the egotistical quest for an expensive thrill

Discussion in 'Boat Design' started by deepkeeler, Dec 26, 2004.

  1. SailDesign
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    SailDesign Old Phart! Stay upwind..

    This post is not really germane to the recent posts in this thread, but I have been trying to decide for days now what it is that annoys me about this whole thread. And I think I have figured it out...
    It's the title! " The egotistical quest for an expensive thrill" Anyone planning on designing custom boats for a living, or even for a hobby, had better get used to the fact that your customers are going to have bigger bank balances, and bigger egos, than you do (OK, that last one may not always be true, but mostly). It is a fact of life, and anyone who cannot live with that fact should not be in the custom design market. Or, at least, will not be happy in that market for long.
    So - back to your regularly scheduled thread contents.
    Steve "rant over"
     
  2. JimCooper
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    JimCooper Junior Member

    Aye Steve
    I ken ye mon.
    A god marketing attention grabber carefully thoughtout guaranteed to irritate and attract. But good worthy thread all the same.


    Cheers
    Jim
     
  3. sharpii2
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    sharpii2 Senior Member

    Dear CT:

    On your first question. Heavy boats are usually slower for two reasons

    One. They push water aside rather than skim over it. In 'skimming over it', light boats are also pushing water aside, but to a much lesser degree. And the amount of energy needed to push the water aside varies with the square of the velocity. What this means is is that when the wind picks up, the heavier boat that is, say twice the displacement on the same Beam and WL, must do four times as much work to go the same speed. It is making much bigger waves than the light boat. Even if it had twice the sail area it still wouldn't be near enough.

    Two. The heavier boat usually has a lower Prismatic Coefficient (CP) than the light boat. Boats with lower PC's have less drag at low speeds (which they usually sail at) and corespondinly more drag at high speeds. The heavier boats are designed this way, so they can have a higher average speed. Since they generally can not go over 1.34 x (WLft^0.5) in knots, the only way to do this is to make them faster in light winds. This is where the low PC comes in.
    The light boat often has a higher PC. This is because, for its length and beam, it can carry much more sail in relationship to its weight. The higher PC, therfore, does not slow it down much in light winds. but really improves its strong wind capability. Light boats often surf and sometimes plane. These two options are denied the heavy boat. So, in any reasonably typical race, the light boat is far more likely to have a significant advantage over the heavy boat than the other way around.

    Now for your second question.

    What we are dealing with here are accelerations. Accelerations are changes in linear speed. The higher the acceleration, the more energy required. And the energy required is the square of the acceleration. To put this in human terms. Say you walk into a wall at 1m/sec. You might get a slight bump in the head. Now walk into that same at 2m/sec and you will probably get a concussion. The reason for this is is because, even though you are hitting the wall at merely twice the speed, you are actually hitting it four times as hard.

    Now, getting away from walls and onto boats. Say a wave hits the side of your boat. The hull is going to move. But the mast and keel, which have not been hit, are going to want to stay right where they were. They are only going to move because they are attached to the boat. And the attachmet points, the stays and keel bolts, are going to take the strain. So if the boat is moved twice as fast by another wave, the stays and keel bolts are going to experience four times the strain.
    A heavy boat, by virtue of its greater weight per surface area (remember my example here: twice the weight for the same Beam and WL), is going to be moved less by a given wave. Say, for simplicity's sake, half as fast. If this is true, its stays and keel bolts are going to experience one fourth the strain per weight. The wave did not hit it with any less force, but the energy was used in turning the wave into spray and stoving the side in rather than shoving the boat aside. (Its energy was also used in sweeping its happless deckhands over the side as well). Heavy boats have heavy construction for good reason.

    This principle is very counter intuitive. My dad's light airplane was able, according to its specification manual, to bank into much tighter turns when it was loaded than it was when it was nearly empty.

    Imagine my dismay when I first read that.

    Hope I have answered your questions.

    Bob
     
  4. jam007
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    jam007 Junior Member

    "What we are dealing with here are accelerations. Accelerations are changes in linear speed. The higher the acceleration, the more energy required. And the energy required is the square of the acceleration. To put this in human terms. Say you walk into a wall at 1m/sec. You might get a slight bump in the head. Now walk into that same at 2m/sec and you will probably get a concussion. The reason for this is is because, even though you are hitting the wall at merely twice the speed, you are actually hitting it four times as hard."

    Not quite. The energy is to the square to the speed not acceleration. You need the same amount of energy for a low acceleration as for a high. The important part is the difference in speed you end up with. The force is the mass times the acceleration. Energy is also force times distance. If you walk into a brick wall you will as stated absorb four times the energy at 2 m/s than at 1 m/s and end up with a concussion. The force will be four times if the collision depth (the distance the wall and head are compressed) stays the same. The force will probably be less than four times the 1 m/s force due to increased compression.

    But the important message about heavy boats lesser acceleration and terefore stresses on fittings and crew is correctly described
     
  5. D'ARTOIS
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    D'ARTOIS Senior Member

    I won't have neither of the two - nor light nor heavy. I have sailed in a 1937 build wooden boat that was faster than any of the modern boats in the club, even that she had an old fashioned rig, my mate and I could lick the field by a couple of boatlengths although we started a hour later than the clubracers.

    A longkeeler, not that narrow, reasonably deep, 13.50 mtr x 3.70 x 2.10 she sailed a bit heavy on the helm (she had e helm, no wheel) but al those boats in that sort of length are heavy on the helm. In 25 knots wind she did 7,5 knots running up to 8 in the gusts.
    It was at that time that my taste started to develop for the more classic designs.

    I have sailed an ULDB that was just like riding a racehorse, though not unfamiliar to me it was a hefty ride in a hefty boat, that needed changing fore triangles often to maintain her high speed of 11 knots. Nice for the time being but fatiguing on a large haul.
    I a boat tires you, eating up your energy, it is there where she can become or may become right out dangerous.

    For the day sailor, the weekenedr, the hobby sailor, the light boat is nice, as it is for the ultimate racer who wants to win races. Those boats are basically designed for their purpose.

    Today, boats are designed to purpose. Here, in Holland we have to deal with the North Sea, where heavy winds are prevailing most of the time. Mosts of the yachts stay therefore on our large interior sea, the IJsselmeer.

    If you want to form an opinion about the lighter boat, try the North Sea in a 30-35 knots wind. Sail then from Iceland to Rotterdam and if you have had a pleasantride, I would be the first to congratulate you with your boat.
     
  6. MikeJohns
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    MikeJohns Senior Member

    Chris



    I think we keep plugging away on diametrically opposed tacks here. I am not involved with racing yacht design, (nor do I have your knowledge of the performance of vessels in this field). I want to see good performance strong safe cruising hulls.

    I do think you work at a tangent when you try toanalyze the suitability of hullform/design simply on the statistics of the racing fleets. Comparing racing boat results is tempting but the problem is of course separating out the crew experience level and the rule advantages.

    A heavier powerful hull design for racing will not necessarily have a rig that shows her to her best advantage. But a rig that gives her the best rule compromise. This I would I think would penalize her in light air. I suspect that is where the complaints arise about the ratings from racers with heavy boats.

    The racing boat designer always calls the toss on the light side of scantling sizes, the opposite sides of the coin are strength and lightness. Lightness wins because the lighter boats will always be faster in her maneuverability higher acceleration after rounding each buoy, the gained time for example in faster tacking and re-filling the sails and getting back up to speed can amount to a considerable advantage over the course.


    For the record we are using ‘Heavy ‘ pretty loosely here and I think the true heavy ie DL ratio over 350 has its place as a comfortable small seaworthy cruiser but as the vessel gets bigger the D/L of around 300 can give a strong able performer. The champion racer Finisterre had a DL of over 400 (which is extreme) but she was still fast . The SAD ratio takes the increased form resistance due to D into account and is a good guide to the relative power available from the rig , but this is meaningless unless she has a sufficient RM for HM max.

    Modern heavier designs generally have more form stability than their predecessors of 20 years ago. As an interesting example Some of Bill Gardens cruising designs were raced with line honors but to quote Bill himself (under CCA rules) "we raced on the basis that if a competitor was visible astern as we crossed the finish line then we lost on points) this does not foster further development of those boats for racing, and as they can be improved upon for cruising the design had little future”.

    But we have been over the effect of the rules on design before!

    As for stresses

    Dynamics is a complex subject, some of the calculations can be challenging. Basically the higher the inertia (and the fluid damping) the lower the accelerations and the lower the dynamic loads on many parts of the vessel. However as I said it is a complex field.

    Flexure

    ….is a result of the stresses, the amount of elastic deformation within a certain safety margin determines the load that can be safely applied. It’s not used as a means but is the result of handling the load induced stresses. Unexpected flexure will often put very high stresses on parts of the structure not designed for such loads. Whether the scantling rules give sufficient guidance for the non-engineering background designer is debatable at times. Commonly with heavy weather and insufficiently rigid boats we see failure of internal bulkhead/hull attachment and furniture attachments, chain plate attachment points, and often hull deck joins (as every boat repair yard knows to their profit).


    Another problem with flexure is the cyclic heavy loading. The wracking forces in a seaway coupled with highly stressed local areas that are suffering fatigue can lead to events which will tear a boat apart. A common problem we are seeing lately is the de-lamination due to shear stresses in the hulls of many foam core materials as the stressed glues fail. Light designs are also seductive to the boat builder because they use less material for a given length.

    The sail away cruising yacht pushed as a cruiser-racer is the output of a hard pressed industry that cuts corners and is very happy to minimize material . They are aware that only a small percentage of buyers actually use their yachts at all for sailing of this group only a few percent will actually go offshore. The so called cruising sailor the industry targets is really a day-sailor. For ocean work he gets inadequate stability, compromised strength and rigidity and poor durability.

    It is a rational economic call to build cheap and fix /payout for problems for those buyers who have structural failures than to design and build for true ocean work. In turn the marketers push this style of boat and in turn the magazines sing their accolades because the whole carnival rotates on economics rather than merit. There is little consumer protection in this industry and I think a lot of mis-information at times.

    Heavier boats represent a good platform to design a strong durable and forgiving hull with a good interior volume and load carrying capability, that also performs well. Forgiving means being able to sail away after you have been pulled off the reef you hit at 7 knots, it means not exhausting the crew in heavy weather, it means coping with tons of gear poorly stowed without becoming dangerously unstable or slow. It means being able to heave-to for periods to affect repairs at sea or await daylight.

    I asked a fast talking salesman at the Brisbane boat show what he thought the chances were of being able to heave-to in a fin/bulb beamy hull, he replied “ No one heaves to any more” This represents to me the willful ignorance of the whole industry, the lack of real seagoing experience once again, at all levels from the designer to the purchaser.


    As an aside but true to the thread which we are wandering off:



    Where are we going when offshore racing officials have been considering escape hatches for upturned mono-hulls as a safety feature!
     
  7. D'ARTOIS
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    D'ARTOIS Senior Member

    What you have said before Mike, is unfortunately the reality of today' s yachtbusiness.
    Straightforward negative reports are absent in any Yacht's magazine - I have had not so long ago a discussion with one of my cascobuilders who advised me to drop a specific well known design from a Dutch design-bureau and using instead another design from another designer because his specifications were more solid and preferrable above the better known design-bureau.
    Of course, the calculations of the design-bureau were good: but only just!

    AND,

    it is not a matter of price only. Those people in the production boats do have large overheads and require hefty profits to keep them going. They have to advertise internationally and to be present at any yacht show. That requires a lot of money too.

    The individal build boat is ALWAYS better than a production unit given that they are build by quality and qualified professionals.
     
  8. CT 249
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    CT 249 Senior Member

    Sharpii, thanks for the thought but I do know why light boats are faster - the question I asked Mike was "Can you please provide us with information on fast heavy boats of the style you are advocating? While heavy boats can move well, I would be interested to know of those that have demonstrated racing performance (in terms of elapsed time) that can compare with good lightweights."

    ie I was asking for an example and desciption of the heavy boats that he spoke of - those that could equal lightweight boats in performance.

    Mike, you gave Finnisterre as an example of a good heavy design. There's a very good example of the Finnisterr style running around in the shape modified/updated (but still very heavy) Finnisterre type Sunstone, at 40' long. She's been outstandingly succesful, ie British champ 4 years under 3 different rating rules, Commodore's Cup and Channel race winner, class winner multiple times in Fastnet and class winner in Hobart etc.

    But Sunstone is never as fast as even an '80s Farr IOR 40 or Beneteau 40.7 - she's about 12% slower. She's something like 25% slower than a Farr 40 OD. She is about as fast as a 1980's 33' IOR boat, and is rated considerably slower than a 30' IMS racer/cruiser- something like 30 seconds per mile.

    The reason the Finnisterre type wins (crew apart) is that she rates so low. She rates so low that the boat was re-rated at the Offshore Racing Council's expense so they could find out what was up.

    She's still a great boat, but she doesn't provide an example of a heavyweight that is faster (or anywhere near as fast) as a lightweight.

    I think some of Bill Garden's boats (ie some of those referred to in Guzzwell's book on
    wooden boatbuilding) were fairly radical and light for their day?????

    Thanks for the info about the structure, I agree about the need for strength (my cabin top has been reinforced with ss straps and another hanging knee, in case she ever ends up bouncing onto the roof!).

    I can't quite see Sharpii's point that a lighter boat will move to wave action faster and therefore put more strain on the rig attachment points, as the inertia of a rig in a boat moving to lee fast would put the load onto the leeward chainplate, wouldn't it? And I've heard of very few LEE chainplates going.

    I was thinking more of pounding loads, where the mass of the boat is already accelerated as the boat falls off the wave, and the greater mass of a heavy boat would lead to greater loadings when it contacts the water again. Wouldn't the answer be not weight or strength per se, but the ratio of weight (inertia/impact force) to strength?

    The concept of "giving' to breaking waves is also interesting, as a boat that is light enough to be acclerated sideways would allow the kinetic energy of the wave to be dissipated through movement sideways, wouldn't it? That would also be connected to lateral area as well as mass/inertia of course.

    I remember reading the tale of the 10,000 ton cruiser HMS Sheffield losing the top of "A" turret (something like a 20 by 30' sheet of 2" armour plating) in a gale in a Russian convoy. It makes me interested in giving with the sea rather than trying to resist its force. But of course I'd like to do both!

    But yep Mike, I think we are talking of different things. As you say, we can't compare cruisers with racers.

    I also wonder whether the cruiser/racer, which is often seen as blend of racer and cruiser, is not better seen as something entirely different from those concepts. And maybe the boatshow "cruiser" types need a new designation - coastal cruiser? They'd seem to have much of the worst of all worlds when seen as a blue-water boat. It'd never work with marketing, of course.
     
  9. sharpii2
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    sharpii2 Senior Member

    This could become a very dangerous issue. How do you protect consumers from boats that look seaworthy but aren't without creating a monsterous bureaucracy that not only heavily disadvantages small building firms (the most likely to build good boats in the first place) in favor of larger, corporate, builders who not only can better afford the staff to keep up with the endless documentation, but can, through 'judiciuous' political contributions, avoid real scrutiny altogether. I guess this is where the good old fasion American lawsuit comes in. At least here in the States, it seems to be the only way to make 'the big boys' accountable. The real problem here, I think, is that cruising boats tend to be styled after racing boats, often without the carefull engineering. This is to keep costs down. I think it would be far better to make the racing boats resemble the cruising boats, but we both know that won't happen (see my "proposed class of small ocean racer" thread. as to how this might be done). But, I suppose, risk is the price of freedom.
     
  10. Milan
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    Milan Senior Member

    Mike, CT 249, during his long career, Bill Garden designed practically every type of boat you can think of, from very traditional heavy schooners to the light flyers, super yachts and every thing in between, so it's difficult to talk about typical Garden's boat. That particular sentence ("…if a competitor was visible astern as we crossed the finish line then we lost on points…"), was about double ended sloop Oceanus, his personal boat built in the fifties. She was quite unusual boat, not a best choice for light versus heavy boat discussion. Although strongly built glued wood construction (either cold molded or strip planked don't remember) and quite deep vee cross-sections, she actually belongs into ULDB category with her very low displacement / water line length ratio. She was very narrow (about 60 ft LOA 14 ft wide), with a short, fin-ish keel. She was very fast and easy to handle for two persons according to Bill, who was very happy with her. probably his favorite boat. .

    Bob, (…"I think your proposed boat would do well safety wise but would not be competitive with her beamier, lighter sisters, speed wise…). My proposition was ultimate safety combined with light displacement. Narrow, foam sandwich, unsinkable, (positive flotation + watertight compartments, positive stability to 180 degrees. Such a boat wouldn't have a chance racing in a classes categorized by the LOA where wider competitors with a more sail area would be faster. that's true. But she would be fast in an absolute sense. I had something like this in mind:
     

    Attached Files:

  11. Vega
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    Vega Senior Member

    You forgot to put some chines on that boat :p

    Before d'Artois (half) convinced me that it was possible to have built an aluminium boat for the same price as a good grp production boat, I have passed a lot of time looking at the right production boat.

    I have reached a similar conclusion. For the same price of a 39' you can buy a narrower boat with 42' or 43'. It will have a superior hull speed and it will be more comfortable, mainly against very steep waves with a very short period, the kind that you find in windy days in the Med. I think it will be safer too.

    This is mainly a feeling, cause I don't know much....but I would love to know more about this.

    I would like very much that people that are around and know a lot, comment on the advantages and disadvantages of this kind of boat (not for racing) but for fast cruising. I am only interested in speed, sea motion and safety and not in comparing this kind of boat with a medium or heavy displacement boat. What I propose is the comparison of this type of boat with another type, the more common light weight craft of the same displacement, but with less length and a lot more beam.

    There are not many production boats with these characteristics, but there are some. One of them is the Faurby 424:

    [​IMG]

    http://i19.photobucket.com/albums/b152/vega1954/Faurby424.jpg

    http://www.faurby.dk/gb/faurby424.html
     
    Last edited: Oct 2, 2005
  12. Vega
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    Vega Senior Member

    They have made just that in Europe. The gigantic bureaucracy of the European Community, in its endless pursuit of protecting consumers has done that. A comprehensive method of establishing a boat classification according to boat characteristics.

    Every boat in the EC is now subject to a lot of tests, by certified independent naval firms, before being classified in one of the categories.

    The "superior" categorie (A class boats) are considered to be oceangoing boats. A no limit boat.

    The result:

    Would you believe me if I said that the Dehler 29 is a certified Class A boat, supposedly a go anywhere boat? :

    http://www.dehler.com/

    :rolleyes: :p :p :confused: :confused: :mad: :mad: :mad: :mad:
     
  13. sharpii2
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    sharpii2 Senior Member

    Advantages:

    1.) More likely to have a ballanced helm, because differently shaped ends make less difference on a narrow hull than on a wide one.
    2.) More likely to recover from a capsize, because to carry a given amount of sail it will need more and/or deeper ballast.
    3.) Better wave penetrating ability because it will likely be light for its length but heavy for its beam and will likely have a sharper bow.
    4.) More likely to be able to excede traditonal hull speed without control problems due to the fact that it will probably make less of a bow wave.

    Disadvantages:

    1.) Likely to incure higher docking fees due to greater length.
    2.) Likely to need deeper anchorages due to the likely need for a deeper keel that is needed to recover sail carrying ability lost to decrease in beam.
    3.) likely to need more than one mast due to the need to get the center of area (CA) of the sails lower so that the keel doesn't have to be unreasonably deep and the staying system doesn't have to be so complex (get by with maybe just one or two spreaders on the main mast rather than two or three).
    4.) Likely to have less internal volume and less useable deck space. A beamy boat can (and should) have higer sides than a narrow one.

    Bob
     
  14. Milan
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    Milan Senior Member

    "…You forgot to put some chines on that boat…"

    Well, you could almost say she had them in the way- that boat, Bill Lee's Merlin, is basically round bilge version of John Spencer's single chine plywood flyer Regtime.

    http://www.fastisfun.com

    She doesn't completely qualify for my proposition but she's quite close. A bit heftier scantlings, watertight bulkheads, somewhat smaller rig and little shallower keel and result would be more docile, slower than original but still very fast cruising boat.

    "…2.) More likely to recover from a capsize, because to carry a given amount of sail it will need more and/or deeper ballast…"

    I would ad that recovering would also be easier because of low form stability of the hull. On the negative side, in the upright position they initially heel easier then wider boat. It takes some heel to put the ballast in to action.

    Narrow boat should be economical to build (in one-off, custom production). More length means more hull material, but that's actually the cheapest part of the boat. Expensive stuff as engine, electronics, interior, e.c.t. are the same as for the shorter one. Longer boat could be faster to build because more spread accommodation could mean easier access resulting in a less time needed to build everything in. (And work-hours are expensive).

    Vega's proposition for comperation on the basis of displacement makes a lot of sense as displacement is very good indication of the price (if everything else is the same, material, level of complexity, e.c.t.).

    I like many different kind of boats, but I always had a special affection for a low drag, efficient, skinny hulls. They move fast with a minimum fuss in the water and don't need a lot of energy to go.

    I'm designing minimum cost, very simple, spartan, fast, (in cruising context) schooner. Here are the basics:

    LOA = 15 m
    Beam = 3.10 m
    Displ = 10 tons max (fully loaded), aiming for less
    wetted surface 37 m2
    whole (hull) surf. area 74 m2
    sail area working +/- 55 m2, around 80 - 90 m2 max in light airs
     

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  15. Vega
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    Vega Senior Member


    This one, also a small production boat, is closer to your proposal.
    She has lovely interiors. ;)

    [​IMG]



    http://i19.photobucket.com/albums/b152/vega1954/Wasa3.jpg


    http://i19.photobucket.com/albums/b152/vega1954/wasa510.jpg

    http://i19.photobucket.com/albums/b152/vega1954/Wasaint.jpg

    http://i19.photobucket.com/albums/b152/vega1954/wasaint2.jpg
     
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