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Old 09-22-2010, 11:08 AM   #21
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RE: Basic Trawler questions

Some good thoughts this time around.sunchaser,
Earlier some were alluding that the charm of a Nordic Tug was'nt worth paying for. Hogwash! These boats of ours are YACHTS and "charming" should be one of the very most important elements of desirability. Well worth paying for as it gives us satisfaction and that should be at least close to the bottom line.
John,Keith,
"Also Keith, for it to be a proper comparison the total horsepower would have to be the same." Yes. AND the engines would need to be VERY similar in type and design. Not a GB 36/42 w a 240 hp electronic and turbocharged state of the art modern engine compared to 2 old 120 Lehmans. The 50/100hp Yanmar question w no load is an interesting question but I don't see the point in it. If both engines had the same displacement per hp, ran at the same engine speed (rpm), had the same type on combustion chamber, had the same type of injection system, developed the same torque at the same rpm, developed their power at the same rpm, had the same exhaust back pressure, weren't widely different in bore/stroke relationship................... This is just off the top of my head. Perhaps if Ford had made a 165 cu in 3 cyl version of the 120hp/380 cu in we could come close to a good comparison but that wouldn't be ideal either as each engine would have half as many and twice as many cylinders per cu in. With same displacement and other things being equal (and of course they never are) the engine w fewer cylinders will be most efficient. REmember the economy car contest a week ago? The winning car had one cylinder and this was not a mini * * *..it was a 4 passenger car. "Do you think the fuel burn would be the same? Or better for either example? And why. Under load?"
This is a very big question with many more variables than above but the answer to "under load" is meaningful to us. If an engine is propped right and has the appropriate propeller and reduction gear ratio one can use the "specific fuel consumption" figures provided by the engine manufacturer to predict fuel burn. One can see at what rpm the engine is most efficient too and one would want to cruise if efficiency was most important. There are variables here too as the engine marineizers and installers can induce variables like exhaust system back pressure, cooling fans or no fans v/s water pumps. One can shoot from the hip and come surprisingly close on older NA engines by figuring 20 hp per gallon per hour (I think I've got that right). FF will correct me if not.
Does this raise more questions than answers? I will say this to your question John. If both engines were basically the same regarding the variables above and their torque max was at 2000 rpm and the engine load was the same the fuel consumption would be the same plus or minus very small fly stuff.
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Old 09-22-2010, 11:55 AM   #22
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RE: Basic Trawler questions

Right on Eric, charming is what it is all about, for some of us anyway.* The bottom line in this whole single vs twin thing to me is, I don't care about an extra few tenths of a GPH. I want a charming, safe, reliable, fairly new, high quality, seaworthy boat with a good pedigree that helps resale. And the*BIGGEST I can afford to own and operate!!
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Old 09-22-2010, 12:31 PM   #23
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Basic Trawler questions

My study of Cummins b series shows the 6 cyl engines as more effificient that the 4 cyl even though they have more jugs.


-- Edited by jleonard on Wednesday 22nd of September 2010 12:32:07 PM
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Old 09-22-2010, 02:00 PM   #24
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RE: Basic Trawler questions

Quote:
sunchaser wrote:

Right on Eric, charming is what it is all about, for some of us anyway.* The bottom line in this whole single vs twin thing to me is, I don't care about an extra few tenths of a GPH. I want a charming, safe, reliable, fairly new, high quality, seaworthy boat with a good pedigree that helps resale. And the*BIGGEST I can afford to own and operate!!
I made the mistake of going to a Seattle Boats Afloat show this past weekend.* This is my new dream boat (and, unfortuantely will likely remain a dream).
http://www.seaspirityachts.com/passagemaker60.shtml

Besides the superb layout, fittings, etc, the boat has the nicest ass-end I've ever seen.*

Single engine with the get-home-system being either of the two generators which can turn the main shaft hydraulically.* Range up to 7,000 nms!

So, if about 2 million of you would just send me a dollar each....

*
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Old 09-22-2010, 02:35 PM   #25
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RE: Basic Trawler questions

Eric, one thing you are missing is that we are likely trying to power the same boat. So your "same RPM" comment doesn't apply. In reality, the same boats, one with single and one with twins, the one with the twins will likely have more horsepower. Now you run both of those same boats at the same speed(theoretically using the same horsepower since we assume all other things being equal), and you will likely have a higher fuel burn with the twins. There are inefficiencies that are compounded by two engines. Mainly drag caused by the components on the engine....pumps...alternators etc. Even if we cut an engine in half and had two "half engines" that equaled the one single engine with all thins equal, I still think you would suffer this added drag due to the accessories. But back to reality, that is usually not how it turns out. You end up with more total horsepower in the twin boat.

There are a lot of theoretical "in a vacuum" type scenarios. In reality, the way manufacturers power boats, the single is gonna burn less fuel for a given speed in a given boat.
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Old 09-22-2010, 03:08 PM   #26
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RE: Basic Trawler questions

It is always fun to read these debates... single vs. twin......
everyone of us has an opinion... usually related to the boat they already own!
what kind of a moron would I be if I ranted in favor of a twin vs the single ... when I own a single!.*** I for one... and I think Delfin will chime in.... just do a happy dance around my engine room with all the extra room afforded by my single.... why dance? ... because I can!
HOLLYWOOD
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Old 09-22-2010, 04:55 PM   #27
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RE: Basic Trawler questions

Not all singles have good ERs. Some Selenes and*Nordhavns are quite cramped. I was looking at a Nordhavn 62 a few weeks ago - not a good single ER.
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Old 09-22-2010, 09:38 PM   #28
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RE: Basic Trawler questions

Jay,Variables variables variables. If you looked at the specific fuel consumption for 100 engines you'd prolly find that fewer cylinders = more efficiency.
Tonic,
I did just the same thing several years ago when the Seasprit 60 was the Ocean Queen 58 or some such thing. A dreamship to be sure. Does it still have the beautiful VG Douglas Fir interior? I don't really like big boats but was completly Ga Ga over this one. Looked at the ads in the magazines and it was just another boat but to see the real thing!!! This boat is more than charm.
John,
I'm not missing that at all. It's an assumption if you want apples and apples you must have the same load on the engines and the same boat, at the same speed would come close enough * *..I think. As I say * * .... they (the twin and single being compared) must have very close to the same power or the comparison is'nt valid.*I mean within about 5%. Drag from auxiliary equipment would probably be FAPP the same as water pumps, gear boxes ect will be half size on the smaller engines.
SO * ... if you want to say the average boat w twin engines is less efficient than the average boat w one engine * * ..I'll throw you the blue ribbon. I thought the discussion was what is more efficient * *twins or singles? In other words which configuration is more efficient. To that I will say the twin is more likely more efficient but by a small margin.
Sunchaser,
Most trawlers are semi-displacement and that tells us that most trawlermen feel as you do. Low fuel burn is not the holly grail as most trawlers are SD BUT most trawler owners didn't buy the boat new. If you can afford a new Nordic Tug the fuel burn is fly stuff. But if you want to do Passagemaking with your trawler, range is no longer fly stuff. To some degree trawlermen see their trawler as a passagemaker and like to brag about their range even though they never go that far. My boat has a range of 6 or 700 miles * ....
ridiculous for a 30' boat. I understand someone took a W30 to Hawaii but why should the rest of us have to deal w those big fuel tanks? Anyway * * ...if fuel burn and efficiency was the most important thing most all of us would have full displacement trawlers. Right now I'd like to have an 8 knot boat that burned 2 gph * *..twice my current burn.
Hollywood,
I hope you don't think I'm ranting as that would mean I've been called a moron.
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Old 09-22-2010, 11:32 PM   #29
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RE: Basic Trawler questions

My name is John....and I am a moron.....

Eric....to be continued!!!!
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Old 09-23-2010, 12:58 AM   #30
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RE: Basic Trawler questions

Quote:
Tonic wrote:


sunchaser wrote:
I made the mistake of going to a Seattle Boats Afloat show this past weekend.* This is my new dream boat (and, unfortuantely will likely remain a dream).
http://www.seaspirityachts.com/passagemaker60.shtml

Besides the superb layout, fittings, etc, the boat has the nicest ass-end I've ever seen.*

Single engine with the get-home-system being either of the two generators which can turn the main shaft hydraulically.* Range up to 7,000 nms!

So, if about 2 million of you would just send me a dollar each....

*

Yeeeaaaah.* Mind if I dream along with you Tonic?* That's one fine vessel all right.

*
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Old 09-23-2010, 03:27 AM   #31
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RE: Basic Trawler questions

Great house afloat , but I was unable to find build specks?

LLoyds or anyone ever take a look below the acre of teak?
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Old 09-23-2010, 07:56 AM   #32
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RE: Basic Trawler questions

Twin vs. Single....the endless debate. having owned both newer twin engine sedans and now our older/slower single screw Monk, I can see the merits of both set ups. Obviously a single is going to be more cost effective. However, handling obviously will be less nimble. My monk has a SERIOUS walk to starboard in reverse to the point I wish I had a thruster sometimes. Other than that I love the single. That said, I love the handling a twin screw set up affords.
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Old 09-23-2010, 10:43 AM   #33
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RE: Basic Trawler questions

My Krogen backs to starboard, and I can use that to advantage. To back in a straight line, I can either use my thruster, or the "back and fill" maneuver. I've done both.
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Old 09-23-2010, 11:40 AM   #34
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RE: Basic Trawler questions

If I go about 2 knots my rudder will steer going backwards.My little Albin did that too w a smaller rudder.
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Old 09-23-2010, 12:25 PM   #35
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RE: Basic Trawler questions

I learned a very long time ago when I had my old single screw Mainship that the boat only did one thing. It backed to port and did that very well and consistantly.
Once I got that thru my thick skull *I had no problems at all. Backing into anywhere was a* matter of planning for the wind/current because the boat only did one thing...it backed to port.
Some days were a 2 slip wind, some a 3 slip wind, etc. depending on how hard it was blowing.
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Old 09-23-2010, 12:41 PM   #36
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RE: Basic Trawler questions

I've seen a lot of chatter about articulating and fish tail rudders and such on other lists.* All seem to agree that they provide enormous maneuvering improvements when going forward.* Performance in reverse isn't quite as clear to me.* But ... it's a low cost mod so I'm going to give it a shot and cobble something up over the winter.
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Old 09-23-2010, 01:35 PM   #37
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RE: Basic Trawler questions

Ah the old twins versus singles.* And as they say, people will defend whichever one they have so... I have twins and love them.* They are beautiful.* If I only had one I'd have half as much to love.* And changing the oil on Saturday only took about an hour, and that was including dealing with onlookers, borrowing things from people, etc.* A small price to pay for TWO things of beauty.* AND I can stand in the MIDDLE of the engine room.* Who cares if there is a side to each engine I can barely see, let alone access?* Those with a single have a motor in the middle of the engine room.* Can they even stand up on the outsides of the engine?* What is the big deal with being able to walk ALL THE WAY AROUND?* Aren't you all stooped over??*

Ok I am being facetious, but my engines ARE beautiful and I do like having two as I can spin my boat in circles very easily.* You never know when THAT will come in handy.
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Old 09-23-2010, 01:58 PM   #38
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RE: Basic Trawler questions

PG,You must like blue. We single screw dudes (nothing to do w one night stands) are jealous and NEEEED to criticize Something. Yes PG your twins are pretty. But many twins are a bear to service. You must be lucky. Engine manufacturers try to put all the service things on one side of the engine but when thats on the outboard side of a twin * * ...... .
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Old 09-23-2010, 02:32 PM   #39
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RE: Basic Trawler questions

mmmmm... shiny.....



changing the fuel filters on the port engine is going to be ENTERTAINING to say the least.
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Old 09-23-2010, 02:52 PM   #40
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RE: Basic Trawler questions

Quote:
BaltimoreLurker wrote:

I've seen a lot of chatter about articulating and fish tail rudders and such on other lists.* All seem to agree that they provide enormous maneuvering improvements when going forward.* Performance in reverse isn't quite as clear to me.* But ... it's a low cost mod so I'm going to give it a shot and cobble something up over the winter.
Yes* O ambitious one,

*Please do and let me know how it works out.
*
I am not worthy and am afraid to try something such as your intent.

SD

*
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