Reply
 
Thread Tools Display Modes
 
Old 03-31-2012, 08:00 PM   #41
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
Makes me wonder what the effective horsepower is generated from sails on the typical 35-to-40-foot sailboat produce with winds of 15 knots or so.
__________________
Advertisement

__________________
Kar-KEEN-ez Koot
markpierce is offline   Reply With Quote
Old 03-31-2012, 08:44 PM   #42
Guru
 
Tony B's Avatar
 
City: Joe Wheeler State Park, Al
Country: Cruising/Live-Aboard USA
Vessel Name: Serenity
Vessel Model: Mainship 36 Dual Cabin -1986
Join Date: Jul 2011
Posts: 1,250
Quote:
Originally Posted by Anthonyd View Post
Actually, those lines at the stern are made to reduce the amount of energy from making waves, thereby reducing the amount of energy needed to propel the boat through the water.
I don't really know what lines you are referring to.

The stern coming to a point at the waterline reduces drag from eddy currents produced by a flat stern. Very similar to how a hatch back car produces eddy currents on the rear window most noticably by the dirt and soot it collects from a vacuum like force much more so than a sleek, sloped and tapered window.
A full displacement hull is designed to slip through the water with the least amount of effort. The downside to this is a very limited speed. A planing hull is designed to lift itself out of the water and go like a bat out of hell with the limits of speed being the engine size. A semi-displacement hull design is somewhere between the 2.
__________________

__________________
Cruising the Eastern U.S. Inland Waterways and Gulf Coast. Presently on the ICW in Louisiana and heading Back to Texas.
Tony B is offline   Reply With Quote
Old 03-31-2012, 09:14 PM   #43
Guru
 
Tony B's Avatar
 
City: Joe Wheeler State Park, Al
Country: Cruising/Live-Aboard USA
Vessel Name: Serenity
Vessel Model: Mainship 36 Dual Cabin -1986
Join Date: Jul 2011
Posts: 1,250
Quote:
Originally Posted by markpierce View Post
Makes me wonder what the effective horsepower is generated from sails on the typical 35-to-40-foot sailboat produce with winds of 15 knots or so.
Good question Mark. I have a 37HP Westerbeke in my boat. It is 39' and weighs over 10 tons empty. At about 16 to 1800 RPM I will go about 6 kts and at that sustained speed I will burn about 1 gal/per hour. At 5.5 kts I will burn about .75/GPH. I can easily do these speeds at 10-12 kts of wind.
At 15 kts of wind, I can do about 7.5 kts. with 90 gals of fuel and 150 gals of water.
This is done with worn 20 year old sails.
Maybe someone here can do the math with what info I provided.
Keep in mind that I can sail faster than I motor.

I think the simplest way to come up with the answer to your question is for me to find the total sq footage of the 3 sails using the 15kts of wind as the other constant. I'm too lazy to look this all up right now. I just finished working for the day.

The interesting thing would be the answer. I would suspect that the sails generate more HP than most would expect and the sailboat reuires much less HP than most would suspect.
__________________
Cruising the Eastern U.S. Inland Waterways and Gulf Coast. Presently on the ICW in Louisiana and heading Back to Texas.
Tony B is offline   Reply With Quote
Old 04-01-2012, 04:52 AM   #44
Senior Member
 
City: Maine
Country: USA
Join Date: Feb 2011
Posts: 109
Quote:
Originally Posted by Tony B View Post
I don't really know what lines you are referring to.

The stern coming to a point at the waterline reduces drag from eddy currents produced by a flat stern. Very similar to how a hatch back car produces eddy currents on the rear window most noticably by the dirt and soot it collects from a vacuum like force much more so than a sleek, sloped and tapered window.
A full displacement hull is designed to slip through the water with the least amount of effort. The downside to this is a very limited speed. A planing hull is designed to lift itself out of the water and go like a bat out of hell with the limits of speed being the engine size. A semi-displacement hull design is somewhere between the 2.
Sorry Tony, I wasn't very specific. I was referring to the shape of the hull and the way it tapers from aft of mid-ships to the stern. I say lines as a reference to the design plan. Full displacement hulls are also designed to achieve a balance between moving through the water and stability. Semi-displacement and planing hulls are made more towarde the speed factor.
Anthonyd is offline   Reply With Quote
Old 04-01-2012, 07:26 AM   #45
FF
Guru
 
FF's Avatar
 
Join Date: Oct 2007
Posts: 16,531
It takes roughly 17K of breeze to create 1 lb of force per SQ ft of sail.

So going down wind 750 Sq ft would create about 750 lbs of push (more because of the hull and rigging) so lets sat 1000lbs.

A cheap prop and not fancy drive setup will create about 20 lbs of push for each HP delivered to the prop.
Bigger bucks and better engineering will get close to 25lbs per hp.

1000 divided by 20 is about 50 hp worth of push.

17k will easily push most sail boats to "hull speed" , and 50 hp will be 2.5 to 3 GPH with most marinized engines.

Most folks would happily give up a K and cut the fuel burn in half. Give up 2K and even better range is possible from the same tankage.

These are all rather crude rules of thumb , but are fine for noodeling.

The first edition of Passagemaker has better tables if you wish to plan a fuel burn for a voyage with a known boat.

FF
FF is offline   Reply With Quote
Old 04-01-2012, 11:26 AM   #46
Guru
 
Tony B's Avatar
 
City: Joe Wheeler State Park, Al
Country: Cruising/Live-Aboard USA
Vessel Name: Serenity
Vessel Model: Mainship 36 Dual Cabin -1986
Join Date: Jul 2011
Posts: 1,250
Quote:
Originally Posted by FF View Post
It takes roughly 17K of breeze to create 1 lb of force per SQ ft of sail.

So going down wind 750 Sq ft..................
A cheap prop and not fancy drive setup will create about 20 lbs of push
..............1000 divided by 20 is about 50 hp worth of push.

17k will easily push most sail boats to "hull speed" , and 50 hp will be 2.5 to 3 GPH with most marinized engines.................These are all rather crude rules of thumb , but are fine for noodeling............
FF
Those rules of thumb you quoted are not quite as crude as you might think.
My sailboat is 39'. Factory supplied sails are 700 Sq. FT
My boat is smaller than the one in your example and my engine is 37HP.
Most sailboats my size and just a few feet longer do fall into the 50HP range.

The only reason I dont travel near hull speed is because the engine noise is deafening. At 5.5 kts, you dont hardly hear my engine outside but it is noisy inside the boat. At 6 kts it sounds like 2 skeletons **************on a tin roof.
My theoretical Hull Speed is around under 7.5 kts Most sailboats will reach their theoretical hull speed at 12 to 15 kts of wind.
17 Kts of wind speed is usually way too much for most sail boats to travel without having to reduce (reef) their sails.
There are also other factors that come into play with sailboats but are not all that relevant to this topic.

All in all, your calculations are very close.
Thanks for the info.
__________________
Cruising the Eastern U.S. Inland Waterways and Gulf Coast. Presently on the ICW in Louisiana and heading Back to Texas.
Tony B is offline   Reply With Quote
Old 04-08-2012, 03:46 PM   #47
Member
 
Join Date: Aug 2011
Posts: 5
ah wrong

Quote:
Originally Posted by koliver View Post
The ultimate semi-planing hull is the Canadian Navy Frigate, Halifax Class. It pokes along under diesel power, to 16 knots, displacement speed. When the gas turbine engine is used, it planes at 40 knots.
Actually the canadian patrol frigate has a cross connect gearbox and the ability to run on either a single cruise diesel to a maximum of 18 knots. At this speed it is using 1.7 cubic meters of fuel an hour. When the gearbox switches over and the gas turbine is used the single engine produces 26 knots and a fuel burn of 5.55 m3. At this pt the second gas tubine can be brought online and the combined speed of the two is 31.8 knots which is the rated speed of the canadian patrol frigate. Of course this is also a 4800 ton ship. The power is there to drive it faster but it is subjected to the gearbox. As for displacement speed well it is four hundred feet so that comes into the ratio.
nskarlgreen is offline   Reply With Quote
Old 04-08-2012, 11:19 PM   #48
Guru
 
Nomad Willy's Avatar
 
City: Concrete Washington State
Country: USA
Vessel Name: Willy
Vessel Model: Willard Nomad 30'
Join Date: Oct 2007
Posts: 13,714
Don,s east bay has a bit of displacement character because of it,s deep deadrise. If you had 45 Degrees of deadrise the boat would run even more like a displacement hull but would still be a full planing boat. The quarter beam buttock line angle tells the story. If 100 percent of the transom is out of the water at rest it,s a FD hull. If giv,in enough power a planing hull will run 40knots. Semi-Planing hulls can,t qualify as either full planing or full displacement. Almost all Trawlers are semi-displacement. Most or all DeFevers are semi disp. Many trawler owners think their boats are Full disp. A full disp.boat will have almost all of her transom out of the water at rest. Just trying out my i-pad. I,ll take it on the boat and pop up now and then.
Nomad Willy is offline   Reply With Quote
Old 04-09-2012, 01:13 PM   #49
Guru
 
Phil Fill's Avatar
 
City: Everett Wa
Country: US
Vessel Name: Eagle
Vessel Model: Roughwater 58 pilot house
Join Date: Oct 2007
Posts: 2,919
The hulls speed for a 300 ft boat is 17 to to 25 knots. That is why large ferry’s ships can go so fast. They can be pushed faster with a lot more HP. It does not take that much HP to push a boat through the water at full displacement speed. We/I calculated based on the fuel burn that the Eagle, 51 ft on the water and 40+ ton uses about 75 hp at 1500 rpm, 3 to 5 gph. The DD 671 total Hp is 165. The Eagle hull is tapered toward the back so as the speed increases the bow tends to raise out of the water creating a larger bow/hull wake with very little increase speed. To bad we lost our hiastory as there where some good discussion about hp required.


I read this morning that the Washington State ferry’s are going to convert to Natural Gas as the price of diesel keeps going up and the price of Natural Gas has gone down. The tanks are going to be installed on the roof which sort of surprised me. Be interesting how they convert the diesel engines or if they replace them. Probable have to replace them.


I did talk to a local rigger about adding sails to the Eagle when I heard it had been done on a sister boat. He figured about 1,000+ square ft of sail would be needed at a cost around 30+ grand, so the discussion was very short. I don’t understand people think that over all cost of a sail boat is cheaper and when out sailing its free. I mean sails and rigging are not cheap.
Phil Fill is offline   Reply With Quote
Old 04-09-2012, 01:24 PM   #50
Senior Member
 
Larry H's Avatar
 
City: Pacific Northwest
Country: USA
Vessel Name: Jacari Maru
Vessel Model: 2014 Ranger Tug R-27
Join Date: Nov 2010
Posts: 359
Quote:
I did talk to a local rigger about adding sails to the Eagle when I heard it had been done on a sister boat. He figured about 1,000+ square ft of sail would be needed at a cost around 30+ grand, so the discussion was very short. I don’t understand people think that over all cost of a sail boat is cheaper and when out sailing its free. I mean sails and rigging are not cheap.
And, sails and rigging wire and line must be replaced as they wear out. A full time cruising sailboat probably needs new sails after 5 years.
__________________
Larry H
Cruising the Pacific Northwest
Larry H is offline   Reply With Quote
Old 04-09-2012, 04:10 PM   #51
Art
Guru
 
Art's Avatar
 
City: SF Bay Area
Country: USA
Vessel Model: Tollycraft 34' Tri Cabin
Join Date: Feb 2011
Posts: 7,981
May I recommend an older 70’ to 80’ wooden schooner that has top sail and flying jibs with tall wood masts and wood boom and of course with oodles of varnished bright work all over her superstructure... so there is plenty of relaxation due to reduced engine upkeep and savings due to truncated fuel usage... as compared to trawlers, that is. Not!

No offence meant to sail boats or their owners. Just fact about boat styles regarding efforts and $$$ spent... portrayed in sardonic tongue-in-cheek manner.

PS: With sail boat one must also remember to plan way ahead on any IWW journey to be sure and call-ahead or completely miss bridges.
Art is offline   Reply With Quote
Old 04-09-2012, 04:23 PM   #52
Guru
 
Nomad Willy's Avatar
 
City: Concrete Washington State
Country: USA
Vessel Name: Willy
Vessel Model: Willard Nomad 30'
Join Date: Oct 2007
Posts: 13,714
The Coot is Full displacement. It,s not unlike some Seaton designs. A very small amount of submersed transom but a quarter beam buttock line that is quite steep. The QBBL is an imaginary line half way between the keel and the Chine. The angle of this line reveals the hull type. There is a specific angle in degrees that is considered a norm that separates the three types of hulls. I. Don,t know the actual numbers. But it would,nt be easy for you to measure the angle on your boat anyway. The TT,s are, as far as I can recall all semi-disp. Ditto the CHB 34's, the DeFevers, the GB,s and many others. Willard,s and Krogens are Full disp except the Krogen Express. Mainships and Camano,s are planing hulls. There are some that are hard to classify like the GB. I,d say they are semi- disp because of how they perform but a case for planing hull could be made by their fairly straight QBBL and very submerged transom. Show me your stern when hauled out and I,ll give my opinion on your hull. I think I have a good understanding of this but of course it will just be an opinion. That,s what forums are for ....right. Opinions. Or I better get the fluck outa here.
Nomad Willy is offline   Reply With Quote
Old 04-09-2012, 06:08 PM   #53
Scraping Paint
 
City: -
Country: -
Join Date: Oct 2007
Posts: 13,748
Quote:
Originally Posted by manyboats View Post
There are some that are hard to classify like the GB. I,d say they are semi- disp because of how they perform but a case for planing hull could be made by their fairly straight QBBL and very submerged transom.
The GB hull is semi-planing. Add enough power and you can get the thing to mush along on something of a plane a good five to seven knots above hull speed. But with the weight and the big keel I don't think the boat is large enough to hold an engine or engines powerful enough to fully plane the boat.

American Marine initially chose the semi-planing hull even back when they didn't put enough power in them to take advantage of the speed possibilities because of the stable nature of the ride. Or so they said in all their literature and brochures at the time. No mention was ever made in the 60s and 70s of being able to cruise the boat fast. With one or two FL120s in them, "fast" was not really an option. But AM made much of the hull's stabiity and efficiency. As I've mentioned before, AM never used the term "trawler" in describing and marketing their Grand Banks line of boats. To them, a trawler pulled a trawl net. The Grand Banks slogan was "Dependable Diesel Cruisers" and their literature spoke only of comfort, stability, and efficiency.

Even with one or two FL120s in them, the GBs of the 60s and 70s normally cruised at a wee bit above hull speed. Some of the photos of Spray, the 1963 prototype for the first GB model, the GB36, show her moving along at a pretty impressive clip. But speed was never anything the company marketed until the early 80s based on all the GB literature I've read over the years.

As customers began wanting more speed out of their GBs starting in the 1980s, AM and then Grand Banks, LLC began installing larger and larger engines to take advantage of the GB hull's ability to semi-plane. So you ended up with GB42s with a couple of 400+ hp engines in them. They can do 15 knots or so, but burn about 25 gph to do it.

We just had our boat hauled this morning for a long-overdue bottom paint job (every time we scheduled one Boeing sent me off to some other part of the world). Looking at the boat out of the water, that hard-chined, flat afterbody that Eric speaks of as being an essential component of a planing hull is very evident. But that massively deep forefoot and large, full-length keel makes it pretty obvious that the only way our hull is every going to achieve anything resembling a full plane is for us to bolt a GE-115 turbofan (115,000 pounds of thrust) to the top of it
Marin is offline   Reply With Quote
Old 04-09-2012, 06:49 PM   #54
Guru
 
Gulf Comanche's Avatar
 
City: Baton Rouge, Louisiana
Country: U.S.A.
Vessel Name: Old School
Vessel Model: 38' Trawler custom built by Hike Metal Products
Join Date: Dec 2007
Posts: 799
Full displacement, I assume.
Attached Thumbnails
Click image for larger version

Name:	DSCN4786b.jpg
Views:	82
Size:	151.9 KB
ID:	10853   Click image for larger version

Name:	DSCN4787.jpg
Views:	88
Size:	151.4 KB
ID:	10854   Click image for larger version

Name:	DSCN4788.jpg
Views:	86
Size:	185.2 KB
ID:	10855  
Gulf Comanche is offline   Reply With Quote
Old 04-09-2012, 06:58 PM   #55
Art
Guru
 
Art's Avatar
 
City: SF Bay Area
Country: USA
Vessel Model: Tollycraft 34' Tri Cabin
Join Date: Feb 2011
Posts: 7,981
GC - That's a darn pretty hull. Great entry edge! With correct engine bet she just sips fuel at hull speed or just below. Looks like displacement to me... even with a just touch of flatter bottom in water at rear.
Art is offline   Reply With Quote
Old 04-09-2012, 07:02 PM   #56
Guru
 
Gulf Comanche's Avatar
 
City: Baton Rouge, Louisiana
Country: U.S.A.
Vessel Name: Old School
Vessel Model: 38' Trawler custom built by Hike Metal Products
Join Date: Dec 2007
Posts: 799
Thanks Art, uses about 1 gallon/hour at 1600 rpm. But, that round bottom is damn uncomfortable in 2-3 foot beam waves. Hence, going back to the paravanes.
Gulf Comanche is offline   Reply With Quote
Old 04-09-2012, 09:08 PM   #57
KJ
El Capitan
 
KJ's Avatar
 
City: N Myrtle Beach, SC
Country: USA
Vessel Name: Avalon
Vessel Model: Chung Hwa 46 LRC
Join Date: Dec 2010
Posts: 896
[QUOTE=manyboats : A very small amount of submersed transom but a quarter beam buttock line that is quite steep. The QBBL is an imaginary line half way between the keel and the Chine.

Show me your stern when hauled out and I,ll give my opinion on your hull. I think I have a good understanding of this but of course it will just be an opinion. :[/QUOTE]

So, is the power plant requirement of any given boat determined by the vessel's hull type, or weight, or if both, which is the more dominant factor?

Here's my baby's bottom:
Attached Thumbnails
Click image for larger version

Name:	TRANSOM.jpg
Views:	82
Size:	62.2 KB
ID:	10856  
KJ is offline   Reply With Quote
Old 04-09-2012, 10:01 PM   #58
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
Quote:
Originally Posted by manyboats View Post
The Coot is Full displacement. It,s not unlike some Seaton designs. A very small amount of submersed transom but a quarter beam buttock line that is quite steep. The QBBL is an imaginary line half way between the keel and the Chine. .... Show me your stern when hauled out and I,ll give my opinion on your hull.
__________________
Kar-KEEN-ez Koot
markpierce is offline   Reply With Quote
Old 04-10-2012, 01:37 AM   #59
Guru
 
Nomad Willy's Avatar
 
City: Concrete Washington State
Country: USA
Vessel Name: Willy
Vessel Model: Willard Nomad 30'
Join Date: Oct 2007
Posts: 13,714
Marin,
Sounds like you did'nt realize the GB was so flat and straight aft.
Gulf Comanche,
Full Disp to be sure .....but a fast FD hull as it looks like there is a bit of submerged transom and that lowers the QBBL angle and makes it faster. You've got a FD hull but not quite "pure". You should be able to cruise faster than a full Disp hull of the same length. No doubt it could use the stabilizers. So could my Willy.
KJ,
A planing hull w a big keel very similar to the GB but w a lower QBBL. Your boat should be faster than the GB but less efficient at slower speeds.
Mark,
Your QBBL is a bit flatter than I remembered and there is a bit more submerged transom. Too close to a FD hull to call it SD so I stand by my original assessment of a FD hull. I'll bet the designer would agree.
The 34 Mainship actually has a negative QBBL angle and is a planing hull. The bottom is referred to as a warped bottom. The bottom keeps getting flatter as it goes aft all the way to the transom. The opposite of a constant deadrise hull like a "deep vee". A problem w this type of hull is that most of the stability is realized from the very aft end of the boat. They are level riding and quite efficient as well. The helmsman needs to do a lot of work in following seas but this hull type is very level and smooth riding with a minimum of pitching. Next?
Nomad Willy is offline   Reply With Quote
Old 04-10-2012, 01:43 AM   #60
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
Quote:
Originally Posted by manyboats View Post
Mark,
Your QBBL is a bit flatter than I remembered and there is a bit more submerged transom. Too close to a FD hull to call it SD so I stand by my original assessment of a FD hull. I'll bet the designer would agree.
Thank you, Doctor Eric.
__________________

__________________
Kar-KEEN-ez Koot
markpierce 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
Type of caulking and bedding material rusbet General Maintenance 31 04-13-2016 07:15 AM
Dinghy - What type? Tony B Dinghys and Smaller Boats 77 02-27-2014 01:57 AM
Which type of circuit breaker? Shoalwaters Electrical and Electronics & Navigation 0 02-02-2012 01:29 PM
Your throwable type 4 markpierce General Discussion 22 11-12-2011 05:55 PM
Thruster Battery Type? Keith Electrical and Electronics & Navigation 6 02-24-2010 06:22 AM




All times are GMT -5. The time now is 08:11 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