Stability Calculations (Boatbuilding / Tally Ho EP125) 

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 :)

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.

Refreshing to see actual boat building. Properly done, with math and knowledge.

I love the paper modelling, Leo!

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.

Those details are part of the reason your channel continues to fascinate.

Finally, my weekend is complete! I can stop going through Leo withdrawals. I would think that these calculations are very important for racing.

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!

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.

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'.😁

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.

What the heck? It's Sunday. I'll take it!

That was a really cool explanation. Many thanks to Jack for his hard work.

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.

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.

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.

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.

Important part of re-building TallyHo… do not underestimate the math involved in this kind of project. Excellent as always TallyHo crew ✊

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! :)

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!

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!

The professor at his best, helping even a dunce, like me, to understand just a bit of this stuff.

I can’t believe it’s been 125 episodes. Love your show. Best channel on RU-vid.

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

Impressed with your LGI (Leo Generated Images) in your explanation.

I'm not a sailor though I've always been interested in boats. I found all of this episode very educational so thank you.

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!

Your little illustrations are golden bro!

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.)

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!

As always having an expert on hand is an excellent idea, he certainly knows his stuff.

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 usually don't like videos that are mostly talking, but you made this very interesting. Thank you

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.

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 naval architect is solid as stone! LOVE to see all this detailed effort - Tally Ho will live for a thousand years!

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.

Wonderful episode. The challenge comprehended by the the goal to restore not just a boat, but it's sailing characteristics. Cool.

Hey this would be a GREAT video for Doug at SV Seeker to watch! Oh... wait.... er.... um........

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.

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

That was an amazing summary of naval engineering principles. I was blown away. This was an awesome one, Leo.

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.

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.

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

Welcome back Leo! Great to see things back in swing, and very glad you were able to get some much needed down time!

Any understanding of the build is allways a good thing. Glad you're vacation was good.

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!

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.

The narration combined with the moving drawings did a fantastic job of explaining the concepts you shared. Excellent work!

Welcome back, Leo! This was a fascinating explanation of the charcteristics of sailing vessels. Very well done (as always.)

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.

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

Now I am happy, seeing another episode with Leo and Tally Ho is great therapy to start a working week. Thank you!

You presented this brilliantly! I especially like your reference drawings accompanying the explanation. Well done - again!!

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 🙂

Leo, thanks for taking this topic on! So many questions addressed and many brought forward

200 years ago Herreshoff & Fife made all these calculations with pencil & paper, just shows have clever these guys were.

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.

Absolutely fascinating! Love it when you go into the technical details of boatbuilding and sailing.

Extremely informative and interesting info to hear, Leo! Thanks for sharing it with us, and I'm happy that your visit to the UK went well.

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.

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!

Love your work and approach. Can't wait to see deck finished.

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.

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.

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.

Really interesting show today. It's fun to hear things explained, which make great sense and validates experiences I've had with sailing different boats. thanks!! Weil done!

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 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.

Fascinating. Thanks for sharing. This is a very important part of the build and an eye-opener for most of us I suspect.

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!

Stiff boats also place extremely high loads on the sails and rigging.

Thanks Leo, that's a brilliant explanation and if I had known all this when I was young, I probably would have sailed differently! ❤️❤️❤️

THANK YOU for this! Definitely understandable and well-presented, especially the pinned ship and cg/cb markers - brilliant.

What more beautiful gift for my birthday than watching a video about Tally Ho's boat stability! Thanks Leo!

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!

Great to see you -great ship can't wait to see finally product. Very happy to view your progress all the time. Create a tshirt for sale!!

Well done glad you were able to make the trip home. Great to hear the technical details of the CG, CB and GZ.

This kind of videos are also very interesting, as part of the total series. It so great to follow not just the practial wood work, but also theory and calculations. Thanks Leo!

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.

Most interesting and informative - well done Leo. I, like most uneducated sailors, thought lower center of gravity was best.

I learned much, for that and your videos... I'm very grateful! Continued fair weather on this great project!

Fantastic and worth the wait. Glad you got a chance to recharge Leo. These technical videos are welcome. Your mix is spot on and captivating.

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

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 !!!

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.

I always love your little diagrams! The naval architect was very informative. Can't wait for the next video!

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!

What a brilliant explanation, so clear and good use of visuals.

Great video, I personally really enjoy the insight into how things work the way they do and engineering adjustments that can greatly change performance characteristics. Thank you.

Very interesting video. Wonderful to see a bit more deeply into the design characteristics. Thank you for sharing.

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

Geeky stuff normally makes me sleepy, but this was GREAT!! Thank you 🙏

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!

Superbly presented as always. Thank you for furthering my education!

Leo is an "uneducated sailor" (1:40) in the same way I am an uneducated scientist. (I have a Ph.D. in biophysics, and thus am trained in two sciences at once.) Leo has sailed solo across the Atlantic with no electronic navigation. He has been the First Mate on a three masted sailing yacht, which means he was manager of all the deck crew. He has made 125 extraordinary videos, demonstrating supreme skill as a cameraman, film editor, gaffer, grip, best boy, ADR, music editor, and Star. He apprenticed as a wooden boat builder, and throughout these videos has demonstrated a complete mastery of wooden boat building. In addition, Leo has mentioned the administrative side of this operation a couple of times. He is spectacular at all of the administrative tasks or this project would have crashed and burned years ago. At EP125, we are 5 years into this project and it is still going strong. Like many geniuses, Leo thinks what he does is trivial, but thinks, "what that person over there does is hard." I only support three channels and this is one of them. Leo is amazing !