modifying a staysail schooner

Discussion in 'Sailboats' started by drewcathell26, Feb 3, 2009.

  1. PAR
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    PAR Yacht Designer/Builder

    Maybe it's just me, but am I the only one on this thread that recognizes that schooner pictured above? Possibly I'm the only one with the spec's and sail plan in my data base. Could it be, I'm the only one that knows where the CE is on that particular design or how much lead, Bill Luders incorporated into it's sail plan.

    Then again maybe I'm just talking out my *** and haven't a clue.

    Look anyone with even reasonable design experience understands that a sailsail schooner will crush a gaff schooner close hauled and that as the sheets are eased the roles will reverse. This of course assumes the hulls are the same, the boats sailed equally, neither hoists additional sails and they're not fouling each other. It's the very reason the rig was invented.

    It's also the rig that continues to this day, to win races and by no means requires you to take a speed or performance penalty in any fashion. Hell, a well designed schooner will usually show it's transom to any boat of similar hull and appendage configuration on a reach.

    The rig can be changed, but it's not a very practical thing to do. The boat has a primitive liner and grid, making moving masts quite troublesome and costly. You can hang half the main off the stern and double (+) the length of the bow sprit, to gain back the area you remove from the top of the rig, but it will not be especially pretty in terms of traditional schooner proportions. The foremast is just to far aft for that at the very least. This change, when all said and done, will rival the full value of the boat, which has been around 30 to 40K for brokerage average examples.

    If you intend to do this and can't be convinced other wise, might I suggest you start with one of the ketch versions of this particularly heavy vessel (D/L 465, 8 tons on a 25' LWL). These can be had at a much less expense, then the one you're currently looking at, with the savings placed toward the revamped rig. It goes without saying (I hope) that you'll need a designer to arrange a new sail plan and structural accommodation to the grid, liner and possibly interior.
     
  2. Tcubed
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    Tcubed Boat Designer

    <<<<Look anyone with even reasonable design experience understands that a sailsail schooner will crush a gaff schooner close hauled and that as the sheets are eased the roles will reverse.>>>> Par

    Sounds a little bit like one of those self evident truths that when actually scrutinized a little more critically turn out to be not so true.

    I thought there was an actual aerodynamic reasoning behind it rather than just a 'everybody knows that' justification.

    I don't mean to be irritating just like to see real reasons.
     
  3. PAR
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    PAR Yacht Designer/Builder

    You're the boat designer, at least the line below your handle suggests such.

    Gaff schooners have huge windage issues, short luffs, heavy spars and gear making for a fair amount of weight well aloft. Staysail schooners have longer luffs, cleaner rigs, much less weight aloft, etc. This coupled with typical gaff schooners having considerable appendage drag and wholesome hull forms, it's would seem reasonably obvious.

    On the other hand a particularly well designed staysail schooner I'm familiar with, has the obnoxious habit of repeatedly winning the Regatta Del Sol Al Sol, the race from St. Pete, Florida to Mexico as well as other events.

    I've sailed on the Cherubini 48' staysail schooner (the 44' ketch as well) and it's not slow by any means and can hold it's own with the best in style and comfort too.

    Most have many misconceptions about schooners, much of which is unfounded wives tails and handed down rumor or speculation. Both the traditional and staysail versions, like all rigs have advantages and disadvantages. I too love the look of a traditional gaffer, but would rather the performance of the Cherubini.
     
  4. drewcathell26
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    drewcathell26 Junior Member

    I don't have the background of either of you but would appreciate help clarifying a few simple questions. It would help me for a minute if we could set aside the question of staysail and gaff efficiency and focus on center of effort.

    If you replace the marconi mainsail on the cheoy lee with a gaff and a topsail of the same relative size and combined shape won't the center of effort when both are flying be the same as the single marconi?

    If you drop the topsail don't you end up with a size and shape similar to a reefed main?

    I am bringing little more than a basic undersatnding of geometry so I may be missing something critical.

    I do agree with PAR that the Cherubini is sweet. If I had an extra million I might even buy one. In fact it was the reason that the Cheoy lee caught my attention. It certainly speaks to the combined value of subtle differances.

    drew
     
  5. drewcathell26
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    drewcathell26 Junior Member

    I don't have the background of either of you but would appreciate help clarifying a few simple questions. It would help me for a minute if we could set aside the question of staysail and gaff efficiency and focus on center of effort.

    If you replace the marconi mainsail on the cheoy lee with a gaff and a topsail of the same relative size and combined shape won't the center of effort when both are flying be the same as the single marconi?

    If you drop the topsail don't you end up with a size and shape similar to a reefed main?

    I am bringing little more than a basic undersatnding of geometry so I may be missing something critical.

    I do agree with PAR that the Cherubini is sweet. If I had an extra million I might even buy one. In fact it was the reason that the Cheoy lee caught my attention. It certainly speaks to the combined value of subtle differances.

    drew
     
  6. drewcathell26
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    drewcathell26 Junior Member

    Opps. I just sketched out the marconi I just wrote about and realized that when you reef the marconi the center styas forward and when you drop the topsail over the gaff main the center moves back. So clearly the center of effort move once the sails are reduced.

    Are sail plans typically draw so that the rig can stay balanced throughout reefing?
     
  7. Tcubed
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    Tcubed Boat Designer

    Yes you are right , if the new gaff main + topsail has the same total planform as the sail it is replacing the center of effort will indeed be unchanged. However, drop the topsail and it does not have the same planform as the original sail when reefed. Rather its center of effort will be further aft and this must be taken into consideration, when rebalancing the entire sail plan, naturally.

    However i think that if you merely do that you would not be gaining any kind of advantage over what is already there.

    I would say replacing the mule and staysail with a gaff foresail (not nescessarily with tosail) would be an improvement for not much more cost than a new sail and spar, especially if it is loose footed. This is because you would get more area, lower down , less divided , with a better shape and a better planform.
    Changing the mainsail is a lot more complex as its cenetr of effort would move aft and would thus require changes to the foretriangle in order to balance, or you're stuck with no significant change or advantage to what you already have with the mainsail. In fact it would be a disadvantage.
    To make the mainsail change into gaff be a improvement requires taking advantage of the the gaff's qualities, thus changing more than just replacing the same shape and area into two sails.

    I get where you're coming from Par, and i am not saying staysail schooners are slow as your examples and many others have demonstrated. My point on the efficiency of a gaff rigged planform must be compared with other things equal or it is not really a meaningfull comparison. So just because it is gaff rigged does not imply solid spars etc... And when you compare the gaff rig made with the same level of technology , weight, aspect ratio , to a marconi sail it turns out the gaff planform is considerably superior simply due to its closer aproximation to the elliptical planform at all angles. Of course if you give the marconi sail some generous roach this difference disapears . Bottom line, triangular sails due to their area distribution suffer from much greater induced drag than their aspect ratio alone would suggest. This is known as the k factor in Prandtl's induced drag equation.
     
  8. Tcubed
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    Tcubed Boat Designer

    Crossed posts there.

    Yes reefing is taken into consideration. The boat must always be balanced. However it is important to realize the center of effort is not set in stone, can and does move around slightly in any rig as it goes through the various sail reductions and combinations. Also as i already said lowering it means it needs to move aft slightly.
     
  9. drewcathell26
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    drewcathell26 Junior Member

    It sound like changing the foresail into a gaff would be the simplest of the desired changes and improve the look of the rig as well. Thanks to all who responded.

    drew
     
  10. timothy22
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    timothy22 Junior Member

    Drew-

    On the off chance you would like to have some fun with scale drawings, I attach one longhand way of finding the centers of areas of sails and groups of sails. If you do the current rig first, you just need to make sure your changes keep the center of areas the same or perhaps a few inches further forward to account for the gaff sails and the schooner rig. As far as efficiency goes, in a small schooner it is hard to beat the drive of an overlapping foresail. With the staysail rig, the gollywobbler, or foursided fisherman's staysail sheeted to the main boom end is a wonder reaching in light air, almost like an asymmetrical spinnaker in its effect. A smaller foursided fisherman is good if it is cut flat for windward work. Both of them can be the devil's own job to set, tack and strike shorthanded or in a strong breeze without a lot of experience. A threesided mule might be better sold to someone else. Few staysail schooners bother with them.
     

    Attached Files:

  11. drewcathell26
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    drewcathell26 Junior Member

    Thanks for the diagrams. Anyone want to answer the more complicated question of how to calculate the center of effort of the jib and staysail on cutter.
     
  12. robherc
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    robherc Designer/Hobbyist

    Find the center of area (viewed from directly abeam the ship) of each sail, and calculate the total area of each sail. Draw a line between the two Centers of Area. Now, find the ratio of the two areas, and place a point at the same ratio along the line. There is your CE between the two sails.
    You can actually find the CE of an unlimited # of sails in that way, by simply pairing them up, finding the CE of each pair, then pairing up the pairs in the same manner as you did the single sails.
     
  13. Tad
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    Tad Boat Designer

    Oh lets have a good argument.....

    Talking about center of effort in a schooner is (almost) a total waste of time. The reason for having a schooner is that the boat can easily be balanced on all points of sail in any amount or angle of wind. You can do this because you have (literally) dozens of controls instead of the sloop's handful.

    Who here can point out an normally proportioned schooner that had balance problems? Balance.....let (one of 4-6) the sheet out a bit, or pull it in a bit.

    Catboats and sloops have one or 2 sails that we can find a theoretical center for and pretend that we know whats happening. Far less margin for error, fewer options. With a schooner you have four or five sails to adjust on the wind, the chance that one will overpower the others is almost nil.

    Topsails do not enter into the CE equation. Just like spinnakers, yes you can feel it in the helm if there's a problem, but calculating a geometric center is a waste of time. Hoist them when conditions are right, drop them when they're not.
     
  14. robherc
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    robherc Designer/Hobbyist

    ...Can't argue that Tad, but I'll still answer his question. ;)
    ...and I'll still try to figure the CE of my schooner-rigged boats & try to put the CE of the keel close to there, so it's EASIER to balance it while underway (or, at least, so I feel better about it :p).
     

  15. Tad
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    Tad Boat Designer

    rob...

    In a schooner put the foremast about at station 2 and the mainmast at station 6....she'll probably work just fine. A masthead sloop has the mast at station 4, frac sloop station 3, ketch main at station 3 and mizzen at station 8.

    Be aware you are calculating geometric centers of what are 3 dimensional foils. All sails aft of the headstay lose effectiveness due to the junk (masts, sails, etc) ahead of them. When calculating CE I use a sail area loading system devised by Davidson Laboratory. Load the fore triangle (clean leading edge, no mast ahead) to 1.7 * SA, set the main (or fore'sl on a schooner) at 1, and the mizzen (schooner main) at .5.
     
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