Scow with a hint of bow?

Discussion in 'Sailboats' started by Terje Dahl, Nov 22, 2022.

  1. Terje Dahl
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    Terje Dahl Junior Member

    Having studied the thread From Classic Bow to Scow Bow by @Dolfiman,
    and the post Latest Evolutions and Revolution in the Class40 by François Chevalier,
    I am convinced that scow bow is the way to go for the boat I am developing - a 26-foot "performance cruiser".

    A reputable Dutch firm had this to say about my project:
    "When you are not restricted by class we think it's worthwhile to add some length to the boat (and not put any interior in it but keep it empty and light) to improve the sailing characteristics."

    My question(s):
    If it wasn't for the "20/45" bow constraint rule for Class40, would the designers be going for a pure scow bow? Would you?

    Or would you (or they) have added a bit of wave-piercing bow anyways?
    And if so, would it ideally be shaped differently than what we currently see in Class40 (a plum bow starting low above the water)?
     
    Last edited: Nov 23, 2022
  2. gonzo
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    gonzo Senior Member

    That depends on too many variables. You need to write down all of them, and then develop a design that fulfills that as much as possible. It is usually called the Statement of Requirements (SOR). As you indicated, racing formulas eventually develop a limited range of designs. If you don't design to a formula, what are you designing to? That is what the SOR does: gives you guideline of what you are designing to.
     
  3. Dolfiman
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    Dolfiman Senior Member

    Same preliminary remark than @gonzo, you should tell us a bit more about your project. But if "... cruiser" is in your objective, be care that the current racers with a scow bow are very specialised for oceanic races (i.e. with a low proportion of upwind close hauled times), they are overcanvassed and hard sailed by top sailors without much concern about comfort. I mean that they are not really oriented to amateur sailors which aim fun times through a mix of oceanic and coastal sailing/racing+ some cruising times. I think you should better take your inspiration from boats like the Sun Fast 3300 or the JPK 1030, two top boats for racing with exciting all around performance but also use for some cruising, accessible for the average sailors, for which there is a resale market.
     
  4. CT249
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    CT249 Senior Member

    Why are you convinced the scow is the way to go? They are an old idea that normally only really works in classes with big rigs and length restrictions.

    As the Dutch firm said, just draw the bow lines out into a conventional bow and you will get a longer waterline and better entry into waves for very little extra weight and wetted surface.

    Have you tried sailing a scow or a yacht with very full bow sections? Upwind in slop they often bang, rattle and slow down in a very annoying fashion.
     
  5. Terje Dahl
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    Terje Dahl Junior Member

    Thank you, guys, for your responses, and for challenging me, forcing me to clarify or reconsider.

    I would like to turn the question around: Why not scow bow?

    Clearly, the hull shape has such significant advantages that anyone who cares about speed is pushing towards it as hard as rules permit. Correct me if I am wrong, but didn't the Class40 committee rush to adjust the rules - changing them just 3 months after Raison won with his mini in 2011 - so as to prevent full scow bow?

    So why not bring scow to the people?
    Just because I want to cruise around the archipelago or around the world in comfort, do I not also want to go fast?

    The main objections I am hearing are:
    1. Pounding.
    2. Drag.
    3. Poor upwind performance.

    The main benefits I am seeing are:
    1. Increased efficiency.
    2. Improved performance overall.
    3. Increased volume.

    The effect of the hull shape is shown, and the pros and cons well summarize here:
    As for increased drag (relative to a standard hull of the same length), that is easily countered by increasing the sail area:
    And poor upwind performance? I am not sure. Scow bow may or may not deliver an improvement in upwind. But is it worse that a standard hull?
    And is head-on waves a factor in this assumption? If so, then this brings us to ...

    Pounding! This is constantly raised as a major issue.
    But do not all boats experience some degree of pounding irrespective of bow shape?! What type of bow would be optimal to reduce pounding? How long should it be? How fine? What shape? And what is the tradeoff?
    And that brings me back to my original question:

    And yes, I am working on a design myself. See attachment.
     

    Attached Files:

  6. Terje Dahl
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    Terje Dahl Junior Member

    @gonzo, I am not sure what a SOR would look like.

    I am designing for a specific market and price segment.
    Boat size will be a function of that, as well as what might be practical in usage scenarios.

    I want a boat that is fast and fun to sail. But I want a bit of space and comfort under deck, including 2 double beds, a comfortable kitchen, and a bathroom with a separate shower. And I want to be able to stand up straight when shaving at 190cm (6'3").

    I imagine a 24-ish foot scow with another 2-3 feet added for a wave-piercing bow. So I arrive at 26 feet (7.9m x 3.3m)
    ... and a target retail price of 150.000 EUR.
     
  7. skaraborgcraft
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    skaraborgcraft Junior Member

    Your comment contradicts, how can you design for a "specific segment" if you do not know the SOR?

    150K buys a lot of bigger second hand boats and the market is saturated. What makes you believe there is a market for a sub 8m yacht at that price, and what would you make it from?
     
  8. Terje Dahl
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    Terje Dahl Junior Member

    I DuckDuckGo-d SOR and found this description of a SOR. So it turns out I most certainly have a SOR. I just haven't written it down.

    Yes, you certainly can get a lot of boat second-hand for that price on Blocket. But I am not building a second-hand boat.

    I observe, talk to people, and read what the press says when a new boat in that market segment comes out. But I agree: I can't know. So I must therefore find a way to test the market before committing to building anything.

    Aluminium, of course!
     
  9. skaraborgcraft
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    skaraborgcraft Junior Member


    France is the cheapest place in the EU for building in aluminium. Have you seen this? The scow-bowed Revolution 24 is certainly weird, but is it wonderful? - YouTube

    Might be worth an email to see how many orders they have before you go any further.
     
  10. CT249
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    CT249 Senior Member

    "The main benefits I am seeing are:
    1. Increased efficiency.
    2. Improved performance overall.
    3. Increased volume."


    All those points appear to only apply IF you have a boat that is limited in overall length and that has a big rig. Given what we see in other craft, if you took a scow shape and drew the bow out to a point, it is likely that it would be faster and have more internal and external space for little, if any, extra cost.

    Let's flip the concept around. Take a typical boat; maybe the Seascape 27. Now, cut the front 1.5m off to turn it into a scow. Exactly what has been gained? There is some loss of skin material in the bow so some weight has probably been dropped - but you have a bow that smashes into waves, less deck space, less interior space, and less waterline length. Yes, it would be faster for its length overall, but it's certainly not a better boat overall. Apply the same to another boat, even a Laser, and we see the same effect. You make the boat shorter, but not better.

    The point is that increasing a hull's volume for its length overall does not make a boat better per se. It makes it "better" if the boat is under a class rule that forces boats to be short for their rig size, cost, and speed - but a short, fat boat with a big rig is not a great overall recipe for speed. The boats are NOT all that fast overall if you look at their sail area, beam, cost, etc; look at the French national PHRF style handicap, OSIRIS. It rates the Mini Proto at 24, the same as a Seascape 24. The Mini has about 49m2 of upwind sail, 109m2 of downwind sail, and a Pogo Foiler costs around 199,000 Euros. The Seascape figures from the same source are 42m2 of upwind sail area, 92m2 of downwind sail area, and a price of 42,000 Euro. Why may FIVE TIMES as much to go the same speed with a Mini scow and have less space down below and a boat that is far more complicated to sail, run, and tow? How is that "efficient"?

    If we ignore the foilers and Protos, then look at the Pogo 3. It is still more expensive than a Seascape, but significantly slower than the Seascape, with a rating of 21. Again, the Mini style makes sense for Mini racing, but not overall.

    A J/88 is rated at 27 by Osiris, so it's significantly faster than a Mini Proto. The J/88's figures from the same source are 47.5 upwind sail area, 122.5m of downwind sail area, and 92,000 Euros. So what is "efficient" about a design that requires spending twice the cash to go slower, have less accommodation, and a more complicated rig?

    Similarly the Open 40 rates a bit faster than a "conventional" boat like a Farr 40, but the Open 40 is a bigger boat - it has more beam, more waterline length, significantly bigger upwind sail area and much larger downwind sail - so whether it is actually faster for its true size is another issue.

    The effect of the hull shape is shown, and the pros and cons well summarize here:

    This show that, within the frame of class rules with a beam restriction but otherwise open, this design can give a slight but determinant bonus of performance. In the pro's are, with heel, a floatation surface more leeward and more parallel to the boat axis, leading to more RM and sooner/faster planning when downwind (as long as the boat is light enough). In the con's are more wetted surface in light winds and a bumping bow in short waves when upwind.
    As for increased drag (relative to a standard hull of the same length), that is easily countered by increasing the sail area:


    Sure, you can "easily" add sail area - but adding sail area means adding structure to handle the higher rig loads; adding bigger winches and sail controls to handle the bigger sails; adding bigger spars, and having bigger, costlier sails. So why is that better than having a more slender but longer hull with a rig of similar (or smaller) size that will go the same speed or faster?

    "Clearly, the hull shape has such significant advantages that anyone who cares about speed is pushing towards it as hard as rules permit."

    Nope. Look at a TP52, the new Julian Bethwaite sportsboat, the European lake boats like the Psaros 33 and 40, International 14s, A Class catamarans, Cape 31..... no scow bows there.

    Re reading the press - sadly, the sailing press these days seems to consist almost entirely of people who don't own boats like the ones they enthuse about (at least in the English-speaking countries). Speaking as a former sailing magazine editor, many sailing writers don't write from a position of knowledge about boat ownership, they are biased towards novelty for a bunch of reasons connected with their job, and examples like the totally unrepresentative nature of coverage and recent "boat of the year" awards show that most of them are very bad at working out what it actually going to sell. Plenty of boats that the press have raved about have not sold many boats at all; look at the Flying Phantom cats that got so much publicity and are now out of production. The Quant 23 was European Boat of the Year, I think, and production stopped at about 12 boats.

    It does seem funny that a year or two ago, people were going ape about wave-piercing bows as if they were something inherently better than a "normal" bow. Now people are going ape about scows, which are completely opposite to wave piercers. It seems to just show that rules and fashion, not function, are ruling many of the choices in design.
     
    Last edited: Nov 27, 2022
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  11. gggGuest
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    gggGuest ...

    Mind you I can think of one usage where the scow bow type would really score - the marina living boat that primarily serves as a high status caravan by the seaside and doesn't venture out of sheltered water. It gives maximum internal volume for the length, important where berthing is charged by the metre/foot, and plenty of static stability. The unpleasant pounding and wave impact would not be a major concern in sheltered water, so all in all it feels to me as if it could be a good choice for the role. Its not, of course, a particularly trendy or exciting design space, but commercially I suggest its not insignificant.
     
  12. CT249
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    CT249 Senior Member

    Commercially that seems to be a very significant design space indeed! The same factors seem to drive many of the other long-term trends in yachts.
     
  13. DVV
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    DVV Junior Member

    I dont think the wave piercing bow is a good comparison.
    Scows are nothing new, they have been developed many times: garveys, ausrialian scows, even the first moth were square bowed.
    The fact that for a limited length the scow shape is faster is not new. These types of vessel have been banned from competition in the past due to their superior speed.
    They are still banned in Class 40 and in IMOCA, but they are not banned in Mini class, and they win.
     
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  14. gonzo
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    gonzo Senior Member

    They win in races that are mostly reaching or downwind. They are not so superior upwind in a chop.
     

  15. DVV
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    DVV Junior Member

    For sure they suffer from a chop. But are they slower in a chop than traditional design?
    The Route du Rhum that has just ended has been upwind for the first half, two weeks of upwind racing.
    In Class 40 - where scow bows and traditional bows race together - big bows were all at the top. They did not appear to be slow in any way.
    Manuard says scows are not slower upwind, they are just unconfortable.
     
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