I am a BIG Jack Gifford fan. He designed and oversaw the build of a new keel for my modern performance yacht. He was recommended to me by on of the worlds greatest yacht designers. Not only is he a great naval architect but a top bloke too! A really smart guy who will steer you through the complexities of yacht design and manufacture. I really cannot praise him enough. Very pleased to see him working with Leo. Top team!
As a retired project manager and licensed Professional Engineer I appreciate your practice of utilizing experts advisors. Your associate, Jack, is another example of one of those experts. A shout out to Jack, please. Also, your graphical presentations were perfect. Thanks and well done. Cheers
Stability of ships was a big area of research in the 17th, 18th and 19th centuries. The Royal Society contains quite a few documents relating to the issue which attracted some top drawer people of the day. Imagine working out a surface area of a hull without modern software. Newton's Principia (which dates from the 17th century) contains a calculation of the shape of minimal resistance of an object travelling in water. It is highly geometrical and essentially impenetrable to modern people (I know because I've tried) and I can recall a physicist solving the problem with modern techniqes and being absolutely stonkered to find that Newton was spot on.
So true. Science and math are useful, Who knew? Not to be too much of a hater but this project is so much different than project Yaba, which is being tossed together with more time and effort being put into seats, swim platforms, decorative rails etc. than paying any attention to sailing safety, trim, and stability. I really hope Yaba isn't an accident waiting to happen when people start going out on her.
@@Mark-zi4dd Yaba is to be a dive boat ie coastal vessel. It won't be crossing the Atlantic and with a bit of luck will last longer than the 15 year-old wreck they bought at the start.
There is also a THIRD measure and it's called the "center of pressure". Firearms take this into account with their projectiles: If you imagine a bullet flying their the air, there is a relationship between the air pressure pushing on the nose of the bullet and the center of gravity of that bullet; and this is very much effected by the shape of the nose. These boats go slow enough that it doesn't matter as much, and it's already a set design, so you can't change anything anyway; but there is another dynamic happening when she's full steam ahead.
Great video Leo. An idea: You could offer the 3D model of Tally Ho for sail so geeks like me could print their own little Tally Ho. It'd be awesome to have as a model on my desk :)
At first I thought this was a pun (clever word joke) but then I saw your name and realised you were writing in a foreign language. (Respect for that.) Ships have sails, but we offer something for sale. "Sail" and "sale" sound identical. Whether you intended a pun or not, it made me smile. :)
As an aerospace engineer I found this a very well done explanation. Afterall, water and air are both fluids and this is fluid dynamics. Great you have a navel architect to verify everything, too. I'd like to see a similar presentation on the sails and rigging when the time is right. I've been a Patreon since you offered us that chance to support you and feel it is a worthwhile donation on my part. Keep up the good work.
any episode with your architectural cut out animations is solid content dont apologize. this was very informative and props for finding a way to get an episode out while on vacation i figured we would not see anything while you were gone.
When I was in Engineering School every student had to take two courses: Vector Statics & Vector Dynamics. This is basically what you are showing in this video. It has never failed to amaze me how useful the study of vectors would wind up being, and how often it comes up.
I'm not sure about "proper" racing yachts, but in the RC world for most of the established classes the hulls and weight are very similar to eachother now we've found the "ideal" setup, and most tuning actually comes from the size and shape of the keel fin (and to an extent the sails, but i'm not really experienced enough with the maths there yet)
Early last week, someone mentioned this series on a thread on The Hull Truth, and I looked it up. Over about a five-day period I have binge-watched almost all of the 125 episodes. The craftsmanship here is amazing, and the episodes are fun and educational. I am dealing with some of these calculations now as I figure out where to place batteries, fuel tanks, and etc. on an 18.5' fiberglass fishing boat I am rebuilding. I especially like the episode about using the Live Oak from Georgia. I live in Brunswick, and the Oak used for the USS Constitution (Old Ironsides) was cut from Gascoigne Bluff here on St. Simons Island. Definitely subscribed and hit the bell so I don't miss any.
Loved this episode.... What made me chuckle was how similar an approach I used in ascertaining the CoG for a very large rocket (Reliant Robin Space Shuttle - there's a vid on my channel somewhere). Dervied from this you can also ascertain the Inertia of the vehicle too, this is important in ascertaining whether it manouevres like a cow or like a ferret! In aeronatics we use the centre of Pressure Cp (opposed to the Centre of bouyancy). We used a Wind tunnel for this. Thereafter You have most (not all) of the data required to develop a simulator to characterise the flight of the vehicle, design it's thrust lines, mass/location of ballast, simulate failure, wind shear characteristics etc. etc. In a simliar fashion just like you are doing here etc. etc. Great Stuff Leo. ABSOLUTELY love your work! :)
These technical vids about boatbuilding are what make this series extra unique! There is sooo much calculation involved. And you don’t see that once the build is complete. But it can make you crazy for sure!
Leo, As you go forward into the interior design and mast design please continue to discuss this idea around centerlines as part of conversation. The more technical side of the final build is very interesting. Great stuff.
Most sailors I know are also largely uneducated on this technical side of boat design. We just always assume the weight/center of gravity should be low as possible to keep the green-side down 😄. Thanks for the dope slap!
yup learned ... high winds ... lower down rougher ride ... but less tippy ... lower winds higher up smoother ride ... a bit more tippy but more comfy ... nice to know
Schutt Rostig yeah I was confused on that point too. I know for the old J class boats the overhangs were so extreme because the waterline length was set but not length over all and by heeling over hard they’d increase the hull speed. But I don’t really get why, outside of that one context. you’d sail poorly in light wind with a stiffer boat.
@@schuttrostig5729 It's very much borne out in practice, when the breeze is just a few knots. Look at Olympic dinghies in light winds, the helm will be lying along the lee gunwhale, and a good way to get yelled at on a bigger boat in a competitive drifting race is to start to move towards the high side unless your job absolutely cannot be done from leeward. On boats of any size, gravity will cause the sails to drop to their cambered shape if there's 5-10 degrees of heel. Sitting bolt upright, the sails will lazily flog between opposite cambers, meaning that they can't develop enough drive to build up steerage way (essential for constant sail trim) or - just as important - to build the apparent wind which is the key to sailing in very light winds. It's a fragile process of bootstrapping, and even when the sea is dead flat (in which case shifting the crew to leeward might be enough), a certain leeward heel is essential.
Loved the technical talk. Not a sailor or boatbuilder, but am fascinated by the technical aspects of this rebuild. It's been a bit like taking an online lecture. Just excellent!
Excellent video Leo. Took me back to when I was doing my mechanical engineering degree in the late 1970s and we shared some of our classes with the Naval Architects who in those days before widespread computer aided design were learning how to do those calculations the hard way, using calculus to determine the areas and volumes of sections of the hull. Nowadays the tools make lighter work of the lifting but the thinking is a real as ever.
I have been an aircraft mechanic and inspector for 40+ years and just getting into sailing. I found this video fascinating and will wait eagerly for the next installment
As a professional builder, I found this to be extremely interesting. So much more than most people realize translates between building a floating body and a land bound one. Great video Leo!
Oho! Very interesting! Speaking as a ludicrously top-heavy woman who's been mocked and ridiculed ever since she left school for her... um... high centre of gravity [10 stone, 5'6", NN-cup...☹️], I love the idea of being able to describe myself in pukka nautical terms as 'tender'. Also 'squishy'.😁
Lovely job explaining boat stability to this old engineer. Your narrated animations and drawings always make things crystal clear. Watching the center of bouyancy migrate around as she heels over was a real Aha moment for me. so cool . I'll be working the terms stiff and tender into conversations at every opportunity. Albert is up there smiling from the great beyond but only slightly chagrined that Tally Ho will be better than ever.
I used to watch the Deadliest Catch and saw the episode when Capt. Sig was informed of the sinking of FV Destination and death of his friend. At the end it was determined that the boat had a bit too many cages high up and they had iced and moved the center of gravity so far up that the boat overturned and sank.
@@cliveramsbotty6077 There was a sister ship of the same construction & design. Simple stability tests (moving weights on deck) showed the actual margin of stability was far smaller than originally planned. The expected icing rate, combined with the larger/heavier pots made the math impossible to contradict.
Fantastic explanation and graphics. While I didn’t know the terms before today, “tender” and “stiff” make sense to me as a mechanical engineer, akin to the natural frequency of a spring-mass system being proportional to the square root of stiffness divided by mass-so long as the mass center stays below the buoyancy center. Also, the longer the moment arm between those two points, the better the boat’s ability to right itself. Thanks for sharing, Leo!
Fascinating description. When I was required to get my forklift license, we had to learn about the stability triangle and how moving the centre of gravity outside of this triangle means tipping over your forklift.
Nice explanation. As a sea captain on cargo ships long ago I had to experience a particular stiff boat many times. One leg stood out. We loaded full containers in New York and Miami and dropped them off in a few places in the Caribbean, Barbados being our last port south. The return trip from Barbados to New York was almost all empty containers, and far too much stability. Being the open water crossing, we always rolled too fast side to side. Very uncomfortable. Three four day of this always made you very tired. (Greetings from Anacortes.)
Well Leo you don't have to apologize to me for the detailed explanations and calculations that are involved in boat stability, these calculations are rather important. I find this topic very interesting I know its important stuff that is if you want a sea worthy vessel that will be fuel efficient and safe to sail. Thanks for including this in educating us mere mortals in the technology that goes into the design and stability and sailing performance of Tally Ho. cheers have a good one Leo.
Merchant sailor here, calculating the stability of the ship before, during and after cargo operations is normal routine. You pretty much nailed it. Ofcause there are more factors in play as you said, but this shows and teaches the basic understanding really well. Edit: Im very happy that you mentioned that displacement is equal to the vessels weight. One of my pet peeves is people calling the GT as the weight of the ship.
Your family must be so proud of you. What a pleasure it is to see someone recognize the value of something from the past and care enough about it, to try to restore it in both function and beauty. Your illustrations are a great enhancement to explaining difficult concepts. Congratulations.
The technical discussion here is really excellent. Experienced sailors will have picked it up, one way or another, but for someone like my wife, who is intelligent and interested in sailing but not fully knowledgeable, this kind of information helps to put the knowledge she has into a more meaningful context. I want to elaborate a bit about the dynamic nature of buoyancy and mass. For simplicity, Leo mostly dealt with the static effects, hinting however with his references to stiffness and tenderness that something dynamic emerges once dynamic forces like wind come into play. Mass distribution can have a meaningful effect on how a vessel handles in a seaway. It's the same principle as a pendulum: the more you concentrate mass in the ends (for example heavy anchor and chain in the bow, heavy engine toward the stern) the more forcefully the vessel will tend to pitch rhythmically, ploughing or wallowing along instead of maintaining a steady trim. If this becomes a problem, to some degree the point of resonance can be tuned by moving cargo or ballast toward or away from the ends. Usually you want to keep the ends light. The same pendulum effect takes place with mass distribution in the vertical direction. Described as "top hamper" when excessive, any mass concentration toward the masthead will tend to make a vessel roll more forcefully in a seaway. With gaff rigs this dynamic effect has to be taken into account early in the design. There isn't as much mass aloft in a marconi rig, but it still excites interest among performance sailors to change from wire rope to synthetics in order to shave off a bit of excess weight. The boat may feel less tender yet more responsive as a result. Then there's the matter of dynamic buoyancy, wetted area, and waterline length. It's a big subject and I don't claim to fully understand it, but I think its existence is worth noting at least, because the effects of hull shape can be so profound. Consider a floating sphere with a fixed weigh somewhere off center inside it. That sphere will of course tend to right itself with the weight at its lowest point. But it will also roll very easily because nothing but the position of the weight is resisting the roll dynamics. Put the weight exactly on center and the sphere will roll dizzyingly. It has zero righting moment, zero stability. Any other shape but a sphere will tend to right itself through buoyancy. A more ellipsoidal or dish shape has positive buoyant stability. A more conical shape than a sphere has negative stability. We somehow end up with ballasted keelboats which have some turn to the bilges, sometimes considerable rise, sometimes nearly flat bottoms, sometimes considerable overhang in the ends and sometimes none. Subtle differences in shape will make a hull stiffer or more tender at different degrees of heel. And different degrees of heel may significantly increase the waterline length of the hull, increasing its hull speed as well as the buoyancy of the ends. It's fascinating how much is going on dynamically as a result of choices in static hull form.
I really enjoyed that, thanks. I've built some small boats where all that work is done by a designer, and any changes were done by instinct and experiment. it's great to get a workman like perspective on the theory.
What a wonderful demonstration of calculating efficiency as it determines ballast placement. What I didn't understand was why sail efficiency likes a bit of heel . Thank you Leo for such a detailed understanding about how a boat might be blasted.
An exemplary presentation of a fairly complex matter! I’ve made my own interpretation of Tally Ho in 3D using Sketchup, and in order to find the floating lines I used the same procedure of building a spreadsheet giving me an estimate of the center of gravity. To assess the center of buyancy I used rough models in 3D giving me the volume of the hull. Combining the calculated weight and the volume I then found the place of the buyancy center for 0 degrees, 15 degrees, 30 degrees and 45 degrees of heeling. Not being an engineer, nor having done any kind of this work before I was really looking forward to this episode and I was not disappointed because the methods described by Leo very much looked like the methods I have used. I am posting a drawing of my version of the Tally Ho on the Tally Ho Facebook group shortly.
If you have a body of water around you even a small lake, buy yourself a small sailboat, 12-16 feet or so! Super easy to learn and so much fun, I had never sailed in my life bought a boat and just went out and had fun
Love this! The serious problem solving of boat building is so great to watch. In my opinion, I prefer this content to just montages of some work being done. The lofting episodes were so great to set up the framing episodes, can’t wait to see progress after this.
Fascinating. I've never even met a naval architect let alone being privy to all the detail of the obviously valuable contribution that they make to the all important stability issues with a sailing vessel. Thanks for this detailed insight into this aspect of boat building.
Great video! Love the very clear diagrams as well. I now see the advantage of having "loose" internal ballast as you can be there at the end of the build and just position where and how much inside until the boat "sits" right. It is really hard to do that before hand, but once you are in the water, it is much simpler.
Thanks Leo, I was beginning to get Tally Ho withdrawals. I binged the whole series again, but in the end it doesn't compensate for the new fresh video, which is a remarkable topic.
Absolutely great video! Great explanation of the principals. I'm glad that the balance of the boat worked out so well for you and that there were no surprises. It's amazing to me how Albert Change and his contemporaries figured this stuff out manually 112 years ago!
That was a fascinating insight: the characteristic of the original's sailing performance should be maintained. As a landlubber carpenter and builder, it wasn't something I had considered while watching this series, but this video was very informative. Great! Still the best show on youtube
Very interesting Leo. Great to see what is involved in making a vessel sea worthy. I'm a flyer and we are always concerned with weight and balance of the airplane. Obviously, the same concerns are at play in an ocean vessel only in rather different ways. Good to see real professionals at work. Cheers
When I looked the title of this EP I was sure I would not be able to follow you. I was wrong. The way you explained the process was simple, logical and easy to follow. Thank you Leo
You know as I have watched your videos and the construction of TallyHo I am constantly amazed at your depth of knowledge in every aspect of the construction of TallyHo. You sir are way more intelligent than you give yourself credit for and much of your knowledge includes older “knowledge” not just new technology. Well done.
Very interesting discussion that was perfect for me as a non-techy marine engineer. Obviously of vital importance in her stability but this put some words and principals to it and how it's done. This was way easier to understand than the "lining off" of the hull for planks.
It's nice that you put as much effort into visual aids and explaining hard to picture concepts. Keep changing the job title "sailor, boat builder, film maker, educator". Probably throw cook and mechanic in there as well
I hope while you were home I hope you got to see your lady friend, Checka, I think was her name? Anyway, I hope you two are still together and everything is well. I miss her in your videos. She made it feel more like a home/family project and not a work job.
I for one, do not mind a but of tech talk. It brings a much clearer picture of what a vessel is doing on the water and the forces that are in play. Very fascinating!
I was told years ago (probably before much of the 3d modelling) that, at least initially, boats rarely sat exactly on their designed waterline. It may be that the ballast approximation on the original drawing was intentional to allow fine-tuning later.
WOW ! AMAZINGLY INTERESTING !! As my buildings stand relatively solid on the ground, I’m an architect, this video was sincerely eye-opening thank you very much !!!
Skyscrapers can be immensely affected by wind pressures acting on design features e.g. the "square" shaped building with a corner as the "leading edge" always turned into the prevailing wind... causing vibrations and twist in the building?
@@JohnSmith-yv6eq - Tall buildings especially must be designed as objects in a wind environment, where negative pressure can suck the outer skin & windows off the frame, & systems meant to circulate interior air can be bollixed by exterior winds. Indeed, a new skyscraper can have unplanned effects on the wind environment of its neighborhood.
Excellent video! Didn’t mind at all that it was more “talky”. Also, I thought I was pretty well versed regarding sailboat stability, CG vs center of buoyancy, righting moment, etc… but I learned something! As a racer of modern sailboats, I have always assumed that “the stiffer, the better” (hold the “that’s what SHE said” jokes please). I never thought of the negative effects of too much stiffness on the motion of a boat like Tally Ho, as well as on her light air capabilities. Great stuff!
I sailed A-Class catamarans for many years and stiffness is good when the complete boat is lighter than the sailor. Your body is movable, infinitely tunable ballast. If a boat's too stiff longitudinally, then you'll get jerky motion when sailing up wind and that disrupts the airflow over the sails and you lose lift. You can effect the stiffness by the way the buoyancy is distributed along the hull. Lots of buoyancy up front gives a smoother ride in a very light boat like an A-Class. Looking at Tally Ho's situation is very interesting to me. It's a very complex subject and heaps of fun for young and old trying to get the optimum balance.
Another top notch Tally Ho video production. Leo your explanation of the weight and balance using the paper cutouts was excellent. Thanks for pulling this episode together. I found the content interesting and it really is the foundation of producing a stable sailing craft. Cheers!
Excellent episode! It wasn't mentioned, but would you not want to position fuel and water tanks close to the longitudinal CG so that the longitudinal CG does not change much as you consume fuel and water? I am an aerospace engineer familiar with aircraft design, and this is a stability issue there. Don't know whether it's considered sensitive for small sailing craft.
I'm trying (and failing) to imagine the genius needed to do this work before computer modeling was available. Even with it the level of detail is mind blowing. Thank you again for sharing this level of explanation. For those of us with no experience with anything like this it is eye opening and mind expanding!
Heh Leo, I know that you know that the folks who watch this series and your project hang on every word technical or otherwise. So never an apology needed. You could literally do 60 minutes on head design historical and modern in relationship to your choice for the Tally Ho and you would get in the high ninety percentile of watch minutes. We love, I'm going to go there, we love this project, we love your style, your attention to detail, your work ethic, your clear concise explanations, the light hearted, diligent, dedicated comradery of your crew. You are a man among men, a mensch in a world that celebrates the mere utterances of the ridiculous. Your steadfast perseverance is exactly the balm needed for my soul weary of the charlatans who abound.
As a retired aerospace engineer I echo R. smith observations of your video. Just like a ship, airplanes deal with center of gravity and center of lift. Your definition of stiff and tender in roll are identical to Lateral stability of an airplane. This parameter is adjusted by wing dihedral primarily and tail size secondarily. Like you mentioned you can have too much roll stability. I am sure if transport aircraft had high stability, the high frequency oscillation would not do well with meal service. Kudos and keep ‘‘em coming.
Very much enjoyed yours and Jack's detailed explanation... got most of it first time but I did have to rewind on a few occasions to get it into my layman's brain. Hope you had a nice visit back home Leo as friends and family are everything in these trying times. 🇬🇧
Thank you Leo for the update. Good to see you back. Enjoyed the explanation on determining the various aspects that affect the sailing characteristics. Have a productive week ahead.
I've done complex mass property studies with pencil and paper of axial compressor and turbine assemblies (whirling speed analysis). Just before computers took the graft away. It gets really tough when calculating the stiffness of each chunk, before the days of finite element analysis.
I found this video probably more interesting with the quick lesson you gave in working out pretty much the center of gravity ( all directions ) vertical and horizontally , What an epic journey you have brought us all on so from me here in Dublin Ireland to all the Tally Ho family best regards and now onto the next episode ( this is my version of my wifes soaps for me ) so im so looking forward to the future still a long ways to go BUT who cant wait for her first hull wetting and all the good stuff leading up to that,, Take care mate 🙂
Thanks Leo, fascinating to compare with aerodynamic stability which is reasonably familiar to me. Didn't know about the heel angle, not being a sailor... Looking forward very much to mast and spar construction.
Great topic. I opened the thumbnail with great enthusiasm. Fascinating! Thanks for including this aspect Leo. Of several builds I follow, yours is the most rewarding. In terms of information and it's application to my own project , for example. There must come a time when the subject is enjoying the spray and the wind in your sails.
One of the best video that you have done. Go to college Nav Engineering. You will turn out one of the best. Never is to late. Your further explanation of both centers in a vessel was excellent. You are a perfectionist. Good job
Are you planning on doing any inclining experiments to validate the computer modeling? This was a nice revist of the elective Naval Architecture class I took in my ME studies. Back in the late 80's the computer support wasn't as polished as what Jack is using. We did a WWII Liberty Ship as a project and doing all the analysis was pretty laborious! Great job as always!
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I am a BIG Jack Gifford fan. He designed and oversaw the build of a new keel for my modern performance yacht. He was recommended to me by on of the worlds greatest yacht designers. Not only is he a great naval architect but a top bloke too! A really smart guy who will steer you through the complexities of yacht design and manufacture. I really cannot praise him enough. Very pleased to see him working with Leo. Top team!
As a retired project manager and licensed Professional Engineer I appreciate your practice of utilizing experts advisors. Your associate, Jack, is another example of one of those experts. A shout out to Jack, please. Also, your graphical presentations were perfect. Thanks and well done. Cheers
Another one of his admirable qualities - Leo is not at all shy of asking for advice when sailing in unfamiliar waters !
Stability of ships was a big area of research in the 17th, 18th and 19th centuries. The Royal Society contains quite a few documents relating to the issue which attracted some top drawer people of the day. Imagine working out a surface area of a hull without modern software. Newton's Principia (which dates from the 17th century) contains a calculation of the shape of minimal resistance of an object travelling in water. It is highly geometrical and essentially impenetrable to modern people (I know because I've tried) and I can recall a physicist solving the problem with modern techniqes and being absolutely stonkered to find that Newton was spot on.
Newton was a genius after all.
Refreshing to see actual boat building. Properly done, with math and knowledge.
Naval architecture is properly done with rules of thumbs and overenginerring
What you have been Seeking for
So true. Science and math are useful, Who knew?
Not to be too much of a hater but this project is so much different than project Yaba, which is being tossed together with more time and effort being put into seats, swim platforms, decorative rails etc. than paying any attention to sailing safety, trim, and stability. I really hope Yaba isn't an accident waiting to happen when people start going out on her.
@@Mark-zi4dd Yaba is to be a dive boat ie coastal vessel. It won't be crossing the Atlantic and with a bit of luck will last longer than the 15 year-old wreck they bought at the start.
There is also a THIRD measure and it's called the "center of pressure". Firearms take this into account with their projectiles: If you imagine a bullet flying their the air, there is a relationship between the air pressure pushing on the nose of the bullet and the center of gravity of that bullet; and this is very much effected by the shape of the nose. These boats go slow enough that it doesn't matter as much, and it's already a set design, so you can't change anything anyway; but there is another dynamic happening when she's full steam ahead.
Great video Leo. An idea: You could offer the 3D model of Tally Ho for sail so geeks like me could print their own little Tally Ho. It'd be awesome to have as a model on my desk :)
Take this comment to the top!
Same but so can look at in maxsurf
I'd absolutely pay for a model of Tally Ho. I know he's mentioned a couple of people have 3D scanned it for him.
At first I thought this was a pun (clever word joke) but then I saw your name and realised you were writing in a foreign language. (Respect for that.) Ships have sails, but we offer something for sale. "Sail" and "sale" sound identical. Whether you intended a pun or not, it made me smile. :)
@@anwalt693 English is my first language and I didn't notice that
As a mere electrical engineer, I’m impressed by this work and the models you both have presented. You are an excellent educator too, Leo.
As an aerospace engineer I found this a very well done explanation. Afterall, water and air are both fluids and this is fluid dynamics. Great you have a navel architect to verify everything, too. I'd like to see a similar presentation on the sails and rigging when the time is right.
I've been a Patreon since you offered us that chance to support you and feel it is a worthwhile donation on my part. Keep up the good work.
ERAU AE here, and I'm impressed Leo can explain the theory so clearly.
Navel architects design belly buttons. Naval architects design ships and boats. :-)
Any man who has cut an umbilical cord can call himself a navel architect.
Well, here's a concurring aerospace engineer and navel architect 😁👍🏼
Hey-thank YOU I have no resources to contribute. People like you have kept this beautiful project going.
I love the paper modelling, Leo!
It's real nice!
any episode with your architectural cut out animations is solid content dont apologize. this was very informative and props for finding a way to get an episode out while on vacation i figured we would not see anything while you were gone.
Agreed! He could do a whole series like that just explaining sailing physics and other nautical concepts the same way and get a lot of traction.
Those details are part of the reason your channel continues to fascinate.
When I was in Engineering School every student had to take two courses: Vector Statics & Vector Dynamics. This is basically what you are showing in this video. It has never failed to amaze me how useful the study of vectors would wind up being, and how often it comes up.
Finally, my weekend is complete! I can stop going through Leo withdrawals. I would think that these calculations are very important for racing.
do you fancy him then ??
@@brian.7966 What do you mean "fancy him"? I find his videos addicting and love the work he is doing to Tally-Ho.
@@brian.7966 come on now you know what he means🤣
I'm not sure about "proper" racing yachts, but in the RC world for most of the established classes the hulls and weight are very similar to eachother now we've found the "ideal" setup, and most tuning actually comes from the size and shape of the keel fin (and to an extent the sails, but i'm not really experienced enough with the maths there yet)
Brian always Cracking one off.
Early last week, someone mentioned this series on a thread on The Hull Truth, and I looked it up. Over about a five-day period I have binge-watched almost all of the 125 episodes. The craftsmanship here is amazing, and the episodes are fun and educational. I am dealing with some of these calculations now as I figure out where to place batteries, fuel tanks, and etc. on an 18.5' fiberglass fishing boat I am rebuilding. I especially like the episode about using the Live Oak from Georgia. I live in Brunswick, and the Oak used for the USS Constitution (Old Ironsides) was cut from Gascoigne Bluff here on St. Simons Island. Definitely subscribed and hit the bell so I don't miss any.
Loved this episode.... What made me chuckle was how similar an approach I used in ascertaining the CoG for a very large rocket (Reliant Robin Space Shuttle - there's a vid on my channel somewhere). Dervied from this you can also ascertain the Inertia of the vehicle too, this is important in ascertaining whether it manouevres like a cow or like a ferret! In aeronatics we use the centre of Pressure Cp (opposed to the Centre of bouyancy). We used a Wind tunnel for this. Thereafter You have most (not all) of the data required to develop a simulator to characterise the flight of the vehicle, design it's thrust lines, mass/location of ballast, simulate failure, wind shear characteristics etc. etc. In a simliar fashion just like you are doing here etc. etc. Great Stuff Leo. ABSOLUTELY love your work!
:)
That was a really cool explanation. Many thanks to Jack for his hard work.
These technical vids about boatbuilding are what make this series extra unique! There is sooo much calculation involved. And you don’t see that once the build is complete. But it can make you crazy for sure!
Leo, As you go forward into the interior design and mast design please continue to discuss this idea around centerlines as part of conversation. The more technical side of the final build is very interesting. Great stuff.
What the heck? It's Sunday. I'll take it!
Same
Most sailors I know are also largely uneducated on this technical side of boat design. We just always assume the weight/center of gravity should be low as possible to keep the green-side down 😄. Thanks for the dope slap!
yup learned ... high winds ... lower down rougher ride ... but less tippy ... lower winds higher up smoother ride ... a bit more tippy but more comfy ... nice to know
i am not sold on the theory that the sails need the heeling to have the right shape, but i totally agree unnecessary weight is bad in light winds.
Schutt Rostig yeah I was confused on that point too. I know for the old J class boats the overhangs were so extreme because the waterline length was set but not length over all and by heeling over hard they’d increase the hull speed. But I don’t really get why, outside of that one context. you’d sail poorly in light wind with a stiffer boat.
@@schuttrostig5729 It's very much borne out in practice, when the breeze is just a few knots. Look at Olympic dinghies in light winds, the helm will be lying along the lee gunwhale, and a good way to get yelled at on a bigger boat in a competitive drifting race is to start to move towards the high side unless your job absolutely cannot be done from leeward.
On boats of any size, gravity will cause the sails to drop to their cambered shape if there's 5-10 degrees of heel. Sitting bolt upright, the sails will lazily flog between opposite cambers, meaning that they can't develop enough drive to build up steerage way (essential for constant sail trim) or - just as important - to build the apparent wind which is the key to sailing in very light winds. It's a fragile process of bootstrapping, and even when the sea is dead flat (in which case shifting the crew to leeward might be enough), a certain leeward heel is essential.
@@Gottenhimfella Ok, that does make sense. So i understand there can be reasons to have the weight not as low as possible.
Loved the technical talk. Not a sailor or boatbuilder, but am fascinated by the technical aspects of this rebuild. It's been a bit like taking an online lecture. Just excellent!
Excellent video Leo. Took me back to when I was doing my mechanical engineering degree in the late 1970s and we shared some of our classes with the Naval Architects who in those days before widespread computer aided design were learning how to do those calculations the hard way, using calculus to determine the areas and volumes of sections of the hull. Nowadays the tools make lighter work of the lifting but the thinking is a real as ever.
I have been an aircraft mechanic and inspector for 40+ years and just getting into sailing. I found this video fascinating and will wait eagerly for the next installment
As a professional builder, I found this to be extremely interesting. So much more than most people realize translates between building a floating body and a land bound one. Great video Leo!
Oho! Very interesting! Speaking as a ludicrously top-heavy woman who's been mocked and ridiculed ever since she left school for her... um... high centre of gravity [10 stone, 5'6", NN-cup...☹️], I love the idea of being able to describe myself in pukka nautical terms as 'tender'.
Also 'squishy'.😁
:-D
I guess if your a AA cup..your very stiff😄😄
Get some lead soled shoes and you'll be fine.
Lovely job explaining boat stability to this old engineer. Your narrated animations and drawings always make things crystal clear. Watching the center of bouyancy migrate around as she heels over was a real Aha moment for me. so cool . I'll be working the terms stiff and tender into conversations at every opportunity. Albert is up there smiling from the great beyond but only slightly chagrined that Tally Ho will be better than ever.
We are really privilaged to have this level of detail and engineering for us more ignorant yachtsmen. Another quality video. thank you!
I used to watch the Deadliest Catch and saw the episode when Capt. Sig was informed of the sinking of FV Destination and death of his friend. At the end it was determined that the boat had a bit too many cages high up and they had iced and moved the center of gravity so far up that the boat overturned and sank.
Yes. It can happen within half an hour of the start of buildup. The water is 32, the wind chill is colder.
I believe that also prompted Sig to have the Northwestern surveyed and a new stability study that prompted changes in his gear load.
thanks that's interesting. so they managed to locate the wreckage and reach that conclusion?
@@cliveramsbotty6077 Why would they need to, the ICE MELTED WHEN IT SANK
@@cliveramsbotty6077 There was a sister ship of the same construction & design. Simple stability tests (moving weights on deck) showed the actual margin of stability was far smaller than originally planned. The expected icing rate, combined with the larger/heavier pots made the math impossible to contradict.
Fantastic explanation and graphics. While I didn’t know the terms before today, “tender” and “stiff” make sense to me as a mechanical engineer, akin to the natural frequency of a spring-mass system being proportional to the square root of stiffness divided by mass-so long as the mass center stays below the buoyancy center. Also, the longer the moment arm between those two points, the better the boat’s ability to right itself. Thanks for sharing, Leo!
I can’t believe it’s been 125 episodes.
Love your show. Best channel on RUclips.
Fascinating description. When I was required to get my forklift license, we had to learn about the stability triangle and how moving the centre of gravity outside of this triangle means tipping over your forklift.
Nice explanation. As a sea captain on cargo ships long ago I had to experience a particular stiff boat many times. One leg stood out. We loaded full containers in New York and Miami and dropped them off in a few places in the Caribbean, Barbados being our last port south. The return trip from Barbados to New York was almost all empty containers, and far too much stability. Being the open water crossing, we always rolled too fast side to side. Very uncomfortable. Three four day of this always made you very tired. (Greetings from Anacortes.)
Well Leo you don't have to apologize to me for the detailed explanations and calculations that are involved in boat stability, these calculations are rather important. I find this topic very interesting I know its important stuff that is if you want a sea worthy vessel that will be fuel efficient and safe to sail. Thanks for including this in educating us mere mortals in the technology that goes into the design and stability and sailing performance of Tally Ho. cheers have a good one Leo.
Impressed with your LGI (Leo Generated Images) in your explanation.
Important part of re-building TallyHo… do not underestimate the math involved in this kind of project. Excellent as always TallyHo crew ✊
Merchant sailor here, calculating the stability of the ship before, during and after cargo operations is normal routine.
You pretty much nailed it. Ofcause there are more factors in play as you said, but this shows and teaches the basic understanding really well.
Edit: Im very happy that you mentioned that displacement is equal to the vessels weight.
One of my pet peeves is people calling the GT as the weight of the ship.
I usually don't like videos that are mostly talking, but you made this very interesting. Thank you
Wonderful episode. The challenge comprehended by the the goal to restore not just a boat, but it's sailing characteristics. Cool.
Your family must be so proud of you. What a pleasure it is to see someone recognize the value of something from the past and care enough about it, to try to restore it in both function and beauty. Your illustrations are a great enhancement to explaining difficult concepts. Congratulations.
As always having an expert on hand is an excellent idea, he certainly knows his stuff.
The technical discussion here is really excellent. Experienced sailors will have picked it up, one way or another, but for someone like my wife, who is intelligent and interested in sailing but not fully knowledgeable, this kind of information helps to put the knowledge she has into a more meaningful context.
I want to elaborate a bit about the dynamic nature of buoyancy and mass. For simplicity, Leo mostly dealt with the static effects, hinting however with his references to stiffness and tenderness that something dynamic emerges once dynamic forces like wind come into play.
Mass distribution can have a meaningful effect on how a vessel handles in a seaway. It's the same principle as a pendulum: the more you concentrate mass in the ends (for example heavy anchor and chain in the bow, heavy engine toward the stern) the more forcefully the vessel will tend to pitch rhythmically, ploughing or wallowing along instead of maintaining a steady trim. If this becomes a problem, to some degree the point of resonance can be tuned by moving cargo or ballast toward or away from the ends. Usually you want to keep the ends light.
The same pendulum effect takes place with mass distribution in the vertical direction. Described as "top hamper" when excessive, any mass concentration toward the masthead will tend to make a vessel roll more forcefully in a seaway.
With gaff rigs this dynamic effect has to be taken into account early in the design. There isn't as much mass aloft in a marconi rig, but it still excites interest among performance sailors to change from wire rope to synthetics in order to shave off a bit of excess weight. The boat may feel less tender yet more responsive as a result.
Then there's the matter of dynamic buoyancy, wetted area, and waterline length. It's a big subject and I don't claim to fully understand it, but I think its existence is worth noting at least, because the effects of hull shape can be so profound.
Consider a floating sphere with a fixed weigh somewhere off center inside it. That sphere will of course tend to right itself with the weight at its lowest point. But it will also roll very easily because nothing but the position of the weight is resisting the roll dynamics. Put the weight exactly on center and the sphere will roll dizzyingly. It has zero righting moment, zero stability. Any other shape but a sphere will tend to right itself through buoyancy. A more ellipsoidal or dish shape has positive buoyant stability. A more conical shape than a sphere has negative stability.
We somehow end up with ballasted keelboats which have some turn to the bilges, sometimes considerable rise, sometimes nearly flat bottoms, sometimes considerable overhang in the ends and sometimes none.
Subtle differences in shape will make a hull stiffer or more tender at different degrees of heel. And different degrees of heel may significantly increase the waterline length of the hull, increasing its hull speed as well as the buoyancy of the ends. It's fascinating how much is going on dynamically as a result of choices in static hull form.
I really enjoyed that, thanks. I've built some small boats where all that work is done by a designer, and any changes were done by instinct and experiment. it's great to get a workman like perspective on the theory.
What a wonderful demonstration of calculating efficiency as it determines ballast placement. What I didn't understand was why sail efficiency likes a bit of heel . Thank you Leo for such a detailed understanding about how a boat might be blasted.
The narration combined with the moving drawings did a fantastic job of explaining the concepts you shared. Excellent work!
An exemplary presentation of a fairly complex matter! I’ve made my own interpretation of Tally Ho in 3D using Sketchup, and in order to find the floating lines I used the same procedure of building a spreadsheet giving me an estimate of the center of gravity. To assess the center of buyancy I used rough models in 3D giving me the volume of the hull. Combining the calculated weight and the volume I then found the place of the buyancy center for 0 degrees, 15 degrees, 30 degrees and 45 degrees of heeling. Not being an engineer, nor having done any kind of this work before I was really looking forward to this episode and I was not disappointed because the methods described by Leo very much looked like the methods I have used. I am posting a drawing of my version of the Tally Ho on the Tally Ho Facebook group shortly.
I'm not a sailor though I've always been interested in boats. I found all of this episode very educational so thank you.
If you have a body of water around you even a small lake, buy yourself a small sailboat, 12-16 feet or so! Super easy to learn and so much fun, I had never sailed in my life bought a boat and just went out and had fun
Your naval architect is solid as stone! LOVE to see all this detailed effort - Tally Ho will live for a thousand years!
Love this! The serious problem solving of boat building is so great to watch. In my opinion, I prefer this content to just montages of some work being done. The lofting episodes were so great to set up the framing episodes, can’t wait to see progress after this.
Fascinating. I've never even met a naval architect let alone being privy to all the detail of the obviously valuable contribution that they make to the all important stability issues with a sailing vessel. Thanks for this detailed insight into this aspect of boat building.
Great video! Love the very clear diagrams as well. I now see the advantage of having "loose" internal ballast as you can be there at the end of the build and just position where and how much inside until the boat "sits" right. It is really hard to do that before hand, but once you are in the water, it is much simpler.
Thanks Leo, I was beginning to get Tally Ho withdrawals. I binged the whole series again, but in the end it doesn't compensate for the new fresh video, which is a remarkable topic.
Absolutely great video! Great explanation of the principals. I'm glad that the balance of the boat worked out so well for you and that there were no surprises. It's amazing to me how Albert Change and his contemporaries figured this stuff out manually 112 years ago!
GREAT - GREAT - GREAT! Never too old to learn something new in this life. Pete 78 years young - Somerset, UK
The professor at his best, helping even a dunce, like me, to understand just a bit of this stuff.
Your little illustrations are golden bro!
That was an amazing summary of naval engineering principles. I was blown away. This was an awesome one, Leo.
That was a fascinating insight: the characteristic of the original's sailing performance should be maintained. As a landlubber carpenter and builder, it wasn't something I had considered while watching this series, but this video was very informative. Great! Still the best show on youtube
Any understanding of the build is allways a good thing. Glad you're vacation was good.
Very nice explanation of the factors in boat stability. Thanks Leo
Very interesting Leo. Great to see what is involved in making a vessel sea worthy. I'm a flyer and we are always concerned with weight and balance of the airplane. Obviously, the same concerns are at play in an ocean vessel only in rather different ways. Good to see real professionals at work. Cheers
For "center of buoyancy", read "center of pressure". Glad he doesn't have to venture into the thrust and drag vectors.
When I looked the title of this EP I was sure I would not be able to follow you. I was wrong. The way you explained the process was simple, logical and easy to follow. Thank you Leo
Leo, glad you got to go home and visit family. And, very glad you're back safely. I have enjoyed every video, especially the technical ones.
You know as I have watched your videos and the construction of TallyHo I am constantly amazed at your depth of knowledge in every aspect of the construction of TallyHo. You sir are way more intelligent than you give yourself credit for and much of your knowledge includes older “knowledge” not just new technology. Well done.
Hey this would be a GREAT video for Doug at SV Seeker to watch! Oh... wait.... er.... um........
Excellent graphics and presentations it made the problems of centers of gravity easy to understand
Now I am happy, seeing another episode with Leo and Tally Ho is great therapy to start a working week. Thank you!
Very interesting discussion that was perfect for me as a non-techy marine engineer. Obviously of vital importance in her stability but this put some words and principals to it and how it's done.
This was way easier to understand than the "lining off" of the hull for planks.
Stiff boats also place extremely high loads on the sails and rigging.
A very sound observation, hopefully your comments will help people prevent damage.
It's nice that you put as much effort into visual aids and explaining hard to picture concepts. Keep changing the job title "sailor, boat builder, film maker, educator". Probably throw cook and mechanic in there as well
You presented this brilliantly! I especially like your reference drawings accompanying the explanation. Well done - again!!
I enjoyed the explanation of the points of reference and issues.
I hope while you were home I hope you got to see your lady friend, Checka, I think was her name?
Anyway, I hope you two are still together and everything is well. I miss her in your videos. She made it feel more like a home/family project and not a work job.
Talking is good. I get a great education and feel involved in the conversation. Keep it up. Don't apologize.
Welcome back, Leo! This was a fascinating explanation of the charcteristics of sailing vessels. Very well done (as always.)
No worries Leo; this episode was not boring at all, in fact it was fascinating! Welcome back, hope you enjoyed your vacation!
Welcome back Leo! Great to see things back in swing, and very glad you were able to get some much needed down time!
I for one, do not mind a but of tech talk. It brings a much clearer picture of what a vessel is doing on the water and the forces that are in play. Very fascinating!
I was told years ago (probably before much of the 3d modelling) that, at least initially, boats rarely sat exactly on their designed waterline. It may be that the ballast approximation on the original drawing was intentional to allow fine-tuning later.
I didn't understand all the maths but the explanations and the diagrams with the movable centre made sense. I feel I have learnt a lot. Thank you.
WOW ! AMAZINGLY INTERESTING !! As my buildings stand relatively solid on the ground, I’m an architect, this video was sincerely eye-opening thank you very much !!!
Skyscrapers can be immensely affected by wind pressures acting on design features
e.g. the "square" shaped building with a corner as the "leading edge" always turned into the prevailing wind...
causing vibrations and twist in the building?
@@JohnSmith-yv6eq - Tall buildings especially must be designed as objects in a wind environment, where negative pressure can suck the outer skin & windows off the frame, & systems meant to circulate interior air can be bollixed by exterior winds. Indeed, a new skyscraper can have unplanned effects on the wind environment of its neighborhood.
Great work with the digarms explaining a complex idea.
Excellent video! Didn’t mind at all that it was more “talky”. Also, I thought I was pretty well versed regarding sailboat stability, CG vs center of buoyancy, righting moment, etc… but I learned something! As a racer of modern sailboats, I have always assumed that “the stiffer, the better” (hold the “that’s what SHE said” jokes please). I never thought of the negative effects of too much stiffness on the motion of a boat like Tally Ho, as well as on her light air capabilities. Great stuff!
I sailed A-Class catamarans for many years and stiffness is good when the complete boat is lighter than the sailor. Your body is movable, infinitely tunable ballast.
If a boat's too stiff longitudinally, then you'll get jerky motion when sailing up wind and that disrupts the airflow over the sails and you lose lift. You can effect the stiffness by the way the buoyancy is distributed along the hull. Lots of buoyancy up front gives a smoother ride in a very light boat like an A-Class. Looking at Tally Ho's situation is very interesting to me.
It's a very complex subject and heaps of fun for young and old trying to get the optimum balance.
Another top notch Tally Ho video production. Leo your explanation of the weight and balance using the paper cutouts was excellent. Thanks for pulling this episode together. I found the content interesting and it really is the foundation of producing a stable sailing craft. Cheers!
Excellent episode! It wasn't mentioned, but would you not want to position fuel and water tanks close to the longitudinal CG so that the longitudinal CG does not change much as you consume fuel and water? I am an aerospace engineer familiar with aircraft design, and this is a stability issue there. Don't know whether it's considered sensitive for small sailing craft.
I'm trying (and failing) to imagine the genius needed to do this work before computer modeling was available. Even with it the level of detail is mind blowing. Thank you again for sharing this level of explanation. For those of us with no experience with anything like this it is eye opening and mind expanding!
Heh Leo, I know that you know that the folks who watch this series and your project hang on every word technical or otherwise. So never an apology needed. You could literally do 60 minutes on head design historical and modern in relationship to your choice for the Tally Ho and you would get in the high ninety percentile of watch minutes. We love, I'm going to go there, we love this project, we love your style, your attention to detail, your work ethic, your clear concise explanations, the light hearted, diligent, dedicated comradery of your crew. You are a man among men, a mensch in a world that celebrates the mere utterances of the ridiculous. Your steadfast perseverance is exactly the balm needed for my soul weary of the charlatans who abound.
Well said, FLA.
As a retired aerospace engineer I echo R. smith observations of your video. Just like a ship, airplanes deal with center of gravity and center of lift. Your definition of stiff and tender in roll are identical to Lateral stability of an airplane. This parameter is adjusted by wing dihedral primarily and tail size secondarily. Like you mentioned you can have too much roll stability. I am sure if transport aircraft had high stability, the high frequency oscillation would not do well with meal service. Kudos and keep ‘‘em coming.
What a brilliant explanation, so clear and good use of visuals.
Very much enjoyed yours and Jack's detailed explanation... got most of it first time but I did have to rewind on a few occasions to get it into my layman's brain. Hope you had a nice visit back home Leo as friends and family are everything in these trying times. 🇬🇧
Very interesting and clear explanation.
clear as mud.
@@brian.7966
One should always keep a balanced view..
Hugely interesting explanation of a complex subject. Thx a million.
Most interesting and informative - well done Leo. I, like most uneducated sailors, thought lower center of gravity was best.
Thank you Leo for the update. Good to see you back. Enjoyed the explanation on determining the various aspects that affect the sailing characteristics. Have a productive week ahead.
200 years ago Herreshoff & Fife made all these calculations with pencil & paper, just shows have clever these guys were.
Unbelievable how this was all done without the benefit of modern tech!
I've done complex mass property studies with pencil and paper of axial compressor and turbine assemblies (whirling speed analysis). Just before computers took the graft away. It gets really tough when calculating the stiffness of each chunk, before the days of finite element analysis.
Something about apes and typewriters....
They had slide rules too...who made those?
I found this video probably more interesting with the quick lesson you gave in working out pretty much the center of gravity ( all directions ) vertical and horizontally , What an epic journey you have brought us all on so from me here in Dublin Ireland to all the Tally Ho family best regards and now onto the next episode ( this is my version of my wifes soaps for me ) so im so looking forward to the future still a long ways to go BUT who cant wait for her first hull wetting and all the good stuff leading up to that,, Take care mate 🙂
Thanks Leo, fascinating to compare with aerodynamic stability which is reasonably familiar to me.
Didn't know about the heel angle, not being a sailor...
Looking forward very much to mast and spar construction.
Great topic. I opened the thumbnail with great enthusiasm. Fascinating! Thanks for including this aspect Leo. Of several builds I follow, yours is the most rewarding. In terms of information and it's application to my own project , for example. There must come a time when the subject is enjoying the spray and the wind in your sails.
One of the best video that you have done. Go to college Nav Engineering. You will turn out one of the best. Never is to late. Your further explanation of both centers in a vessel was excellent. You are a perfectionist. Good job
What more beautiful gift for my birthday than watching a video about Tally Ho's boat stability! Thanks Leo!
Happy birthday 😊🎂
@@Linusgump Thanks! 👍
Are you planning on doing any inclining experiments to validate the computer modeling? This was a nice revist of the elective Naval Architecture class I took in my ME studies. Back in the late 80's the computer support wasn't as polished as what Jack is using. We did a WWII Liberty Ship as a project and doing all the analysis was pretty laborious! Great job as always!
Thank you for sharing some of the science behind ship building. Very interesting.