The whole time I was thinking “this is way more than I need to know!” But I watched to the end anyway and learned a lot. Thanks!

@Rockingoodman

4 жыл бұрын

And I'm over hear saying out loud... tell me more, tell me more.

@tyroneshulace3203

3 жыл бұрын

That was informative. But, I was hoping for more info on . 1. How does "rocker" in hull design profile, affect dynamic drag (suction) by vertical or rocking movement of the hull? 2. How does depth of hull affect drag vs displacement? eg. comparing a "V" cross-section having the same displacement as a wide curved but flatter hull cross-secton. Taking into account wetted surface influence 3. How does hull symmetry along the hull centreline affect performance & drag? eg. What if the centerline is not along the centre of the beam but more to the outboard of each hull. Making a wider distance between the centrelines of the two hulls. 4. Are the Port & Starboard hulls both pulled from the same mold?

It would be interesting to see a chart of the slenderness ratio and all the other variables for various 45'ers, lagoon, leopard, seawind, outremer.

I think this comes down to what are your priorities. (Not disputing the analysis, the engineer did a great job of presenting the design/performance theory). Is your priority to sail as quickly as possible? Are you buying a yacht to experience the maximum sailing performance? Are you looking for maximum comfort? Are you looking for minimum draft? If you are looking for performance, are dagger boards a requirement? Etc. This seems to suggest its like Americas Cup and the fastest boat wins. For some this may be accurate, for others its more about the experience of travel and adventure. At one time on early Ruby Rose video’s I remember hearing only a monohull was the preferred sailing vessel. We all watch several sailing channels and obviously the journey is accomplished in MANY different ways. They all seem to achieve their individual objective. I have two cars. One is a GMC Suburban and the other is 911 Porsche. Both will allow be to drive from California to New York however, (and as with everything) there will be tradeoffs. For me my goal is to travel and share an adventure of a lifetime and much less about the design of the yacht. It seems to me The Wynns, UMA, SLV, Delos, O’Kelly’s etc. are all out sailing and achieving their dreams. For me this is the most important criteria.

To be straight up, I was worried about getting something less than this, dare I say it im looking forward to it now. Congrats on the new boat, sure your looking forward to it. I remember saying no rush on announcing it as long as you went into all the technical details like you said you were going to. Now you have set the bar high, keeping your word, I like it. You have me looking forward to the rest of this series. Thankyou, in depth technical stuff, if you can do this on everything its bloody awesome. Everyone else does drooling over double sinks and different fabrics and bar areas. This is what I am after myself. Thankyou Terysa for putting up with him while he delivers this content :P.

Several years ago I read a book from the 1890's on steam locomotive design and was quite surprised at how much the engineering was based on ratios. Ex. If a part for a certain function needs to be X inches long then it needs to be at least X/12 inches thick. These ratios were derived from what worked in the field and what didn't work rather than from material science and complex maths. Although we now have computers which can perform hydrodynamic calculations in fractions of a second it is interesting to me that we still use ratios when talking about the properties of a boat.

GREAT show, waiting in anticipation for the next installment of this series, learnt a hell of a lot from this episode, thanks for bringing in the naval architect to explain this in more detail

As an Ocean/Naval Engineering student, this is a fantastic exchange of information within the industry. I'd consider myself a customer more concerned with technical aspects rather than the lush and plush stuffed in.

Well done, Nick and guest! Looking forward to the next installment!

Awesome video from all parties here, very informative (and surprisingly fun) and i look forward to the others in this series.

I enjoyed the interview but the click bait pic was unnecessary.

Technical Tuesday!! WOW WAY more info than I thought I needed to know! Thanks Nick, you just made it harder for me to choose a catamaran now LOL !! Fair winds and following seas Ruby Rose!

Absolutely loved it thanks!!

Boat design simply explained! Nice. I have watched most of your reviews several times each - good detail.. thank you

Tech Tuesday ! YES ! Thanks Nick

Please keep banging on about this stuff!! And a hearty congratulations for finding the yacht for your needs! I'm a year into research for finding a catamaran for a currently non-sailing couple retiring in a few years time. Finding opinions like 'performance cruising catamaran' and 'usable living space' is easy. But, finding any detailed facts about the science behind this is very difficult. With very little digging, I can easily know almost all of the dimensions and performance specifications regarding my laptop computer and all of its internal components. And all that info for a small machine that costs only a few thousand dollars! But, it seems catamaran manufacturers expect us to spend hundreds of thousands of dollars, if not millions, on the vessels they produce, while telling us very little about what actually makes them tick. I get the feeling they hope to sell us on the romance of the adventure without wanting us to really know what the vessel can and cannot do. With all machines, I am very, very interested in what they cannot do. That knowledge is what allows us to make decisions that keep us safely in the 'can do' zone. And when buying used, there seems to be even less information available. So please do keep banging on about this stuff!

Thanks Nick, I’m feeling like a geek now :)

This is my new Favorite Playlist from Ruby Rose. So many things I am thinking about but just dont seem to be talked about in an approachable fashion. Looking forward to more.

@sailingrubyrose

4 жыл бұрын

Ah thanks mate

I love this series thank you so much!

@dallaspaul5401

2 жыл бұрын

thanks for focusing on the details

It’s 2:37 HST. I have insomnia . What a joy to find new episode. 👍😀❤️🌴

Slenderness ratio = Length / Hull Volume. The formula at 8:00 is the DLR (Displacement Length Ratio), which is inversely proportional to the Slenderness ratio. Also the SR is in SI units, the DLR in Imperial units. Since he is talking about actual numbers this is relevant.

@sethc3333

3 жыл бұрын

Saw this too

2 жыл бұрын

These statistics are for the under water portion of hulls. Very little, if any, of a cruising sailboat interior is under water. Waterline beam plus flam determines the interior more than any technical statistic.

That makes so much sense now, in fact it`s why I binned my first missus all those years ago! Over time, her slenderness ratio decreased to the point it dramatically reduced performance and as her wetted surface area increased it had a negative impact on speed, comfort etc and I had to have her bottom scraped more often. Seriously, thanks Nick, I did enjoy this first foray into the design process and look forward to more of the same , cheers easy.

@sailingrubyrose

4 жыл бұрын

🤣🤣🤣🤣🤣🤣🤣🤣 FFS Mate!

@JodyJ

4 жыл бұрын

Quality Bert lol

Are catamarans stronger in collitions? It is may impresion that if you hit a reef a catamaran is more prone to break apart. They seem more fragil with thinner hulls.

Thank you, very valuable information, waiting for the rest.

I’m not currently not a Blow-Boater but this discussion was fascinating for me. Cat’s have become more and more popular on the Power Boat scene and I am currently thinking about “next” for us and whether to go cat or Knot... (with focus on comfort versus performance) so even for a Motor Head this was an exceptional vid... looking forward to the rest of this discussion!

Great information ! Thank you both !

Prismatic coefficient!! Ha ! Now I’m off to impress my friends Thanks Nick looking forward to more

@sailingrubyrose

4 жыл бұрын

Haha. A pleasure mate

Very good wish I had this info in 89 when I started building my Simpson 12m I would have gone on a diet! Cruised it for 20 years so I must have done something right

Interesting info Nick and it's good top know these things thanks. But will the Prismatic Coefficient really be a factor to discuss for anyone buying a family cruiser, It's a bit slower but we can shower, keep the beer and wine chilled and will get less wet would be the selling point I think. I'd loved to know how they work out the position to place the mast for optimal performance, who decides that it goes further aft or toward the bow for better upwind or down wind sailing. Hopefully you will have that come up in one of your videos.

Great video, love how you get into the tech sides of the boats instead of just the shiny stuff. A discussion on hull performance rating to rig performance would be a great follow up video. Keep up the great vids!

Great information in understanding catamaran design for the uninformed. Really helpful. Thanks

@sailingrubyrose

4 жыл бұрын

Glad it was helpful!

Please continue to make these technical videos. I loved it.

This is great!

Geek Tuesday, but a great overview of the principles

This is awesome, thanks!

Beautiful the scenery is so beautiful and stunning.Very enjoyable! Reminds me of my trips where I take the good music like the Guns N Roses, Imagine Draongs or the Delta Parole and then enjoy the powerful feeling of the sea. ¡vamos!

Great stuff Nick, I always learn something valuable from these talks. Thanks, very eye opening, cant wait until the next boat show...lol...vocabulary quizzes.....hahahaha

F' me, this was brilliant! Thanks ,you guys have really stepped up your game. Signing up as a Patron.

@sailingrubyrose

4 жыл бұрын

Ah thanks mate! Happy to see you on Patron and hope to chat on the WhatsApp group

Just subscribed. Good topic, looking forward to more of the physics in design.

Tony & Susan here, Thank you so much for including us in your detailed discussions with the designer. I am kind of a geek . And am always interested in the details. Susan would love to see the interior design and colors and plates and glasses. Cheers

How to reduce the slapping of the waves against the inner haul when sailing up wind, I'm wanting to know can a double skin haul with dense padding to reduce the sound can be acheive.

My own view is that if one is after a performance catamaran stick with something over fifty feet, otherwise it's too much of a battle between narrow hulls and comfort.

Thank you very much, Nick! Quite informative and educational! I can honestly say that you were busy while in quarantine/isolation (and while waiting for Terysa to return from australia)...

But the light weight of the boat is the more the wind would take it if it’s on top of the water to less control with very strong winds to and big waves to would it just skip on top of the water ? With no control?

Thanks for the information Is good general knowledge

One of my favorite TT videos so far. Very, very informative. I, like you, want a performance cat, but what Antoine might also be saying is that if you buy a performance cat, and you try to load it the way you would a monohull, you will seriously decrease performance AND comfort, create more slamming, and maybe even hurt stability. In that case, someone who is buying a catamaran mainly as a coastal live-aboard to mainly sit at anchor/moored/tied to a dock with short island hops, might actually want one that is less suited to performance and more tolerant of heavier loads, which might mean a lower hull volume/length number, lower coefficient, etc.? What a journey we're all on here. Knowledge = enlightenment. Thank you Nick.

@sailingrubyrose

4 жыл бұрын

A pleasure mate

Great video! Thanks!!!!

The way I design hulls is to choose a fish that encapsulates the boats personality, the bottom half of that fish is now your hull design below the waterline. :)

I'd love to pick his brains myself. Great interview choice. I've always wondered what made the great clippers so fast and just what the architects of the day knew and how that knowledge is applied today.

Thanks guys. Very informative. I’d love to have some statistics of the various Seawind models over time. Any chance of getting those?

for some reason I can seem to figure out what prismatic coefficient is and how it affects performance/comfort. they showed a chart but then went on to the next aspect affecting hull performance/comfort. that being said, I've seen vids of people sailing cats and complaining that the waves "slap" the hulls or the bridge deck and now I understand why. they probably had it overloaded or design was so that the bow waves were crossing into the bridge deck and or hitting the opposite hull. (no idea what cat it was) very informative and interesting. Thank you.

Nice work on this video! I was told this series is worth a look and it sure is. I believe style on a lot of new performance cruisers is still being put before cruising function quite a bit. Immersed transoms is a great example of racing style looking cool but not functional for cruising. The wider shorter sterns with immersed transoms only offer more performance once at high speed. They are slower in light air and for performance cruising light air performance is actually more important than a few % more at the top end when your likely slowing down anyway. If you have anti foul pain on your transom you have wet heels... Mick

@nsmena

Жыл бұрын

Helo miss, i am a part of an undergraduate student team of Naval Architecture, who is participating in Ferry design compettition , we are designing a catamaran and we require the range of coefficients best for catamaran for e.g Cb ,Cp LBr e.t.c. so we request you to help us in any way you can for that. Thanks a lot.

LOVE the more technical information. It's something that seems really lacking on the net in any real organized way. Everyone just says "go read The Principles of Yacht Design" which I plan on, but it would be nice if there was an organized repository of this knowledge for those of us who learn better that way than reading whole books of dry information.

Always liked your show. I think there was a typo though. Slenderness ratio is LWL/(HVol)^1/3, the higher the faster, not the other way around. Nowadays mostly the weight+Length+sails determines boat performance. I liked seawind 1260, but the cabin ceiling too low to be comfort. Seems like Seawind 1370 improved. Looking forward to more info on pricing etc.

@SMSabriIsmail

4 жыл бұрын

Yep. There's a typo in that Slenderness Ratio slide at 7:58 . The slde gave the formula for Displacement to Length Ratio instead.

@aceventura1442

4 жыл бұрын

There is more than just that one typo which makes it hard to watch as an engineer, but nice effort for braking down the engineering side of things!

For customers that will spend big money on a Catamaran, I would think they spend a lot of time going over this type of information. But I think everyone knows most buyers just go for the boat that has a nice finish and a great sound system. The science behind fluid dynamics regarding lift and resistance in the water is the most important. Thank's for a great look into a small but complex part of Catamaran design.

2 жыл бұрын

This information is not usually readily available.

What did you use to make those handwriting animations?

Great chat. Love the geeky stuff

This is great information.

I love these videos!

@sailingrubyrose

4 жыл бұрын

Thank you mate.

That was informative. We never hear anything about hull design, if you want to know you have to go looking. Other important factors that effect slamming are the distance from the bow to where the bridge deck starts and the shape of the leading edge of the bridge deck. Having the hull shape with a flat section in the stern helps reduce hobby horsing. The charter industry has turned cats into max volume to minimum length boats, at the detriment of sailing ability. What is called a performance cat today is really just a well designed cat that should sail well in all conditions. Cats with all lines led to a single helm with 2 winches and a bank of jammers would have been considered suicide 30 years ago, today it's just a cheap option for under powered cats. If you are interested in buying a cat it's best to sail on as many different brands/designs as possible, there is no substitute for experience. Cheers Rustie.

@sailingrubyrose

4 жыл бұрын

All that good stuff is coming in the next episodes my friend

co efficient : drag, prismatic. lengtht beam ratio, bridge deck ,clearence slenderness, shape ,rocker, transom wet area, drawing waterline, got it! cheers! i gonna get building!

Amazing

Good job Nick. I want to know these calculations to know what to expect from a boat, and to know what I can’t expect from a boat.

Hehe, looks like you had fun with that intro. Good information, thanks.

I enjoyed this immensely, getting a Bali 5.4 (6 cabins ) by Catana, for business. I need volume, that so much performance, plus structural strength is important to me.

Absolutely #OfTheEpic work once again Nick. You are completely filling or think bank to its brim. Much appreciated. I wish there was a way that somehow we could combine this with all of the other catamaran footage you have and come out with a finished product that is the brainchild/catalyst of everyone’s buyers guide to catamarans and cruiser life there in.

I think you are growing into becoming a true catamaran design analyst! I’m like probably the vast majority of your viewers became excited watching this video about your venture into opening the pandora box of hull/boat design science. You are doing an outstanding job in educating us about the various hull design features impacting performance and comfort. Understanding and awareness of the hull features of your boat has also an undeniable positiv impact in managing the boat more safely by knowing the range and limits of its capabilities! I truly love what you do and the way you go about educating us and most important handing us the tools to understand boat design. Job very well done! A BIG THANK YOU, keep on going, excited to see what’s coming next!

I'm here because the information is sound.. See ya next video

I'm not getting the slenderness ratio (7:52 ) what units are we talking? Not only that, higher ratio number means faster boat? but as the volume increases the ratio increases (More displacement, is heavier, so slower...) but as the length increases the ratio goes down (but more length = faster boat!). Is that ratio the right way around?

Awesome and informative video . Loved it answered a lot of things I did not know but wondered about . cheers to a great video . From Steve Stott in Sutherlin Oregon U.S.A.

Is there some design constraint that makes aluminum or titanium, other than cost/performance, that makes it impractical for catamarans or trimarans?

@wileycsg

4 жыл бұрын

Early Antares videos say something about it, and supposed to have an optimized hull on their product, hope you find the vids, they are well done

Bravo!

Thanks for the interesting interview. I couldn't get the slenderness ratio that was written on one of your blackboards to work out. So, after a little research I found this equation which seems to be correct. SR=Lwl/Vol^0.333 ; SI units

@thomasvilhar7529

2 жыл бұрын

Thanks.

Thank you for this magnificent video. In the category of fast-cruising catamaran we can assume that the GunBoats are in the top of the list . in the videos when they fly a hull out of the water, we can look the hull shape and see a gigantic rocker, can you tell what's the advantage of this hull shape ? isn't it a bit counter intuitive as it increases the wetted area ?

This really helped me understanding engineering behind the catamarans, as i am a design graduate taking part in a design competition with no idea about boats and how they work, this was very informative !

@sailingrubyrose

3 жыл бұрын

A pleasure mate. There’s 5 or 6 episodes of theory in this series, and the actual build video drops tomorrow.

@nsmena

Жыл бұрын

Helo sir, i am a part of an undergraduate student team of Naval Architecture, who is participating in Ferry design compettition , we are designing a catamaran and we require the range of coefficients (e.g 0.345-0.5)best for catamaran for e.g Cb ,Cp LBr e.t.c. so we request you to help us in any way you can for that. Thanks a lot.

Displacement / Lenght = >7 for performance catamarans? How does it make sense to have a better performance the shorter & heavier the boat gets?

What you need to know about a boat to make a well-informed buying decision are all the things you can NOT change. So yes, the hull ratios and shapes are way more relevant than the number of fabrics for the saloon, the size of the winches or the controller of the electrical power system (just to name a few).

As with any product, they are designed for the customers. If the customers are more technically savvy then the catamaran companies will pay more attention to these details. Videos like this are great for promoting good design. I am becoming familiar with these ratios and fluid dynamics because of a more humble project. I am trying to design and build an ultra-lightweight (

That was cool. And yes you need dagger boards

@nobody46820

4 жыл бұрын

Or a centerboard, preferably one that can be raised and lowered.

@SailingNoRegrets

4 жыл бұрын

For performance yes, cruising I'd disagree. When you kiss the bottom with daggerboards you snap stuff off, and potentially bust up your sail drive and rudders. Mini keels protect all that and if done right can still offer some performance. Seawinds 1160 and 1260 models are mini keeled and perform well

"Vertical dynamic lift" Is that also called 'planing'? (Factoid: The Aleuts were planing at about 8 knots and could sustain 10 knots over distance. This was reported by Captain Cook's navigator, probably the best technical source available in the 18th century. Maps they made of New Zealand were used into World War Two). Loading the boat. I'm a terrible backpacker. Some backpackers walk thousands of mile and their backpacks never exceed 20 lbs. Me 4-5 days 50 lbs. However, I weigh everything, make a spreadsheet, sweat every ounce - otherwise my pack would be 80 lbs. I don't think cruisers get this extreme, but I'll bet a couple of good scales, a spreadsheet and some obsessiveness would shave a lot of excess weight and also point out where it is. Instead of canned goods maybe another freezer might give you more and better vegetables at less weight - just maybe, I have no experience (yet). Great series. Probably going to save me a lot of money, and a lot of disappointment when I buy a multihull.

This is an interesting and massively useful subject I am only surprised that someone else has not done so before this.

@sailingrubyrose

4 жыл бұрын

Cheers mate

Great channel, I enjoy it very much and learn a lot. In fact following the excellent reviews you have done I have been exposed to a seawind company and I am seriously considering the new and promising model the 1370 ( RR2 version of course...) A layman question: Does the Performance catamaran necessarily mean that it will be less stable on the water? I.e. Less stable in the sense that staying on it while sailing at a given speed will feel more bouncy than in a charter catamaran at the same speed?

You could have asked once you have arrived at your final design what is the additional ‘TPI’ (tonnes per inch immersion) if at DWL. To be honest the basic waterline is an academic (although necessary design datum) I would insist that the DWL includes - All tanks including holding tanks at 95% full, specified dinghy and outboard weight, life raft, specified anchor cable and anchor (otherwise they will ‘short chain’ you😉), solar panels and associated control gear and invertors, an allowance for engineering stores (fluids) and spare gear, Weight of passengers- if boat licence for 6 or 8 so be it - with luggage allowance (say 40 kilos each), food and provisions for certified number of passengers for 3 weeks. If the DWL then compromises the key numbers including bridge deck clearance then the NA has to ‘go round the buoy’ and iterate hull form to achieve the objective. Good vid.😀👍⛵️

2 жыл бұрын

Half full tanks are usually used in displacement calculation.

@normanboyes4983

2 жыл бұрын

@ I was talking about TPI and DWL - not a displacement calculation.

Interesting. One shape to consider is hull asymmetry. When viewed from above, a Hobie 16's hull has an airfoil shape: the hull is flat on the outside but curved on the inside. The idea is that it co.pensates for lack of a centerboard: it generates lift for windward performance and reduces leeward drift by presenting a flat surface to the water on the outboard hull. Do modern cruising cats do this?

@evangatehouse5650

4 жыл бұрын

Nope. Too inefficient

@robertcain3426

3 күн бұрын

Yes, my new hull design does. It is an improvement on the Hobie design hull. I have tested many 5m prototype hulls and compared to conventional modern dagger board hulls, the results show advantages which are; Superior lateral resistance at all speeds. High and low speed efficiency without foils. Excellent sea keeping capabilities. Cheers

I appreciate a lot the discussion like all the followers intrigued by the technical aspects in the catamarans world...we love being light and fast! (Owning a full foiling A class cat)But is awesome understand the design process of modern Bluewater cruising cat. ciao Terysa!

Great information! Thanks for sharing! Will the subject of what the sailors call "hobby horsing" be discussed? It seems worse on the shorter lighter catamarans.

2 жыл бұрын

Repetitive pitching is mostly caused by narrow sterns such as in Wharram cats. It is also wise to separate the LCB and the LCF when designing catamarans, to reduce pitching.

What is the music at the very beginning of this video? I think I heard it used in one of your canal videos as well. Please reply with name if you don’t mind.

my preferred concept...how fast can I make this thing go, comfort be damned! These engineering concepts and detailed analysis, is also applicable to automotive design. I want to know spring rates, alignment specs, tire specs, and all the pedantic details. As an enthusiast, I love this analysis series!

@chippyjohn1

Жыл бұрын

Except that the tyres, suspension and bushes are not just for the driver but for the vehicle. Comfort plays a role in speed, if the ride is harsh it puts a lot of stress on the hull/chassis, which means they need to be stronger, which means more weight. Engineering is fun. Just think of why F1 cars still have suspension.

Thanks...great video explaining some of the concepts. Learned some good information and it caused me to think more about our hull design. What about the balanced load of the contents.... Like the balance in a plane? What are the effects for instance if the weight is unbalanced and you drag your stern or plow your bow? Is part of the performance also a well balanced boat? Port and starboard, bow and stern. Are there optimal balanced loads.... Also will you be selling Ruby Rose merchandise with the wording..."I like your Prismatic Coefficient."

nice lighting, very PM 👍

This is good stuff! And I didn't have to go to university to learn it!! 😉 Sort of kills my idea of buying an old 60 ft Sunreef and glassing in some daggerboards to make a faster luxury cat. 😲😂😂

Two Comments 1) Love the intro. I was waiting for Duran Duran to start singing and Nick to start dancing in parachute pants! 2) What a great job working with an engineer that is immersed in the complexities of physics, and simplifying the concepts. As an engineer I run into folks everyday that do not appreciate your questions are NOT simple to answer (in our complex world of design). Nick showed respect for him and his knowledge, while trying to simplify his answers for the audience. Brilliant.

@sailingrubyrose

4 жыл бұрын

Thanks mate

Great episode! Anything on asymmetric hull shape coming? Looking forward to rest of series!!

Interesting. But, one important consideration that was addressed but passed over very quickly, is the law of buoyancy or Archimedes principal. Regardless of the ratios that impact performance and lift at speed (i.e. dynamic performance), one has to understand that for any given weight of boat and load, the volumetric displacement of the hull will be the same. Archimedes Principal basically states that the weight of, in this case, a fully loaded boat, will have to displace the volume of water of that same weight. In other words, a cruising boat or a performance boat of the same weight, will have to have the same volume of hull below the waterline (i.e. the volumetric displacement will be equal). That is why, I am assuming that performance boats have to be lighter which is intuitive, but also required, because narrower hull for any given length of boat will have has less volumetric displacement therefore, will only support a lighter fully loaded boat. Therefore hull DISPLACEMENT will always be directly related to the boat weight.

@akathesquid5794

4 жыл бұрын

correct, but that's the whole issue, these superficial videos about hull design never really expose the impacts of specific design decisions. They cover generalities and make the viewer believe they understand better. They do not. All they should understand is that is the topic way more complicated than they understand. Engineering is hard. Dunning-Kruger is real. To carry a specific load (boat + gear + people) It is not the displacement that is important, it is the shape of that displacement and the vast tradeoffs in that shape design...

@FamilyGoneRogue

3 жыл бұрын

Ignorance is a curious thing.

2 жыл бұрын

What is your point? Displacement can be bare hull, fully loaded, loaded for offshore, loaded for living aboard, loaded with half full tanks, etc.

@andrewturner7952

2 жыл бұрын

@ My point was simply that in my experience many people don't know the law of buoyancy - it isn't necessarily common knowledge and it wasn't explicitly explained in the video. So, I was just pointing out that for any given designed displacement or weight of a boat, that in itself, will define the displacement of the hull (or the volume of hull that is below the waterline). So, it you want the hulls to be narrower, then they will have to be longer or conversely if you to the length of hulls to be shorter, than the hulls will have to be wider. In other words, from a design perspective, if someone wants to build a boat that fully loaded is say 20 tons and they also want it to be no more than 45m long, than the choice of how wide the hulls are be will not be much of a choice, as the hulls will have to be as wide as they need to be at 45m long to displace a volume below the water line that equal to 20tons of water. More simply, if someone had a row boat and wanted to know how much weight it could carry, then they could put it on a scale and weigh it and then fill it full of water to the point that water is spilling over the gunnels. Take that total weight and subtract the weight of the boat and the result is how much it can carry before it sinks.

Brilliant. I've only ever listened to one other presentation from a marine architect... It fascinates me... Odd really, they do understand what goes on. I'm looking forward to the numbers of the advantages of dagger boards over keels. There is so many myths about both, that a design expert can clarify so much...

@finfanfifteen9659

4 жыл бұрын

Don't forget the center boards with the "break away" design like McConaghy.

I asked the builder of my Whitehaven 11.7 (designed Mark Pescott) what the Prismatic Coefficient was and he informed me that he could tell me but then he'd have to shoot me! (I never did find out what it was). This was a boat that had hull length/beam ratio of around 12.7 (displacement of 4 tonne) and was capable of outsailing most other cats both upwind and downwind.

Lad might not look as if he has started shaving yet, but he knows his stuff! Still not convinced hull shape would influence my future choice of Cat. Key would be not to overload even a slower cruising cat, but price will be the main factor for me, and in the used market you can get a cheaper FP, Lagoon or Leopard that is still a great safe boat that will cross oceans.(steadily not speedily) I could not get the wife to agree to live aboard a performance cat with narrow hulls. If what your research pans out, Seawind seem to be trying to find a sweet spot between cruising & performance. Hope it does not end in the middle doing neither particularly well, but don't think it will, your future Cat looks awesome, with above average cruising & liveaboard comfort and good potential performance. Looking forward to watching your journey & logging all the lessons learnt for mine!

@sailingrubyrose

4 жыл бұрын

Exactly that mate! There are a few old salts on here who seem to think that to have any credibility in the sailing world you have to have skin like sandpaper and a beard you can hide a badger in

Right up my street, I have a slight advantage as I studied stability at south tyne side marine college and found this very interesting. In my opinion I would have dagger boards due to 9 x out of 10 I'm always sailing to windward.

@sailingrubyrose

4 жыл бұрын

Excellent

@SailingNoRegrets

4 жыл бұрын

I'd check the performance of a seawind first. We sail ours comfortably at 30 degrees AWA with main and jib. They point pretty well for a cat

@kingneptune8937

4 жыл бұрын

I've just put the euro lottery on, its £42 million, after watching all of your you tube videos on cats I'll be purchasing one, with that kind of cash I could go OTT on a yacht but any thing over 55ft is a waste for two people in my opinion 🚣‍♂️🚣‍♂️🚣‍♂️🚣‍♂️🚣‍♂️

I watched and enjoyed the whole thing, which must only mean one thing. I'm turning into my engineer father! (Thanks for keeping it conceptual, and the actual math as minimal as possible. Math is usually were my brain tunes out.)

I would love to know more about bridgedeck clearance, how low can it be. And on construction about strip planked wooden hulls!

Great technical bit on design! Look forward to future ones on the build. Especially for build materials - there is so little information out there when you get into the details.