Coca ta este prea subțire? | Înțelepciunea navigată

43 thoughts on “Coca ta este prea subțire? | Înțelepciunea navigată”

1. So at around 19 mins you are claiming that 25mm solid glass is about as strong as 25mm cored laminate? Then how come a 10mm thick solid hull need to be 29mm thick when cored?

   There is a difference between strength and stiffness, and they should not be confused with eachother.

2. I have a book by Dave Gerr called Boat Strength it is an excellent and very accessible text and covers this topic in great detail. Just as important as hull thickness is the internal structures that are built into the hull. This seems to be an area that builders skimp on by not installing the correct number of longitudinal stringers, ring frames etc. 👍

3. David Gerr's book is an excellent read. I have it aboard.
   I have a 1985 Marine Trader Ketch, center cockpit. Very good build quality by that yard, solid hand layed up hull: around 5/8" at the sheer, 3/4"+ at the bilge turn, and 1"+ below waterline. Longitudinal, and transverse stringers, with bulkheads everywhere! Cruising weight: 55k lbs.

4. Herbie this was just what I was looking for . I have a Cheoy Lee Herschoff 31 off shore ketch built in1968. The hull is rock solid sound but removing the 80 percent inside I was cking hull thickness which kinda of made me go ,oh no ! Is she to thin ? For numbers your Alberg and my Herschoff has only a length difference of around a foot ,beam is the same and depth pretty much the same. My only second thoughts on keeping it ghe same is I'm going to be sailing in the upper North Atlantic, Rocks for as far as the eye can see and the occasional tree log . To what point do you increase the hull thickness or install hollow glass ribs perpendicular to the keel line ?

5. WOW! Never really thought about it in terms of skin thickness. Just material, wood, balsa, etc. THANKS FOR ANOTHER REALLY GREAT TUTORIAL! YOUR THE BEST!! 🙏❤️🇺🇸⛵️👣😊👍

6. Great answers and questions. Land locked on solid core construction, the plastic elasticity is remarkable.

7. Unfortunately. This excellent discourse ignores common techniques and technologies that greatly skew this basic math. For example my modern Hunter has DuPont Kevlar glass that provides for much stronger layups with less mass. Boats made after the 90’s have leveraged many material science and construction techniques to provide for the strength required by the naval architect without a direct relationship to thickness alone.

8. Gotta take issue with this video. Structural engineering of boats has moved beyond rule of thumb type equations to more rigorous approaches. As a retired structures naval architect, there's much more to consider than gross hull dimensions and core v. no core when specifying scantlings of FRP hulls.
   Principles of Yacht Design by Larsson, Eliasson and Orych gives a good discussion of monohull structures with calculation methods to determine scantlings.
   I don't mean to be a negative on this, but the risk is someone may see this and think they can do a repair or build a boat component based on this and have disastrous consequences. There's too many factors that go into sailboat structural design to think the basic scantling equation presented here has any meaning for structural adequacy.

9. Awesome video, I've always wondered about this! Thanks Herby!

10. Thank you for the informative video,that was something I never new plus lots I don’t know 🤣but
    I always thought that the older boats were thicker and heavier than the newer boats
    So the formula you explained is still used in today’s production boat building?
    But surely for the boat that’s made for speed is going to be lighter than the boat that’s made for ocean cruising
    In any case very interesting watch
    Thank you ⛵️

11. A tanker trailer floating in the water just below the surface. Kevlar hull sunk in minutes.

12. This why i advocate sturdy steel hulls with ultra low center of gravity because you can throw up a huge amount of sail with enough energy to charge batteries.

13. I thought you said Skull!

    I have a thick one.

14. So with my skull in mind….the thicker it is the larger the inner volume. Obviously, in my case this lack of volume constrained my brain's size.

    I call this the scant IQ number….sorry no formulae as I wouldn't understand it anyway. But I believe that my forehead is probably scant IQ multiplied by 1.15 as it's most likely the part that crashes into lampposts, doorframes and other skulls.

    Anyway, I digress.

    How come you didn't mention the relationship between solid v cored thickness and internal volume.

    My brain also tells me that non-cored boats float longer when holed, as their greater internal bigness would take longer to fill up.

    So where's your formula for THAT smarty pants?

15. I don’t know……I’ve sailed a 31 ft. Norwalk Islands Sharpie designed by the late Bruce Kirby since 2001 and its hull weight I believe is 8,500 lbs. which is cold molded west system cedar hull. Draft 18” board up and 6’06” down. Beam 9’. She’s a great racer/cruiser. The deck core is marine ply with fiberglass and awlgrip paint. S/V Mudlark. Cheers.

16. How would an aluminum hull compare? More or less weight, but stronger? More cost? Distant Shores has built an aluminum boat, so I have had a chance to see the design, and it looks to be very strong, with a thin skin welded to a frame.. Thanks for your time. :¬) Webhead USA

17. My Brain hurts now 🙆

18. Cool to geek out on the numbers, thanks! We used to have a 1979 Tanzer 26 that was more than an inch of solid fiberglass at the bow. Now we have a 1977 C&C 30 mk1 which also has a solid glass hull. I'm sure you know that C&C/Bruckman built the first engineered cored hull boat, Red Jacket in 1966, length 40 ft. I guess they wanted the security of a solid glass hull on the production boats, even 10 yrs later, so they only used balsa coring on the decks.

19. My 39’ modern product sailboat is solid core to about 1.5’ above the waterline and balsa cored to the deck/hull joint where it is solid core again where it ties in. The hull next to the fin keel is approx 1.2” thick and is made from eGlass. The hull below the waterline is supported by a solid glassed in grid and the hull above the waterline is supported by glassed in bulkheads. Chainplates supported by extended supports glassed in place and integrated from the deck to the keel supports. My point is that your math is great for a uniformly built hull, which pre 1990’s boats might have been, but difficult to draw any conclusions from these figures for a more modern fibreglass boat. Too many other design factors to consider.

20. Nice explanation Herby

21. I have a cape dory 25D, always heard they are heavy built. I wonder if they are close to the Alberg…
    Great vid. Thanks

22. The deck core of a Pearson Triton 28 from late 50s – early 60s is 3/8ths of an inch. I have 3/8th core material in Divinicell and white oak. The sheer strength and weight of white oak is nine times that of the Divinicell, but my plan is to use the white oak core material in areas where there will be any fasteners to be attached, to get the added sheer strength. (but a buddy said that is why you use backing plates, which I will use also.) The downside I figure could be rot of the white oak eventually if water gets in there.. so.. keep it sealed. And heck, the boat is heavy already.

23. How long can this man possibly take to explain the difference between thick and thin?

24. So when someone loads a boat up to cross an ocean…. the percentage of hull weight to gross tonnage goes down. At what point does a heavier hull become somewhat of non-point? People who want to race generally have a very sparse interior and put up with no shower and freeze dried food…. every ounce matters. When one starts adding a big battery bank for cooking, water making, washing machine, dish washer…. and oh motive power as well. Then add a rubber dinghy rather than a wood dinghy and electric bikes and SUPs for each person. We have not started talking food, water stores, clothing, etc. Add on top of that a cruiser is not going to replace their sails before each crossing as a racer might maybe every two years but likely less and so a less efficient sail as well. This might well be why most cruising catamarans are slower than similar length mono-hulls, it is hard not to overload them. It would seem a slightly heavy hull probably makes less difference than the raw numbers might suggest. A light, fast hull might not be a good cruising boat either….How is the boat going to be used?

25. 👍👍👍

26. So how did the Alberg 30 work out in real life? And do your changes affect anything? I am a newbie so I know nothing.

27. Excellent video

28. I have steel sailboat. My hull thickness is Schrodinger. I its 5mm and none at the same time. Depends on measurement.

29. If a boat gets bigger, its hull gets thicker therefore stronger ??
    Youre confusing thickness and mass rather badly
    See 26 ft steel boat versus Fibreglass versus Ferroconcrete.
    Your whole premise is badly flawed.

30. I like your premise of this video, but this video is technically really bad. You’re not opening up a discussion or ‘awareness’ of hull thickness, because it’s clear you don’t quite fully grasp the concept and use case of Scantling Numbers.

    Scantling Number is a base line Coefficient to calculate other aspects of boat design. While you do touch on that, it’s clear you don’t understand the rest of the equation. Hull thickness is not defined purely by LOA, Bean displacement. But actually from the core design of the semi-monocoque design. The spacing of ribs, longitudinal stringers, size of the ribs, use case of the hull, hull pressures are all factors of hull thickness. More ribs (tighter space) = thinner hull thickness.

    Even the type of fibreglass used to calculate Scantling is used 90degree axis glass Matt. Modern fibreglass is either triaxial or even quadaxial fibreglass mat. These modern materials again change the load characteristics and requirements of a hull.

    The idea in your video that you can define someone’s boat as either being too thick or too thin is quite simply creating stress and drama of owners who would look up to you as a source of information. This information is quite clearly, very wrong. It is not the full picture and it’s not even a full of thumb. It’s not offering any value or guideline for owners of boats. It is only going to create drama and concerns, because you don’t provide all the complex information, because as above, it’s clear you don’t actually understand the complexity yourself.

    Here are some actual publish resources that clearly describe the full picture, and reference my claims above. In both separate publications, they both mention that it is critical to factor in the hull structure, and not just Scantling number alone. For reference I am an aviation structural and mechanical engineer. There are many naval architects that have already commented similar problems with your application of the Scantling model. Structurally, what you are implying in this video is incredibly wrong and a huge misdirection to owners.

    https://www.foils.org/wp-content/uploads/2018/01/Scantling_Handbook.pdf

    https://www.gerrmarine.com/ELEMENTS_OF_BOAT_STRENGTH/BoatStrengthIBEX.pdf

31. I often ask this question when i see people say "these hulls were laid up nice and thick" so on and so on, about how that is great for ocean cruising while at the same time we see boats like the Albin Vega 27 with paper thin sides, yet it is well known as a go anywhere boat. I get the feeling it doesn't really matter as much as the reputation of the boat, unless you plan on hitting stuff. In any case i think the keel design is just as important in a collision.

32. OOHHHH Thin like "thickness". Makes sense to me. My hull I think is Too Thick. Unfortunately I think "Wide", So yea, the Width is what I'm talking about. With my 50 year old "lake boat. MMMmabe 1968 or so Whatever that would be. For me, a tree fell on my "Chrystler Built Buccaneer" 19 feet long and pretty fast. But lo and alas there was a tree right across the bow about 18 years ago. Motivation to "refurbish" was (up to a new brilliant idea about a month ago) to make the hull much Thicker. That would be much Wider. Break the transom and spread the hull with sides added for freeboard. NO No NO. I am now looking at building two AMA's. Yep AMA's Ill tell ya. But This means that I am making my sailboat into a Canoe. Yep make the boat THINNER. LIke a Canoe. Got to cut triangular sections out of the hull and push everything togeather to be more narrow. A very narrow (Thin) hull. Crossing with three aluminum poles (I have a fabricating job at a dock making place ~ all aluminum welding ~ So sweet) Well I guess a Trimaran would be much "Thicker" if you're going to talk about the "Width." But my hull is the middle part must be more like a Canoe. I still have the very nice tiller/rudder, the Centerboard and well in the middle, the mast step and mast with all rigging and even "NORTH SAILS". Oh my goodness! They are yellow with black striping. Not to mention that I have two mainsails. Not sure why but a wishbone boom would allow a double rig for the main for wing on wing. ~ And my son nearly had me convinced to pay to have it "demolished." So yea. Thinner is better for me. 🥹

33. Nice introduction/overview. However, I would point out however that these are only rules of thumb. I don't count myself an expert here, but to my knowledge, there is an important difference between strength and stiffness, and it is not like there is some specific absolute point where something is 'strong enough' for a given weather state. Also the strength and weight of the glass depends on many factors including what kind of resin, type of weave . vacuum bagging, etc. I would also add that hull weight – especially low – in a sailboat probably adds to 'sea kindly' where like slower to get moving, it is also slower to bounce in the waves, and slower to change directions, and slower to slow down. In other words, heavy "overbuilt" boats should track better in heavy weather and be more comfortable.

34. Nice explanation and informative

35. Much appreciated
    Thank you 🙏

36. 0:14: ⛵ The video discusses the importance of hull thickness in boats and how it affects performance.
    3:52: 🛠️ The video explains how the thickness of boat components is determined using a simple formula based on the boat's size.
    7:14: ⛵ The video discusses the importance of scantling numbers in boat design and how they are affected by the boat's dimensions.
    10:30: 🛥️ Comparison of boat sizes and scantling numbers, showing the Beno, Hunts Christians, Bararia 44, and Morgan.
    14:21: 🛥️ The video discusses the varying thickness requirements for different parts of a boat's hull to ensure structural integrity.
    18:10: 🛥️ Understanding the construction and strength of boat hulls with fiberglass and cores.
    21:43: 🛳️ The video discusses the varying hull thicknesses of different boat types and the impact of being corded on the thickness and strength.
    Recapped by TammyAIarticle

37. Well done! You didn't stray into the weeds, which made the basics easy to understand.
    BTW, I used you chain+magnet trick to install a new messenger line today – worked like a charm 🙂 Thanks!

38. 😀👍👍👍❤

39. Good video but it should be noted that all of these formulas are rough estimates from a very old book. Composite technology has come a long way since Gerr's Boat Strength. These formulas are assuming balsa cores, woven roving/chop strand matting e-glass, and polyester resin with hand layup techniques. Modern composites maximize stiffness and strength with fiber orientation, fiber type, layup process, and lots of different core materials. Good bit of knowledge for the curious but certainly not enough to safely design your own boat!

40. All this is a gross generalisation. There is no real structural engineering behind this. It depends on internal, frames, floors, stringers etc. I am feeling you are misleading people. Really you need to study naval architecture before handing out information like this?

41. Better methods: https://ww2.eagle.org/content/dam/eagle/rules-and-guides/archives/special_service/37_offshoreracingyachts/pub37_ory_guide_op.pdf

42. I have a 1966 Ericson 35. I cant find any info on exactly how thick my hull is, but Im hoping its overbuilt. Anyone have knowledge of hull thickness of this type of boat?

43. Some food to thought here, great video. 
    I am considering to build my first sailing dinghy and the first thing to decide is if I will use e.g. PVC foam panels as core or plywood which is heavier and may rot in some cases but it has its inherent strength. So I wonder where can I find additional data on how to calculate the required dimensions when various materials are used.

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