Stability Calculations (Boatbuilding / Tally Ho EP125)

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EPISODE 125
This episode may not be for everyone - It is all about the basic theory of sailing boat stability, and the details of the stability calculations that we have done to ensure that Tally Ho floats properly to her designed waterline and maintains her original sailing characteristics.
I’ve been back in the UK for a month and no physical work has been done on Tally Ho during that time, so this video is entirely dialogue and diagrams! However, this less glamorous work is extremely important for authenticity and sailing performance.
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Music;
Uptown - Topher Mohr and Alex Elena
125. Stability Calculations (Boatbuilding / Tally Ho EP125)

[@jorgenr]

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 :)

[@etlapin2244]

Take this comment to the top!

[@abyssaljam441]

Same but so can look at in maxsurf

[@aristotles-lantern]

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.

[@anwalt693]

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. :)

[@abyssaljam441]

@@anwalt693 English is my first language and I didn't notice that

[@yallaimshi8091]

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!

[@johnmooney9444]

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

[@frederickstibbert7389]

Another one of his admirable qualities - Leo is not at all shy of asking for advice when sailing in unfamiliar waters !

[@peterhall6656]

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.

[@stephenshort839]

Newton was a genius after all.

[@vibratingstring]

Well...then we have the cod's head/mackerel tail theory, then the waveline theory of JS Russell, etc. I think we've made a little bit of progress since Newton, LOL

[@aserta]

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

[@abyssaljam441]

Naval architecture is properly done with rules of thumbs and overenginerring

[@mrbfox1775]

What you have been Seeking for

[@Mark-zi4dd]

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.

[@loloaqici82qb4ipp]

@@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.

[@calholli]

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.

[@rcs6401]

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.

[@thomasbecker9676]

ERAU AE here, and I'm impressed Leo can explain the theory so clearly.

[@pauleohl]

Navel architects design belly buttons. Naval architects design ships and boats. :-)

[@SilasMoleCatcher]

Any man who has cut an umbilical cord can call himself a navel architect.

[@BluesAlmighty]

Well, here's a concurring aerospace engineer and navel architect 😁👍🏼

[@edwardschmitt5710]

Hey-thank YOU I have no resources to contribute. People like you have kept this beautiful project going.

[@tombrown9460]

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

[@kevint1910]

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.

[@danokeefe7116]

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.

[@dannyarcher6370]

I love the paper modelling, Leo!

[@NoiseMakerX]

It's real nice!

[@thomasdavison8996]

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

[@brian.7966]

do you fancy him then ??

[@thomasdavison8996]

@@brian.7966 What do you mean "fancy him"? I find his videos addicting and love the work he is doing to Tally-Ho.

[@ryno9732]

@@brian.7966 come on now you know what he means🤣

[@roseroserose588]

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)

[@yepyep340]

Brian always Cracking one off.

[@EleanorPeterson]

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'.😁

[@leifvejby8023]

:-D

[@2nickles647]

I guess if your a AA cup..your very stiff😄😄

[@miheadhurts]

Get some lead soled shoes and you'll be fine.

[@michaelmclaren7373]

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!

[@0623kaboom]

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

[@schuttrostig5729]

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.

[@DanielWebbon]

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.

[@Gottenhimfella]

@@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.

[@schuttrostig5729]

@@Gottenhimfella Ok, that does make sense. So i understand there can be reasons to have the weight not as low as possible.

[@kurtwerner4258]

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

[@ThatOldMan2112]

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.

[@DhulstDirk]

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.

[@westpacificmarketanalytics2384]

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.

[@damianhall4554]

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! :)

[@PatNetherlander]

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!

[@cyclingbutterbean]

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

[@henrylucas8780]

Same

[@ciberbri59]

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.

[@bmunday]

We are really privilaged to have this level of detail and engineering for us more ignorant yachtsmen. Another quality video. thank you!

[@r.p.3192]

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

[@quietwarf1019]

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

[@michaelc.3812]

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.

[@asakurad]

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!

[@runningray]

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.

[@apollo5751]

Yes. It can happen within half an hour of the start of buildup. The water is 32, the wind chill is colder.

[@radamus210]

I believe that also prompted Sig to have the Northwestern surveyed and a new stability study that prompted changes in his gear load.

[@cliveramsbotty6077]

thanks that's interesting. so they managed to locate the wreckage and reach that conclusion?

[@apollo5751]

@@cliveramsbotty6077 Why would they need to, the ICE MELTED WHEN IT SANK

[@YouveBeenMiddled]

@@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.

[@millwrightrick1]

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.

[@dlb603]

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

[@randrew89681]

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!

[@malakai651]

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

[@mdouglaswray]

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

[@jdwxly]

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

[@colinsutherland8965]

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.

[@SportSoulLife]

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.

[@johnraymond7189]

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

[@andrewcarter1599]

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.

[@haroldshawhan3917]

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

[@mvalexandra2230]

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.)

[@thomasutley]

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!

[@fonhollohan2908]

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.

[@thomaswaldorf9141]

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

[@cliffstevenson5773]

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

[@NikkiN777]

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.

[@AustNRail]

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

[@philipbrailey]

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

[@douglasfrank9323]

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

[@Marts1499]

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

[@jimmcdonald9244]

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.

[@georgewoodzell1315]

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

[@burgle66]

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

[@oldwillie313]

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!

[@bsauve2669]

Your little illustrations are golden bro!

[@robertcarkeek8391]

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.

[@floridalifestyleapparel5477]

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.

[@alexandermenzies9954]

Well said, FLA.

[@kadover732]

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

[@peteturton2307]

GREAT - GREAT - GREAT! Never too old to learn something new in this life. Pete 78 years young - Somerset, UK

[@cuzinevil1]

In 100 years, I hope there will be someone who loves Tally Ho as much as Leo does now. Good catch with the fuel tanks.

[@silasmarner7586]

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

[@bruderbro907]

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.

[@davidc6510]

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!

[@banba317]

No worries Leo; this episode was not boring at all, in fact it was fascinating! Welcome back, hope you enjoyed your vacation!

[@rjenglan]

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

[@LiftRanger]

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.

[@fordcortina3730]

Great video Leo. I am a warship Naval Architect. I was surprised to see in Jack's weight spreadsheet that he does not account for the TCG (Transverse Centre of Gravity). Whilst the chance of weight being far off the centreline in a V shaped hull is limited, the position of 'heavy' items such as the head(s), the washing machine, cooking equipment, etc needs to be checked. Even a small TCG off the centerline will result in heel and trying to fix it requires a relatively large amount of ballast as the lever distance is low (that is if the ballast is positioned in the bilges). You cannot assume that the TCG will be on the centreline and it should always be checked.

[@petertrollejakobsen7681]

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.

[@nigelprendergast2595]

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.

[@frankstocker5475]

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

[@bridgetcastle7102]

Unbelievable how this was all done without the benefit of modern tech!

[@984francis]

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.

[@thomasbecker9676]

Something about apes and typewriters....

[@carlvandenberg140]

They had slide rules too...who made those?

[@tomnietz4158]

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.

[@howiesmith120]

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

[@matthewsellers82]

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.

[@tomoakhill8825]

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 !

[@frederickstibbert7389]

Another important aspect: Leo is not at all shy of searching out expertise & asking for advice, whether to double-check a decision he's made or when he's exploring unfamiliar waters.

[@propulsar]

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.

[@randomix4023]

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

[@Linusgump]

Happy birthday 😊🎂

[@randomix4023]

@@Linusgump Thanks! 👍

[@Linusgump]

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.

[@Utahdropout]

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

[@benters3509]

For "center of buoyancy", read "center of pressure". Glad he doesn't have to venture into the thrust and drag vectors.

[@jeffreynelson3294]

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.

[@mattevans-koch9353]

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.

[@jacquesicard6200]

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

[@felipep.4022]

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!

[@roadie3124]

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.

[@StephanieElizabethMann]

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.

[@buildingourdaydream9804]

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.

[@mikebattis8684]

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!!

[@wisedupearly3998]

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

[@robinalbert9028]

A very sound observation, hopefully your comments will help people prevent damage.

[@ApexWoodworks]

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.

[@baukejoosten]

Yeay, you're back! My weekend feels complete again. Enjoy guys!

[@chrishalstead4405]

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

[@robertmiller9687]

Ohbmy gosh! I thought I was going to have to wait a lot longer for another episode!

[@mcpheonixx]

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!

[@vlf126]

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 🙂

[@Ydnar6929]

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

[@billywhizz6483]

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

[@Nomad5d]

As an aerospace engineer, I found this to be an excellent discussion about sailboat design.

[@jonmassey8124]

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. 🇬🇧

[@madrew2003]

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!

[@lespr52]

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

[@papawheelie5835]

Fascinating stuff. Having had mostly powerboats in my lifetime, it's nice to hear these principles discussed in a way that has shed light on the character of each vessel's memories. Some are rather a handful and others just seemed like a breeze to operate. Well presented!

[@ladamyre1]

Finding it hard to wait to see those cover boards fitted. That deck is gonna be a beautiful thing to behold, especially with that hatch cover you've saved on top of it. Still this update on the new "weights and measures" of the rebuild was yet another example of why I love to watch your classes on wooden boat technology.

[@whereistheedge]

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 !!!

[@JohnSmith-yv6eq]

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?

[@frederickstibbert7389]

@@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.

[@markgreen7701]

I sure hope Doug over at SV Seeker watches this video...

[@proto57]

But it's far too late to do any good. The problems with that build are already built into the boat in ways that are probably not fixable, without hauling it and adding blisters, or cutting off and moving the keels, etc.. For one thing, as Leo points out, the port/starboard CB and CG are assumed on the center-line of any boat. Boats are supposed to be symmetrical on end view. But the Seeker inexplicably lists something between 4 and 6 degrees to port (I think it is to port). My guess is that this is because of the massive twist of the boat, which makes it NOT symmetrical from side to side. Not sure that is even fixable. It would take tons of internal ballast if possible to do, and the boat already sits something like a foot or more below its waterline. But it is about 40% over its "designed" displacement, and adding more will only add fuel to the unstable fire. Watching this video is too late to fix the unfixable Seeker. What should have been done is watch other videos, and maybe read a book or two, before folding it up and welding it, at the very beginning.

[@ericfrancis7816]

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

[@jackrichards1863]

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.