap my weeping butt furunkles after hours on the helm chair. Jay Benford, Tad Robets, and Lou Codega can surely speak of butt furunkle chap ratios and quotients, but they probably don't really have butt furunkles. You guys do.
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Old 08-11-2013, 01:15 PM   #58
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IMHO - I think the GH make a fantastic boat for what the vast majority of trawler owners use them for. They appear to be spacious and comfortable, low draft for the Bahamas or similar areas, the built in buoyancy is a plus, an engine room that I have wet dreams about, and have salty-ish good looks (maybe a bit cartooney) I would love to cruise the PNW and Inside Passage with an N47.

What puts me off is their over the top marketing. "Go Anywhere Capability" trawler is on almost every page of their website. A big call to make. They may be good; but not that good. A lot of other debatable statements & claims are made, without factual supporting evidence.
From what I see of them, I don't think they are any more "go anywhere" than the average recreational trawler. I certainly wouldn't classify them as a passagemaker.

I feel they would be better off toning down some of their marketing hype, and just rely on the fact that they have built a boat that suits many owner's actual use.

Perhaps they know people often buy boats based on their dreams rather than their use.
That was an excellent post!!!

I would love to have a GH, not to use as a passagemaker, but to use as Coastal Cruiser.

BTW, I've myself crossed the Gulf of Alaska, TWICE in BAYLINERS.

Every large boat in the harbor at Seward, Whittier, Kodiak, Cordova has crossed the Gulf of Alaska. Hundreds of boats of all shapes and sizes.

Almost none of these boats are passagemakers!

The Gulf of Alaska is Coastal cruising. You could do it in any boat with enough fuel onboard to make the voyage of 260NM to Whittier from Yakutat.

Coastal cruising could and should be defined as any cruising where you have reliable weather prediction capability. My experience is we have very reliable weather prediction out to 72 hours. At 7 knots thats 504NM, which is less than my range at even 8 knots including a 20% reserve.
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Old 08-11-2013, 02:45 PM   #59
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Great Harbour Hull

Let's see.... conjecture and opinion based on no formal NA or PE education without factual data or actual experience cruising in the hull in question trumps all? I guess if you shout loud enough and often enough someone may believe you know what you are talking about regardless of facts. I doubt many of these self proclaimed pundits of naval architecture have even seen a Great Harbour hull out of the water let alone sea trialed one prior to condemning it's sea keeping ability. I will include some pictures to clear up some of the "conjectures". The GH hull is a very unique sophisticated, and complex design, not just a simple flat bottomed boat. I guess the "Webb Institute MIT NA/PE who designed the hull, the GH owners who have cruised 1000s of miles off shore, inshore, the Great Lakes, Canadian Maritimes, North Atlantic and the South Pacific are fantasizing how comfortable and capable their boats have seemed in all their travels.
I am stunned to realize that all my years of personal boating experience in many different hull forms (6yrs in a GH N-37) both power a sail is meaningless compared to forum opines.
I guess I need to stay in a Holiday Express.

Cheers

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Old 08-11-2013, 02:48 PM   #60
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Can you post more overall pictures of your boat?
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