Bermuda Rig Schooner Vs. Bermuda Sloop

Discussion in 'Boat Design' started by Bill PKS, Sep 28, 2009.

  1. Bill PKS
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    Bill PKS Junior Member

    Just read an '05 Post re Schooner Rigs, and have some follow up questions regarding a proposed 44' CB CC equal Ht. Fore and Main, high roach Bermuda Rig Schooner
    Advantages considered:
    -Sails smaller so easier handling ( single handed) than single large Sloop Sail?
    -Lower CLE = less heel than Sloop = Less Ballast ?
    -More sails spread along fore to aft for better load distribution along the hull structure ?
    -More Sails = better able to balance power.
    -More Sails = more power reaching.
    But regarding Close Hauled .
    Is the advantage of a Bermuda rigged sloop vs. a Bermuda rigged schooner the higher sail to the wind, or cleaner air?
    - Wouldn't height of sail be a Trade-off against lower CLE ( less ballast)?
    - Regarding Lifting Air Flow to Windward, wouldn't turbulence around the mast , and area of lift, be the issue? Chappell wrote that for some New Haven Sharpies ( schooners ) of the late 1800's the Masts rotated on a Coin which smoothed mast turbulence to the Sails. Of course they used Gaffs, Leg of Mutton, Wishbones etc..
    I wonder how fully battened fore and main supporting a high roach would perform with 2 Wind slots providing wider luffs all the way up, for more lift?
    Essentially, I understand why a Mono Plane with less drag is faster than a Bi Plane, but the Airplane uses a prop for power. A Sail Boat uses Sails for power. Why wouldn't the greater luff length ( lifting surface area) provide more power, if mast turbulence is moderated?
    Thanks for any comments.
    Bill PKS
     
  2. PAR
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    PAR Yacht Designer/Builder

    There isn't more lifting surface with a schooner rig, just more drag, unless you're not willing to compare apples to apples. SA/D ratios or WS/SA ratios haven't any rig type segregation to the formulas. Given the same "power to weight" ratio, the rig with the least amount of "encumbrance" will get to weather better.
     
  3. Bill PKS
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    Bill PKS Junior Member

    Hull or rig drag?

    - Re Hull drag> With a Schooner, theoretically, couldn't I have less ballast due to lower CLE ( to carry the same amount of sail) = less required displacement = less necessary wetted surface = less relative hull drag for a Schooner of the same SA to a Sloop.?

    - Re Rig drag> certainly a Mono vs Bi Plane has more air drag requiring more prop power, but if a Schooner had say 50% more luff, than a Sloop, why wouldn't that translate to more Lift to windward?
    (At maybe the same ht. of CLE = Same ballast = same hull. )

    Of course more sail surface = more air drag, but for this analysis I'm just thinking about the the portion of the Sail and rig necessary to providing lift, ( erase all the rest by some technical wizardry ). The mind game being to maximize lift of the sails relative to a lower CLE??

    Or is there an unmodifiable turbulence between the Sails that overwhelms any possible gain?

    Thanks for comments,
    Bill PKS
     
  4. PAR
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    PAR Yacht Designer/Builder

    Your assumsions are incorrect. Lets say you have a yacht that carries 1,000 sq. ft. of sail. As a sloop this is two nearly equal length luffs. As a schooner it's at least 3 luffs, unless a cat and you'd still have the same amount of area for the same SA/D, but laterally arranged, so where is this extra area coming from and why would you compare a 1,000 sq. ft. sloop with a 1,200 sq ft. (for example) schooner? The resulting lower aspect ratio (of two equal area boats with different rigs) alone diminishes windward ability. Reduced sheeting angles on largest sail, further reduces abilities. Increased weight aloft from the extra spars and rigging, plus the mainsail itself, continues the reduction of ability.

    This of course assumes the hulls are identical for comparative reasons. Again, apples for apples. On the other hand you could get a sight amount of ability back by optimizing the schooner's hull and appendages for it's rig, but then this isn't the a fair test any more.

    If you wanted to make the schooner compete against the sloop, then you'd have to have apples against oranges. A cat schooner with equal height, free standing masts and big roaches, plus an optimized hull and appendages will do very well against a more conventional sloop. Though in the interest of fairness, the sloop should also be a free standing rig with an optimize hull form. Now which one do you think would fair best and why . . .
     
  5. tom28571
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    tom28571 Senior Member

    There are many reasons for preferring a schooner or other split rig to the sloop but beating to windward is not one of them. This battle has been fought many times over and already settled on the water. Then there is the ability of the sloop to carry huge spinnakers off the wind. There have been notable exceptions like Enza New Zealand, but they often look like huge tandem sloops rather than a schooner.
     
  6. tkk
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    tkk Junior Member

    But is it a fair test if you put a schooner rig into a hull optimized for a sloop rig? ;)
     
  7. Perm Stress
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    Perm Stress Senior Member

    From personal experience skippering bermuda schooner of 45feet /14m, I could say that most benefits against sloop are:
    1. better "self steering" upwind, sometimes also beam wind
    2. much more flexibility when reefing, to suit the conditions
    3. pile of sail for reaching
    4. when yankee jib on long bowsprit is set, even on brad reach "self steering" is possible
    5. it most always more difficult to stall the scooner rig by imperfect helming as it is to stall the sloop rig

    by "self steering" I mean lashed helm for 1 hour or more

    minus points are:

    1. never so close winded as sloop
    2. a nightmare dead downwind
    3. more cost and more weight of masts (if CG of rig a bit lower)
     
  8. Timothy
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    Timothy Senior Member

    In the end isn't it just a question of aspect ratio. If a sloop had a very short mast and an equal sail area to the schooner but spread out very low so that the aspect ratios were the same would there be a signifigant difference in performance? And if this is true is not the real advantage of the sloop that a single mast with sails for and aft is the best way to hoist the maximumum sail area with the least weight penalty?
     
  9. Gilbert
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    Gilbert Senior Member

    There is a lot of good information in this thread.
    There seem to still be a lot of questions, too. There were seven questions in the original post.
    One thing I have learned over the years is that a tall rig and a shallow hull are not a very good match. Since the boat in the original post is a 44' centerboard hull, I would assume it is a shallow hull, but of course that could be incorrect. If so, using two masts to spread the sail area fore and aft seems to be a very appropriate decision regardless of other considerations.

    I can't resist repeating a comment Frank Fredette made on the question of how many masts a cruising boat should have. "There's one stickers and there's two stickers and a man should have what he wants. I always though it was enough trouble and expense rigging up one."
     
  10. Bill PKS
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    Bill PKS Junior Member

    Great Great Comments....
    Well , comparing apples to apples, mono hull to mono hull, CLR to CLR ,,, let's very very roughly assume ≈ 1,000' SA for either rig on the same unoptimized hull.
    Further assume :
    Sloop ≈ 2 Luffs x 15’ E or J x 67' P triangles ≈ 1,000’ SA
    Schooner ≈ 3 Luffs x 15' E or J x 44' P triangles ≈ 1,000’ SA
    ( For simplicity > Ignoring J, Overlaps, Roaches, Topsails, Staysails, Spinnakers etc. etc. etc. ), say the CLE is between 20% and 40% above E.. Let’s use 30% ,,,
    CLE for Sloop would be 20’ above E.
    CLE for Schooner would be 13’ above E.
    That’s a big difference in lever arm, and should make a big difference in theoretical ballast for a displacement hull.
    So if all sails and rigging are optimized to reduce superfluous drag surfaces and enhance Lifting surfaces, wouldn’t that enhance Power , or , alternatively, make a big difference in ballasted weight = reduction in displacement = reduction in wetted surface... Either way it should be faster.
    I know “on the water” > boat to boat ,,, Sloops have always been faster to windward,, but I still don’t understand why.
    Bill PKS.
    Of course for a +40' boat the Main on a Sloop is a hand full for a Geezer.
    Schooner on a shallow draft CB helps.
    I'm mainly trying to understand what the theoretical problem is to windward.
     
  11. Timothy
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    Timothy Senior Member

    Its my understanding that to compare upwind performance the aspect ratio is calculated as the square of the longest luff divided by the total sail area and that the extra luff length on a split rig has no positive effect which I think indicates that theoretically an uni rig (Yellow Pages) is the best. I think in practical terms for windward performance its sloops first yawls second and schooners last.
     
  12. PAR
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    PAR Yacht Designer/Builder

    The bottom line is it's a number of things that determine windward ability. All contribute to or detract from a boat's abilities.

    Dividing the rig up into more "pieces" (as in a schooner) means the sheeting angles necessary for windward work aren't as possible as they are on a sloop. This single reason alone will prevent a schooner from getting as high up as a sloop and it has nothing to do with hull forms, appendages or aspect ratio.
     
  13. Timothy
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    Timothy Senior Member

    I agree . But then a sloop is a split rig on a single mast The argument is that a jib is supposed to benefit from the main even without over lap. Does that mean that a cat schooner could conceivably point as high as a sloop? I noticed that Nigel Irens design for the replacement for Maggie B is an unstayed square topped cat schooner with a boomless foremast, the foresail overlapping the mainsail. It looks great but is it better than a sloop. Why have the additional mast?
     
  14. tkk
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    tkk Junior Member

    Thank you Paul! This finally made me understand it. I have also been trying to understand why the luff length divided in two is not equal to on long luff.

    Also having worked with (model)airplanes a lot and studied aerodynamics in that field I was comparing a schooner to a triplane but now I understand that a triplane approach would require the masts to be side by side to see the same apparent wind. In a schooner the "wings" of a triplane are one after another.

    This brings an idea to me: did anybody try side by side masts on a catamaran or a tri? Could this give the best of the two: low loads and CE of a split rig and the windward ability of a sloop?
     

  15. Timothy
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    Timothy Senior Member

    here is M2 m2.jpg
     
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