Reply
 
Thread Tools Display Modes
 
Old 04-10-2012, 11:56 PM   #81
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
With a large-keel-for-a-powerboat vessel like that, she deserves a couple of sails. Otherwise, what's the purpose of the huge keel?
__________________
Advertisement

__________________
Kar-KEEN-ez Koot
markpierce is offline   Reply With Quote
Old 04-10-2012, 11:59 PM   #82
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
I really like it but I've decided to keep my Willard.
Great! We/I love your Willard.
__________________

__________________
Kar-KEEN-ez Koot
markpierce is offline   Reply With Quote
Old 04-11-2012, 12:49 AM   #83
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
We hav'nt needed sails for a long time. Keels are for boats. Keels give lots of directional stability and roll stability as well ...not to mention propeller and rudder protection. I would'nt want sails on Willy.....could'nt even get into covered moorage. You have a wonderful boat Mark but sails are an also ran in my book.
Nomad Willy is online now   Reply With Quote
Old 04-11-2012, 02:00 AM   #84
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
OK, Eric. Meanwhile I can enjoy less "rock and roll" and add a half or knot or so whenever I get the gumption to hoist my sails (with only a fraction of that boat's keel).

__________________
Kar-KEEN-ez Koot
markpierce is offline   Reply With Quote
Old 04-11-2012, 08:20 AM   #85
Guru
 
Portuguese's Avatar
 
City: Salvador - BA
Country: Brazil
Vessel Name: Rainha Jannota
Vessel Model: Curruira 46
Join Date: Jun 2011
Posts: 662
Send a message via MSN to Portuguese
Rainha Jannota will be a full displacement with a D/L 347. The D/L (displacement / length) is the ratio that defines displacement, semi displacement or planning hulls. – hulls, not trawlers! The reason to state “hulls not trawlers”, is because G. Buehler boats, the dieselducks, are not full displacement by definition, but are definitely trawlers.
The D/L is the result of the following formula:
(Displacement in pounds/2240)/(LWL/100)3
The “experts consider that any hull with D/L above 260 is a displacement hul. Below 220 is a planning hull. What is left in the middle is a semi-displacement. A good design with nearly perfect hydrodinamics will evntualy kills this theory.

Regards

Fernando
Portuguese is offline   Reply With Quote
Old 04-11-2012, 08:45 AM   #86
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 Portuguese View Post
......The “experts consider that any hull with D/L above 260 is a displacement hul. Below 220 is a planning hull. Fernando
I have to disagree with this. A "displacement hull" is a function of shape. I'm sure I can come up with a box or a barge shape and have a D/L above 260.
The D/L has nothing to do with shape. If I take a Rectangular shape and put a motor on the narrow end, then the length of the water line is measured using the long side of the rectangle.
If on the other hand, I take the same shape and put the motor on the wide end (understandably not the normally desired configuration) then the length of the water line would be the short side of the rectangle.
The displacement had not changed since the boxes are identical. The D/L ratio will have changed dramatically which upsets the whole premise. And we are still stuck with a box or barge shape which is not a displacement hull shape.

I would think that the D/L ratio would be something used for speed calculations when comparing boats of the same designed water line length. For example, I am looking at 4 semi-displacement hull motoryachts of the same waterline lengths with the same HP. The one with the higher D/L would be the slowest. Not only is the higher numbered one heavier, requiring more HP to move it, but it will also have the greater wetted surface creating more friction in the water and having more water to push.

So, to me, the only useful purpose of the D/L ration would be to compare similar sized and shaped boats to determine which class I could put them into for comparison purposes, such as light cruiser, medium cruiser or heaver cruiser.
__________________
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 04-11-2012, 12:35 PM   #87
Scraping Paint
 
City: -
Country: -
Join Date: Oct 2007
Posts: 13,748
Quote:
Originally Posted by markpierce View Post
OK, Eric. Meanwhile I can enjoy less "rock and roll" and add a half or knot or so whenever I get the gumption to hoist my sails
If one is willing to do the work I think a sail assist on something like Mark's boat is a good idea. Fuel saved is fuel saved. If the stuff was $1.63 a gallon that would be one thing but at $4-$5 a gallon, knocking a bit off the bill--- or being able to use the same amount to go a bit further--- seems a good idea to me. If our boat could accommodate a sail rig and the boat's configuration was such that it could get some benefit from it we might be inclined to use it, particularly on longer runs when the wind was favorable.
Marin is offline   Reply With Quote
Old 04-11-2012, 01:02 PM   #88
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
Marin:

"If one is willing to do the work I think a sail assist....." In the open, as long as you are not changing course, there isn't much work. Wind direction usually dont change unless a front is coming through. The sails on a motor-sailor are relatively small and easy to handle. There are times when just being able to not rock are worth the trouble. In a river, especially with turns like most rivers have, it would be a lot of trouble to deal with and not worth it.
__________________
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 04-11-2012, 01:11 PM   #89
Guru
 
Anode's Avatar


 
City: Missourah
Country: USA
Vessel Name: M/V Scout
Vessel Model: Sundowner Tug 30'
Join Date: Jul 2010
Posts: 645
I'll stick with my little Kubota...
having that piggy screaming 'weeeeeeeeeee..waaweeeeee' in my ear is just not worth the fuel savings.
Anode is offline   Reply With Quote
Old 04-11-2012, 01:53 PM   #90
Art
Guru
 
Art's Avatar
 
City: SF Bay Area
Country: USA
Vessel Model: Tollycraft 34' Tri Cabin
Join Date: Feb 2011
Posts: 7,981
Having cruised on working boats and pleasure boats in open waters (various models, designs, sizes, and power-ratios) I found to restrict every boat’s hull design as belonging strictly to any level of a three tier category (FD, SD, or P) is simply not applicable in all instances (however it is in some). Having experienced boats categorized FD well exceed their “hull” speed without much extra power as well as boats considered SD to have broken into full plane without exorbitant power I copied the following from Wikipedia. I feel this best explains the notable per-hull-shape variables as well as the speed/efficiency potentials for hull-shapes. The hull category I have noticed that most often holds true to its definition/capabilities is P... and, in that category there are hull-bottom design details that can increase their high-speed-planing efficiency, such as “stepped” and other hull designs to further reduce wetted surface or to produce “skipping”. From what I’ve noticed each hull-design category holds a broad range of added potentials that can be developed upon by incremental design improvements. Being a person who designs and co-engineers mass airflow apparatus I appreciate the capabilities of what minor apparatus design adjustments can afford in the movement of fluids past stationary material items as well as the movement of material items through, over, or into fluids or gasses. Some material items we use in CFD tests are rigid configuration while some are flexible and/or expandable with capability to alter their shape in accordance with needs apparent to coincide with the properties of fluids or gases encountered. For water and air, many appreciable similarities exist between fluid-drag, fluid-release, fluid-bounce, fluid skipping, and fluid-deflection. High end CFD programs at times reveal unexpected fluid dynamic efficiency relationships between the design of material items and fluids or gasses. In my opinion, correlation between power ratios, water, and boat-hull-designs in fluid mechanics offer grand opportunity for fluid design research; as is consistently ongoing in the marine industry. Loving boating as I do maybe in future I will direct my efforts toward hull designs... just no time to indulge right now!

WIKIPEDIA:

Hull speed, sometimes referred to as displacement speed, is the speed of a boat at which the bow and stern waves interfere constructively, creating relatively large waves, and thus a relatively large value of wave drag. Though the term "hull speed" seems to suggest that it is some sort of "speed limit" for a boat, in fact drag for a displacement hull increases smoothly and at an increasing rate with speed as hull speed is approached and exceeded, with no noticeable inflection at hull speed. Heavy boats with hulls designed for planing generally cannot exceed hull speed without planing. Light, narrow boats with hulls not designed for planing can easily exceed hull speed without planing; indeed, the unfavorable amplification of wave height due to constructive interference diminishes as speed increases above hull speed. For example, world-class racing kayaks can exceed hull speed by more than 100%, even though they do not plane. Semi-displacement hulls are intermediate between these two extremes.

Hull speed is often called the "speed-length ratio", even though it's a ratio of speed to the square root of length. The concept of hull speed is not used in modern naval architecture, where considerations of speed-length ratio or Froude number are considered more helpful.

Froude number: Dimensionless number defined as the ratio of a characteristic velocity to a gravitational wave velocity. It may equivalently be defined as the ratio of a body's inertia to gravitational forces. In fluid mechanics the Froude number is used to determine the resistance of a partially submerged object moving through water, and permits the comparison of objects of different sizes. Named after William Froude, the Froude number is based on the speed/length ratio as defined by him.
Art is offline   Reply With Quote
Old 04-11-2012, 02:36 PM   #91
Guru
 
skipperdude's Avatar
 
City: Whittier AK
Country: USA
Vessel Name: Apache II
Vessel Model: 1974 Donald Jones
Join Date: Oct 2007
Posts: 3,147
Quote:
Originally Posted by Tony B View Post
Thanks, that is what I thought they were. Just wanted to make sure.
I have also seen them in disk shapes where the disks are stackes with spaces inbetween.

Tony B
Those are called flopper stoppers. They are used mostly at anchor to quiet roll from passing wakes and waves.
They would also be usefull while drifting to fish.
I have a set of paravanes that I deploy when waves are 3' or better.

SD
__________________
If you can't repair it maybe it shouldn't be on the boat
skipperdude is offline   Reply With Quote
Old 04-11-2012, 02:44 PM   #92
OFB
Guru
 
OFB's Avatar
 
City: Richmond bc
Country: Canada
Vessel Name: Invader no1
Vessel Model: Kishi Boat works
Join Date: Mar 2012
Posts: 636
Invader is a full displacement full keel soft chine vessel.

I like the soft chine. Hard chined vessels present the water with flat sufaces that creat a bang and shudder in some conditions. As a live aboard I also love the lack of chine slap.

The other side of this is the wanting of the boat to roll a bit more than a hard chined boat.

I find hard chines play a major factor in todays designs. For stability , directional stability, strength for materials used on a lighter platform, lift for faster vessels, less wetted surface with the reduction of keel and rudder size.

Chines or lack of play a large roll in any hull design.

Reading through the thread I did not see much about the subject.
OFB is offline   Reply With Quote
Old 04-11-2012, 03:32 PM   #93
Art
Guru
 
Art's Avatar
 
City: SF Bay Area
Country: USA
Vessel Model: Tollycraft 34' Tri Cabin
Join Date: Feb 2011
Posts: 7,981
Patented Boat Stabilizer:

1968 we designed and built prototypes, 1969 we began and then for years continued ocean testing, 1971 patent pending, 1973 patent issued.

Patent Quote:
“It is therefore a principal object of this invention to provide an improved boat stabilizer of very simple construction which, in response to the roll of the boat to either side, automatically adjusts its camber to provide a hydrofoil shape which, with the boat underway, generates forces to oppose and diminish the roll. A more specific object is to provide such a stabilizer which does not require any parts to extend or to be sealed through the hull of the boat and which can be used to stabilize a wide variety of types and sizes of vessels.”

This efficient, inexpensive to construct, and simple design was culmination of my dad’s WWll RCAF Spitfire piloting and his penchant as an engineer to utilize the fluid design efficiencies of airplane wings to enable self actuating “vertical wing” stabilizers for boats (he designed boat hulls too – generations in my family love the water and boats). I was his right hand man throughout this stabilizer design and testing process. This stabilizer’s details are emblazoned on my mind and I’ve designed some improvements. There is nothing I have seen that will steady a moving vessel as efficiently and completely as these “Attitude-Affecting” stabilizers.


If anyone would like to learn more... send me a PM. - Art
Art is offline   Reply With Quote
Old 04-11-2012, 04:20 PM   #94
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
I dont agree with the Wikipedia version of Hull Speed.
My comments are in Blue

WIKIPEDIA:

Hull speed, sometimes referred to as displacement speed, is the speed of a boat at which the bow and stern waves interfere constructively, creating relatively large waves, and thus a relatively large value of wave drag. As a boat moves through the water, it creates a bow wave. At real slow speeds there will be many little wavelets following it. As the speed increases, the bow wave gets bigger and longer. If you keep increasing the speed, there will be a point at which you create a wave the same exact length of the waterline of the boat. Picture a sine wave if you will. This wave form will actually start just ahead of the boat because the boat is pushing some water ahead of it as it also slices through it. This single wave form happens at what is considered 'hull speed' or 'theoretical hull speed'. If you make a sketch of this, which I am too lazy to do right now, you will notice that if you go any faster, the wavelength will get a little longer and the stern will slowly ride down into the trough and the bow will rise due to the shape of the wave form. This will cause you to push disproportionately more water to move forward, than the speed you are gaining, which translates to a much, much greater amount of HP and fuel required for a just a tad more speed. Though the term "hull speed" seems to suggest that it is some sort of "speed limit" for a boat, in fact drag for a displacement hull increases smoothly and at an increasing rate with speed as hull speed is approached and exceeded, with no noticeable inflection at hull speed. This preceding statement is total hogwash. I agree only with the part about it not being a speed limit. It is not a speed limit, but a point at which you are pumping way more HP and fuel for a little gain in speed. Mainly because the boat is now trying to climb it's own wave. Heavy boats with hulls designed for planing generally cannot exceed hull speed without planing. Wrong again. Take a typical 40' trawler with say a 36' waterline. The calculated Hull Speed would be 6 (the sq. root of 36) X 1.34 = 8 Kts for the Theoretical Hull Speed. How many of you with 40 footers get into a plane and maintain it under 8 Kts. This is for a semi-Displacement hull. With a true full displacement hull, you will never plane. Light, narrow boats with hulls not designed for planing can easily exceed hull speed without planing; indeed, the unfavorable amplification of wave height due to constructive interference diminishes as speed increases above hull speed. For example, world-class racing kayaks can exceed hull speed by more than 100%, even though they do not plane. Semi-displacement hulls are intermediate between these two extremes.

Hull speed is often called the "speed-length ratio", even though it's a ratio of speed to the square root of length. The concept of hull speed is not used in modern naval architecture, where considerations of speed-length ratio or Froude number are considered more helpful. Maybe for naval architects, but for average boaters with full displacement hulls such as sailors, the term theoretical hull speed is alive and well.

Oh well, I'm tired and busy at work so I'm sure some of my notes are flawed. Please feel free to shoot holes in it. I never take offense.
I am originally from NY and we are born obnoxious.










__________________
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 04-11-2012, 04:34 PM   #95
Art
Guru
 
Art's Avatar
 
City: SF Bay Area
Country: USA
Vessel Model: Tollycraft 34' Tri Cabin
Join Date: Feb 2011
Posts: 7,981
Quote:
Originally Posted by

Tony B;82409
I dont agree with the Wikipedia version of Hull Speed.


Oh well, I'm tired and busy at work so I'm sure some of my notes are flawed. Please feel free to shoot holes in it. I never take offense.
I am originally from NY and we are born obnoxious.









Yup - There are some flaws Tony - In everything any of us do or say! I'm not going to shoot holes in your copy, some are self evident. I'm a multi generation NYer myself, SF Bay Area currently... ain't life grand! - Art
Art is offline   Reply With Quote
Old 04-11-2012, 04:39 PM   #96
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
Anode,
What on earth kind of engine is a "piggy"?
Art,
That's what you get for going to non-marine sources for marine information. No wonder you lack a clear comprehensive understanding of hull speed and displacement craft. The majority of boaters do. I'll PM you.
OFB,
On most boats chine design makes little difference. Planing and fast semi-planing hulls are more sensitive to hard or soft chine choices but chine design relative to hard or soft is usually decided by structure and materials in construction. For example......very seldom will you see a smaller metal boat with soft chines as they are considerably harder to fabricate. And soft chine boats can have chine slap too. I'm very glad my Willard does not.
Open comment:
I just filled my 100 gallon water tanks in the stern and the bow rose 1.25".http://www.trawlerforum.com/forums/i...s/sk/blush.gif
Nomad Willy is online now   Reply With Quote
Old 04-11-2012, 04:50 PM   #97
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 Art View Post
..... I'm not going to shoot holes in your copy, some are self evident. I'm a multi generation NYer myself
....- Art
Art, I have found Wikipedia is not a source that can be trusted. There are many things on many subjects that I know to be false. I don't even want to get into family history here.

Anyway, I am a born and raised Brooklynite. I broke family tradition and apparently so did you when it comes to the evolutionary scale of transplanting. A Brooklynite is supposed to migrate to Long Island and eventually settle in Florida.
I went rogue. Went from Brooklyn to Newburgh, NY in the Hudson Valley. Then went to Arkansas, Ms, Virgin Islands, back to Ms. then La. and now in Texas soon to move to Ky. I got the gypsy in me from my mothers side of the family.

Tony B
__________________
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 04-11-2012, 04:56 PM   #98
Guru
 
psneeld's Avatar
 
City: Avalon, NJ
Country: USA
Vessel Name: Freedom
Vessel Model: Albin 40
Join Date: Oct 2011
Posts: 15,904
Quote:
Originally Posted by manyboats View Post
Anode,
What on earth kind of engine is a "piggy"?
Art,
That's what you get for going to non-marine sources for marine information. No wonder you lack a clear comprehensive understanding of hull speed and displacement craft. The majority of boaters do. I'll PM you.
OFB,
On most boats chine design makes little difference. Planing and fast semi-planing hulls are more sensitive to hard or soft chine choices but chine design relative to hard or soft is usually decided by structure and materials in construction. For example......very seldom will you see a smaller metal boat with soft chines as they are considerably harder to fabricate. And soft chine boats can have chine slap too. I'm very glad my Willard does not.
Open comment:
I just filled my 100 gallon water tanks in the stern and the bow rose 1.25".http://www.trawlerforum.com/forums/i...s/sk/blush.gif
And some boaters "think" they do...
Heck even popular naval architects/engineers/hydrodynamicists describe it differently and are always trying to "beat" the numbers because it's not nailed down as exact as far as I can tell and I've been reading about it and learning since Officer Candidate School back in 1977.

From the immediately abve posts.... I see stuff that I have seen before as correct or not correct...depends on how literal you take some sentences.
psneeld is online now   Reply With Quote
Old 04-11-2012, 05:16 PM   #99
Art
Guru
 
Art's Avatar
 
City: SF Bay Area
Country: USA
Vessel Model: Tollycraft 34' Tri Cabin
Join Date: Feb 2011
Posts: 7,981
Quote:
Originally Posted by manyboats View Post

Art,
That's what you get for going to non-marine sources for marine information. No wonder you lack a clear comprehensive understanding of hull speed and displacement craft. The majority of boaters do. I'll PM you.
Eric – You a naval architect/engineer? Just wondering because I can tell by your posts that you do know a lot about hull designs. I used Wiki example to provide simple explanation on my past experiences and hull design doings from years ago. I.e. D, SD, and P hull designs have availabilities beyond what is normally stated and there are design intricacies for each that may/can improve their performance, in one range or another. Nearly every design detail has a trade-off! I look forward to reading your PM. Also... I couldn’t get the link on your post to come up! – Cheers – Art
Art is offline   Reply With Quote
Old 04-11-2012, 07:17 PM   #100
OFB
Guru
 
OFB's Avatar
 
City: Richmond bc
Country: Canada
Vessel Name: Invader no1
Vessel Model: Kishi Boat works
Join Date: Mar 2012
Posts: 636
Quote:
Originally Posted by manyboats View Post
OFB,
On most boats chine design makes little difference. Planing and fast semi-planing hulls are more sensitive to hard or soft chine choices but chine design relative to hard or soft is usually decided by structure and materials in construction. For example......very seldom will you see a smaller metal boat with soft chines as they are considerably harder to fabricate. And soft chine boats can have chine slap too. I'm very glad my Willard does not.
Open comment:

?????????????

Eric the chine effects the handeling characteristics. So will a full keel like Invader compared to a semi keel like you have on willy the willard. Agreed the hard chine has construction advantages ( price of build )with some materials like metal. However there is a difference in handeling in a following sea betwen soft chine and a hard chine even on displacement vessels. As an example.
__________________

OFB 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 02:56 PM.


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