Reply
 
Thread Tools Display Modes
 
Old 05-14-2015, 04:29 PM   #21
Guru
 
Nomad Willy's Avatar
 
City: Concrete Washington State
Country: USA
Vessel Name: Willy
Vessel Model: Willard Nomad 30'
Join Date: Oct 2007
Posts: 13,724
The beauty of the FD hull in big seas is that going slower reduces the power required a lot. That power can then be applied to penetrating wind or picking up speed after being slowed down by a big wave. As you slow more and more power becomes availible.

The notion that one must maintain the pre-selected cruising speed is nonsense. We bucked a strong ebb in Knight Inlet BC and much of the time went only 2 and 3 knots. 3, 4 or so hours were spent like this. Didn't ruin the day and we continued at 2300rpm (normal cruise). If the speed had dropped to one knot Iwould have been looking for a place to throw the lunch hook and take a nap. My navigation style allows me to do things like that. Many here would be very upset having to slow down. Those would be happier w a boat having more speed flexability and range.

I've said this many times before. One does not need much additional power above what is required to drive the boat at a speed/length ratio of about 1.1. I have never used more than 25hp (500rpm down from max) and am powered at 5hp per ton. Five max hp per ton.
__________________
Advertisement

__________________
Eric

North Western Washington State USA
Nomad Willy is offline   Reply With Quote
Old 05-14-2015, 04:51 PM   #22
TF Site Team
 
Baker's Avatar
 
City: League City, Tx
Country: Texas
Vessel Model: Carver 356
Join Date: Oct 2007
Posts: 5,633
Quote:
Originally Posted by hollywood8118 View Post

I personally know of a different N46 that had to use all of its main engine hp and all of the wing engine's hp to fight up river in a massive current while doing less than 1/2 knot.. he was wishing for more.

HOLLYWOOD
And my somewhat rhetorical question would be....what if he had more(hp)???? Would that have helped??? Probably not. What he needed was a different hull shape!!!! And THEN the extra power would have helped!!!
__________________

__________________
Prairie 29...Perkins 4236...Sold
Mainship Pilot 30...Yanmar 4LHA-STP...Sold
Carver 356...T-Cummins 330B
Baker is offline   Reply With Quote
Old 05-15-2015, 12:29 AM   #23
Guru
 
Wayfarer's Avatar
 
City: Oneida Lake, NY
Country: USA
Vessel Name: Radio Flyer
Vessel Model: Wilderness Systems Aspire 105
Join Date: Aug 2014
Posts: 784
The N46 was one of my first boat loves. I used to know that brochure back to front. She's a classic.
__________________
Dave
Just be nice to each other, dammit.
Wayfarer is offline   Reply With Quote
Old 05-15-2015, 01:28 AM   #24
Guru
 
hollywood8118's Avatar
 
City: Port Townsend Washington
Country: USA
Vessel Name: " OTTER "
Vessel Model: Ocean Alexander Europa 40
Join Date: Nov 2009
Posts: 1,482
Quote:
Originally Posted by Baker View Post
And my somewhat rhetorical question would be....what if he had more(hp)???? Would that have helped??? Probably not. What he needed was a different hull shape!!!! And THEN the extra power would have helped!!!
Well think of it this way...the boat wouldnt make it without the 27hp of the wing..did the extra hp help?? You bet. I know some here would rather run a boat harder with a smaller hp motor..for a bluewater boat I would rather have a bigger hp motor and run it at less of a load and have more power when needed.
Hollywood
hollywood8118 is offline   Reply With Quote
Old 05-15-2015, 01:42 AM   #25
Wannabe
 
Britannia's Avatar
 
City: SF Bay Area
Country: USA
Vessel Name: Stillwater
Vessel Model: Kadey-Krogen 54
Join Date: Dec 2014
Posts: 766
Using the calculator here

Boat Speed Calculator

which is based on Gerr's DL ratio - it gives 66HP for the N46 at 7.3kt (one knot below HS). I have copy of VUP and confirm the numbers given with Bebee's curves. Not sure which are more accurate.

However, I do feel I want the extra HP in a blue water boat. I have already been out in some pretty nasty seas in Stillwater and felt safer being able to increase power without going to WOT. Maybe that's just psychological, or maybe I'm a Spinal Tap fan who wants to know his dial goes to 11 (in case 10 just isn't enough).

Richard
Britannia is offline   Reply With Quote
Old 05-15-2015, 01:49 AM   #26
Wannabe
 
Britannia's Avatar
 
City: SF Bay Area
Country: USA
Vessel Name: Stillwater
Vessel Model: Kadey-Krogen 54
Join Date: Dec 2014
Posts: 766
Quote:
Originally Posted by Wayfarer View Post
The N46 was one of my first boat loves. I used to know that brochure back to front. She's a classic.
The N46 was very high on my list before I ended up looking at bigger boats. My KK54 is very similar in many ways - sailboat hull, canoe stern (the N46 almost has one if you look at the hull), raked bow, set back pilot house, asymmetric (starboard) walkway, two speeds - slow and slower.

My boat was built one year before the first N46.

I still like them

Richard
Britannia is offline   Reply With Quote
Old 05-15-2015, 07:14 AM   #27
Guru
 
City: Carefree, Arizona
Country: usa
Vessel Name: sunchaser V
Vessel Model: DeFever 48
Join Date: Apr 2008
Posts: 6,376
When James Hamilton ordered his N52 he rejected Nordhavn's chosen HP and went up to the next size motor for the exact reasons Hollywood cites.

Having excess motor capability is not a negative in the eyes of many N owners with some preferring wet exhaust, twin engined N55/60s being built to satisfy this urge.

Nordhavn can design and build a faster hull, witness the N57, stretched 47 to the 52 and 55 to the 60 and 63.

Dashew's FPBs have both speed and economy. Currently In build are 4 more 64s, two 78s, 97 just done and a 130 in the final design stages. The 130 has twin Scania 675s and can cruise at 40% power @ 14 knots. All one needs is money to buy speed and economy, kinda like the model T, comes in one color.

The design and quest for speed in the FD ranks is alive and well.
sunchaser is offline   Reply With Quote
Old 05-15-2015, 10:26 AM   #28
Guru
 
Nomad Willy's Avatar
 
City: Concrete Washington State
Country: USA
Vessel Name: Willy
Vessel Model: Willard Nomad 30'
Join Date: Oct 2007
Posts: 13,724
Yes Tom It's urges not needs based on reality. On a SD boat having more power than usually used can be sorta justified ... but not on a FD.

But on a FD boat one at least has the choice of installing power that will permit running at a normal cruising speed and be at least at a 50% load .......... for whatever that's worth.
__________________
Eric

North Western Washington State USA
Nomad Willy is offline   Reply With Quote
Old 05-15-2015, 10:45 AM   #29
Guru
 
City: Carefree, Arizona
Country: usa
Vessel Name: sunchaser V
Vessel Model: DeFever 48
Join Date: Apr 2008
Posts: 6,376
Don't you think Eric some people need a Nordhavn or Dashew FPB as much as you need Willy? If it weren't for urges, boating and the human race would not exist.
sunchaser is offline   Reply With Quote
Old 05-15-2015, 11:08 AM   #30
Guru
 
Codger2's Avatar
 
City: San Diego
Country: US
Vessel Name: "Sandpiper"
Vessel Model: 2006 42' Ocean Alexander Sedan
Join Date: Oct 2007
Posts: 5,421
Quote:
Originally Posted by hollywood8118 View Post
..for a bluewater boat I would rather have a bigger hp motor and run it at less of a load and have more power when needed.
That pretty much sums up my philosophy in power boats! I just met a guy 2 weeks ago that has a 48' OA with twin 500 Yanmars. He commissioned the boat in 2005, has put 2,000 hours on it and cruises it at 10 knots. (Goes much faster if the Tuna are off shore!)
__________________
Codger2

My passion for improving my boat(s) exceeds my desire to constantly cruise them.
Codger2 is offline   Reply With Quote
Old 05-15-2015, 11:20 AM   #31
Wannabe
 
Britannia's Avatar
 
City: SF Bay Area
Country: USA
Vessel Name: Stillwater
Vessel Model: Kadey-Krogen 54
Join Date: Dec 2014
Posts: 766
Quote:
Originally Posted by manyboats View Post
But on a FD boat one at least has the choice of installing power that will permit running at a normal cruising speed and be at least at a 50% load .......... for whatever that's worth.
According to the online calculators I can find, my boat is at that point. It supposedly takes 106 HP to get Stillwater to 8.3 kt (HS is 9.3 kt) and the engine is rated at 225 HP. According to the same calculators the N46 also runs at 50% load at cruising speed (HS - 1 kt)

Richard
Britannia is offline   Reply With Quote
Old 05-15-2015, 11:20 AM   #32
Guru
 
hollywood8118's Avatar
 
City: Port Townsend Washington
Country: USA
Vessel Name: " OTTER "
Vessel Model: Ocean Alexander Europa 40
Join Date: Nov 2009
Posts: 1,482
The reality is that some drive Prius's, some drive Vipers

I am in the viper camp.. but I do have a attraction to trawlers

Eric's opinion is great for the protected waters of Puget Sound and has served him for the way he boats, I wouldn't knock him for it as it works for him.

The other issue is that if you had to cross and ocean, or make a 48hr+ coastal run I would rather listen to a 1700 rpm drone of a 120hp main in a N46 than the 2500+ rpm racket of a 4 banger 50hp diesel at max continous hp..

For me, extra power =

HOLLYWOOD
hollywood8118 is offline   Reply With Quote
Old 05-15-2015, 11:39 AM   #33
Guru
 
N4712's Avatar
 
City: South FL
Country: U.S.A
Vessel Name: Oliver
Vessel Model: Nordhavn 47 Hull# 12
Join Date: Apr 2013
Posts: 3,613
Quote:
Originally Posted by hollywood8118 View Post
The reality is that some drive Prius's, some drive Vipers

I am in the viper camp.. but I do have a attraction to trawlers

Eric's opinion is great for the protected waters of Puget Sound and has served him for the way he boats, I wouldn't knock him for it as it works for him.

The other issue is that if you had to cross and ocean, or make a 48hr+ coastal run I would rather listen to a 1700 rpm drone of a 120hp main in a N46 than the 2500+ rpm racket of a 4 banger 50hp diesel at max continous hp..

For me, extra power =

HOLLYWOOD

Very well summed up!
__________________
Thanks, Oliver
M/V Oliver
Nordhavn 47 Hull #12
N4712 is offline   Reply With Quote
Old 05-15-2015, 11:55 AM   #34
Guru
 
BandB's Avatar
 
City: Fort Lauderdale
Country: USA
Join Date: Jan 2014
Posts: 13,183
Quote:
Originally Posted by manyboats View Post
Brit,
Then the one in Voyaging Under Power was not original.

143hp? Then like most boats it was overpowered. I'm sure it only takes 40hp to cruise that 46. 60hp should be enough but I'm only talking about a true FD hulled boat. And the stabilizers would bump that power requirement to maybe 80hp. Most FD boats can't use more than double their cruise power requirement even in the worst conditions. ... IMO
Wifey B: To you a bicycle with two pedals is over powered...... Just teasing you but really you're fighting a losing battle against the rest of the world. Guess humans are overpowered with twin lungs.

Zoom zoom zoom....I like power under me.

Just out of curiosity, what kind of car do you have and what is it's power? Guess you'd consider my 560 hp overpowered?
BandB is online now   Reply With Quote
Old 05-15-2015, 12:01 PM   #35
Guru
 
City: Carefree, Arizona
Country: usa
Vessel Name: sunchaser V
Vessel Model: DeFever 48
Join Date: Apr 2008
Posts: 6,376
Hollywood

The drone of a diesel at say the 1500 to 1800 RPM range is designed into most of them. Most of our diesels were designed to power gensets for very long hours. Harmonics, fuel mapping, piston speeds etc were optimized for this RPM range. So with a few prop and gear ratio settings this indeed is the sweet spot for our boat diesels too. No coincidence.
sunchaser is offline   Reply With Quote
Old 05-15-2015, 12:08 PM   #36
Guru
 
Northern Spy's Avatar
 
City: Powell River, BC
Country: Canada
Vessel Name: Northern Spy
Vessel Model: Nordic Tug 26
Join Date: Feb 2012
Posts: 2,673
Quote:
Originally Posted by sunchaser View Post
Hollywood

The drone of a diesel at say the 1500 to 1800 RPM range is designed into most of them. Most of our diesels were designed to power gensets for very long hours. Harmonics, fuel mapping, piston speeds etc were optimized for this RPM range. So with a few prop and gear ratio settings this indeed is the sweet spot for our boat diesels too. No coincidence.
My peak torque is exactly at 1800. Coincidence? I don't think so. One of the variables for choosing the "overpowered" engine for my boat.
Northern Spy is offline   Reply With Quote
Old 05-15-2015, 12:17 PM   #37
Guru
 
cardude01's Avatar
 
City: Victoria TX
Country: USA
Vessel Name: Bijou
Vessel Model: 2008 Island Packet steadysailer
Join Date: Nov 2012
Posts: 3,184
Nordy 46 for sale

Question on these power required calculators:

My boat displacement is 23000 lbs as listed by the builder, and it has 5000 lbs of ballast. Do I just use the 23000 for the calculator or do I need to adjust for the ballast somehow?

http://www.psychosnail.com/boatspeedcalculator.aspx
cardude01 is offline   Reply With Quote
Old 05-15-2015, 12:24 PM   #38
Curmudgeon
 
BaltimoreLurker's Avatar
 
City: Stoney Creek, MD
Country: USA
Vessel Name: Moon Dance
Vessel Model: 1974 34' Marine Trader Sedan
Join Date: Oct 2007
Posts: 2,631
I think I'd be OK with a little extra HP if I was cruising like this!

Egret’s Circumnavigation | Yachting Magazine
BaltimoreLurker is offline   Reply With Quote
Old 05-15-2015, 01:13 PM   #39
Wannabe
 
Britannia's Avatar
 
City: SF Bay Area
Country: USA
Vessel Name: Stillwater
Vessel Model: Kadey-Krogen 54
Join Date: Dec 2014
Posts: 766
Quote:
Originally Posted by cardude01 View Post
Question on these power required calculators:

My boat displacement is 23000 lbs as listed by the builder, and it has 5000 lbs of ballast. Do I just use the 23000 for the calculator or do I need to adjust for the ballast somehow?

Boat Speed Calculator
It should be total displacement including ballast. If 23000 lbs includes the ballast (it probably does) then go with 23000, if not then add the 5000.

Richard
Britannia is offline   Reply With Quote
Old 05-15-2015, 01:27 PM   #40
Wannabe
 
Britannia's Avatar
 
City: SF Bay Area
Country: USA
Vessel Name: Stillwater
Vessel Model: Kadey-Krogen 54
Join Date: Dec 2014
Posts: 766
Quote:
Originally Posted by Northern Spy View Post
My peak torque is exactly at 1800. Coincidence? I don't think so. One of the variables for choosing the "overpowered" engine for my boat.
Yes indeed. Mine rises steeply to 1400 RPM, then almost flat (slight increase) to 1800 RPM and then a steady decline above that. At 1800 RPM my boat is doing a knot below hull speed.

Richard
__________________

Britannia is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off





All times are GMT -5. The time now is 12:23 AM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012