skipperdude
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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
Your hull type
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If you have answers, please help by responding to the unanswered posts.
If you have answers, please help by responding to the unanswered posts.
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
OFB
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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.
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.
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
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
Tony B
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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.
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.
Tony B;82409 said:
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
Nomad Willy
Guru
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/images/trawler/smilies/sk/blush.gif
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/images/trawler/smilies/sk/blush.gif
Tony B
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..... 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
psneeld
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And some boaters "think" they do...:lol:
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.
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
OFB
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?????????????
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.
Portuguese
Guru
Tony B wrote:
" 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."
.... We are in the Trawler Forum and therefore far from sailing "boxes". All scientists will have different opinions but in this particular case, common sense prevails and we must establish limits for all line of thinking, otherwise we risk to mix apples with oranges, or melons. Yet, I am certain that no matter how much science and theory we put into these floating things, we will never invent in this Forum, another type of hull but the ones already mentioned in the messages above.
As the thread is called “Your hype of hull”, here I go
Mine is a multichine full displacement hull, calculated for 9 knts maximum speed, 7 knots cruising.
Sheers
" 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."
.... We are in the Trawler Forum and therefore far from sailing "boxes". All scientists will have different opinions but in this particular case, common sense prevails and we must establish limits for all line of thinking, otherwise we risk to mix apples with oranges, or melons. Yet, I am certain that no matter how much science and theory we put into these floating things, we will never invent in this Forum, another type of hull but the ones already mentioned in the messages above.
As the thread is called “Your hype of hull”, here I go
Mine is a multichine full displacement hull, calculated for 9 knts maximum speed, 7 knots cruising.
Sheers
Daddyo
Guru
y. 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.
Our DeFever 48 is really much more of a displacement then a semi-displacement. Might be why it was referred to as a LRC and is much more of a sea boat then many.
Tony B
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I was not the one who strayed. I saw what I thought was mis-statement and made a comment.
Anyway, I'm sure glad you cleared that up.
Tony B
Anyway, I'm sure glad you cleared that up.
Tony B
markpierce
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CPseudonym
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Eric, maybe he's referring to this little piggy:
Who'd a thunk it? Pigs really do fly. At about 7 knots.
QB
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Scary
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4788
The 4788 most definitely planes with 330 b's. 22 knts light and 19 knts heavy. The 4788 planes out at about 14knts. The stern wave pulls away and the wake flattens out. At 26k wet with a very flat hull section it's only compromise is round chines and a partial keel. A full displacement boat cannot plane as the stern will squat deeper and deeper as you add power. There is not enough lift created in the stern sections to begin to skim. Semi displacement boat have flat enough sections in the stern to plane if sufficiently powered. My 48 lrc Hatteras with its 5' draft is a full displacement hull. It has fully round bilges , not chines, with a flatter aft section to keep her from squatting. Double enders have full round bilges and normally no flat sections and squat like mad at anything over hull speed. I guess the bottom line is if you can put enough power to it and it planes its a planing hull.
Nomad Willy
Guru
Art,
I've been a bad man. I was much more critical of your post on page 5 than I should have been. Much good and interesting stuff in there. A lot of the Wikipedia stuff was not good or not relative to us. It's interesting how canoes and kayaks can exceed hull speed so well but they can. I have an 18' narrow stern canoe and I've powered it w 6 and 8 hp. Makes about 14 knots. Need weight (wife) to keep the bow down to reasonable attitudes. Without the fwd ballast and w the bow sky high I can do very interesting figure eights. A friend said I was doing canoegies. No I'm not a NA. I've studied it lightly for 55 years. I spent a lot of time in the university branch library in Seattle reading Atkin and other great designers. That was in the mid 50s. My mother was an art teacher and I did lots of drawing.
You're right. One cannot neatly classify many boats like the GB or the DeFevers. The GB is not that far from a planing hull. Take away the big keel, lighten it quite a bit, give it 600hp and off you go planing away without changing the hull shape one bit. The DeFevers act mostly like a full displacement hull most of the time but they have a rather flat QBBL and lots of immersed transom at rest. A flat run aft and a deep flat transom are clearly the features of some kind of planing hull. An underpowered SP or planing hull dos'nt become a displacement hull by adding a big keel and a small engine. I've seen a lot of trawlers in the water that looked like displacement or even FD boats only to see them hauled out to expose their SD or even planing hulls. If I had to make a call on a Camano Troll I'd say it is a planing hull. In the water it looks like it has a deep draft fishing boat hull under but not so. The Camano is a beautiful boat and a good one too from what I hear. I personally can almost always make a call but some seem to be equally two types ......but not many. Anyway I was fiddling around w my i-pad reading posts as in mostly scanning ....and one of those posts was yours.
So I'm glad to hear you're not easily offended.
I've been a bad man. I was much more critical of your post on page 5 than I should have been. Much good and interesting stuff in there. A lot of the Wikipedia stuff was not good or not relative to us. It's interesting how canoes and kayaks can exceed hull speed so well but they can. I have an 18' narrow stern canoe and I've powered it w 6 and 8 hp. Makes about 14 knots. Need weight (wife) to keep the bow down to reasonable attitudes. Without the fwd ballast and w the bow sky high I can do very interesting figure eights. A friend said I was doing canoegies. No I'm not a NA. I've studied it lightly for 55 years. I spent a lot of time in the university branch library in Seattle reading Atkin and other great designers. That was in the mid 50s. My mother was an art teacher and I did lots of drawing.
You're right. One cannot neatly classify many boats like the GB or the DeFevers. The GB is not that far from a planing hull. Take away the big keel, lighten it quite a bit, give it 600hp and off you go planing away without changing the hull shape one bit. The DeFevers act mostly like a full displacement hull most of the time but they have a rather flat QBBL and lots of immersed transom at rest. A flat run aft and a deep flat transom are clearly the features of some kind of planing hull. An underpowered SP or planing hull dos'nt become a displacement hull by adding a big keel and a small engine. I've seen a lot of trawlers in the water that looked like displacement or even FD boats only to see them hauled out to expose their SD or even planing hulls. If I had to make a call on a Camano Troll I'd say it is a planing hull. In the water it looks like it has a deep draft fishing boat hull under but not so. The Camano is a beautiful boat and a good one too from what I hear. I personally can almost always make a call but some seem to be equally two types ......but not many. Anyway I was fiddling around w my i-pad reading posts as in mostly scanning ....and one of those posts was yours.
So I'm glad to hear you're not easily offended.
Awww Shucks, Eric... don't be too hard on yourself! Anyway, thanks for posting that, and heck, you're way too nice a guy to really offend me. I've got thick skin; you ought to see how heated some biz meetings get. The only people who are never wrong are those who never try. We all make mistakes in understanding others, or in self professed knowledge, or...???
This forum discussion stuff is simply a communicative learning experience for us all; as well as fun and games, at least for me. I do forum time to clear my mind from writing biz documents and working on product plans. Forum offers great relaxation for me while chatting/learning/teaching about boats and other marine items – which I adore! BTW, much of what you post is very interesting and I learn from you, as well as from others. Hope my input also adds a bit of positive influence. I can get a bit opinionated, raspy at times too; I’ve been known to be condescending, as well as occassionally, on the other side, even somewhat thoughtful and understanding. You just never know bout me – that's part of what keeps my nature exciting! Ain’t life grand and boating fun! – Best to ya, and... Cheers, Art
SOMERS
Senior Member
semi displacement
Tony B
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Didn't this originally start as a Poll?
I thought I voted. Did it get erased with all the other changes?
I thought I voted. Did it get erased with all the other changes?
FF
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"A full time cruising sailboat probably needs new sails after 5 years."
The sails may be shot after 5 years of exposure to the sun.Tho new fabrics are better.
Since 90% of a circumnavigation (2-3 years) is static , in port or anchored that translates to DECADES OF ACTUAL USE.
Assuming the use of a sail cover.
FF
The sails may be shot after 5 years of exposure to the sun.Tho new fabrics are better.
Since 90% of a circumnavigation (2-3 years) is static , in port or anchored that translates to DECADES OF ACTUAL USE.
Assuming the use of a sail cover.
FF
Tony B
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I hope that they can retrieve the original data from the poll.
My best guess is that over 90% of the boats on here have semi-displacement hulls.
There has been enough discussion in this post for most people to now know what they have. Even with overlapping designs, the rules are pretty much in place for full displacement and full planing. Everything else inbetween will probably be a semi-displacement.
My best guess is that over 90% of the boats on here have semi-displacement hulls.
There has been enough discussion in this post for most people to now know what they have. Even with overlapping designs, the rules are pretty much in place for full displacement and full planing. Everything else inbetween will probably be a semi-displacement.
FF
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"the rules are pretty much in place for full displacement and full planing. Everything else in between will probably be a semi-displacement."
IF true that is very sad , because most folks are not willing to pay the SD fuel/noise price to cruise a couple of K faster and sadly have to live with for the SD compromise hull shape 24/7.
At displacement speeds the dragging transom and larger engine /engines cost , perhaps 15 -20% in added fuel burn ,
and the usual flat rear or chines give a poorer displacement speed ride with a snappier roll.
All to do 12 -15 K perhaps 3 times in 30 years?
FF
IF true that is very sad , because most folks are not willing to pay the SD fuel/noise price to cruise a couple of K faster and sadly have to live with for the SD compromise hull shape 24/7.
At displacement speeds the dragging transom and larger engine /engines cost , perhaps 15 -20% in added fuel burn ,
and the usual flat rear or chines give a poorer displacement speed ride with a snappier roll.
All to do 12 -15 K perhaps 3 times in 30 years?
FF
Tony B
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Phil:
Dont ask a guy my age to remember Reply #3 when the the next post is Reply #114
Dont ask a guy my age to remember Reply #3 when the the next post is Reply #114
Nomad Willy
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KJ,
If you understood what the QBBL is then you'd know it would be 0 degrees.
The QBBL stands for Quarter Beam Buttock Line. It is an imaginary line running fore and aft outboard from the keel half way to the chine along the bottom of the aft section of the boat. A steep QBBL will be found on a full displacement boat. A straight QBBL on a full planing boat. Semi-displacement boats will have a QBBL that is moderate. A boats best operational speed will be fortold by the QBBL. By looking at lots of boat buttocks soon you will be able to estimate fairly accurately the operational speed of most any boat, especially slow boats. A boat w a steep QBBL that is also curved (convex) will be even slower. Below is a picture of such a boat.
At the top of page 4 you can see another example of a boat w a steep QBBL. The planing hull you presented is the opposite ........straight.
If you understood what the QBBL is then you'd know it would be 0 degrees.
The QBBL stands for Quarter Beam Buttock Line. It is an imaginary line running fore and aft outboard from the keel half way to the chine along the bottom of the aft section of the boat. A steep QBBL will be found on a full displacement boat. A straight QBBL on a full planing boat. Semi-displacement boats will have a QBBL that is moderate. A boats best operational speed will be fortold by the QBBL. By looking at lots of boat buttocks soon you will be able to estimate fairly accurately the operational speed of most any boat, especially slow boats. A boat w a steep QBBL that is also curved (convex) will be even slower. Below is a picture of such a boat.
At the top of page 4 you can see another example of a boat w a steep QBBL. The planing hull you presented is the opposite ........straight.
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