QuadOct Superclass

Discussion in 'Sailboats' started by sharpii2, May 1, 2016.

  1. sharpii2
    Joined: May 2004
    Posts: 2,246
    Likes: 329, Points: 83, Legacy Rep: 611
    Location: Michigan, USA

    sharpii2 Senior Member

    A Proposed “QuadOct” Box Scow Super Class


    Objective

    To create a super class where various versions of the 8 ft by 4 ft box scow can race together. Such boats include the Bolger “Brick”, the “pdracer” (invented by “Shorty” Routh, the “Oz Duck” (created by Mike Storer), The “Kiwi Duck” (designed by John Welsford) and others, which may be created later.

    Methodology

    1.) To loosely define the Hull type as a 4 ft wide by 8 ft long box, with parallel, vertical sides, which are at least 10 inches high, and a fore and aft curved bottom, which is flat, side to side.

    2.)To restrict the sophistication of the sails, and

    3.) To limit the Sail Area (SA) in proportion to the weight (Displacement) of the Boat with Crew.

    I know the third part of my methodology is bound to be controversial, but I believe it is crucial to making this concept work.

    Let me explain.

    To make a faster than usual boat of this type calls for a shallow “Rocker” (fore and aft curve of the bottom), light weight, in both Boat and Crew, and lots and lots of Sail Area.

    This type of Hull has a great deal of initial stability, and can stand up to a very large SA, even when relatively light weight. This, in my opinion, gives a huge advantage to lighter boats and crews, as they can have much greater sail carrying power for their weight than their heavier counter parts.

    The reason for this is simple.

    As the weight of the boat goes up, the size of the SA, to give it the same proportion of SA to over all displacement volume (expressed as SA to Displacement, or S/D) goes up, but the Beam does not. This means the heavier boat is likely to be more tender, for the same S/D than the lighter boat. This happens for two reasons:

    1.) the heavier boat sinks deeper into the water, so its Hull Depth to Beam ratio is less. This means a smaller lateral buoyancy shift, as the boat heels.

    2.) The larger SA needed for the heavier boat is almost certain to have a higher Center of Area (CA) than the lighter boat with the same S/D.

    So, my solution is to not only limit the S/D to a level less than the lighter boat can handle, but give the heavier boat a slight S/D advantage over the lighter boat.

    This is for two reasons:

    1.) to avoid overly large monster rigs on the heavier boats, and

    2.) to give the heavier boat a slight light wind advantage.

    My thinking goes like this:

    On windier days, the lighter boats will probably be faster, as their initial stability is more than enough to stand up to their rigs.

    On lighter wind days, the heavier boats will have an advantage, as they are likely to have slightly less Whetted Area than their lighter counter parts and will have slightly higher S/Ds.

    The hope is that neither the heavier nor the lighter boats will have a commanding advantage in all conditions.

    Considering the fact that pdracers have been built which weigh as little as 55 lbs and can have one person crews who weigh less than 150 lbs, it is more than possible to end up with a 200 lb Boat and Crew.

    But most pdracers are built of relatively cheap materials, where weight must be increased to get adequate strength, most pdracers weigh in closer to 100 lbs.

    The average one person crew is probably closer to 200 lbs than 145, so the typical Boat and Crew of this type is likely to weigh in at around 300 lbs or more, one and a half times as much as the lighter Boat and Crew. Some may weigh in at as much as 400 lbs total, twice as much as the lightest boat mentioned.

    I have devised a simple formula to keep the S/Ds of the lighter boats close to those of the heavier boats, which can be solved with a dollar store calculator.
    The formula is this:

    (((Wt Boat + Crew, in lbs) - 180)/6)) + 45 sf

    So, lets see what we end up with.

    For our 200 lb Boat and Crew, we get:

    ((200 lbs - 180)/6) + 45 sf, which give us a SA of 48.3 sf

    For our 300 lb Boat and Crew we get:

    ((300 lbs - 180)/6) + 45 sf, which gives us a SA of 65 sf.

    And for our 400 lb Boat and Crew, we end up with:

    ((400 lbs - 180)/6) + 45 sf, which gives us 81.7 sf.

    Now lets look at the S/Ds of these three boats:

    The 200 lb Boat and Crew has an S/D of 22.6
    The 300 lb Boat and Crew has an S/D of 23.2
    The 400 lb Boat and Crew has an S/D of 24.1

    There is less than a 7% difference in S/Ds between the lightest boat and the heaviest one. Pretty close, considering the heavy boat is twice the displacement of the light one.

    The sails would be limited to poly tarp material, with just one dart each, cut into them, or rounded spar edges, builder’s choice.

    There would be no limits on the type or number of sails, other than those already mentioned, providing the total Sail Area does not exceed the rules.

    Boats that show up with excessive Sail Area will have two choices, other than not racing:

    1.) they can add crew members, or
    2.) they can add compensating weight in the form of sand bags, water jugs, or water bags. Denser compensating weight, other than 20 lbs, for an anchor and perhaps some tools, will not be allowed due to safety concerns. These weights may be placed anywhere in the boat the skipper pleases.

    As tempting as it is to go on a banning binge against sophisticated spars, including ones made of carbon fiber, I think it’s best to resist. The reason for this is this particular hull type doesn’t sail well when heeled anyway.

    Same goes for underwater foil design, for rudders, dagger boards, centerboards, and lee boards. The reasoning is that foil shapes are easy enough to make, if one is willing to go to the trouble. This would be racing, after all.

    External ballast, more than 4 lbs per appendage, would not be allowed.

    Conclusion

    I think this proposed super class is an easily doable experiment, as it will not only require cheap, easily built hulls, but will be able to use many that have already been built.
     
  2. upchurchmr
    Joined: Feb 2011
    Posts: 3,287
    Likes: 259, Points: 83, Legacy Rep: 579
    Location: Ft. Worth, Tx, USA

    upchurchmr Senior Member

    Lets call it the "Sandbox"

    There are more rules than value in a sandbox.
     
  3. messabout
    Joined: Jan 2006
    Posts: 3,367
    Likes: 510, Points: 113, Legacy Rep: 1279
    Location: Lakeland Fl USA

    messabout Senior Member

    Sharpie2, I claim that such a boat, if carefully designed, would sail better at some angle of heel than it would if sailed flat.
     
  4. sharpii2
    Joined: May 2004
    Posts: 2,246
    Likes: 329, Points: 83, Legacy Rep: 611
    Location: Michigan, USA

    sharpii2 Senior Member

    I think that really depends on the load.

    A pdracer has a 6 inch rocker height, which means when the boat displaces 300 lbs the bow and stern transoms are 3.0 to maybe 3.5 inches above the LWL.

    Since the boat is 48 inches wide, this does not leave much room for heel before the lee bow corner digs in, maybe 7 deg.

    With a lighter boat of the same design, with say, a displacement of 200 lbs, the Bow and Stern transoms end up higher, maybe an inch or so. this will allow the boat to heel about 9.5 deg. before its Bow transom digs in.

    With Oz duck or the Kiwi duck, the rocker is only 5 inches high, which puts the transoms even closer to the LWL at 300 lbs.

    With most flat bottom boats, a reasonable amount of heel, say 15 deg., more or less, improves the performance. This is for two reasons:

    1.) The boat presents a shallow "V" to the water, which helps it pound and slap less, and

    2.) The CB shifts more to the lee side of the boat, which increases its Righting Arm (RA).

    But, because pdracers have full width transoms, the lee corner of the Bow transom digs in before the boat heels far enough to develop much RA.

    This is all the more true as the total displacement increases.

    For this reason, this type of boat is best sailed nearly level.

    And, if the boat is sailed nearly level, less rocker produces less drag than more rocker, pretty much the opposite one would expect with a flat bottom boat, with a scow plan form.
     
  5. messabout
    Joined: Jan 2006
    Posts: 3,367
    Likes: 510, Points: 113, Legacy Rep: 1279
    Location: Lakeland Fl USA

    messabout Senior Member

    Sharpie, I too have never learned a much, or anything, from an argument that I won. I salute you for that bit of philosophic wisdom.

    Your original premise did not force me to use a flat plate bow like the PDR. I'd have curved the whole of it like an inland lakes scow. Dammit you may have forced me to go to the drawing board to see if I can pull off the better when heeled deal. I concede that if the stern could be narrowed the wetted lines would be more favorable when heeled.

    Given your screen name I would suppose that you are a sharpie/flattie guy. As such you will know that a simple flat bottomed boat can become a una-maran when heeled appropriately. The waterline becomes more narrow, longer, and wetted surface is significantly reduced. In such a case it can be a formidable match for far more sophisticated designs.

    Cheers for simplicity.
     
  6. sharpii2
    Joined: May 2004
    Posts: 2,246
    Likes: 329, Points: 83, Legacy Rep: 611
    Location: Michigan, USA

    sharpii2 Senior Member

    Thanks for your kind words, messabout.

    Having sprung sides helps a lot in scow design, because the added
    buoyancy of these sprung sides helps lift the bottom/transom corners
    out of the water, so, if the spring is enough, these bottom/transom
    corners never dig in.

    But, according to Howard Chapelle, this was not the main reasons many
    if not most scows had sprung sides.

    The main reason, according to him, was that when you combined sprung sides
    with outward flair, you ended up getting some natural fore and aft curve in the bottom.

    Take a piece of stiff card stock, such as a 3 x 5 card and bed it fore
    and aft while on its side edge. You get a nice curve, but an absolutely
    flat bottom. The curved edge fits gapless against the flat table top.

    Now tip the top edge of this bent card outward.

    A gap opens up at both ends, and the card only touches the table top
    with the middle of the bent. A Closer look would reveal that the bottom
    edge of this card has formed a vertical fore and aft curve that is a
    lesser version of the horizontal one.

    This was a big help when boats were constructed out of planks. This is
    because they either had to have caulk driven between them, or they had
    to be riveted together. Having planks with splinter like ends was a
    definite no no.

    So, scows, such as the New Jersey Garvey had sprung sides with generous flair,
    combined with sharper curves cut into the ends of the sides.

    This avoided the splinter plank ends.

    Indeed, building a pdracer with planks would be fare more difficult
    than building one out of the usual plywood. Such would probably require butting
    shorter planks against one another, so they formed the
    approximate profile of the Rocker, along the bottom edge of the sides.

    Then the inner side planks would have to be let into the upper edges of
    these planks, with the use of notches cut into them.

    Other than that, the sides could be vertically staved, which would look
    very un-boat like. Other than that, double planking could be used, with
    thin horizontal planks going over the thin vertical staving, with
    generous amounts of roofing cement going in between them. Either way,
    it would have been a huge hassle.

    Now, we use plywood, at least as long as the timber straight enough, to
    shave the veneers from, is still around.

    Since plywood already comes with triple planking, we can cut just about
    any side profile our hearts desire.

    The problem of the transom corners digging in can be solved, or at leas
    mitigated, by increasing the Rocker to Beam ratio.

    This can be done in two ways:
    One, increasing the Rocker, and
    Two, decreasing the Beam.

    The first attachment is a sketch of what I call a “Duckoid”.

    Its hull follows the same Rocker profile of a pdracer, but is scaled
    up. The boat is 20 ft long, so the Rocker is 15 inches high. The Beam
    is only 8 ft, so the Beam/Rocker ratio is 6.4 instead of the 8.0 of a
    pdracer.

    This boat, by the way, was meant to be a shallow water cruiser, which
    would carry two bicycles under the foredeck. It would displace
    approximately 3300 lbs and have a floating draft of about 7.5 inches.

    Even before the pdracer came onto the scene, I was working on my own
    straight sided scow concept. It was to have a much more pronounced Rocker,
    which was L/12, instead of the L/16 of a pdracer. The Beam was to be narrower
    too, only 3 ft. But the Length was to be much longer, 12 ft.

    (See 2nd attachment)

    This produced a Beam/Rocker ratio of only 3.0.

    This way, the boat could heel quite a bit before the transom corner dug
    in.

    I designed a similar hull back in the mid 90’s for a WOODENBOAT
    magazine design contest, for a sailboat for very young children to
    learn to sail on. Kind of a pre-Optimist class. I probably put too much
    Rocker and not enough SA in it, so it didn’t do well in the contest.

    But I must say, it was a far safer design than the one that won the
    contest. It had all its emergency flotation in the bottom, so refused
    to be righted, after it capsized. (they built a prototype and tried
    it).

    The boat in my 2nd attachment is a grown up version of my entry.

    This brings me to the pdracer itself.

    If I had small children whom I was willing give some autonomy to, in
    letting them take their own sailboat out, I could do far worse than a
    boat of this type.

    (See 3rd attachment)

    As you can see, its Beam precludes easy capsize, unless under an
    extraordinary press of sail. Not only that, but its short Length and
    generous enclosed volume preclude easy swamping on any protected water
    (which is the only water I would even consider letting set sail on).

    It’s also easy to beach and big enough carry a few of their friends on.

    This boat is designed for casual sailing, so the bow is open, so you
    can step onto the beach, over the bow transom.

    I can imagine may enjoyable outings on this boat, in which I could sail
    to picnics or even fishing grounds on any number of small lakes.

    The sail is designed to be reefable, but such should best be done
    ashore.

    Another pdracer I drew.

    (See 4th attachment)

    was intended for more ambitious sailing. It was intended to answer
    the challenge, put out by the “Water Tribe” to sail the “Everglades Challenge”
    in a pdracer. Such would be an iffy venture at best, and one likely to be
    foiled by rough conditions or foul winds.

    This boat is built with higher sides and more SA than the one in the 3rd attachment.
    It also has a decked over Bow, which has its deck high enough to get my feet under.
    The idea is to sleep aboard under a boom tent.

    The twin Side Centerboards (nope, they’re not really Lee Boards ) were
    meant to provide directional stability, as this boat was to be sailed
    as long as 20 hours at a time (to make the check points on time).

    The bigger sail is very similar to a Chinese Lug, but with fewer
    “Boomlets” (some times called “Battens”. It can be reefed only twice,
    but doing so is almost as easy as with a Chinese Lug. The halyard will
    be led aft to the skipper and cleated there, so the sail can be sorted
    even when under way.

    This boat, even if it never dared the EC, would be a nice minimal camp
    cruiser on protected waters. (though a good number of pdracers have
    been known to sail on not so protected waters).

    Over all. This style of boat, along with my deeper, narrower
    counterpart, deserves far more consideration than it usually gets.

    No, it’s not fast.
    No it’s not glamorous.
    And No, it’s not all that pretty (but I do think it has a certain
    abstract cuteness to it).

    But its certainly very useful, especially as a first sailboat (and
    maybe a last one).
     

    Attached Files:


  7. sharpii2
    Joined: May 2004
    Posts: 2,246
    Likes: 329, Points: 83, Legacy Rep: 611
    Location: Michigan, USA

    sharpii2 Senior Member

    In my hurry to post my drawings and to make my essay easier to follow, I neglected to post the top and section views of the three boats I designed.

    The duckoid shown first has no section view, but the CC-12 and the two pdracers do.

    So, here are their section and profile views, starting with the CC-12, then my first pdracer design, Motha Jugs, then finally, my second pdracer design, Haiku.
     

    Attached Files:

Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.