Facet Boat

Discussion in 'Sailboats' started by sharpii2, May 6, 2008.

  1. sharpii2
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    sharpii2 Senior Member

    Now here's a whacked out idea for some of us would be designers with little or no money.

    How about a challenge to design a boat that has absolutely no curves in it.

    It would be comprised of all flat surfaces angled together.

    How about a length of 61 cm (24 inches) and a displacement of of 4.0 kg.

    The heavy weight is to make the challenge, well, challenging. It is easy to make a light boat of crude shape work.

    I would put other design limits on it as well:

    1.) Draft + Beam must not exceed 45 cm,

    2.) Exterior ballast must not exceed 1.0 kg. Exterior Ballast will be counted as any ballast that goes on or in any keels or leeway preventing fins. After all, a real boat must be able to carry real cargo, and

    3.) 'Cargo', anything stored anywhere but inside the keel(s) or leeway preventing fins or rudders must be less dense than water.

    4.) The number of facets will be limited to 20, including all sides and transoms as well as the bottom. All the facets on all the hulls would be counted, for multi hulls for example. A 'Keel' must be at least as deep as it's widest point to be counted as such. The deck, keel(s), and rudder(s) will not be counted as Facets

    Sound interesting?

    Or is this just one of my dumb ideas?


    1.) Length----------------61 cm (24 inches)
    2.) Displacement-----------4 kg
    3.) Beam + Draft----------45 cm (8.8 lbs)
    4.) Max numb. of Facets---20 (including everything except the deck and keel fin) (cross beams, if any, will be counted as part of the deck and will not be counted as facets, nor will ballast struts)
    5.) Exterior Ballast---------1.0 kg max.
    6.) 'Cargo' to be less dense than water.
    Last edited: May 7, 2008
  2. rwatson
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    rwatson Senior Member

  3. Trevlyns
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    Trevlyns Senior Citizen/Member

    The simple response :p ... Why?
  4. rwatson
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    rwatson Senior Member

    Thats easy Trevs - because you are stuck on a desert island with only 1 metres square bits of plywood to build your escape boat :)
  5. sharpii2
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    sharpii2 Senior Member

    Just to provide a bit of an intellectual challenge.

    I even thought of proposing a handicap system that would reward using less than 12 facets (but not punish using up to 20)

    I was thinking it would work like this:

    Time allowance = ((12/ number of facets used)/10)+1 with no number less than 1 being used.

    How would a good boat designer go about this?

    How many facets would he/she use?

    How would they be positioned and proportioned?

    I was thinking that those of us who are interested could post their design ideas for others to review and criticize.

    A good way to show how clever we all are ;)
  6. sharpii2
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    sharpii2 Senior Member

    Revised R/C Facet Boat Competition proposal

    Hi, All.

    After some serious thought and examination of my previous proposed rules, I decided to make some changes.

    I decide to change the former handicap rule from:

    ((12/(number of facets used))*6 = seconds per minute added

    to this:

    (20-(number of facets used)) = allowed seconds per minute added

    This way an eleven facet boat would be allowed 9 seconds per minute, while a four facet boat would be allowed sixteen.

    A four facet boat would be quite crappy and would not be up to completing the course in just 125% of the time a good one would be able to.

    The real advantage to this change is that now there would be no absolute limit to the number of facets used. The limit would come as the added facets improved the performance less and less.

    I also decide to cut the size of the boats down to 30.5 cm in length. This would give them 1/8th the displacement and make them much easier to cart around.

    Below are the revised proposed rules:




    Would be a competition to make R/C sail boats that have absolutely no curves in the hull, but are made up of flat surfaces called facets that are angled to each other to approximate curves as close as possible. These boats would be sailed around an equilateral triangular course

    A handicap would be set up to reward using as few facets as possible. The handicap would work as follows:

    (20-(number of facets used)) = seconds per minute time allowance.

    A boat that had only ten facets would have an allowance of ten seconds added to its time to get around the course.

    A.) The dimension limits of these boats would be as follows:

    1.) Length---------= 30.50 cm
    2.) Beam + Draft* = 22.75 cm
    3.) Displacement = 500.00 cc
    4.) Ballast keel--= 125.00 gm
    5.) Max Keel Vol.= 63.00 cc

    Facets forming only the hull would be counted.

    B.) The deck would not be counted as long as:

    1.) it’s lowest point is at least half the Hull Draft** above the at rest Water Line, and
    2.) is sloped or cambered upward up to a no more than 0.25 times its maximum width.

    The Deck can have end facets that aren’t counted as well, as long as they do not fill in more than the maximum allowed pitch or camber

    C.) The Fixed Keel(s) would not be counted either, provided:

    1.) it displaces no more than half its/their weight in total and
    2.) weighs no more than 125 gm.

    D.) Rudders and un ballasted fins would be allowed providing:

    1.) they do not cause the boat to exceed its maximum allowed Beam + Draft limit when fully extended,
    2.) weigh no more than 1.50 times the amount of water they displace, and
    3.) displace no more than 50 gm total.

    E.) Internal Ballast will be allowed as long as:

    1.) is placed only in the hull, and
    2.) weighs no more than 3.0 times what it displaces.

    F.) Multihulls would be allowed provided:

    1.) they satisfy Beam + Draft limits,
    2.) they satisfy min. displacement, and
    3.) all the facets of all the hulls are counted.

    G.) R/C channels:

    1.) two will be allowed.

    *Draft = distance from at rest Waterline to lowest point of Keel, Rudder, or Fin.

    **Hull Draft = distance from at rest Waterline to lowest point of hull.

    Any comments or suggestions?

    Also attached is a drawing of a crude 5 facet boat to help illustrate my proposed rules.

    Attached Files:

  7. sharpii2
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    sharpii2 Senior Member


    Just for the sake of perverse curiosity, I decided to draw some “cartoons” of the most primitive Facet Boats possible with my 30.5/500 rule. (later in this post).

    Because of a generous Beam/Draft Sum,(2)4 facet boats appear to be possible.

    The first one is a scow, which I will call “SEB 4”. Its bottom is made of just two facets at an angle. It has no transoms (see rules), straight vertical sides, and decks pitched to the maximum extent allowed by the rules.

    (see first and second attachments)

    The biggest possible problem I see with this wee beastie is the sharp angle at the bottom. The way I see it, the water going past the bottom of the hull will have to make an abrupt turn, of just under 30 deg., to continue on its way. My guess is this will form a rolling vortex, which will summersault upward. The faster the boat goes, the bigger this vortex will get, increasing the drag exponentially.
    My guess is this will happen well before the boat reaches the roughly 2.33 ft/sec, which is it theoretical hull speed. I suspect it will bog down well short of that.

    The second problem is the leeward bow corner digging in as the boat heels. This too will create a significant amount of drag. But, due to the extreme pitch of the decks and the sizable “Deck End Facet”, such will probably not cause it to stuff its bow.

    The question is whether it will be ever able to go fast enough for its keel to be effective enough to enable it to make upwind progress.

    Here are the rules:

    30.5/500 FACET BOAT RULES

    I.) FACETS
    A.) Are absolutely flat surfaces that are angled to one another to approximate a curved surface. There are three types of Facets: Deck Facets, Deck End Facets, and Hull Facets.
    B.) Boat bottom and topside surfaces are to made of Hull Facets which are counted. Deck Facets and Deck End Facets are not.
    C.) Deck Facets are level or have a pitch of no more than 1:2, rise over run.
    D.) Deck End Facets share an edge with just one Hull Facet, and do not project outward past any Hull Facet.
    E.) Keels, Rudders, Centerboards, Dagger boards, and Lee boards do not have to be made of Facets and are not counted as such.
    F.) A racing handicap allowing extra time for boats made up of fewer Facets will be based on the following formula:
    Boat with most Facets - number of Facets of boat with fewer Facets = extra seconds per minute added
    A six Facet boat racing an eight Facet boat, for example, would be allowed 8 - 6, or 2 seconds more per minute to finish the course, than the eight Facet boat.

    A.) Hull Length must not exceed 30.5 cm.
    B.) Beam and Draft added together must not exceed 23 cm, including Keels, Boards, and Rudders
    C.) Displacement must be at least 500 cc with Ballast Keel and 440 cc without.
    D.) Internal Ballast must not exceed 3.0 times the density of water.

    A.) Keel(s), must not displace more than 62 cc, combined, must be at least as long at the top as at the bottom, and cannot weigh more than 125 gm, combined.
    B.) Bulbs extending past the leading and trailing edge of the keel are not allowed.
    C.) Un Ballasted Dagger boards, Center boards, and Lee boards are allowed and are allowed to be retractable, providing they do not exceed the Beam plus Draft rule when fully extended. They, combined with the Rudder(s) must not displace more than 30 cc.
    D.) Keels, Boards and Rudders may only be rounded at their thickest, at the leading edge, and tapered to twice their thickness at their trailing edges.

    A.) is restricted to 950 square centimeters.

    V.) R/C
    A.) only one channel is allowed, for the rudder.

    Attached Files:

  8. gggGuest
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    gggGuest ...

    This seems a bit too much to me. Plywood, indeed all wood does bend, and bends readily: that's one of its attributes.
    The point of ultra simple to build boats is a very good one though, but I suggest its worth looking at a slightly different restriction. After all, if you replace a single piece of one dimensionally bent plywood with multiple facets, have you in fact made the boat easier or harder to build: especially when you consider the framing and number of joins?
    I was mightily impressed when I saw the drawings of John Spencer's Firebug, which stuck me as a really easy to build boat and still boat shaped. It might be the constraints he used for that would be a better basis for an ultra simple boat.
    Those might be summarised for a challenge as:
    All panels bent in one dimension only.
    Every chine angle the same throughout its length.
    No twisted panels.
    No more than n panel joins or maybe n panels
    (have to figure out what a good value for n is, but a flush deck double chine flat bottom boat with pram bow and transom is what, 8 panels and 18 seams?)
  9. sharpii2
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    sharpii2 Senior Member

    Thank you, ggg, for taking the time to respond. I am quite aware of cylindrical developed hulls and have even designed a few myself.

    This particular thread is not intended as easy way to build a boat system.

    It is intended as an intellectual exercise, hence the diminutive size of the proposed boats.

    The idea is to make the best of a bad situation (a boat with no curves).

    The size and orientation of the facets become primarily important, even with a simple 4 facet boat.

    There will come a point when adding more facets not only fails to improve the performance but actually detracts from it, hence the one second-per-minute-per-difference-in-facets handicap rule. Such will not mark this point but will be a good indication when this point is fast approaching. If a boat with one facet less the it's competitor consistently wins by this handicap, it will mean that it is less than 1.66% slower.

    Probably 99% of the time, if not more, there will be no practical reason to build a boat with no curves. But it might come up.

    It did during the American civil war, when the Confederate navy needed iron clad warships to fight the north. The ships were built primarily out of wood with iron plates attached to the outside. The hull planking had to be very thick in order to make this work, and the wood they used did not steam bend well.

    So they had to use faceted construction to make these hulls.

    Plywood is indeed a wonderful materiel. I love it. But due to deforestation, and very poor panels, due to crappy 2nd growth trees, I feel there is reason to suspect decent plywood panels may become a thing of the past.

    In short, there may come a time when one has to build a boat out of a material one does not dare bend.
  10. messabout
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    messabout Senior Member

    Some of we boat nuts are strange people. RC modelers are willing to depart from mainstream thinking too. A popular internationally subscribed class of model boats is the footy. A development class that is a strictly "sail what you brung" boat. It has to be no more than a foot long and fit inside a box of officially determined dimensions.

    My first notion of the faceted boat would be something like a PDR with parallel sides. Draw the bottom curve and divide it into a series of secant lines which would become the facets. Say seven bottom facets, two sides and two ends for a total of 11 facets.......subject to further study.

    The intellectual pursuit would attempt to determine whether the flatter angled breaks would be more efficient than that of more severely angled breaks that resulted from fewer facets. Eddy making drag of a larger number of facets would, intuitively, be less than the drag produced by a single angled bottom as in the one you have drawn. Intuition is not to be trusted in cases such as this. Would the sum of eddy making drag of several lateral bottom breaks be more or less than the drag produced by a single, but more severe break?

    Are we having fun yet?
  11. sharpii2
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    sharpii2 Senior Member

    Oh yes we are.

    I now have three versions of SEB: SEB 4, SEB 5 and SEB 6.

    I plan on introducing all of them on this thread over time.

    But first I'd like to introduce the other 4 facet alternative.

    It is called SAP. (see attachments)

    It is nothing but a pie slice shape with a greatly sloped aft transom.

    This was the best way I could think of to get the gentlest aft flow while maintaining the required 500 cc displacement. There may be better ways, but I haven't been able to think of them.

    As you see, I put the fin keel quite far forward, as I expect there will be a great deal of drag quite far aft, as the leeward stern corner goes under.

    Just about all the forces I can imagine acting on this wee beasty seem to conspire to give it a lee helm.

    If I build this boat, I will arrange to be able to move the keel fore or aft, as needed.

    It is the antithesis of SEB 4 in that it should prove quite hard to balance with its sail plan. I feel its sharp bow may be of benefit. It would be interesting to to race the two of them (SEB 4 and SAP 4), to see which one is faster.

    Any guesses?

    When designing a boat with so few facets, the object is not to make a good boat, but one that simply works. And that means being able to make windward progress.

    There are two more versions of SAP already drawn: SAP 5 and SAP 6. I will introduce them over time.

    Attached Files:

  12. gggGuest
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    gggGuest ...

    Well, if I say my boat has 50 gazillion facets each 1 molecule square...

    The handicap might be a bit harsh though.

    That's always the problem with design competitions. There's always a tendency to be designing against the rule, not the laws of physics, when you'd rather be doing the latter. A very difficult thing to manage, simply because creating genuinely even handicap/measurement rules is next to impossible.

    I suppose you could argue that steel ships constructed of plates tend to be faceted, with only a minority of panels actually curved. One may also view, for very different reasons, faceted shapes in modern warship design.
  13. sharpii2
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    sharpii2 Senior Member

    The purpose of my handicap rule is to encourage people to design boats with as few facets as possible.

    Otherwise, you'd be right. They would simply design rounded shapes and claim they were made of very, very small facets.

    Kind of like dividing one by zero.

    A remedy for that, of course, would be to stipulate a minimum size (in square centimeters) of such facets.

    I just thought not limiting anything, in regard to the number or size of the facets, and providing an incentive plan to use fewer facets, instead, would be more fun and interesting.

    A faster boat, as we all know, even one as heavy as these are supposed to be (a 2.44 m one would displace around 256 kg), would certainly have curved fore and aft panels.

    Such is plain common sense.

    There is a possibility, though a very slight one, that a facet boat of this weight, could end up being faster than one with the usual curved panels.

    I am considering the idea of allowing boats with curved bottom panels, or even round bottoms, to compete, if they follow the rest of the rules. To make this possible, such would need to be assigned a number of "Virtual Facets". I am thinking of, perhaps 8 per curved panel, multiplied by eight "Virtual Panels", if a rounded bottom is chosen. So the defacto maximum number of Facets would end up being 64, which is kind of interesting. Such would predict that a round bottom design would be exactly twice as fast a four faceted one.

    I went with a Sum Rule rather than a Box one in order to add another interesting trade off, more Beam vs. more Draft.

    The Beamier boat may be faster in heavier winds, while the deeper one
    might do better in the light stuff.

    If the great single-handed races had such a rule, we'd might never have ended up with canting ballast keels.
    Last edited: Jan 13, 2016
  14. sharpii2
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    sharpii2 Senior Member

    Round Bottom And Chine Bottom Inclusion

    After some thought, I decided it would be a good idea to include chine hulls and round bottom hulls in this proposed competition.

    The problem quickly became; how do I set up a reasonable handicap?

    Originally, I thought of having every curved panel on a chine hull to have eight virtual facets, with a round bottom hull having eight virtual panels. A chine hull having this many panels would certainly come far in aping a round bottom.

    This would give a round bottom hull 64 virtual facets, an almost impossible burden. It would have to be almost twice as fast as an 8 facet boat (64 - 8 = 56 sec/min faster) and half again faster than a “V” bottom chine hull. (64 - 32 = 32 sec/min faster)

    Both seemed quite unreasonable to me, especially the latter.

    A simple get-out-of-jail-free-card for this dilemma would be to consider all hulls with curves, whether round or chine bottom, to essentially equal. In that case, I could assign them all the same number of virtual facets.

    But is this true?

    Most probably not. Or all we would see is single chine flat bottom sailboats. Certainly having more panels, i.e. chines, does provide some advantage. And almost certainly having a round bottom, rather than a chine, one provides an advantage on top of that.

    But how much of one?

    My guess is that, after having three curved panels, the amount of additional advantage drops off noticeably.

    I expect the same thing to happen with facets too.

    I expect, as the number of faceted panels increases, the number of facets needed on each panel will decrease as well.

    This is really just a guess on my part, but it seems somewhat intuitive. The reasoning goes something like this: With more faceted panels, each panel moves a lesser amount of water aside.

    But, as with the chine hull, adding more and more panels will quickly run into rapidly diminishing returns. Also, having Facet Boats with a gazillion facets wouldn’t be much fun either.

    So I decide on a system which, however clumsy, makes these considerations. It also had to be relatively simple, requiring no exponents or roots.

    My system works on the assumption of diminishing utility.

    I started off imagining a boat with only one curved panel, such as a pdracer. Since most of the water going past the hull has to pass this panel, the curve of this panel has very high utility, so I gave it a value of 8 virtual facets.

    Then I considered a hull with two curved panels (believe it or not, such is possible. Wharram catamarans once had this shape.). In this situation, I gave the second panel a value of 7 virtual facets. It is not as big an improvement as the one curved panel, but is still a considerable one. It allows a pointed bow, for example, without resorting to a SAP plan form (see first attachment), and it allows a "V" bottom.

    Next, I added a third panel.

    This, I believe most will see as real boat. Boats of this type are seen all over the planet, and some have even sailed around it. Such a boat is familiar as a “sharpie” or a “dory“, in the west, and maybe a “sampan“, in the east. So, I think most would agree, though not as big an improvement as the second panel, adding a third panel is still a profound one. So I gave it a value of 6 virtual facets.

    Since round and multi panel chine bottom boats are burdened (by handicap) by so many facets, I decided to not count the first two transoms, allowing each a free bow and stern transom.

    Now, following my original thought pattern, one would assume adding a fourth panel would mean adding 5 more virtual facets.

    But I decide this is the wrong way to go.

    Is a boat with four curved panels really about 8% faster than one with only three curved panels?

    I would think not.

    So this is what I decided to do. I decided that each curved panel, in excess of 3, to be worth only one virtual facet. This would mean that a single chine “V” bottom boat would have 22 virtual facets, giving it a perceived speed advantage of only one second per minute (22 - 21 = 1). This may not actually be the reality, but it is certainly closer to the truth than my old system.

    From this point on, one virtual facet will be added for each added panel, after three curved panels, until the total number of such panels reaches 8. At this point, it should be the equivalent of a round bottom. Therefore, a round bottom will have the equivalent of 26 virtual facets ( 21 + (8 - 3)).

    So here’s my inclusion system: (“VF” = virtual facets)

    1.) chine hull with only one curved panel*:

    8 VF + all flat hull panels, including transoms.

    2.) chine hull with two to three curved panels:

    7 VF per panel + all flat hull panels, except a bow transom and a stern transom.

    3.) Chine hull with three or more curved panels:

    21 VF + (number of curved panels in excess of 3), up to eight panels, (at this point the boat is considered to have a round bottom).

    * “curved panels” can be cylindric or conic, or any combination of the two, but can not have compound curves.

    Attached is a drawing of a pdracer with a curved bottom panel and one of a pdracer with a facet one.

    According to my handicap system, the pdracer with the curved bottom should be about 8% faster than the one with the faceted one ((8 + 4), for the curved bottom one, - 7 facets, for the facet bottom one)/60.

    Attached Files:

  15. gggGuest
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    gggGuest ...

    But, you know, here's the move from a beat the laws of physics challenge to a beat the rule maker challenge.

    I still suggest, though, that a limitation of single dimension curvature only (with no twist) and constant chine angles might be an interesting one. Folk could start by posting photos of cardboard models...
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