Displacement vs Planing Hulls
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- Опубликовано: 27 фев 2017
- Displacement vs Planing Hulls; what is the definition? What are the properties? What are the advantages and disadvantages?
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PUFFIN is a deep draft sailing ketch with a Dutch steel hull. My wife and I live aboard PUFFIN and are currently slipped in Charleston South Carolina.
6 years later and it’s one of the most helpful videos I’ve came across while on my Yachting journey. Thanks a lot
I particularly enjoy the lack of BS in this video. Overall very informative and clear without being boring.
Joe, thanks for watching!
For years people have been telling me that displacement is not the same as the weight of the vessel. If I understand this correctly, they are wrong, as I have argued for years. Thank you for the clarity. This solves it.
Well you are one of the only videos on RUclips explaining this so I understand and when I look at your comments everybody else feels the same thank you buddy
I'm in full agreement
I like quick, I like simple, but just like a semi displacement hull this video has the best of both worlds. Thanks for this video!
Thank you for this video! An excellent simple and well diagramed visual aid for differences in hulls.
It's quite a bit too simplified from my understanding.
There's issues like where the buoyancy is located etc.
And how the water is shaped during movement.
The traditional Norwegian shallow draft fishing vessels I've sailed intentionally where trying to create vortexes in the water, increasing stability while sailing and in theory also reducing the amount that the boat is pushed sideways by the wind allowing it to tack closer to the wind then with another hull shape when at optimal speed.
Really nice explanation. As an example of the effect of wind speed on hull speed, crossing the Gulf of Tehuantepec in S.W. Mexico we ran at the designed hull speed for 8 hours with a reefed storm jib and Main reefed below the spreaders - 65 square feet of sail on a 27 foot 3/4 kee[ boat.
What a beautiful explanation and drawings! Your wish to make it good is seen in every detail. Thank you
Perfect explanation for absolute beginners, very good.
I've been enjoying your informative videos. Hope Puffin finds/found a good new home. Wish u both well in Colorado!
Really appreciate your videos. I always learn something new. Thanks!
Finally, by feeling I was right....semi displacement it is....and i find your great vid which concluded my goal...Thanks
Thanks for the feedback! I wish you happiness and luck with your new boat!
thank you for the good explaining, also the hull speed video is really good!
Thank you for this information. Need it to pass my boating safety and security test.
Thank you for this, much appreciated!
Very educational video man. Well put. Good stuff. Thanks.
Good explanation for us landlubbers. Thanks for the clarity and succinctness.
You did a great job explaining this… thank you so much
This was incredibly helpful for me. Thank you.
Lifted from an online article on the (inter-war/) WW2 German Schnellboot:
"- After experimenting with the S-1, the Germans made several improvements to the design. Small rudders added on either side of the main rudder could be angled outboard to 30 degrees, creating at high speed what is known as the Lürssen Effect. This drew in an "air pocket slightly behind the three propellers, increasing their efficiency, reducing the stern wave and keeping the boat at a nearly horizontal attitude". This was an important innovation as the horizontal attitude lifted the stern somewhat, allowing even greater speed, and the reduced stern wave made E-boats harder to see, especially at night."
E boat
You made displacement so easy to understand, i wish you were my teacher:)
Super explanation...would be neat to hear your take on flat bottom and where they fit in the mix. Cheers
Excellent video.
For us dinghy sailors is a far easier equation.
Some of the boats I've sailed were not realistically planing hulls because the windspeed required to make them plane was not appropriate for the kind of sailor that would be sailing them typically.
Mirrors, Toppers and even Wayfarers.
They will all plane but no kid is ever going to be out in the conditions that would let that happen.
I sailed amongst others an international 420 that would plain on a three sail reach in about a force three and would get very exciting in a 5.
We used to sail past ospreys in high winds due to the propensity for the 420s lightweight hull to pop up onto the plane with one pump of the spinnaker.
It was a great boat.
After that we sailed a Laser 4000. That thing was a surfboard with a sail.
It would plane upwind slightly off in a force 3 and would make better vmg for it.
Of the wind it was both a riot and a pussycat.
Even in a force 5 we used to scale the river on a beat 3 miles then come back on a 3 sail reach in 10 or so minutes. That's what it felt like anyway.
I've got tracks on a GPS of 25mph+
That thing was crazy but oddly completely compliant. You could take your hand off the helm in low gusting conditions at speed and the boat would just plane on.
It was clearly designed to be most balanced on a full on three sail reach and it was wonderful for it.
Deathbed memories.
Love and Peace.
This is why sea levels are rising. Too many boats on the water displacing it.
Ha! A couple more to go and we can get a cool inland sea over Kansas again!
I thought I was the only one who thought of that! I have been told if you have ever seen the Pacific ocean you wouldnt think that. I suppose its rather insignificant in the grand scheme of things, but its still a funny thought. I have wondered if you could magically make every boat on the sea disappear instantly.......how far would the water go down?
Well if you think about it, most boats are moored around islands and low lying marina areas and there is where the sea levels seem to "rise" more, especially during storm season.
You forgot an important after effect. Fewer boats on the water means that everyone who boats will have more money in their pocket. Beer sales will skyrocket, and treatment facilities will be straining to handle the 'flow'. So, boats leave and the water level falls, By the following Saturday, the sea levels are back up where they started. Cause and effect.
Ha! In Florida this is especially true, judging by what's happening with Lake Okeechobee.
Great presentation, thanks.
Thanks for the video.
Very informative.
I was a little disappointed to find you only made 2 videos like this, they're very good!
Revolver_11, Thanks for watching! I ended up selling Puffin. I 'swallowed the anchor' and moved to Colorado to be near my folks, who are getting on in years. So, no boating vids for awhile. Perhaps videos on making beer and building flintlock pistols?
simple and nice explanation. thanks !
Great video! Thanks!
Thank you I just learned more about drag on a hill then I knew before.
John, Thanks for watching!
thank you! this is explained well
I'm watching this while designing a hill for a custom ship in a video game called Stormworks. Now I can make a better decision on my hull type, thanks m8!
I love stormworks
You are designing a *HILL* ...for a ship....? That sounds like an impossible mountain to climb???
@@joatmofa0405 bruh, he made a mistake by typing “hill”, it should’ve been “hull”. Can’t u look at your key board and see how close the “I” and “u” is?
@@jeddelse9036 Yeah, I normally proofread my text before pressing the "SUBMIT" button - else one can make a hug mistake (OOPS...see how I made a mistake there - it should have been "huge" not hug) - when one uses that extra 5 seconds of time (call it an "investment" in your education) to proofread your post - it makes the world of difference! [This took me just over 5 seconds to proofread - similar to wiping one's arse - do it until you are sure it's done correctly]
@@joatmofa0405
Correction:
(OOPS…see
should be
(OOPS… see
You are missing a space. For someone with such a rod up your’e arsehull aboot corect speling, yu shurely did’nt take the tyme to propperly doubble check yo’ur’e work.
Thank you sir! Great explanation
I really like this video!
Thanks Franklin great video 📹👍
Thankyou so much sir! It helped a lot
I used to have a laser, sailing dinghy. It definitely had a planning hull. On a broad reach with a decent breeze you could feel the boat, lift out of the water and onto the plane..
G'day Brad. Thanks mate!
Thanks for your useful info!
Wow very educational, thank you ! :)
Thank you for this excellent video. I’m completely into semi displacement yachts. I love comfort but also some speed :) fair winds, captain!
nice
Simply amazing explanation. I used to only draw boats, make models, and prepare details until the boat floats, but never have the interest about how it works on waters. Never learned this in my decade-long of being in boat design industry until i saw this 5min video. Why those engineers i met couldn't explain to me this simple.? I'm not a Marine architect and i'm not an Engineer as well, i'm just a guy that loves to drawing boats- a Naval Draftsman (if that title exist)
Jocoriah, Thanks for watching. I am envious of your profession!
Thank You, great tutorial.
*** RESPECT = Great presentation
Again super interesting, thank you
SV Satoshi, Again, thanks!
Good stuff. I now understand why pontoon boats are rather slow, as they rarely plane. I'd love to see an explanation on the better designed catamarans though, like the WorldCat 235 CC. It's supposed to plane easy (even on one engine), has a very shallow 9" draft, yet rides smooth and comfy, and handles chop and swells very well. How so?
Super thanks. I was wondering "what is displacement for ship" while I was checking spec for my warships for my game. Thumbs up !
Great explanation of planing. It gets confusing to me, when hull design gets more in depth: dead rise angle at the prow, amidships, and at the stern. Add in chines, reverse chines, strakes, keel designs...Its all too much for a novice such as myself. What interests me is a power boat in the 18-22’ range, without much draught < 14”, with lots of bow dead rise 45-50 degrees to cut chop, fairly steep angle amidships to help planing, 16 degrees at the stern for a bit of roll stability, high gunwales & full transom with a splash guard, and a sizable reverse chine running back nearly to the helm and a Carolina flare to ward off spray as well as possible. An efficient design to cut through chop, get up on plane reasonably fast, run efficiently, have a dry ride, and decent stability drifting or trolling at low speeds. Two boats are in the running after a decent amount of searching...A Sea Hunt 188 Triton CC and an Eastern Boats 22 CC. If Eastern made a 19’, it would be an easy choice. I love the tried and true down east hull design of the Eastern. To me, a 19’ is the “sweet spot” for a capable bay boat with off-shore survivability in < 6’ chop. I’d rather run a 115 hp 19’ than a 150 hp 22’. Any thoughts on either builder/boat? Thanks for straight forward informative videos.
Great video
Great vid, thank you very much!
Another awesome video! Keep these coming :)
well done, thank you
excellent tutorial
What do you think about the norwegian pioner boats? For example the 15 allround or 17 flexi or the multi thats a small katamaran type hull.
hi sir .. this is good information for me..
great stuff
Thanks that helped a lot
NIce video. Thanks.
Thanks Captain.
YOu can also have planing displacement hull. How does this work?
re the big Freemans? 33 etc
Clear as glass ty much
Good Video, I am more of a Wana Be, I learnt something. Thanks
Great...
Thanks...
Excellent 👌
Hi, I'm Puffin, skipper of Brad.
cicci0salsicci0, not sure I ever get that drunk before filming:) Thanks for watching!
I have spent months researching into constructing boats and found a fantastic resource at Denelle Boat Builder (google it if you're interested)
Thanks Cap'n.
NEW SUBSCRIBER
VERY WELL EXPLAINED
- And a displacement hull isn't necessarily slower. The 'Nazi' Schnellboot was not only faster than the comparative 'single step planing' hull used by we British (& shared with the US) but it was more suited; read efficient; for the North Sea/Atlantic use that it (they) were designed for. And worked better in the open Med under most conditions as a Planing hull is decelerated by wave strike; that is before you even consider that the Planing hull only has a relatively narrow 'sweet spot' of efficiency - the inter-web is full of 'learned' sites on just this matter.
How about mounting a folio under the boat? Can it be done on a wide and deep boat?
Thank you 😊
got it. thank you
I enjoyed the Calculus, Geometry and Physics lecture. I have found most of the information on the internet is like getting a weather forecast. Everyone repeats what they have heard; no one verifies the facts or even knows what the facts are.
Allow me to ask you a simple physics question; take two round objects the same length and size, both have the same nose cone similar to a jet aircraft.
Object A; starts the gradual curve to the end (tail/stern) point at 50% of the length.
Object B; starts the gradual curve to the end (tail/stern) point at 75% of the length.
Simple Question: which object is faster given everything else is constant; Object A or Object B.
Last question what is making Object A or B slower given everything else is the same (constant)?
Hi, thanks for the great vid. Why is it cat hulls transit between a plaining hull to a displacement shape?
Very informative thanks for another great video ! !!
Jack, Thanks for watching!
So where can I buy a good quality displacement kayak?
What about Azimut Grande Tridecks Hull ? is it a mix of both ?
Full keel or fin keel and rudder, what is safe to Atlantic crossings.
I have collectiv you videos in a fb group.
I come from a boat building family and still find boats fascinating. I wish to comment on this subject in that displacement hulls are only displacement hulls when they are stationary as when they move the dynamics around their hull provide regions of higher and lower pressures and these are vectors and so the hull even though we may call it a displacement hull, it still experiences the dynamic forces that a planing hull experiences. Really no hull is a displacement alone and no planing hull is planing alone as even if it rises on foils there is still the displacement of the foils in the water.
The dynamic pressures along the moving displacement hull are very complex as at the bows the pressure rises due to the fact that the half angle of the bow is accelerating the water laterally so that t he hull can go through the water. Since the water is not compressible, then the water rises causing a bow wave while the bow becomes more immersed and so displaced more water causing this action to raise the bow. Midway on the displacement hull, the water dynamics will cause the mass of water to drop down below the normal surface due to the momentum of the water coming down the elevated bow wave. As the water moves away from the hull, the hull sinks a little as the narrow bow angle does not have enough displacement nor dynamic lift to replace the buoyancy of the voluminous middle part of of the hull. So when a displacement hull moves then it sinks a little and it tries to fit into a wave of its own making. At the stern the water will try to move in to fill in the trough that the hull creates as it moves forward. Filling in this trough is the most difficult part of the function of a displacement hull as the water has a lot of inertia and it is reluctant to move back into the stern part or under it one might say. Now the moving read underside of a displacement hull is raked up and this is because a truncated stern as that of the planing hull creates a lot of drag. The underside of the rear part of a displacement hull creates a lot of low pressure trying to suck in the water under the stern and also causing a partial vacuum which tries to pull back the hull and this is a form of drag. Since the water is so reluctant to fill the understern part then then design angle of the manner in which the stern rises is very critical and for faster buoyancy hull it is this rise angle of the stern that decides how fast and how much sucking back is created. In a hull with a powerful engine, the moving displacement hull raises its bows and digs its stern and this is a waste of money as the fuel is used in making waves rather than moving the boat at a faster speed. The raised stern in a displacement hull makes a very comfortable ride with a read wave attacking the boat and broaching is avoided .
Nowadays with such powerful engines, the rear part of a displacement hull is truncated and rather than filling the void with water one permits air to fill in behind the truncated transom, Fast commercial passenger catamarans use this technique and they can go faster because there is no vacuum forms just ahead of their transom.
With planing hulls there is an even bigger story as while the centre of gravity stays put, the centre of lift moves ahead and astern of the CG and so a planing hull can oscillate and porpoise and it is very difficult to design a stable planing hull for all conditions, we try, but no one has yet succeeded in optimising a planing hull for all sea and weight conditions.
The owner of the Puffin seen in this video is a very wise man in selecting the boat he wanted. It looks as if he is wise enough to appreciate all the benefits and disappointments provided by the displacement or the planing hull. I feel that at my age a displacement hull is my preference but the hull I prefer is one where I would summarise through saying that the under curve of the hull would be something like an inverted sine curve and no displacement hull should be designed on a straight line representing the horizontal surface of the sea as that is a static condition. When a displacement hull moves in the water it creates a bow and a rear wave and the whole hull must fit in it with the same draft all through the curve. This may sound far fetched but I say that a displacement hull moving at its maximum natural speed through the water is in fact a planing hull as the dynamics come in to support the hull in a wave of its own making and though it sinks in it a little , the hull is really a semi planing hull. The beauty and elegance and majesty of a displacement hull going at its maximum limiting speed through the water is a situation that will fascinate me to study the situation for the rest of my life.
Carmel, Thanks for watching the video, and thanks for an awesome explanation! Lots of things there I did not consider and fun to think through. I am no engineer or marine designer, so I tend to go (as in the video) with the 'rough' explanation. As you balance the cost of vessel production into the mix, I think you boat builders have come up with some elegant solutions; a tapered stern to reduce the stern vacuum, for instance. I am also fascinated by what an unrestricted budget will produce, such as the shapes and size of the bow protrusions on Navy vessels. If you have the opportunity to use a test tank, I think it would be very interesting to pursue your idea of a curved keel that changes the hull volume to mitigate the bow wave. Another area I think would be fun to study is the work being done using air bubbles (pumped into the laminar flow) to mitigate some of the drag on higher speed surfaces.
This is of course true, although the conventional terminology is accurate enough for normal descriptive use. A displacement hull is designed to go through the water although it generates some lift, a planing hull is designed to skim over the water, and a semi-planing hull to rise up and carve through the water. The most extreme cases are those super short windsurfers which will not support the user above the water level until they are generating lift.
What kind of hull did the orca boat from Jaws, any other information about design it was based off the late 60's warlock fishing boat
I was thinking about building the orca
that was a displacement hull
thank you
Instant sub
Oi! Como vai?
Quero aproveitar seu conhecimento sobre uma dúvida que tenho. O desenho da esquerda vc disse que é necessário motor mais potente, isso acaba gerando mais peso.
O que me diz se ao construir uma embarcaçao com este modelo de casco, em toda a lateral ( norte sul ) fizesse um caixote e colocasse garrafas pet de 2 litros, duas a 3 lado a lado, acha que com isso o empuxo será mais eficiente devido flutuação e com isso o motor fará menos força podendo ser utilizado um motor com potência máxima bem menor ao que seria?
Imagia que as garrafas travadas no casco sendido proa / popa tivesse a largura até onde vai as duas setas vermelhas que usou no esquema do desenho, ficando o meio oco, sem garrafas. Estou pensando quando for encomendar uma embarcação, pedir que faça assim.
O que me diz?
Mines the right one but even more drastic. A flat bottom 5/8ths runner bottom race boat. & a foot pedal cavitation plate on transom. It sure gets scary when u really get up n going. Basically only the prop is in the water.
Wow! Sounds fast!
Rolling at anchor or adrift, is the most uncomfortable situation for a passenger. Planning hulls tend to lift like a raft thereby reducing roll.
Sailboats with a weighted keel is a different animal.
Thanks for an easy to understand explanation.
So what category of hulls are trimarans in? The likes of corsair or dragonfly etc?
Lynda, Thanks for watching! Interesting question. As a general rule, sailboats of all types operate as full displacement hulls, or close to that. There are a number of exceptions, as you would expect. Anything that has a plane that brings lift with speed will operate further and further from a full displacement model as the speed increases. I have not studied trimaran hull physics, but because trimarans are known for their speed it stands to reason that designers would have not overlooked that obvious advantage.
@@sailingpuffin9441 thank you.
Brad!!!!! this is an informative and helpful video please make more :)
Really missing your instructional videos, are you planning anymore in the future.
Thanx.
So if a boat isn't moving its always considered a Displacement boat? Do the AC75 next ;)
thanks 😎
But I don't get how a planning hull costs more on fuel. If you slow down the boat so it doesn't go up on plane, would it cost less in fuel though it has to move more water over a longer period of time?
Vous avez un chantier pour fabriquer les yachts ?
Cliff Lee, 'Fast Dispacement' sounds like sales gibberish. There is such a thing as 'Semi-Displacement'..... You could also claim 'semi-planing' I suppose. There is a range of hull types running from full displacement to planing. At rest, everything is a displacement hull... Then when you start moving, the amount of plane in a hull that gives lift varies from hull type to hull type. Of course, the engine output has to match... People seem to like the fuel economy of displacement hulls, so the sales folk add that to the name. Yet people also like fast boats, so they add that to the name, too. What you are probably looking at is a hull which is a compromise, operating at close to displacement economy when under 10 knots or so, then operating at just under normal planing speeds when you open the throttle. The boat will (probably) not give you the full economy of full displacement, nor the full speed of a fully planing vessel, but the compromise apparently works for a lot of folks. The name is no reason not to consider the boat.
Thanks
I’m looking to build a solar powered boat (over the next 2 years) and I want to be able to go to the north and south poles the boat will only be around 8ft by 20ft give or take what hull type would be best?
It’s going to be made from aluminum
Wow! That sounds like quite an adventure. I would recommend a mono hull for a couple of reasons. First is that you can carry more supplies because the mono is less sensitive to weight than the average cat. Second, you can use metal in the construct for the same reason. Resistance to ice is going to be critical. Yes, you can get in and out faster in an average cat due to the faster speed of the hulls. Just my 2 cents, though. You may want to bring the question to both a mono hull designer and a cat hull designer. That way you can compare the styles by cancelling out the opinion bias.
More!
Can you give me some numbers of what is considered 'light', 'middle' or 'heavy' displacement in sailboats?
Eef BS,
Interesting question! I have no numbers ready at hand, but think it would depend on a ratio of length to weight. PUFFIN is 19 meters length on deck and sits at about 53 tons... figure that to be very heavy. Boat neighbor with an Oyster 65 weighed in at 50 tons... also heavy. I dont have data on the racing hulls in the 20 meter class, but figure them to be much lighter. Probably half that weight? Then there are going to be the data that trends toward the displacement ratio: heavier ratio is logically slower, but could carry more sail? Heavier ratio is logically deeper, giving a better (?) lee slip resistance and therefore a higher point? Heavy would certainly dampen motion.... Lighter would logically be faster....
goodman 👍
in addition to displacement there is "travel" or how a hull moves through water at speed meaning a long but narrow u shaped hull can in fact generate incredible amounts of speed as it has the fewest forces acting against it (just displacement). for example a straight up bath tub used for bathing in your home with properly attached motor can really fly across a body of water because if properly balanced it does work according to your theory namely one only of displacement without any concern with lift at all. a great example is a supertanker for carrying oil...something only "slow" because the vessel has to stop and not because it can't go fast. there is also the material used to cause an item to either sink or float. any material that rests naturally on the surface of water (a rubber raft for example) can generate enormous amounts of forward velocity simply by a: not weighing much and b: being above the waterline to begin with. of course then there are waves, tides, temperature, humidity, the type of water (salt, fresh, etc) and of course currents, structure (above and below depths) as well as the type of shoreline (sandy beach versus mangroves vs shoals) and probably an innumerable other in factors i have failed to list here..
Andrew, Thanks for watching! I cannot dispute any of your observations. The new boat owner is often gullible, and there are some outrageous performance claims out there by sales and marketing people who are willing to lie to get into a wallet. The basic notion of the video was to give that new boat owner some sort of yardstick; some way of getting at least close to the truth on their own. Dialing in the actual hull speed down to the tenth of a knot is almost impossible without actually taking the boat out for a spin.