Reply
 
Thread Tools Display Modes
 
Old 12-21-2009, 11:48 AM   #1
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
Low Powered Cruiser

This boat, Yellow Cedar, shows us how much power we really need to go forth in this world of cruising power boats. Yellow Cedar looks like a retro-boat but it's not. She is 38' X 10' x (about 3') w 15000 disp, 28hp and max speed 9 knots.
See her at:
<http://www.tadroberts.ca>
At the top of the page click on "new design"
On the right side of the page click on "Yellow Cedar"
Surf the rest of the site and try not to miss "Passagemaker Light"

-- Edited by nomadwilly on Monday 21st of December 2009 12:49:27 PM
__________________
Advertisement

Nomad Willy is offline   Reply With Quote
Old 12-21-2009, 12:53 PM   #2
FF
Guru
 
FF's Avatar
 
Join Date: Oct 2007
Posts: 16,537
Low Powered Cruiser

He has a great sense of style ,

and notice a proper sized engine , instead of 100hp too much!

There are still intelligent NA out there ,

AT 10 ft beam she would require a* permit , but would be easy enough to trailer.

Alaska inside passage in summer , Fl Keys or Bahamas , with a few driving days in
between?

Would work for me , tho I would probably prefer a Yanmar to a Perkins.

FF

-- Edited by FF on Monday 21st of December 2009 01:56:06 PM
__________________

FF is offline   Reply With Quote
Old 10-08-2010, 01:55 PM   #3
Master and Commander
 
markpierce's Avatar
 
City: Vallejo CA
Country: USA
Vessel Name: Carquinez Coot
Vessel Model: 2011 Seahorse Marine Coot hull #6
Join Date: Sep 2010
Posts: 10,265
Low Powered Cruiser

Eric, you seem to favor smaller engines*using a higher proportion of their horsepower*rather than*more powerful*engines using a lower proportion.** But would there be enough*power with the "minimalist" engines under extended*high head-wind and heavy-seas conditions?* Is it true one can kill their engine "with gentleness"?

I must be permanently scarred, mentally.* On subjects such as this, the 36-year-old vision/memory of the great white shark chasing Quint's (Robert Shaw's) boat with overloaded/smoking engine comes to mind.* Trivia quetion: what was the name of Quint's boat?


-- Edited by markpierce on Friday 8th of October 2010 05:28:37 PM
markpierce is offline   Reply With Quote
Old 10-08-2010, 04:36 PM   #4
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
RE: Low Powered Cruiser

Quote:
markpierce wrote:.* trivia quetion: What was the name of quint's boat?
orca

*
Codger2 is online now   Reply With Quote
Old 10-08-2010, 11:48 PM   #5
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
RE: Low Powered Cruiser

Mark,Yes. I think a diesel engine in a boat should be run at 65 to 75% load. During break in it should be run frequently at 85% for very short periods becoming longer as break in continues. A diesel engine should be warmed up slowly from chugging to 85% load in about 15 min. time or a bit more. Shut down should take less time (10 min ?).
Percentage of load is determined by fuel burn. Find out from the engine manufacturer how much fuel the engine will burn at WOT at the rpm where the engine develops it's maximum power. Insure that your boat will run at WOT at the rpm that it develops it's maximum (intermittent) power. It will be about 100 rpm shy until broken in. If it burns a maximum of 6 gph at WOT and you cruise at 2000 rpm and at that rpm you burn 4 gph you are loaded at 66% power. If you burn 3 gph it's 50% loaded ect. No one can accurately compute their fuel burn. If one takes into consideration idling through no wake zones, going slow frequently or from time to time and idling at dockside one can come close. Almost everybody burns a lot more than indicated by observing how much fuel one put's in the tank and what the hour meter says. Most engines burn about a gallon for every 20 hp for an hour. In other words if your engine burns 2.5 gph you are developing/using close to 50 hp. Is that more than you wanted to know? Needing extra power in windy conditions just dosn't happen. When it blows 40 or 50 knots and there's 5 to 7' seas I ALWAYS reduce power. My cruising rpm is 2300 and in the above conditions I always reduce engine speed to 2000. Several times I have cruised for 2 or 3 hours like this always making reasonable progress. All the above is opinion but I , of course, believe it all to be true and generally the best practice.
Nomad Willy is offline   Reply With Quote
Old 10-09-2010, 01:10 AM   #6
Master and Commander
 
markpierce's Avatar
 
City: Vallejo CA
Country: USA
Vessel Name: Carquinez Coot
Vessel Model: 2011 Seahorse Marine Coot hull #6
Join Date: Sep 2010
Posts: 10,265
Low Powered Cruiser

Thanks, Eric.* Over the slight objection of my builder some weeks ago, I*requested the installation of a fuel-rate-of-consumption meter.* He said there were other ways to accomplish this, but I want to know what's happening while I'm working the throttle.* I*like *immediate feedback.*... also,*I didn't go along with the builder's recommendation for a turbo-charged version of the*engine.* (After all, I won't be boating at 20,000 feet.)


-- Edited by markpierce on Saturday 9th of October 2010 01:28:59 AM
markpierce is offline   Reply With Quote
Old 10-09-2010, 04:59 AM   #7
FF
Guru
 
FF's Avatar
 
Join Date: Oct 2007
Posts: 16,537
RE: Low Powered Cruiser

A flow scan has many uses , not just in checking the prop is proper , or setting cruise speeds.

The totalizer works well enough (after its set) that sticking the tank or having crap in the tank for a "fuel check" is not needed.

Best was a day in Block island , a pro fish killer boat went to fuel at Chapmans dock.

After the fill up , he read the pump meter , and asked for the owner.


He Knew what he could take on , and the meter showed more than the tank could hold.

FREE FUEL (so he kept his mouth shut) and Chapmans could screw the visitors for the entire holiday weekend.

Running the loop we did the necessary tweaking (one has to go further and further before resetting) during the trip.

It became possible to get within 1 or 2 gallon on the estimate what the 100G tank would take.

The Flow Scan ain't cheap, but its more fun (and use) than most electric toys.
FF is offline   Reply With Quote
Old 10-09-2010, 09:52 AM   #8
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
RE: Low Powered Cruiser

Mark,If you're like me you will become less and less concerned about how much fuel you burn.
But those who burn 5 to 10 gallons an hour may differ in this priority.
Nomad Willy is offline   Reply With Quote
Old 10-09-2010, 01:24 PM   #9
FF
Guru
 
FF's Avatar
 
Join Date: Oct 2007
Posts: 16,537
RE: Low Powered Cruiser

"But would there be enough power with the "minimalist" engines under extended high head-wind and heavy-seas conditions?'

Ordinarily there is enough reserve power for the 40K headwinds and confused seas.

The properly powered boat WILL probably be slowed down, but sea state usually calls for a speed reduction.

Even with those $6000 Stidd seats , the coastie kids have problems with operating very long at 3+ G loadings.

For retired folks with cheap seats, bashing from wave face to wave face is a good way to overstress the boat and the crew.

MY setup in an engine rated (commercial 24/7) of 100 hp would be to shoot for 60 hp for propulsion at LRC , 80 hp for ICW or other places fuel is cheap and easy.

The sometimes extra 5% - 10% for house power , refrigeration , hydraulic needs would be OK with either cruise setup.

100% power could be carried till the fuel or crew is exhausted in heavy weather.

A CPP makes this setup really easy , and now that the prices are lower , I would certainly have it aboard.
FF is offline   Reply With Quote
Old 10-09-2010, 01:48 PM   #10
Master and Commander
 
markpierce's Avatar
 
City: Vallejo CA
Country: USA
Vessel Name: Carquinez Coot
Vessel Model: 2011 Seahorse Marine Coot hull #6
Join Date: Sep 2010
Posts: 10,265
RE: Low Powered Cruiser

Please enlighten the ignorant:


LRC = ??long-range cruise??

ICW = ??intercoastal waterway??

CPP = ????


Also,**is the ideal match of engine and displacement boat one with 80% power*to achieve hull speed (about 1.34 times the square root of waterline)?

Thanks!
markpierce is offline   Reply With Quote
Old 10-09-2010, 03:25 PM   #11
Guru
 
City: Carefree, Arizona
Country: usa
Vessel Name: sunchaser V
Vessel Model: DeFever 48
Join Date: Apr 2008
Posts: 6,380
RE: Low Powered Cruiser

There is no material downside to having a comfortable*power cushion*in a new install. I would size*the engine for about 50 to 60% load at hull speed in smooth water which should give you plenty of cushion for the rough water, maybe adding a cruise gen, pto for ??*etc.

My biggest fuel burn is in rough water with a following sea - about 20% to 30%more than flat water hull speed. I suggest you post this question on boatdiesel.com and use their prop calculator data. Sizing your prop to match your engine and hull is important.
sunchaser is online now   Reply With Quote
Old 10-09-2010, 03:42 PM   #12
Scraping Paint
 
City: -
Country: -
Join Date: Oct 2007
Posts: 13,748
Low Powered Cruiser

I understand the desire for as low a fuel burn as practical, but this is a matter of philosophy. Fuel cost aside I feel about boats the same as I feel about floatplanes---- there's no such thing as too much power if your boat's hull configuration can take advantage of it. Obviously you can put a ridiculously powerful engine in a boat, and considerations like being able to run the engine at it's proper operating temperature have to be kept in mind.

But in twelve years of boating in the GB and the almost ten years of boating in our outboard-powered Arima before that I have NEVER heard anyone complain about having too much power in a boat. But I have heard lots of complaints from people about not having enough power, from the owners of trailer fishboats at one end of the spectrum to the owner of a Grand Banks 52 who ordered it with smaller-than-standard engines in 1998 in the interest of fuel economy and has been bemoaning his decision ever since (along with everyone who charters this particular boat).

If you have a relatively powerful engine in a boat, you don't have to use all that power (keeping in mind operating temperatures and so forth). But if you have a small engine in a boat, you can never develop any more power than that no matter how much an unanticipated situation might call for it.

Carey of this forum has a 420 hp Cat in his custom lobsterboat. For the past couple of years he's been cruising the boat at a bit over 8 knots to keep his fuel costs down, which this does quite effectively. He ensures that the temperatures are correct and he runs the engine at higher loads periodically. But should he need to--- and he has a few times that I know of--- he can run his boat at its normal cruise speed of 14-15 knots. That's a versatility I can appreciate. To be stuck-- as we are with our boat-- with an 8 or 9 knot limit is not a good situation to have in a boat to my way of thinking. We thought when we bought our GB that an 8-knot cruise would be just fine. We have since discovered--- like the owner of that way newer GB52--- that it's not.



-- Edited by Marin on Saturday 9th of October 2010 03:46:54 PM
Marin is offline   Reply With Quote
Old 10-09-2010, 06:21 PM   #13
Scraping Paint
 
City: Fort Lauderdale
Vessel Model: CHB 48 Zodiac YL 4.2
Join Date: Oct 2007
Posts: 3,804
RE: Low Powered Cruiser

Quote:
Marin wrote:
---- there's no such thing as too much power if your boat's hull configuration can take advantage of it.

Hear hear ... that just about nailed it.
RickB is offline   Reply With Quote
Old 10-09-2010, 06:22 PM   #14
Guru
 
Keith's Avatar
 
Vessel Name: Anastasia III
Vessel Model: Krogen 42
Join Date: Oct 2007
Posts: 2,716
RE: Low Powered Cruiser

Yes on the first two; CPP= Controllable pitch propeller.
Keith is offline   Reply With Quote
Old 10-09-2010, 11:05 PM   #15
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
RE: Low Powered Cruiser

Mark,Well as you can see there are many other Thoughts on how much power a trawler should have but all of them come from skippers that are familiar or intimate with semi-displacement craft. There is a very successful trawler/passagemaker that is also well known and documented. Nordhavn 46. She has 101 hp and 48000lbs disp. A top speed of 9 knots and a cruising speed of 7.4 knots (SL1.2). Maximum continuous speed of 8.7 knots w her Lugger Diesel. The Nordhavn 46 has 4.2 hp per ton. Clearly for any normal FD craft 5 hp per ton is enough power to deal with seas and wind as the Nordhavn 46 has proven the world over. The FD hull is the only hull shape that has a fixed power requirement. All other hulls can benefit from more power and to varying degrees but the hulls closest to FD can be benefit from only modest increases in power. Most trawlers need considerably more power to go at hull speed and even more to go faster yet. So at least for a FD hull 5 hp per ton is plenty of power.
Nomad Willy is offline   Reply With Quote
Old 10-10-2010, 01:01 AM   #16
Master and Commander
 
markpierce's Avatar
 
City: Vallejo CA
Country: USA
Vessel Name: Carquinez Coot
Vessel Model: 2011 Seahorse Marine Coot hull #6
Join Date: Sep 2010
Posts: 10,265
RE: Low Powered Cruiser

Quote:
nomadwilly wrote:

Mark,
Well as you can see there are many other Thoughts on how much power a trawler should have ...
Eric, I take your comments to heart,*but am comfortable with a 6 hp/ton engine.* The only boats I've*captained have been auxiliary (inboard and outboard) sailboats, so I'm quite comfortable with cruising 6 to 7 knots.* So much so I'll have*small fore-and-aft*sails for steadying and for a two-knot-crawl-to-safety if the engine ever crashes.* Perhaps the extra windage of mast justifies the extra engine power.

*
markpierce is offline   Reply With Quote
Old 10-10-2010, 06:11 AM   #17
FF
Guru
 
FF's Avatar
 
Join Date: Oct 2007
Posts: 16,537
RE: Low Powered Cruiser

" there's no such thing as too much power if your boat's hull configuration can take advantage of it."

Would agree in an aircraft , but sadly not for a cruiser.

If you don't mind paying for the lack of efficiency , which can be 200% to 300% higher fuel burn per hp,

and the sometimes quire shortened engine life from underloading.

Running a turboed 400hp monster at 50 hp gets very very expensive indeed.

The Oxymoronic "fast trawler" , is only for the thickest of wallets.

How Low can you GO , really depends on the marinization choice.

THe best at low power are the light truck and tractor engines, Lemans , 5.9Cummins and 3208 CATS.

Do it to a DD series 60 , or bigger industrial stock only at great peril.
FF is offline   Reply With Quote
Old 10-10-2010, 07:07 AM   #18
Scraping Paint
 
City: Fort Lauderdale
Vessel Model: CHB 48 Zodiac YL 4.2
Join Date: Oct 2007
Posts: 3,804
Low Powered Cruiser

Quote:
FF wrote:If you don't mind paying for the lack of efficiency , which can be 200% to 300% higher fuel burn per hp,
I would love to see the spec sheets on that engine.

Your "efficiency" claims seem to be based on the very small increase in BSFC at lower power but you carefully neglect to provide the information that despite the the minute loss of fuel efficiency, the fuel burn is greatly reduced.

Recreational vessels are not operated for the purpose of reducing the nation's fuel consumption. The way most of us manipulate the throttle probably burns more fuel during a voyage than the microscopic loss of fuel efficiency created by operating at lower power.

Selecting the most extreme position makes for scary reading I guess but you'll have to back up your opinion with some documentation to show things like increased maintenance costs and 2 or 3 times the fuel burn per HP at reduced power. According to that fantasy, a marine diesel engine driving a fixed pitch propeller might burn the same quantity of fuel just above idle as it does at full power.

EDIT:

Just for grins I ran the numbers on one of those monster 400 hp engines, and a Detroit just to make it a real worst case.

According to the Detroit Diesel specifications for a 6V92TA driving a well matched fixed pitch propeller, the brake specific fuel consumption (BSFC) at 425 hp is .387 pounds per horsepower hour, a pretty good figure that equates to about 23.5 US gallons per hour.

If we slow that engine down to the lowest continuous output that DD plots, and by inference, an approved operating condition, the BSFC increases to .49 lb per horsepower hour which equates to 3.5 US gallons per hour.

The increase in fuel consumption per horsepower due to lower fuel efficiency at the lower output is .014 gallons per horsepower over what it would burn if it had the same BSFC as it did at full power.

That is also equal to about .7 gallons per hour for the entire 50 hp over what the engine would burn if it had the same fuel efficiency at 50hp as it does at 425.

*


-- Edited by RickB on Sunday 10th of October 2010 09:14:29 AM
RickB is offline   Reply With Quote
Old 10-10-2010, 10:01 AM   #19
Guru
 
City: Carefree, Arizona
Country: usa
Vessel Name: sunchaser V
Vessel Model: DeFever 48
Join Date: Apr 2008
Posts: 6,380
Low Powered Cruiser

In perusing the boatdiesel site the other day I noted a*vessel doing the loop loves to cruise his*(newer) Cummins at 925 RPM for 6 knots while burning only 1.2 gph. He does open it up to 2400 RPM for short bursts. This is about 7% power draw based upon fuel consumption. Yes - ridiculous but true.

I* normally run my Perkins Sabres at about 1650 - 1750 RPM or a 20 - 25% fuel burn with no adverse issues. If I 3X the fuel burn to 2200 RPM, I gain only 50% in speed.

As noted by Marin, it is quite easy to slow down an overpowered vessel, it is called a throttle. You CANNOT speed up an underpowered vessel that is normally operating at 80% or "on the pins." Plus for very similar external engine size and not much* more cost, you can often purchase/upgrade 50 to 70% or more power to an engine for reserve.

For a new tierII/III engine I'd go Cummins or JD and quickly skip over* Yanmar and Volvo. A read of the boatdiesel archives would be informative in this regard. Would the 4 cylinder Cummins fit your space?

-- Edited by sunchaser on Sunday 10th of October 2010 10:16:07 AM
sunchaser is online now   Reply With Quote
Old 10-10-2010, 10:18 AM   #20
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
Low Powered Cruiser

Tom,The hull won't allow you to speed up anyway so what's the point? You can't use anymore than 5 hp per ton so anything in excess of that is not only a waste but always produces an underloaded engine.


You were posting while I was. FD hulls DO NOT NEED RESERVE POWER. Most people think they need reserve power to buck head winds but in practice one needs to back off instead.*If you have a huge engine in a FD hull and want to go faster you can get 10 - 15% more speed but it hardly alters you're situation at all. The real reason you NEED more power is FEAR. You are afraid you will be lacking some day for some reason but it's not true. I have never ever needed more power and I'm right at 5 hp per ton. Fear that you're engine is prematurely wearing out. Diesel engines run at 80% loads for at least 10,000 hrs and 99% of us will never see more than a small fraction of that. Another reason people want more power is so that they can run at low engine speeds. Less noise to be sure but mostly guys just want to be more like a Harley Davidson and loaf along rather than sing along at 2 or 3 times the rpm like other motorcycles. With a smaller engine at higher revs it sounds like you're struggling to keep up and while lugging it looks and sounds like it's easy * *....like you're loafing along. So It's partly a hair on the chest thing.
But as the 46 Nordhavn shows us * * *..there is no rational need.


And as Rick points out running an engine at low revs is less efficient.


-- Edited by nomadwilly on Sunday 10th of October 2010 10:52:08 AM
__________________

Nomad Willy 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


Similar Threads
Thread Thread Starter Forum Replies Last Post
Steam powered trawler - side wheeler bshanafelt General Discussion 0 04-19-2011 10:25 AM
Battery Powered Air Conditioning Keith General Discussion 3 06-21-2009 04:37 AM
Low Sulfur Diesel, Ultra Low Sulfur Diesel, and Bio Diesel Phil Fill General Discussion 5 11-14-2007 08:07 PM




All times are GMT -5. The time now is 09:57 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