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Old 02-25-2014, 01:41 AM   #41
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Sure love that Bluewater.
Of course you do! It looks like a streamlined Manatee on steroids.

(BTW, cool looking boat, Capt JB. Watching for pictures.)
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Old 02-25-2014, 06:38 AM   #42
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Wow....again the discussions of full displacement and semi-displacement have gone lost on so many.

There is no sharp dividng line or magic between the two unless you start to get to the upper or lower reaches of each design. There are many trawlers that are discussed here that are classified as SD but so close to FD ....many of the "picture NAs" here have gone back and forth saying SD one time then FD the next depending what the picture is showing.

As far as motion..that's more about shape than full or semi and so is weight carrying capability...semi just means it will do it at a higher speed with less economy along the curve...even at slower speeds.

So many myths here......and propagated by people who seem to gloss over the links by experienced designers....

When you are talking 40 feet and under...there's just not that much wiggle room to make that many significant variations in hull design and still have similar boats. Sure cat versus mono...but be fair...and even then there's huge compromise with other features beyond hull design.

The classic discussion is that a sailboat hull sure can be a slippery hull and very economical. But then the trawler guys say...well look at all the room I have and you don't.

Guess why....
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Old 02-25-2014, 06:52 AM   #43
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Think out side the box.

Bought my Cherubini in January with a Cummins C 450. Hull is somewhere between SD and SP. Purchased a 4 cylinder John Deere (107-137 HP) and will do the swap this summer. The motor is almost an even dollar swap as the one coming out is low hours, still made, and in demand. Will use same transmission and shaft. Will need to change wheel and plumbing. Lot easier to put a smaller motor where a bigger one was.

Here is my point, you may find a fuel guzzling SD that is a hard sell. Save enough on the purchase to repower.

Ted
Exactly what I'm talking about.....no magical jump between boat types.

Other feature plus how the boat will be cruised may become larger deciding factors than what side of a line on a graph your hull falls on, or whether fuel economy is the only issue ....or whether the whole package becomes the point over the minuscule.
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Old 02-25-2014, 08:35 AM   #44
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Some hulls are FD and no tweaking will change that without building a new hull.

The OP wanted a list of FD hulls not a discussion about thoughts and theories.

The boats given clearly fit the FD classification.

At cruise (8 mph) I get 5 mpg if I slow down I get a bit more. 25K lbs feels darn good when pushing into head seas.
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Old 02-25-2014, 08:50 AM   #45
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Some hulls are FD and no tweaking will change that without building a new hull.

The OP wanted a list of FD hulls not a discussion about thoughts and theories.

The boats given clearly fit the FD classification.

At cruise (8 mph) I get 5 mpg if I slow down I get a bit more. 25K lbs feels darn good when pushing into head seas.
Nice boat and a very correct post. Thanks
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Old 02-25-2014, 10:11 AM   #46
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Of course you do! It looks like a streamlined Manatee on steroids.

(BTW, cool looking boat, Capt JB. Watching for pictures.)
Touche, guilty, caught me, I hate to be predictable. Now that I think of it, the boat is very much the style of the KK Whaleback, often called the Manatee on steroids.
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Old 02-25-2014, 11:24 AM   #47
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If you want to observe the difference between FD and SD efficiency look at sailboats. They more likely than not have thirty some hp engines and lots of weight. FD trawlers are almost over powered. My Willard 30 came w 33hp and could easily do w 5 less. But it's was an exception as it was offered at close to ideal FD power of about 4hp per ton. The 36 Willard also was close at (I believe) 85hp but could do w 65hp. Not very familiar w the 36 though. Perhaps Brooksie can amplify. The Willard 40 however is definitely over powered. Eighty hp would easily serve that boat. NWboater w a W40 claims 1.5 gph and that equates to 30hp for his usual cruise.

The SD boats are usually much more over powered (to go slow) as they were designed to go faster and as we all know that takes power at a non linear rate. But dragging their big wide well submerged sterns along consumes lots of power. How much? That varies a lot over the range of SD hulls as there are lots of differences. Some SD boats like the 49 DeFever are practically a FD hull and probably require only about 1.25 more power than the FD. An IG w almost a straight QBBL (run aft) is probably closer to requiring 2X as much power to cruise at .75 knots below Hull speed. A GB should require about 1.4X FD power and I'd say most probably require 1.5.

But that's just my opinion. You can row a typical aluminum skiff but it's a bit of a drag. Pun intended. And if you put a person in the stern it probably equates to a front end loader out on the freeway. One last thought or as close to a last thought as I may ever have is that to see the practical difference one must compare at about .75 knots below hull speed (or less) as that's where they are designed to run. Not at HS.

SCOTTIEDAVIS your FD hull may be the most efficient on the forum for the boat size (not displacement). As for the OP he got his list long ago as we all know the list is short. There are numerous FD boats out there on the market but almost none of us know of their existance as most are old or custom builds.

Larry I like the boot top line on the KK in the pic and assume it was on purpose. A touch of class I think. Looks like the KKs CG is fwd. Much more fwd than my Willy or a typical trawler.
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Old 02-25-2014, 06:27 PM   #48
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Nice boat and a very correct post. Thanks
Just where does FD and SD start and stop? ...and who made that determination? and why? and what's their overall certification in the big, bad world?
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Old 02-25-2014, 07:06 PM   #49
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Just where does FD and SD start and stop? ...and who made that determination? and why? and what's their overall certification in the big, bad world?


Trouble maker
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Old 02-25-2014, 08:17 PM   #50
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Trouble maker
Sorry...I too wish I had had the cash to buy some really great boats...reality just stinks sometimes....

but like the cruisin' thread...I'm out there enjoying semiretirement and cruising a giant POS...it CAN be done even on a SD hull and doesn't break the bank....
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Old 02-25-2014, 08:55 PM   #51
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Some hulls are FD and no tweaking will change that without building a new hull.
The OP wanted a list of FD hulls not a discussion about thoughts and theories.
The boats given clearly fit the FD classification.
At cruise (8 mph) I get 5 mpg if I slow down I get a bit more. 25K lbs feels darn good when pushing into head seas.
I second this.
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Old 02-25-2014, 09:17 PM   #52
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Just where does FD and SD start and stop?

...and who made that determination?

and why?
At the stern.

Eric does.

Cuz he can.
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Old 02-25-2014, 09:26 PM   #53
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At the stern. Eric does. Cuz he can.
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Old 02-25-2014, 09:58 PM   #54
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At the stern.

Eric does.

Cuz he can.
OK RT...oooopps...OK so there's more that one talented wise guy on here.....
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Old 02-25-2014, 10:08 PM   #55
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I second this.
a few flat spots on there or wedges (as discussed in links posted by others from prominent NAs could add a knot or so without great detriment to the overall performance and no "hull shape definition change". But simple things can push a hull from way under the FD curve to above it...but as I said there's really no difference in labeling it...at best it may now be called a "tweener".

Yes not many are going to change the shape of a production boat already made...but many tweak the design of a "set of study plans" including the NA before they settle on "their" boat.

awhile back, someone posted pics of a stock vessel that someone had added a bulbous bow and some other hull mods...most laughed at the results even though they had no idea what the outcome was.
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Old 02-25-2014, 10:54 PM   #56
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I try to make it clear why I think as I do. I saw what psneeld said in his quote by Northern Spy. I'm certified as a teacher in WA and BC but not as a NA anywhere. Most everything I say is my opinion or otherwise labeled and I'm sure most everybody here knows my opinions are just that of a long time boater. I did design and build one boat .. 28' plywood.

Many definitions of a FD hull have been expressed here by quite a number of members and our discussions have helped focus our concept. As we go forward into the future our discussions will be remembered and combined w newer input to form newly evolved concepts of boat hull dynamics. I think the dynamics is the important thing and then maybe definitions. However frequently definitions revolve around the understanding the issue.
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Old 02-26-2014, 12:53 AM   #57
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I'm just funning you Eric.

My parents have a 34' Mainship.

I would suspect that a FD boat under 40' would be much smaller than what you have. So I'm not sure that I understand the quest.

To me, this is like walking into a car dealership demanding a car with a drag coefficient of 0.27 or less.

You may end up driving away in a Prius, or maybe a Tatra.
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Old 02-26-2014, 05:52 AM   #58
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As I read this thread and reflect back on each of your submissions on this and so many other past forum subjects it has to be said.
If there is another boating forum that has the activity, give and take, as this site the world is additionally blessed. From each to each, there is so much informative chatter that allows for the reader to take away some bit of knowledge or question(s) to further enjoyment of being a "trawler" owner. With all due respect to each of you, thanks for entertainment,education, and pure pleasure to all points of the compass of forum subjects. (And to the moderators who keep the traffic on task by clearing the decks of personal minutia.)
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Old 02-26-2014, 06:09 AM   #59
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Just where does FD and SD start and stop?

When someone sticks more than about 5 HP per displacement ton into a boat the boat has more power than a full displacement can use.

So the designer must be creating a plaining boat ,of some sort, or just likes to make huge stern waves.

Another boating hobby , usually enjoyed by real tug boat crews going home on the pin.

Most commercial fish boats can enjoy this sport , but with the owner aboard watching the fuel burn,,,,,
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Old 02-26-2014, 02:06 PM   #60
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As I read this thread and reflect back on each of your submissions on this and so many other past forum subjects it has to be said.
If there is another boating forum that has the activity, give and take, as this site the world is additionally blessed. From each to each, there is so much informative chatter that allows for the reader to take away some bit of knowledge or question(s) to further enjoyment of being a "trawler" owner. With all due respect to each of you, thanks for entertainment,education, and pure pleasure to all points of the compass of forum subjects. (And to the moderators who keep the traffic on task by clearing the decks of personal minutia.)
Al
So well said, Al. It's true that some of the best contributors are so distracted by one party or another in defense (sometime in offense) of their opinion that they don't benefit from the values you speak about. Anyway, after "listening" and gaining from the benefits of the knowledge here, I offer this corrected list:

Legacy 32 (Trawler)
Kasten 40
Bluewater 40 (Trawler)
Fales 32
Pilgrim 40
Lord Nelson 37
Krogen 36
Krogen 39
Nordhavn 40
Willard 40, 36 and 30
Coot
Seahorse Duck 382
Great Harbour GH-37 and N-37
Prairie 29
Schucker 40
Various custom Steel Hull Trawlers
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