50' performance cruising sailcat

Discussion in 'Projects & Proposals' started by vanquishcc, Aug 13, 2019.

  1. Rumars
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    Rumars Senior Member

    Thank's for the correction Alik, I was only expecting double the rate not triple.
     
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  2. rob denney
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    rob denney Senior Member

    The few cruising catamarans that capsize, do so in microbursts or rogue waves, so model testing in conventional wind tunnels and wave pools is fun for undergraduate study but divorced from reality and certainly not worth paying for in a cruising boat design. Each time one does capsize, the statistician/rule maker changes the rules to make them more stable and heavier.

    It is not (or should not) be about how many degrees one has and justifying expensive fees, it is about common sense

    Some of the technology I need rules for is rudders mounted outside the hulls, so they are not damaged in a collision or grounding, unstayed masts and outboard motor arrangements that work in a seaway. If any of your rules cover these, and you can give me examples that are as as light as our first principles plus experience approach, then I will put some business your way.
     
  3. TANSL
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    TANSL Senior Member

    With all due respect I have to tell you, rob denny, I don't agree with your opinions. But I will not enter into discussions, I just want to record that, in my opinion, your "way of analyzing and solving the problem" is not correct. Just my opinion.
     
  4. Alik
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    Alik Senior Member

    No need. We don't work with amateur 'designers'.

    Outboard motors: they are designed mainly for planing craft and on such craft (if installed according to installation manuals) they work properly on seaway. If one installs outboards on 50' sailboat this is illusive 'cost saving' nonsense.

    Collision: there are standards that cover collision loads. Say, IMO HSC Code does specify accelerations in xyz direction following collision, so we do check all heavy items foundations on high speed craft for these inertial loads.

    And so on...

    I am not saying every single element of design should comply to some standards. No, because some innovative features are not covered by standards, and they are done by direct engineering, or taken from experience. Experience is important source of design ideas! BUT every essential safety element of craft, including sailing multihull, should comply to industry standards - if the craft is designed for a client, and not for 'suicide' personal use only. Even for ORC racing yachts now they require compliance to ISO on stability and structure...
     
    Last edited: Aug 21, 2019
  5. Rumars
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    Rumars Senior Member

    It's not about degrees, it's about the market one operates in. Selling plans to amateurs for homebuilding often does not require anything but a lines plan and scantlings, and it does not matter who drew the lines and how they arrived to the scantlings. Selling a design commercially normally requires a stack of documents proving compliance to at least national standards and every single one of them must be signed by someone with the appropiate qualification. The price usually reflects the difference.

    You clearly don't understand what rules and standards are designed to do. First principles mean nothing because they are a tool, usefull only in the context of experience. This experience can be your personal one, or one that is derived from collaboration of several people over a longer time. When experience gets formalized in writing it becomes a rule, and when it is enforced by somebody it becomes a standard. Often such rules and standards offer shortcuts in calculating structures and by doing so seemingly depart from "first principles engineering". What they actually do is set those first principles plus the safety factor according to experience and accepted outcomes and giving the user a shortcut trough the math.
    Example: one has to calculate the beams of a catamaran. First thing one does is determine how to analyse the structure, let's say as cantilever beams. Here experience or "the rule" has dictated a "first principle". Then you do the math and arrive at an objective number. Now "the rule" or your own experience dictate the safety factor to be applied to this number.
    So you see the question is what do you want to use: your own personal experience or the combined knowledge of others. This of course provided you are allowed to only use your jugdement by the jurisdiction you operate in (most jurisdictions provide liberty from the rules by exceptions for "experimental and sportive use").

    What I don't understand is why you complain about the rules and standards? Have you actually designed something according to one of them and compared the result to the same thing designed by your own assumptions by testing both to destruction?
    What are your criteria for labeling something "overweight" and "overstrength"?
     
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  6. Alik
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    Alik Senior Member

    'Rules and standards are reflection of successful engineering practice' (c) me ;)

    The biggest problem for amateur boat designers is that modern standards has became very demanding in terms of engineering background.

    Say, we have one staff in office who is doing only stability calculations - every day. The stability calcs became so complicated that to ISO one needs to analyze 7-8 load cases, and load conditions/weights are defined differently from IMO IS Code. Not the work for dummies, easy to miss, should clearly understand theory behind! Often we have to ask support from software supplier, sometimes we have to argue with maritime authorities which standard to apply and how.

    Instead of facing and overcoming these common engineering problems, it is easy to label all rules as 'resulting overweigth boats'. But this is the voice from underground, I should say.

    I saw too many people who bought 'designs' for 200$ (four sheets of paper, where projections did not match each other, and no calculations!), and then trying to build this creation, register it or buy insurance... Most of them (and luckily) end up standing in backyard forever, as uncompleted hulls.
     
    Last edited: Aug 21, 2019
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  7. rob denney
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    rob denney Senior Member

    An example of "I know so much more than everyone else, I don't need to explain myself" syndrome. Common amongst members of closed societies and 'qualified' people. The only known cure is to get out of your bubble, design , build and sail some radical boats and expand your knowledge base, maybe lose a bit of arrogance along the way.

    A variation on the above.

    Rubbish. Diesel outboards propel many non planing boats that are heavier than a 50' harryproa. Outboards that work in a seaway are less cost, smell, heat and noise, more internal space and easier maintenance than inboards. Mostly though, they are safer as it is easy to clear a fouled prop and no hole is ripped in the bottom of the boat in a collision.

    A 40 hp diesel outboard is $US6,000 incl tank, controls and installation, will push a 50' harryproa at ~8 knots. What inboard configuration makes this " illusive 'cost saving' nonsense"?

    Good for you. But what is the relevance for a family cruising cat? Rules should not be about designing to fix the result of a collision caused by bad design, they should be about designing to minimise the chances of the damage happening in the first place. ie, no fixed props, rudders and daggerboards

    Precisely. So, when I do that, why do you you give me a hard time for not obeying the rules?

    Difficult when there is no standard to apply, and the rule makers default position is to disallow it because they haven't got a rule to cover their arses. A case of the lunatics running the asylum.

    Offshore race boats have been built to rules and standards for a long time. Has not stopped them falling apart, sinking and losing rigs. The same applies to many commercial craft. There is a lot more required than simply applying 'rules'.

    Yes, I know, and most of them are the same as all the other boats, so this is expensive rubber stamping. If the boat is at all different, no one will sign off on it.
    And despite the lack of signatures, the vast majority of home built boats do not have structural problems.

    Which works with boats that have been around for long enough to gather all that information. But for something new, they cannot apply. The history they base the rule on is failures. Each time something breaks, the rule adds more strength. Often regardless of why it broke.

    I have no idea what you are saying here, please try again. Which rule allows "experimental and sportive use" boats to be certified?

    I have employed about a dozen engineers and worked with several others over the last 40 years. I know enough engineering to check their results.
    Those who work to 'rules' consistently supply a result that is heavier than those who work from first principles. A subset of these are the ones who supply outputs to several decimal places, then apply a 'safety factor' plucked out of thin air. The engineers who give the best results do so from first principals, then spend as much time analysing the safety factors as they have the laminate. ie, the skill and qc of the laminators and suppliers is tested with samples, the use (racing/cruising) and the likely abuse (eg, an unstayed mast can not be poorly set up, will not be removed every year or so and will not see flogging loads from out of control headsails and extras xo can have much lower safety factors than a stayed mast) proportioned which is where experience is required.

    I spent several months filling in forms and making and testing samples to get a new material (Durakore) approved for Queensland Maritime Department survey. The rules and attitude of the people enforcing them were mostly inappropriate.

    I designed a sailing boat to replace outboard powered skiffs to access remote villages. http://harryproa.com/?p=2561 and had it engineered to the required standards. The resulting laminate is about double what it 'needs' to be, the required crew number is several times higher than required to safely operate the boat and the rules cannot handle the unstayed rig's automatic depowering so requires a small rig or excessive righting moment. These factors make it unviable so the skiffs continue, capsizing and drowning people every time the breeze gets up. Convincing the rule makers to change the rules is time and money consuming and unlikely to happen. It is much quicker and probably cheaper, to build an example and use it to demonstrate that the rules are wrong (or right). We are building one next year to do precisely this.

    Remaining with unstayed masts as an example: The engineer specifies bench test loads and deflections along the mast based on calculated loads for various wind speeds up to full sail capsize. If the masts pass these tests, their weight is correct, the qc checks out and they work on a boat for ten plus years of hard use, that is acceptable. Anything heavier than this, I would classify as over weight. Almost everything major on a harryproa is overstrength as the main criteria is stiffness. Usually, if these items are stiff enough, they are over strength.

    No, the problem is that the rules have become too difficult to understand, too complex to apply and because they are partly based on failure history they result in heavy boats.

    I am sure this is a regular occurrence with 15m cruising cat designs. sarcasm font off More rules to enforce rules is simply making work, increasing the cost of design and the chances of an error.

    Those plans would be about as much use to the op as plans that needed to "analyze 7-8 load cases, with support from software suppliers and arguments with authorities" to see if the boat would be stable.
    I see no connection between either of them and, for example the 100+ pages of details and measurements, 15 page booklet of instructions, several thousands of dollars of engineering, 40 years of testing/experimenting and 60 years sailing experience behind a 50' harryproa set of plans.
     
  8. Alik
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    Alik Senior Member

    There are basic safety features which are covered by existing rules. For recreational multihulls as well. There will be stability and structural requirements to apply, also deck equipment, systems. Those rules You have to comply on Your proas (well, You have to understand the rules first, but this is not the case). Modern rules are not just based on failure history as You think, they are also based on first engineering principles and modelling.

    Offering designs which are based only on designer's sailing experience, with no any standards in mind, is amateurish (if not to say more!) approach.
    The 18m 4ton multihull will never comply to category A of CE, thus not ocean going and cant be registered as such in most of countries. You claim such boats are family cruisers for 2 parents and up to 4 kids, really?? On a boat where deck safety does not comply to any known standard? On Your 80', You claim up to 40 persons on board for sunset cruise, or 20 in dormitory sleeping. Do You realize that those will be treated as passenger craft, and never allowed, say, in Australia where they have to comply to NSCV standard? Whom are You trying to fool? Are we considering basic public safety here
     
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  9. Rumars
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    Rumars Senior Member

    Wich rule allows experimental and sport boats to be certified? I understand you as an australian not beeing familiar with the RCD (I or II) but you at least must understand why people are allowed to homebuild your boats in the EU. The RCD provides this exceptions. Why do you think all those EU buildt racing boats loose keels and break and so on if the rules are so conservative and produce such heavy overstrength boats?
    And by the way the RCD does not mandate the use of their rules (ISO), if you can prove that your engineering complies to their stated design goals your boat will be certified as fit for market. Doing that will be difficult of course (much arguing and testing to be done) but it is not impossible (at least in theory).

    But I revert to my original point. When it comes to "first principles" you don't differentiate between "the math" and "the axiomes". When you design the connecting beams and decide to view them as cantilever beams you set an axiome that determines the math to be used. You just as well could have decided to view them as always supported at both ends since your boat is not intended to fly a hull. When you design a freestanding mast and decide on a design life of 10+ years that is an axiome that will affect your scantlings regardless of the math. Exactly the same applies to any other engineering decision you make. Any performance driven rule or standard does the same, it set axiomes and the boat must comply. Yes sometimes this axiomes or design goals may seem a little to much, but they are intended for commercial products aimed at the general population. If you insist that your way is the better way you either prove it to the world or accept the fact that your genius will never be recognized.
     
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  10. Alik
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    Alik Senior Member

    They can be self-built build it in EU, but can't re-sell in 5 years, and those boats can only be used by the owner, not for any commercial purpose. I also believe they have problems with insurance, no insurance - no access to marinas, etc. And in many countries those boats won't be registered at all. A real 'underground sailors' :)

    In fact, those proas are classic example of one's fetish promoted to the detriment of safety. Instead of dealing with professional designer who can use the engineering art to design light boats to modern safety standards, the buyers of such designs are dealing with faith-healer who disregards all rules :)
     
  11. Deering
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    Deering Senior Member

    Where can I find me one of these outboards in the US?
     
  12. Steve W
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    Steve W Senior Member

    I wonder how it is that dozens of large Kurt Hughes cats have been reliably carrying tens of thousands if not hundreds of thousands of passengers at locations all over the US for decades when they are built out of low cost door skin plywood. I don't think Kurt is a naval architect or engineer but probably has more dedicated cattlemarans out there quietly doing their job than any other individual designer in the US. There are also many lowly Macgregor 36 cats out there doing the same, absolutely not highly engineered cats built for the job but good reliable lightly built boats out there doing it for a long long time , one I know of has been in continuous service in Texas since 1981 licensed for something like 16 passengers iirc. I presume all these boats are insured. Can someone explain this? I seems at odds with what the NAs and engineer members would like folks to believe.
     
  13. Alik
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    Alik Senior Member

    I believe in US such boats have to comply to CFR, and this is mainly covers stability and equipment. Sure colleagues from US can explain better.
    But in any case, in US there are rules to comply, and for sure those boats are not designed with complete disregard of all standards - they are 'USCG certified'.
    I looked at K.H. ferry specs and in terms of weight they are not much different from sandwich boats we design.
    (Note that 'yacht designers' usually provide optimistic weight estimates, and naval architects will rather give pessimistic figures ;) )
     
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  14. Eric ruttan
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    Eric ruttan Senior Member

    all it takes to go from believing to knowing is a bit of a search. Why not do that first? What could it hurt, excepting your whole point, of course.

    But you already know that there are no standards in the US, and really not many in the EU, or, am I wrong, in that the hundreds of boats built by home builders of many different varieties from many different boat designers are all illegal?

    Yes there are restrictions on some boats in the EU, meaning you CANNOT SELL THEM for 5 years, unless you build something like Robs 80', which bypasses all the regulations, right?

    I mean, the EU is not my bag, and all I did was a few min googleing, so I could be all wrong, but it seems there are no restrictions on 24m+
    The Code of Federal Regulations? The entireity of all US federal administrative law? You cite ISO to the paragraph, but this you go super vague on?
    As far as I can tell, this is completely wrong. Boats are USCG certificated. This means they have papers. It absolutely has nothing to do with assurance of compliance with anything.
    Now I did find reference to a USCG program for manufacturers and importers to provide a sample of a boat, that is sold retail, to see if it meets regulations regarding boats for retail sale.
    But that has nothing to do with this topic.
    why not just link what you found on your google search?
    Or did it not really support you premise?
    so you got time to look at KH's figures and all you got for Rob is vague accusations?
     
    Last edited: Aug 24, 2019

  15. Rumars
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    Rumars Senior Member

    This is not entierly true. The 5 years rule is clear, you can not sell. But you could lease if you wanted to circumvent that rule. Insurance is not a problem. Third party insurance is even mandatory in some countries. Full coverage is a different thing and could be pretty expensive but it is a private contract and as long as you can pay the premiums you will find it.
    Homebuildt registration is handled differently by every country. It ranges from "send us a photo and some invoices and we will send you the papers" to post construction stability tests and up to "plans need to be preaproved and the build registered and inspected".
    As for commercial operation that is something different. If that commercial operation has recreation as it's primary purpose the RCD applies. If not (transport, fishing, etc.) it is extempted, but that only means it falls under the national regulations.

    What I find interesting is that some people always asume that a boat designed respecting "the rules" will be heavy and overstrenght and slow. This people always bring some heavy cruising cat as an example and compare it with some light custom one. You never find someone using an Outremer or a Catana as an example, or compare the light custom to something of the same comfort.
     
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